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Weighing the Milky Way

Using a new measurement technique, researchers have found that the Milky Way (artist rendition above) has half the mass of the Andromeda Galaxy (image below). Credit: NASA/JPL-Caltech

Using a new measurement technique, researchers have found that the Milky Way (artist rendition above) has half the mass of the Andromeda Galaxy (image below). Credit: NASA/JPL-Caltech

Does the Milky Way look fat in this picture?  Has Andromeda been taking skinny selfies? It turns out the way some astrophysicists have been studying our galaxy made it appear that the Milky Way might be more massive than its neighbor down the street, Andromeda.

Not true, says a study published in the journal Monthly Notices of the Royal Astronomical Society by an international group of researchers, including Matthew Walker of Carnegie Mellon University’s McWilliams Center for Cosmology. In the paper, they demonstrate a new, more accurate method for measuring the mass of galaxies. Using this method, the researchers have shown that the Milky Way has only about half the mass of its neighbor, the Andromeda Galaxy.

In previous studies, researchers were only able to estimate the mass of the Milky Way and Andromeda based on observations made using their smaller satellite dwarf galaxies. In the new study, researchers culled previously published data that contained information about the distances between the Milky Way, Andromeda and other close-by galaxies — including those that weren’t satellites — that reside in and right outside an area referred to as the Local Group.

Andromeda image: ESA/Hubble & Digitized Sky Survey 2, Davide De Martin

Andromeda image: ESA/Hubble & Digitized Sky Survey 2, Davide De Martin

Galaxies in the Local Group are bound together by their collective gravity. As a result, while most galaxies, including those on the outskirts of the Local Group, are moving farther apart due to expansion, the galaxies in the Local Group are moving closer together because of gravity. For the first time, researchers were able to combine the available information about gravity and expansion to complete precise calculations of the masses of both the Milky Way and Andromeda.

“Historically, estimations of the Milky Way’s mass have been all over the map,” said Walker, an assistant professor of physics at Carnegie Mellon. “By studying two massive galaxies that are close to each other and the galaxies that surround them, we can take what we know about gravity and pair that with what we know about expansion to get an accurate account of the mass contained in each galaxy. This is the first time we’ve been able to measure these two things simultaneously.”

By studying both the galaxies in and immediately outside the Local Group, Walker was able to pinpoint the group’s center. The researchers then calculated the mass of both the ordinary, visible matter and the invisible dark matter throughout both galaxies based on each galaxy’s present location within the Local Group. Andromeda had twice as much mass as the Milky Way, and in both galaxies 90 percent of the mass was made up of dark matter.

The Expose-R2 experment on the outside of the Zvezda module of the International Space Station (ISS). Credit: DLR

BIOMEX: Exploring Mars in Low Earth Orbit

The Expose-R2 experment on the outside of the Zvezda module of the International Space Station (ISS). Credit: DLR

The Expose-R2 experment on the outside of the Zvezda module of the International Space Station (ISS). Credit: DLR

In their quest to understand life’s potential beyond Earth, astrobiologists study how organisms might survive in numerous environments, from the surface of Mars to the ice-covered oceans of Jupiter’s moon, Europa. For now, Earth is our only example of an inhabited planet, and studying the limits of habitability on Earth is a major component of astrobiology research. For this reason, scientists collect data from places on our planet where life is pushed to the absolute limits of adaptability, from the Antarctic to the Arctic, and from smoldering thermal vents to highly acidic rivers.

But locations like the Antarctic Dry Valleys or deep-sea vents in the Pacific aren’t the only places in which astrobiologists study life as we know it. Low Earth orbit provides an opportunity to observe Earth-life in the harsh conditions of space.

In the early hours of July 24th, 2014, a new astrobiology experiment began its journey from the Baikonur Cosmodrome in Kazakhstan to the International Space Station (ISS). BIOMEX (Biology and Mars Experiment) launched onboard a Russian Progress cargo spacecraft and is one of four experiments that make up the EXPOSE-R2 facility, which will be mounted on the exterior of the ISS Zvezda module. Just six hours after launch, the cargo ship successfully docked with the ISS.

View of a Progress vehicle connected to the Zvezda module of the ISS. The Zvezda Service Module was the first fully Russian contribution to the International Space Station. The module provides station living quarters, life support systems, electrical power distribution, data processing systems, flight control systems and propulsion systems. Credit: NASA

View of a Progress vehicle connected to the Zvezda module of the ISS. The Zvezda Service Module was the first fully Russian contribution to the International Space Station. The module provides station living quarters, life support systems, electrical power distribution, data processing systems, flight control systems and propulsion systems. Credit: NASA

Life on the Station

BIOMEX contains twelve different experimental packages that are designed to help determine life’s potential on Mars. The Institute of Planetary Research at the German Aerospace Center (DLR) is coordinating BIOMEX, but the project involves 25 participating institutions from around the world.

Launch of the Russian Progress cargo spacecraft (03:44 Baikonur Time) carrying BIOMEX to the ISS. Credit: Roscosmos/ESA

Launch of the Russian Progress cargo spacecraft (03:44 Baikonur Time) carrying BIOMEX to the ISS. Credit: Roscosmos/ESA

BIOMEX contains numerous chambers that are filled with biomolecules and organisms that include bacteria, archaea, algae, fungi, lichens and mosses. Replicate samples spread across the compartments are subjected to a range of environmental conditions. Some samples of each biomolecule or organism are embedded in a simulant Mars soil (ranging from just a single layer of soil to multiple layers), and other samples are left on their own to face the space environment without protection.

Various filters are also being used on the sample chambers to test exposure to different levels of radiation. By doing this, scientists are able to simulate the solar radiation present at the martian surface. Some of the sample chambers are even pumped full of a simulated Mars atmosphere that is rich in carbon dioxide and pressurized to replicate conditions on Mars.

“To gain real insights into the behavior of biomolecules within a martian environment, we have to check the different parameters we might encounter on Mars,” explained Dr. Jean-Pierre Paul de Vera of the German Aerospace Center (DLR) and the principle investigator for BIOMEX. “This means we will approach — as much as possible on the ISS — martian conditions, including extreme temperature regimes, martian atmosphere by using Mars-like gases in the compartments of EXPOSE-R2, and the radiation regime, which we can never simulate in the labs on Earth.”

The samples will spend up to one and a half years outside the space station, and the organisms inside will be monitored with temperature sensors and dosimeters, which monitor radiation exposure. The goal is to see how exposure to these varied environmental pressures affects the survival of the organisms and the stability of important cellular components like membrane lipids, pigments, proteins and DNA.

BIOMEX Logo. Credit: DLR

BIOMEX Logo. Credit: DLR

The results of BIOMEX will help astrobiologists understand whether or not these biological materials can cope with conditions in the space environment and on Mars, and if being buried in martian soil might aid in their survival.

Tools for the Future

While the samples in BIOMEX are attached to the outside of the station, scientists on Earth will be working with replicate samples in the lab. Here they will simulate martian conditions as best they can in the controlled environment of the laboratory and monitor the Earth-bound samples with a number of instruments.

At the completion of the experiment, BIOMEX samples will be returned to Earth

where scientists will take a close look at the results. In the laboratory, they will examine the stability of biomolecules after they have been exposed to the conditions in low Earth orbit. This includes studying the signatures they leave behind in the sample chambers, which could be useful on future life-detection missions on Mars.

“BIOMEX is investigating the capacity of instruments to detect selected biosignatures (pigments, membrane composites, lipids etc.) in a Mars-like environment before and after space experiments, and also during Mars simulations in the lab,” de Vera told Astrobiology Magazine.

The Mars Simulation Facility Laboratory. Credit: DLR

The Mars Simulation Facility Laboratory. Credit: DLR

The set of spectroscopic instruments they are using on Earth are similar to those currently being eyed for Mars missions in the near future. They include Raman, IR and UV/VIS spectroscopes. Initial tests in the lab have already turned up some interesting results. Studies at the German Aerospace Center in Cologne and Berlin indicate that biosignatures are altered by temperature and radiation. This causes their appearance to differ from the signatures we normally observe in Earth conditions.

Beyond Astrobiology

Data from BIOMEX could also have some important applications beyond the realm of astrobiology according to Dr. de Vera. Studying how biosignatures survive in a simulated Mars regolith might have lessons for archaeology experts on Earth who are looking for radiation-independent (e.g. not carbon 14-dating) methods to study ancient wooden objects. In particular, the thermogravimetric methodology, which is used by de Vera and his team to test the bounded and remaining water in BIOMEX samples after they have faced the conditions of space, is of special interest for archaeologists.

Raman spectroscopy is also a technique that is growing in prominence for biological studies in numerous fields.

The Mars Simulation Facility. Credit: DLR/German Aerospace Center

The Mars Simulation Facility. Credit: DLR/German Aerospace Center

“Raman spectroscopy is used more and more in microbiology, pharmacology and medicine,” said de Vera. “The Robert Koch institute in Berlin, which is cooperating with us, uses this method (coupled with other methods) to characterize microorganisms that can be harmful to health, and they have to be detected very fast to find out if there could be a risk of an epidemic.”

The studies of biofilms in space could have some interesting implications for the health of astronauts and humans on Earth. On Earth, biofilms are used in some health drinks to trigger the immune system. Studying biofilms in space can help determine whether or not these drinks might be safe for astronauts to consume in orbit, or if the space environment will cause biofilm cultures to rapidly mutate in such a way as to become harmful for consumption.

“Desiccation [removal of water] and radiation protection is also a very important issue,” noted de Vera. “Studies on the exposed samples might give more information about how the most resistant microorganisms are able to shield themselves efficiently, and which substances are responsible for their resistance. The cosmetic and food industries are interested in these results.”

In fact, the Fraunhofer Institute IZI for Cell Therapy and Immunology in Potsdam, Germany is already working with two of the organisms that de Vera and his team are studying. One is a highly resistant cyanobacteria, and the other is a green algae. Thanks to BIOMEX, these organisms now have a home in low Earth orbit, clinging to the outside of the International Space Station.

Dr. Jean-Pierre Paul de Vera (second from left) and his team perform a sample and sensor check before integration into the Mars Simulation Lab. Credit: DLR

Dr. Jean-Pierre Paul de Vera (second from left) and his team perform a sample and sensor check before integration into the Mars Simulation Lab. Credit: DLR

Further Afield with BIOMEX

BIOMEX will help astrobiologists understand the potential for habitability on Mars. If life ever originated on Mars, and if that life operated under the same biological principles as on Earth, could those organisms have adapted to survive on Mars in the present day?

By exploring this question, BIOMEX could help shape the future of Mars exploration, providing guidelines for where robotic explorers might search for signs of life on present-day Mars or signs of ancient life preserved in the regolith.

“With the data obtained by the selected biomolecules as potential biosignatures and which are exposed to the Mars-like conditions in space, we are building up a database that might have significant relevance for future exploration missions to Mars,” said de Vera. “This database might serve as back-up, or a systematically generated reference list that takes into account the martian environmental conditions that might influence the signatures of minerals, and possible fossils or biomolecules from potential extant life forms.”

The BIOMEX project was supported by BMWi (German Ministry of Economy and Technology/Energy), DLR Agency, the European Space Agency (ESA), ASI, UK Space Agency, and INTA.

EXPOSE-R2

BIOMEX is one of four experiments in the Expose-R2 facility. Two of the additional studies are also providing data that could be useful to astrobiologists:

BOSS (Biofilm Organisms Surfing Space), led by Dr. Petra Rettberg of the DLR in Cologne. BOSS will study the different ways in which exposure to the space environment affects single-celled plankton and microorganisms that form biofilms.

BIOMEX will be placed in the Expose-R2 system. Credit: DLR

BIOMEX will be placed in the Expose-R2 system. Credit: DLR

“We want to know what effects UV radiation will have on cell structure and biofilms in space conditions, and the differences between biolfilm and non-biofilm forming organisms,” said Charles Cockell of the University of Edinburgh, whose lab provided some of the biological samples for both BIOMEX and BOSS. “They will help us understand how organisms can be made to be robust against extreme space conditions.”

It is thought that organisms capable of forming biofilms may be more successful in protecting themselves from harsh environmental conditions. The ability to produce biofilms may have been important in the early stages of life’s evolution on Earth, when conditions on our planet were very different than today.

PSS (Photochemistry on the Space Station), led by Prof. Dr. Hervé Cottin from Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA) UMR CNRS in Créteil Paris. Organic compounds and mixtures in both solid and gas form will be exposed to the space environment. The results of PSS will provide information about organic chemistry and the potential formation of prebiotic molecules in the space environment. Scientists can use this information to understand how radiation in space triggers reactions that lead to the formation of these molecules, some of which could have been materials in the origin of life as we know it. The data will also help determine how organic compounds are affected by solar radiation on planets or small bodies that do not have a dense atmosphere to shield their surfaces.

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Venus Express: Up Above The Clouds So High

 

ESA’s Venus Express spacecraft has climbed to a new orbit following its daring aerobraking experiment, and will now resume observations of this fascinating planet for at least a few more months.

The orbit-raising followed a month of aerobraking that saw the spacecraft surf in and out of the atmosphere at altitudes typically between 131 km and 135 km for a couple of minutes on each of its closest approaches to the planet.

Before, normal operations involved an elliptical orbit every 24 hours that took Venus Express from 66 000 km over the south pole down to around 250 km at the north pole, just above the top of the atmosphere.

But, after eight years and with propellant running low, the Venus Express team began a daring aerobraking campaign, dipping the craft progressively lower into the atmosphere on its closest approaches.

The experiment directly explored previously uncharted regions of the atmosphere, while also providing information on how a spacecraft responds when encountering the tenuous upper reaches of an atmosphere at high speed.

Aerobraking can be used to reduce the speed of a spacecraft approaching a planet or moon with an atmosphere, allowing it to be captured into orbit, and to move from an elliptical orbit to a more circular one. Less fuel has to be carried, yielding benefits all round. The technique will be used on future missions and the Venus Express experiments will help guide their design.

Venus Express aerobraking. Credit: ESA

Venus Express aerobraking. Credit: ESA

“We have collected valuable data on the Venusian atmosphere in a region difficult to characterise by other means,” says Håkan Svedhem, ESA’s Venus Express project scientist.

“The results show that the atmosphere seems to be more variable than previously thought for this altitude range, but further analysis will be needed in order to explain these variations properly.”

Between altitudes of 165 km and 130 km, the atmospheric density increases by a factor of roughly a thousand, meaning that the forces and stress encountered by Venus Express were much higher than during normal operations.

It also experienced extreme heating cycles, with temperatures rising by over 100ºC during several 100 second-long passages through the atmosphere.

In addition, the atmospheric drag at these lower altitudes was so great that the spacecraft’s orbital period was reduced by more than an hour.

“The spacecraft has proven to be very robust and has apparently experienced no substantial degradation in any area, but a detailed evaluation is still to take place,” says Joerg Fischer, Venus Express operations engineer.

Artist's concept of lightning on Venus. Image credit: ESA

Artist’s concept of lightning on Venus. Image credit: ESA

At the end of the campaign, 15 thruster burns raised the craft’s altitude, preventing it from dropping into the atmosphere. The last was executed on Thursday evening, boosting Venus Express to a new altitude of 460 km at its closest and 63 000 km at its furthest. This new orbit takes 22 hours 24 minutes to complete.

“During the 15 manoeuvres, each thruster fired more than 8000 pulses and burned a total of about 5.2 kg of propellant to raise the spacecraft to this new altitude,” adds Joerg.

This orbit will slowly decay again under gravity, but with only a few kilograms of fuel at most now remaining further altitude-raising manoeuvres may not be possible. If no further corrections are made, Venus Express will probably reenter the atmosphere again in December, but this time for good, ending the mission.

In the meantime, having survived not only the aerobraking experiment but also the most recent orbit-raising manoeuvres, all of the science experiments will be reactivated, continuing their detailed study of Venus for at least a few more months.

“We are delighted with the success of the experimental aerobraking campaign, and are looking forward to assessing the details over the coming months,” says Patrick Martin, mission manager.

“Meanwhile, we are enjoying the view from our new orbit around Venus, and plan to continue augmenting the scientific return of this exciting mission.”

This graphic shows a 3-D model of 98 geysers whose source locations and tilts were found in a Cassini imaging survey of Enceladus' south polar terrain by the method of triangulation. Image credit: NASA/JPL-Caltech/Space Science Institute

Enceladus in 101 Geysers

This view looks across the geyser basin of Saturn's moon Enceladus, along fractures spewing water vapor and ice particles into space. Cassini scientists have pinpointed the source locations of about 100 geysers and gained new insights into what powers them. Image credit: NASA/JPL-Caltech/SSI

This view looks across the geyser basin of Saturn’s moon Enceladus, along fractures spewing water vapor and ice particles into space. Cassini scientists have pinpointed the source locations of about 100 geysers and gained new insights into what powers them. Image credit: NASA/JPL-Caltech/SSI

Two publications have revealed new details about the plumes of material erupting from the southern hemisphere of Enceladus. Scientists have identified 101 geysers on the saturnian moon, and the results indicate that liquid water might be transported from the moon’s subsurface ocean all the way to its surface.

The two papers were published in the Astronomical Journal and together they represent the first comprehensive study of the connections between geysers, tidal stresses, and thermal emissions at the south pole of Enceladus.

In the first study, researchers used 6.5 years of data from NASA’s Cassini spacecraft to identify 101 geysers erupting from the tiny moon. The geysers were found with techniques similar to those used to triangulate geological features on Earth. The results show that geysers are associated with small ‘hot spots’ on the moon – providing clues about the processes behind these eruptions of ice and water vapor.

This graphic shows a 3-D model of 98 geysers whose source locations and tilts were found in a Cassini imaging survey of Enceladus' south polar terrain by the method of triangulation. Image credit: NASA/JPL-Caltech/Space Science Institute

This graphic shows a 3-D model of 98 geysers whose source locations and tilts were found in a Cassini imaging survey of Enceladus’ south polar terrain by the method of triangulation. Image credit: NASA/JPL-Caltech/Space Science Institute

“There are only two places the materials can originate from,” Carolyn Porco of the Space Science Institute told astrobio.net, “the near-surface, where they would have to be ice melted by friction into liquid and vapor, or the sea. Our work rules out the near-surface.”

Porco is the leader of the Cassini imaging team and lead author of the first paper.

“Once we had these results in hand, we knew right away heat was not causing the geysers, but vice versa,” Porco said in a NASA press release. “It also told us the geysers are not a near-surface phenomenon, but have much deeper roots.”

The work also indicates that water contained in Enceladus’ subsurface ocean might remain liquid as it passes up through the icy shell to the surface. Narrow cracks in the ice can remain open all the way from the surface down to the ocean if the cracks are filled with liquid water.

This artist's rendering shows a cross-section of the ice shell immediately beneath one of Enceladus' geyser-active fractures, illustrating the physical and thermal structure and the processes ongoing below and at the surface. Image credit: NASA/JPL-Caltech/Space Science Institute

This artist’s rendering shows a cross-section of the ice shell immediately beneath one of Enceladus’ geyser-active fractures, illustrating the physical and thermal structure and the processes ongoing below and at the surface. Image credit: NASA/JPL-Caltech/Space Science Institute

Cracks that reach from the ocean to the surface would not affect the potential for life on Enceladus, but they could provide easy access for sampling the moon’s subsurface ocean. If there is microbial life in the liquid ocean of Enceladus, ice particles from the sea could contain the evidence astrobiologists need to identify them.

“It could be snowing microbes at the surface of Enceladus,” said Porco. “All we have to do is get back there with proper instrumentation to find out.”

The second paper published in the Astronomical Journal shows why the plume brightness and height vary over time as Enceladus circles around Saturn. The giant planet’s powerful gravitational field causes tidal flexing of Enceladus as the moon orbits. This causes the fractures in the its icy crust to open and close, modulating the amount of material being vented by the geysers.

Carolyn Porco, Cassini, and Enceladus all feature in the Astrobiology Graphic History, Issue 4: Missions to the Outer Solar System, produced by the NASA Astrobiology Program and available at: http://www.astrobio.net/nasa-astrobio-graphic-novels/. Credit: NASA Astrobiology / Aaron L. Gronstal

Carolyn Porco, Cassini, and Enceladus all feature in the Astrobiology Graphic History, Issue 4: Missions to the Outer Solar System, produced by the NASA Astrobiology Program and available at: http://www.astrobio.net/nasa-astrobio-graphic-novels/. Credit: NASA Astrobiology / Aaron L. Gronstal

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Bacteria manipulate salt to build shelters to hibernate

Artist’s impression of E. coli. INGRAM PUBLISHING/THINKSTOCK

Artist’s impression of E. coli. INGRAM PUBLISHING/THINKSTOCK

For the first time, Spanish researchers have detected an unknown interaction between microorganisms and salt. When Escherichia coli cells are introduced into a droplet of salt water and is left to dry, bacteria manipulate the sodium chloride crystallisation to create biomineralogical biosaline 3D morphologically complex formations, where they hibernate. Afterwards, simply by rehydrating the material, bacteria are revived. The discovery was made by chance with a home microscope, but it made the cover of the Astrobiology journal and may help to find signs of life on other planets.

The bacterium Escherichia coli is one of the most studied living forms by biologists, but none had to date noticed what this microorganism can do within a simple drop of salt water: create impressive biomineralogical patterns in which it shelters itself when it dries. “It was a complete surprise, a fully unexpected result, when I introduced E. coli cells into salt water and I realised that the bacteria had the ability to join the salt crystallisation and modulate the development and growth of the sodium chloride crystals,” biologist José María Gómez told SINC.

This image shows dried biosaline patterns formed by the interaction of Escherichia coli cells with common salt. Credit: J. M. Gomez Gomez

This image shows dried biosaline patterns formed by the interaction of Escherichia coli cells with common salt. Credit: J. M. Gomez Gomez

“Thus, in around four hours, in the drop of water that had dried, an impressive tapestry of biosaline patterns was created with complex 3D architecture,” added the researcher, who made the discovery with the microscope in his house, although he later confirmed it with the help of his colleagues from the Laboratory of BioMineralogy and Astrobiological Research (LBMARS, University of Valladolid-CSIC), Spain.

Until present, we knew of similar patterns created from saline solutions and isolated proteins, but this is the first report that demonstrates how whole bacterial cells can manage the crystallisation of sodium chloride (NaCl) and generate self-organised biosaline structures of a fractal or dendritic appearance. The study and the striking three-dimensional patterns are on the front cover of this month’s ‘Astrobiology‘ edition.

“The most interesting result is that the bacteria enter a state of hibernation inside these desiccated patterns, but they can later be ‘revived’ simply by rehydration,” said Gómez, who highlighted a very important result from an astrobiological point of view: “Given the richness and complexity of these formations, they may be used as biosignatures in the search for life in extremely dry environments outside our own planet, such as the surface of Mars or that of Jupiter’s satellite, Europa“.

In fact, the LBMARS laboratory participates in the development of the Raman RLS instrument of the ExoMars rover, the mission that the European Space Agency (ESA) will send to the red planet in 2018, and this new finding may help them search for possible biological signs. According to the researcher, “the patterns observed will help calibrate the instrument and test its detection of signs of hibernation or traces of Martian life”.

“The challenge we now face is to understand how the bacteria control the crystallisation of NaCl to create these incredible 3D structures and vice-versa, how salt influences this action, as well as studying the structure of these microorganisms that withstand desiccation,” said Gómez, who reminds us that a simple curiosity and excitement about science, although it may be with simple means, still allows us to make some interesting discoveries: “This is a tribute to scientists such as the Spaniard Santiago Ramón y Cajal and the Dutch scientist Anton van Leeuwenhoek, who also worked from home with their own microscopes”.

Mars Transverse Mercator (MTM) –30247, –35247, and –40247 quadrangles cover a portion of southern Hesperia Planum and the highlands of eastern Promethei Terra, east of the Hellas basin. Credit: Scott C. Mest/David A. Crown/USGS

Maps and Marathons on Mars

This month has marked some amazing achievements for missions at Mars and scientists working with the data that robotic explorers continue to send back from the red planet.

A Clear View of Martian Geology

Mars Transverse Mercator (MTM) –30247, –35247, and –40247 quadrangles cover a portion of southern Hesperia Planum and the highlands of eastern Promethei Terra, east of the Hellas basin. Credit: Scott C. Mest/David A. Crown/USGS

Mars Transverse Mercator (MTM) –30247, –35247, and –40247 quadrangles cover a portion of southern Hesperia Planum and the highlands of eastern Promethei Terra, east of the Hellas basin. Credit: Scott C. Mest/David A. Crown/USGS/PSI

Earlier this month, scientists from the Planetary Science Institute (PSI) released a new geologic map of Mars’ ancient highlands. In a press release from PSI, Senior Scientist David A. Crown commented on how the map can be used to show the ways in which water has shaped the surface of this region of Mars:

“This map depicts the complicated sequence of geologic processes that have served to modify ancient, rugged highland terrains surrounding the Hellas impact basin and shows evidence for the persistent effects of water and ice in degrading the martian surface,” Crown said.

The canyon systems of Waikato Vallis and Reull Vallis are of particular note. These systems are unlike any on Earth, and are thought to have formed when the ground collapsed as subsurface water was released to the surface.

The Geologic Map of MTM -30247, -35247 and -40247 Quadrangles, Reull Vallis Region of Mars, was published as a U.S. Geological Survey (USGS) Scientific Investigations Map. The map is available at http://pubs.usgs.gov/sim/3245/.

Heat-Sensitive Mapping

In other martian cartography news, scientists have released a second map of Mars that was created by using more then 20,000 nighttime temperature images from the heat-sensing THEMIS instrument on NASA’s Mars Odyssey Orbiter. It is the most detailed global map of Mars yet created.

A small impact crater on Mars named Gratteri, 4.3 miles (6.9 km) wide, lies at the center of large dark streaks. Unlike an ordinary daytime photo, this nighttime image shows how warm various surface areas are. Brighter tones mean warmer temperatures, which indicate areas with rockier surface materials. Darker areas indicate cooler and dustier terrain. For example, the bright narrow rings scattered across the image show where rocks are exposed on the uplifted rims of impact craters. Broad, bright areas show expanses of bare rock and durable crust. Fine-grain materials, such as dust and sand, show up as dark areas, most notably in the streaky rays made of fine material flung away in the aftermath of the meteorite's impact. Photo by: NASA/JPL-Caltech/Arizona State University

A small impact crater on Mars named Gratteri, 4.3 miles (6.9 km) wide, lies at the center of large dark streaks. Unlike an ordinary daytime photo, this nighttime image shows how warm various surface areas are. Brighter tones mean warmer temperatures, which indicate areas with rockier surface materials. Darker areas indicate cooler and dustier terrain. For example, the bright narrow rings scattered across the image show where rocks are exposed on the uplifted rims of impact craters. Broad, bright areas show expanses of bare rock and durable crust. Fine-grain materials, such as dust and sand, show up as dark areas, most notably in the streaky rays made of fine material flung away in the aftermath of the meteorite’s impact. Photo by: NASA/JPL-Caltech/Arizona State University

In a press release from Arizona State University (ASU), THEMIS principal investigator and ASU professor Philip Christensen explained, “This map provides data not previously available, and it will enable regional and global studies of surface properties. I’m eager to use it to discover new insights into the recent surface history of Mars.”

Nighttime temperature data allows scientists to determine the ‘thermal inertia’ for football-field-sized swaths of Mars. Thermal inertia represents the speed at which areas heat up and cool down. Different features have different thermal inertia, and this helps scientists distinguish between things like bedrock and fine-grained sand. Spotting the details of surface features in the new map will help mission planners select landing sites for future Mars missions.

The global map of Mars can be viewed at: http://jmars.asu.edu/maps/?layer=thm_ti_100m_8bit&z=6&greenlabels

A version of the map that is optimized for research scientists is also available at: http://astrogeology.usgs.gov/maps/mars-themis-derived-global-thermal-inertia-mosaic

Record Breaking Roving

NASA’s Opportunity rover has made headlines around the world by breaking the record for travel across the surface of a celestial body beyond Earth. Opportunity has traversed over 25 miles (40 kilometers) on Mars, surpassing the previous off-world record held by the Soviet Lunokhod 2 rover.

This natural color view from NASA's Mars Exploration Rover Opportunity shows "Lunokhod Crater," which lies south of Solander Point on the west rim of Endeavour Crater. Image Credit: NASA/JPL-Caltech/Cornell/Arizona State Univ.

This natural color view from NASA’s Mars Exploration Rover Opportunity shows “Lunokhod Crater,” which lies south of Solander Point on the west rim of Endeavour Crater. Image Credit: NASA/JPL-Caltech/Cornell/Arizona State Univ.

Lunokhod 2 landed on the Moon in 1973 and, according to images of the rover’s tracks from NASA’s Lunar Reconnaissance Orbiter (LRO), drove a total of 24.2 miles.

“The Lunokhod missions still stand as two signature accomplishments of what I think of as the first golden age of planetary exploration, the 1960s and ’70s,” said Steve Squyres of Cornell University and principal investigator for NASA’s Mars Exploration rovers in a NASA JPL press release. “We’re in a second golden age now, and what we’ve tried to do on Mars with Spirit and Opportunity has been very much inspired by the accomplishments of the Lunokhod team on the Moon so many years ago. It has been a real honor to follow in their historical wheel tracks.”

Opportunity is now cruising along the western rim of Endeavour Crater. Outcrops on the crater rim are providing a view into ancient environments on Mars that had less acidic water than previously studied sites. The observations that Opportunity is making provide new insight into the potential for life on ancient Mars.

As Opportunity continues to roll, the rover is approaching the 26.2-mile-mark of a martian marathon. To celebrate, it’s next scientific destination has been dubbed ‘Marathon Valley.’ At this site, images from Mars orbiters indicate that clay minerals are exposed at the surface.

NASA's Mars Exploration Rover Opportunity, working on Mars since January 2004, passed 25 miles of total driving on the July 27, 2014. The gold line on this map shows Opportunity's route from the landing site inside Eagle Crater, in upper left, to its location after the July 27 (Sol 3735) drive. Credit: NASA/JPL-Caltech/MSSS/NMMNHS

NASA’s Mars Exploration Rover Opportunity, working on Mars since January 2004, passed 25 miles of total driving on the July 27, 2014. The gold line on this map shows Opportunity’s route from the landing site inside Eagle Crater, in upper left, to its location after the July 27 (Sol 3735) drive. Credit: NASA/JPL-Caltech/MSSS/NMMNHS

“Opportunity has driven farther than any other wheeled vehicle on another world,” said Mars Exploration Rover Project Manager John Callas in the press release from NASA JPL. “This is so remarkable considering Opportunity was intended to drive about one kilometer and was never designed for distance. But what is really important is not how many miles the rover has racked up, but how much exploration and discovery we have accomplished over that distance.”

Curiosity Beyond the Safe Zone

Although it hasn’t driven as far as Opportunity, NASA’s Curiosity rover has also made important progress on its journey across Mars. Curiosity recently managed to roll outside of the region that was mapped as ‘safe terrain’ for the rover’s landing in 2012. So far, Curiosity has traveled a total distance of just over 5 miles (8 kilomters).

This June 27, 2014, image from the HiRISE camera on NASA's Mars Reconnaissance Orbiter shows NASA's Curiosity Mars rover on the rover's landing-ellipse boundary, which is superimposed on the image. The 12-mile-wide ellipse was mapped as safe terrain for its 2012 landing inside Gale Crater. Image Credit: NASA/JPL-Caltech/Univ. of Arizona

This June 27, 2014, image from the HiRISE camera on NASA’s Mars Reconnaissance Orbiter shows NASA’s Curiosity Mars rover on the rover’s landing-ellipse boundary, which is superimposed on the image. The 12-mile-wide ellipse was mapped as safe terrain for its 2012 landing inside Gale Crater. Image Credit: NASA/JPL-Caltech/Univ. of Arizona

As Curiosity explores this new area of Mars, the rover will send home additional data about the past environment of Gale Crater. This information will help scientists understand if conditions suitable for life were once present on Mars.

For the Classroom

Check out this excellent infographic from NASA, which shows the recorded ‘Out-of-this-world’ driving distances for past missions as of May 16, 2013. Now it’s time to update the graphic with the Opportunity rover’s Lunokhod-surpassing acheivement! How far do you think Curiosity will make it during its mission on Mars?

This chart illustrates comparisons among the distances driven by various wheeled vehicles on the surface of Earth's moon and Mars. Of the vehicles shown, the NASA Mars rovers Opportunity and Curiosity are still active and the totals for those two are distances driven as of May 15, 2013. Credit: NASA/JPL-Caltech

This chart illustrates comparisons among the distances driven by various wheeled vehicles on the surface of Earth’s moon and Mars. Of the vehicles shown, the NASA Mars rovers Opportunity and Curiosity are still active and the totals for those two are distances driven as of May 15, 2013. Credit: NASA/JPL-Caltech

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Stanford biologist warns of early stages of Earth’s 6th mass extinction event

Elephants and other large animals face an increased risk of extinction in what Stanford Biology Professor Rodolfo Dirzo terms "defaunation." (Claudia Paulussen/Shutterstock)

Elephants and other large animals face an increased risk of extinction in what Stanford Biology Professor Rodolfo Dirzo terms “defaunation.” (Claudia Paulussen/Shutterstock)

The planet’s current biodiversity, the product of 3.5 billion years of evolutionary trial and error, is the highest in the history of life. But it may be reaching a tipping point.

In a new review of scientific literature and analysis of data published in Science, an international team of scientists cautions that the loss and decline of animals is contributing to what appears to be the early days of the planet’s sixth mass biological extinction event.

Since 1500, more than 320 terrestrial vertebrates have become extinct. Populations of the remaining species show a 25 percent average decline in abundance. The situation is similarly dire for invertebrate animal life.

And while previous extinctions have been driven by natural planetary transformations or catastrophic asteroid strikes, the current die-off can be associated to human activity, a situation that the lead author Rodolfo Dirzo, a professor of biology at Stanford, designates an era of “Anthropocene defaunation.”

Across vertebrates, 16 to 33 percent of all species are estimated to be globally threatened or endangered. Large animals – described as megafauna and including elephants, rhinoceroses, polar bears and countless other species worldwide – face the highest rate of decline, a trend that matches previous extinction events.

Larger animals tend to have lower population growth rates and produce fewer offspring. They need larger habitat areas to maintain viable populations. Their size and meat mass make them easier and more attractive hunting targets for humans.

Although these species represent a relatively low percentage of the animals at risk, their loss would have trickle-down effects that could shake the stability of other species and, in some cases, even human health.

For instance, previous experiments conducted in Kenya have isolated patches of land from megafauna such as zebras, giraffes and elephants, and observed how an ecosystem reacts to the removal of its largest species. Rather quickly, these areas become overwhelmed with rodents. Grass and shrubs increase and the rate of soil compaction decreases. Seeds and shelter become more easily available, and the risk of predation drops.

Consequently, the number of rodents doubles – and so does the abundance of the disease-carrying ectoparasites that they harbor.

“Where human density is high, you get high rates of defaunation, high incidence of rodents, and thus high levels of pathogens, which increases the risks of disease transmission,” said Dirzo, who is also a senior fellow at the Stanford Woods Institute for the Environment. “Who would have thought that just defaunation would have all these dramatic consequences? But it can be a vicious circle.”

The scientists also detailed a troubling trend in invertebrate defaunation. Human population has doubled in the past 35 years; in the same period, the number of invertebrate animals – such as beetles, butterflies, spiders and worms – has decreased by 45 percent.

As with larger animals, the loss is driven primarily by loss of habitat and global climate disruption, and could have trickle-up effects in our everyday lives.

For instance, insects pollinate roughly 75 percent of the world’s food crops, an estimated 10 percent of the economic value of the world’s food supply. Insects also play a critical role in nutrient cycling and decomposing organic materials, which helps ensure ecosystem productivity. In the United States alone, the value of pest control by native predators is estimated at $4.5 billion annually.

Dirzo said that the solutions are complicated. Immediately reducing rates of habitat change and overexploitation would help, but these approaches need to be tailored to individual regions and situations. He said he hopes that raising awareness of the ongoing mass extinction – and not just of large, charismatic species – and its associated consequences will help spur change.

“We tend to think about extinction as loss of a species from the face of Earth, and that’s very important, but there’s a loss of critical ecosystem functioning in which animals play a central role that we need to pay attention to as well,” Dirzo said. “Ironically, we have long considered that defaunation is a cryptic phenomenon, but I think we will end up with a situation that is non-cryptic because of the increasingly obvious consequences to the planet and to human wellbeing.”

Titan, Saturn's largest moon, peeks behind the planet's rings in this picture taken from the Cassini spacecraft. Also visible in this picture is Epimetheus, above the rings. Credit: NASA/JPL/Space Science Institute

Titan Offers Clues to Atmospheres of Hazy Planets

Titan, Saturn's largest moon, peeks behind the planet's rings in this picture taken from the Cassini spacecraft. Also visible in this picture is Epimetheus, above the rings. Credit: NASA/JPL/Space Science Institute

Titan, Saturn’s largest moon, peeks behind the planet’s rings in this picture taken from the Cassini spacecraft. Also visible in this picture is Epimetheus, above the rings. Credit: NASA/JPL/Space Science Institute

When hazy planets pass across the face of their star, a curious thing happens. Astronomers are not able to see any changes in the range of light coming from the star and planet system.

This presents a puzzling problem for scientists trying to find out what is inside planetary atmospheres. Usually, astronomers can look at a star before and after a large planet goes across, note the difference in the spectrum, and make predictions about what elements are contained in the planet’s atmosphere. If the atmosphere contains elements consistent with water or ozone, for example, this could be a sign of life.

“It seems to indicate there is something in their atmosphere that is blocking our ability to see the gas in the atmosphere,” said Tyler Robinson, a postdoctoral fellow at the NASA Ames Research Center.

“So along with my coauthors, we realized that we have a perfect example of a hazy world right here in the Solar System —Titan. And we wondered what Titan would look like if you saw it transiting across a star,” said Robinson.

The work was published in the Proceedings in the National Academy of Science in May and is also available in preprint version on the website Arxiv.

Harnessing creativity

NASA has never launched a probe designed to go out in the Solar System and watch our own planets and moons transiting across the sun. Luckily for the researchers, there was a way to simulate this with the Cassini mission, which is in orbit around Saturn and its moons, which include Titan.

A view of Titan's surface captured by the Cassini spacecraft, which probed through the hazy atmosphere with radar. Credit: NASA/JPL/Space Science Institute

A view of Titan’s surface captured by the Cassini spacecraft, which probed through the hazy atmosphere with radar. Credit: NASA/JPL/Space Science Institute

Titan is of particular interest to researchers because its hydrocarbon cycle reminds some biologists of what Earth would have looked like before life. Titan has other features that are similar to Earth as well, such as weather patterns and a liquid cycle in which methane and ethane go between lakes in the ground to clouds in the air and back again.

Titan was first spotted up close in the 1980s when NASA’s spacecraft Voyager flew by Saturn. Saturn’s largest moon fascinated scientists because it was shrouded in orange haze. The haze likely comes from complex organic materials that are produced when ultraviolet light from the Sun shines on the atmosphere, which is made up of nitrogen and methane. This was unexpected, as many had thought that Earth’s airless moon was typical of other moons in the Solar System.

Cassini arrived at Saturn in 2004 and released an atmospheric probe, Huygens, which made it to the surface of Titan and survived for a short while. Cassini is now entering its eleventh year of operations, which includes more than a hundred flybys of Titan. For many of these flybys, the scientists measured how the Sun appears through the moon’s atmosphere, doing what are known as occultation measurements.

The Huygens probe's view of Titan and its landing site as it descended to the surface in 2005. Credit: ESA, NASA, Descent Imager/Spectral Radiometer Team (LPL)

The Huygens probe’s view of Titan and its landing site as it descended to the surface in 2005. Credit: ESA, NASA, Descent Imager/Spectral Radiometer Team (LPL)

“When it does these flybys it does occultation measurements, measuring sunsets and sunrises through Titan’s atmosphere,” Robinson said.

It records data in light waves ranging from 800 nanometers (visible light) to five microns (infrared, or the signature emitted by heat.) These sunset and sunrise measurements normally are used to see how Titan’s atmosphere is transparent to sunlight at different heights, which can be used to detect a variety of gases in the atmosphere, Robinson said. To better understand Titan in the context of a hazy exoplanet, Robinson and his colleagues approached the data from a new perspective, projecting how a distant Titan would appear if it was going across the face of the Sun.

Exoplanet differences

The procedure involves combining all the information from different altitudes into a single “transit” spectrum that would represent how Titan would look from a distance, said Robinson. Also, the scientists had to change the measurements somewhat to represent seeing an entire atmosphere backlit by a star, rather than the current measurements that looked at the Sun through a small portion of Titan’s atmosphere.

Results indicated a few interesting findings. Methane was detected on the moon, which is considered a “biosignature,” or indication of life, because it can be emitted by microbes and other lifeforms. The gas is not a sure thing for lifeforms, however, as it also can be emitted through processes in a planet’s crust, for example.

“The haze also has some interesting effects on the spectrum,” Robinson said.

Specifically, it blocks out blue light better than red light, which makes it look redder when it passes across the Sun. This finding indicates that Titan’s haze is dissimilar to that of hazy exoplanets, he said, because the transit spectrum for the exoplanets shows no change with color.

An artist's conception of hydrocarbon ice on a hydrocarbon sea in Titan. A model from scientists working on the Cassini mission indicated this could be happening on the Saturnian moon. Credit: NASA/JPL-Caltech/USGS

An artist’s conception of hydrocarbon ice on a hydrocarbon sea in Titan. A model from scientists working on the Cassini mission indicated this could be happening on the Saturnian moon. Credit: NASA/JPL-Caltech/USGS

“It sheds some light on what the composition of the hazes might be for these exoplanets,” Robinson added. “Some people thought they are similar to Titan’s haze, and this rules that out because the spectra are not similar to one another.”

One encouraging aspect of the study was the accuracy of the view from orbit. With Cassini, the researchers saw similar haze abundances in the atmosphere as the Huygens probe did. This means that it is possible to get the same accuracy for haze predictions as it would be to send a probe into the atmosphere, Robinson said. Moreover, those abundances remained fairly stable over time, which is important because the haze observations spanned eight Earth years of collection.

“It’s interesting. Those haze properties agree really well with the same properties that were measured by the Huygens probe which flew down through the atmosphere. Huygens gave a lot more information, but this is an example of where they overlap with the data,” Robinson said.

But they have seen some seasonal changes. Cassini has followed Titan through almost half of a Saturnian year, and is now watching the system swing towards summer.

“As the wind patterns slowly change on Titan, you get different haze distributions and different haze thicknesses in different locations in the planet,” Robinson said.

Building a spectrum of Earth

So how do we find out what those exoplanets are made of? Robinson suggests the solution may lie in better resolution. NASA’s James Webb Space Telescope, when it launches in 2018, will be better able to spot the so-called “absorption” features that hazy exoplanets exhibit when they pass across stars.

It’s very hard to predict what elements could be present in super-Earths or mini-Neptunes, which are planets that are somewhat larger than Earth but not as big as a gas giant like Jupiter. This is because there are elements in the interior that could be affecting what is seen in the atmosphere, Robinson said.

A stripe of radar imaging data from Cassini indicates Titan likely hosts lakes of liquid methane on its surface. Credit: NASA/JPL/USGS

A stripe of radar imaging data from Cassini indicates Titan likely hosts lakes of liquid methane on its surface. Credit: NASA/JPL/USGS

The same problem isn’t present in “hot Jupiters” — the large planets that orbit close to their parent stars. Astronomers are fairly confident they have helium and hydrogen, because these planets have similar composition to stars. They just aren’t big enough to kickstart nuclear fusion.

Robinson’s team was the first to transform a sunset spectrum into predictions for exoplanet transits, and it’s a technique that he is hoping to reuse for other locations in the Solar System. A prime example would be to do a “realistic” transit spectrum of our own planet Earth. There was an instrument aboard the International Space Station called the Atmospheric Trace Molecule Spectroscopy (ATMOS) that could do just that, he said.

More broadly, Robinson said he is interested in looking at those missions in the Solar System where scientists have “ground truth” (information obtained from a landing craft) about processes happening on a planet’s surface that could affect what’s happening in the atmosphere.

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Surface Impressions of Rosetta’s Comet

Images of comet 67P/Churyumov-Gerasimenko taken on July 14, 2014, by the OSIRIS imaging system aboard the European Space Agency's Rosetta spacecraft have allowed scientists to create this three-dimensional shape model of the nucleus. Image Credit:  ESA/Rosetta/MPS for OSIRIS Team/MPS/UPD/LAM/IAA/SSO/INTA/UPM

Images of comet 67P/Churyumov-Gerasimenko taken on July 14, 2014, by the OSIRIS imaging system aboard the European Space Agency’s Rosetta spacecraft have allowed scientists to create this three-dimensional shape model of the nucleus. Image Credit: ESA/Rosetta/MPS for OSIRIS Team/MPS/UPD/LAM/IAA/SSO/INTA/UPM

Surface structures are becoming visible in new images of comet 67P/Churyumov-Gerasimenko taken by the scientific imaging system OSIRIS onboard the European Space Agency’s Rosetta spacecraft. The resolution of these images is now 330 feet (100 meters) per pixel. One of the most striking features is currently found in the comet’s neck region. This part of 67P seems to be brighter than the rest of the nucleus.

As earlier images had already shown, 67P may consist of two parts: a smaller head connected to a larger body. The connecting region, the neck, is proving to be especially intriguing. “The only thing we know for sure at this point is that this neck region appears brighter compared to the head and body of the nucleus,” says OSIRIS Principal Investigator Holger Sierks from the Max Planck Institute for Solar System Research in Germany. This collar-like appearance could be caused by differences in material or grain size, or could be a topographical effect.

Even though the images taken from a distance of 3,400 miles (5,500 kilometers) are still not highly resolved, the scientists are remotely reminded of comet 103P/Hartley, which was visited in a flyby by NASA’s EPOXI mission in 2010. While Hartley’s ends show a rather rough surface, its middle is much smoother. Scientists believe this waist to be a gravitational low: since it contains the body’s center of mass, emitted material that cannot leave the comet’s gravitational field is most likely to be re-deposited there.

Comet 67P/Churyumov-Gerasimenko was imaged by the European Space Agency's Rosetta spacecraft on July 20, 2014, from a distance of approximately 3,400 miles (5,500 kilometers). These three images were taken two hours apart. Image Credit: ESA/Rosetta/MPS for OSIRIS Team/MPS/UPD/LAM/IAA/SSO/INTA/UPM

Comet 67P/Churyumov-Gerasimenko was imaged by the European Space Agency’s Rosetta spacecraft on July 20, 2014, from a distance of approximately 3,400 miles (5,500 kilometers). These three images were taken two hours apart. Image Credit: ESA/Rosetta/MPS for OSIRIS Team/MPS/UPD/LAM/IAA/SSO/INTA/UPM

Whether this also holds true for 67P’s neck region is still unclear. Another explanation for the high reflectivity could be a different surface composition. In coming weeks, the OSIRIS team hopes to analyze the spectral data of this region obtained with the help of the imaging system’s filters. These can select several wavelength regions from the reflected light, allowing scientists to identify the characteristic fingerprints of certain materials and compositional features.

At the same time, the team is currently modeling the comet’s three-dimensional shape from the camera data. Such a model can help to get a better impression of the body’s shape. Rosetta will be the first mission in history to rendezvous with a comet, escort it as it orbits the sun, and deploy a lander to its surface.

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Hubble Finds Three Surprisingly Dry Exoplanets

This is an artistic illustration of the gas giant planet HD 209458b in the constellation Pegasus. To the surprise of astronomers, they have found much less water vapor in the hot world’s atmosphere than standard planet-formation models predict. Image Credit:  NASA, ESA, G. Bacon (STScI) and N. Madhusudhan (UC)

This is an artistic illustration of the gas giant planet HD 209458b in the constellation Pegasus. To the surprise of astronomers, they have found much less water vapor in the hot world’s atmosphere than standard planet-formation models predict. Image Credit:
NASA, ESA, G. Bacon (STScI) and N. Madhusudhan (UC)

Astronomers using NASA’s Hubble Space Telescope have gone looking for water vapor in the atmospheres of three planets orbiting stars similar to the sun — and have come up nearly dry.

The three planets, known as HD 189733b, HD 209458b, and WASP-12b, are between 60 and 900 light-years away from Earth and were thought to be ideal candidates for detecting water vapor in their atmospheres because of their high temperatures where water turns into a measurable vapor.

These so-called “hot Jupiters” are so close to their star they have temperatures between 1,500 and 4,000 degrees Fahrenheit, however, the planets were found to have only one-tenth to one one-thousandth the amount of water predicted by standard planet-formation theories.

“Our water measurement in one of the planets, HD 209458b, is the highest-precision measurement of any chemical compound in a planet outside our solar system, and we can now say with much greater certainty than ever before that we’ve found water in an exoplanet,” said Nikku Madhusudhan of the Institute of Astronomy at the University of Cambridge, England. “However, the low water abundance we have found so far is quite astonishing.”

Madhusudhan, who led the research, said that this finding presents a major challenge to exoplanet theory. “It basically opens a whole can of worms in planet formation. We expected all these planets to have lots of water in them. We have to revisit planet formation and migration models of giant planets, especially “hot Jupiters,” and investigate how they’re formed.”

He emphasizes that these results may have major implications in the search for water in potentially habitable Earth-sized exoplanets. Instruments on future space telescopes may need to be designed with a higher sensitivity if target planets are drier than predicted. “We should be prepared for much lower water abundances than predicted when looking at super-Earths (rocky planets that are several times the mass of Earth),” Madhusudhan said.

Using near-infrared spectra of the planets observed with Hubble, Madhusudhan and his collaborators estimated the amount of water vapor in each of the planetary atmospheres that explains the data.

The planets were selected because they orbit relatively bright stars that provide enough radiation for an infrared-light spectrum to be taken. Absorption features from the water vapor in the planet’s atmosphere are detected because they are superimposed on the small amount of starlight that glances through the planet’s atmosphere.

Detecting water is almost impossible for transiting planets from the ground because Earth’s atmosphere has a lot of water in it, which contaminates the observation. “We really need the Hubble Space Telescope to make such observations,” said Nicolas Crouzet of the Dunlap Institute at the University of Toronto and co-author of the study.

The currently accepted theory on how giant planets in our solar system formed, known as core accretion, states a planet is formed around the young star in a protoplanetary disk made primarily of hydrogen, helium, and particles of ices and dust composed of other chemical elements. The dust particles stick to each other, eventually forming larger and larger grains. The gravitational forces of the disk draw in these grains and larger particles until a solid core forms. This then leads to runaway accretion of both solids and gas to eventually form a giant planet.

This theory predicts that the proportions of the different elements in the planet are enhanced relative to those in its star, especially oxygen, which is supposed to be the most enhanced. Once the giant planet forms, its atmospheric oxygen is expected to be largely encompassed within water molecules. The very low levels of water vapor found by this research raise a number of questions about the chemical ingredients that lead to planet formation.

“There are so many things we still don’t know about exoplanets, so this opens up a new chapter in understanding how planets and solar systems form,” said Drake Deming of the University of Maryland, who led one of the precursor studies. “The problem is that we are assuming the water to be as abundant as in our own solar system. What our study has shown is that water features could be a lot weaker than our expectations.”

The findings are published July 24 in The Astrophysical Journal Letters.

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The Most Precise Measurement of an Alien World’s Size

Using data from NASA's Kepler and Spitzer Space Telescopes, scientists have made the most precise measurement ever of the size of a world outside our solar system, as illustrated in this artist's conception. Image Credit:  NASA/JPL-Caltech

Using data from NASA’s Kepler and Spitzer Space Telescopes, scientists have made the most precise measurement ever of the size of a world outside our solar system, as illustrated in this artist’s conception. Image Credit:
NASA/JPL-Caltech

Thanks to NASA’s Kepler and Spitzer Space Telescopes, scientists have made the most precise measurement ever of the radius of a planet outside our solar system. The size of the exoplanet, dubbed Kepler-93b, is now known to an uncertainty of just 74 miles (119 kilometers) on either side of the planetary body.

The findings confirm Kepler-93b as a “super-Earth” that is about one-and-a-half times the size of our planet. Although super-Earths are common in the galaxy, none exist in our solar system. Exoplanets like Kepler-93b are therefore our only laboratories to study this major class of planet.

With good limits on the sizes and masses of super-Earths, scientists can finally start to theorize about what makes up these weird worlds. Previous measurements, by the Keck Observatory in Hawaii, had put Kepler-93b’s mass at about 3.8 times that of Earth. The density of Kepler-93b, derived from its mass and newly obtained radius, indicates the planet is in fact very likely made of iron and rock, like Earth.

“With Kepler and Spitzer, we’ve captured the most precise measurement to date of an alien planet’s size, which is critical for understanding these far-off worlds,” said Sarah Ballard, a NASA Carl Sagan Fellow at the University of Washington in Seattle and lead author of a paper on the findings published in the Astrophysical Journal.

“The measurement is so precise that it’s literally like being able to measure the height of a six-foot tall person to within three quarters of an inch — if that person were standing on Jupiter,” said Ballard.

Kepler-93b orbits a star located about 300 light-years away, with approximately 90 percent of the sun’s mass and radius. The exoplanet’s orbital distance — only about one-sixth that of Mercury’s from the sun — implies a scorching surface temperature around 1,400 degrees Fahrenheit (760 degrees Celsius). Despite its newfound similarities in composition to Earth, Kepler-93b is far too hot for life.

To make the key measurement about this toasty exoplanet’s radius, the Kepler and Spitzer telescopes each watched Kepler-93b cross, or transit, the face of its star, eclipsing a tiny portion of starlight. Kepler’s unflinching gaze also simultaneously tracked the dimming of the star caused by seismic waves moving within its interior. These readings encode precise information about the star’s interior. The team leveraged them to narrowly gauge the star’s radius, which is crucial for measuring the planetary radius.

Spitzer, meanwhile, confirmed that the exoplanet’s transit looked the same in infrared light as in Kepler’s visible-light observations. These corroborating data from Spitzer — some of which were gathered in a new, precision observing mode — ruled out the possibility that Kepler’s detection of the exoplanet was bogus, or a so-called false positive.

Taken together, the data boast an error bar of just one percent of the radius of Kepler-93b. The measurements mean that the planet, estimated at about 11,700 miles (18,800 kilometers) in diameter, could be bigger or smaller by about 150 miles (240 kilometers), the approximate distance between Washington, D.C., and Philadelphia.

Spitzer racked up a total of seven transits of Kepler-93b between 2010 and 2011. Three of the transits were snapped using a “peak-up” observational technique. In 2011, Spitzer engineers repurposed the spacecraft’s peak-up camera, originally used to point the telescope precisely, to control where light lands on individual pixels within Spitzer’s infrared camera.

The upshot of this rejiggering: Ballard and her colleagues were able to cut in half the range of uncertainty of the Spitzer measurements of the exoplanet radius, improving the agreement between the Spitzer and Kepler measurements.

“Ballard and her team have made a major scientific advance while demonstrating the power of Spitzer’s new approach to exoplanet observations,” said Michael Werner, project scientist for the Spitzer Space Telescope at NASA’s Jet Propulsion Laboratory, Pasadena, California.

Alien Atmospheres - Methane, CFCs and Signs of "Intelligent" life

Alien Atmospheres – Methane, CFCs and Signs of Extraterrestrial “Intelligence”

Christine Pulliam (CfA). Used with Permission.

The best way to advance find life – look for signs of it’s Unintelligence? How the search for industrial pollutants could narrow the search for alien civilizations. Credit: Christine Pulliam (CfA). Used with Permission.

Sometimes we get lucky: an exoplanet many light-years away passes in front of its star at the perfect angle. This transit allows us to read certain features of that planet’s atmosphere. The resulting spectra – lines made by molecules like oxygen and methane – allow us a peek into that planet’s chemical anatomy. Certain features of those atmospheres make it more likely that something, or someone, inside is breathing. In the last few months, we’ve found even better ways of looking for these signs of life.

Airborne: Telltale Signs of Life

Never underestimate the power of a tiny molecule. Methane – four hydrogens and a carbon bound by shared electrons – is an excellent candidate as a first clue that life exists on other planets.

On Earth, and perhaps elsewhere in the Universe, methane (CH4) is both a product of life as well as one of life’s basic energy-sources. For example, our ocean floor hosts an immense biodiversity that is literally swimming in methane and methane bi-products. Countless microbes living miles down feast on methane as it seeps to the surface.

“It’s the methane and sulfide – not the heat – that provides the energy source for the bacteria that are at the base of the food chain,” said Mandy Joye, a biogeochemist at the University of Georgia and part of a research team on methane seeps.

In addition to the activity on the bottom, it was recently discovered that SAR11, the most abundant organism in the ocean in general, produces methane when it dines upon to its second-favorite food. Methane emanates from swamps and salt marshes. As the biomass in those places breaks down, methane combines with a substance called sulfate to produce a very distinct and awful odor. This gaseous methane rises from wetlands to the tune of 164 Tg per year – which is about ⅓ of all the natural methane produced annually on Earth. (1 Teragram (Tg) is equivalent to 10⁹ kg or 2.2×10⁹ pounds.)

Even exotic iron-breathing organisms living in acidic, rocky environments make methane. These environmental niches are being studied by astrobiologists as possible Mars-analogs: places where the low-oxygen circumstances may have driven life to adapt in extreme ways.

Even today, Mars may be releasing methane. This highlights a key fact: while most of the methane on Earth comes from living organisms, other sources exist.

Methane is a common biomarker on planets like Earth. Credit: GISS, NASA

Abiogenic methane arises when volcanically heated water reacts with rocks that contain high levels of iron and magnesium. Because of the heating, hydrogen in the water is liberated. That free hydrogen then meets with carbon from carbon dioxide dissolved in the water. The result is life-form-free methane.  These kinds of reactions occur on Earth at mid-oceanic ridges and may occur in mantle as well, where iron is subjected to intense heating, sometimes in the presence of water. Such reactions may be responsible for the recorded methane releases from Mars.

So while not all that makes methane is life, the overwhelming majority of known methane sources are alive. This makes methane a great potential biomarker for finding life on other planets: from the bottom of the sea to the thin-aired mountaintops here, there and everywhere. Knowing that methane exists in the atmosphere of a planet serves another life-related function as well: can help us understand the surface temperature of an exoplanet.

Methane is one of the most notable greenhouse gases. Like carbon dioxide (CO2), atmospheric methane acts as a sort of planetary warm blanket. It wraps around the Earth and reflects back surface radiation that would otherwise make its way into space. In fact, of the two, methane is a far more efficient warming agent. CH4 has at least 20-25 times the global warming potential of CO2, but fortunately for us, only sticks around for a few years after it’s produced.

The Northern Summer Methane release on Mars, origin unknown. It is possibly due to former life, and possibly due to former abiogenic chemical interactions. Credit: NASA

For life in general, a warm planet isn’t always a bad thing. Mars, on outer edge of the habitable zone, would be warmer if it had more methane in the atmosphere. An under-abundance of greenhouse gases like hydrogen, CO2 and methane can lead to a planet too cold for life, even if the planet itself is in a habitable zone (HZ). On the other hand Venus, on the inner edge of the HZ, is far too warm for life due to an excess of greenhouse gases. If we were observing Mars or Venus from afar, picking up greenhouse gases in the atmosphere, or failing to, would help us discern if life was likely there.

For better and worse our planet is a natural generator of methane, as are some of the life forms that dwell upon it. While it might come as a surprise that most of our methane comes from tiny creatures in swamps and oceans, many of us are aware that closer to the top of the food chain methane slips from the digestive systems of animals that ruminante, many of which later become food-sources themselves. At the very top of the pile of methane producers – not for quality but for creativity – are humans.

Human-made methane comes from a fascinating variety of places. A 2014 study estimated that pit latrines, used as a waste-disposal system in the developing world, will be responsible for 1% of the human-produced methane on Earth this year: about 3.8 Tg. Then there’s industry, agriculture, animal husbandry, and the mining of natural gas. The amount of methane emissions generated by the natural gas industry itself is difficult to pin down. It has been cited as likely ranging from 2-4% of the total methane emissions since 2000.  At the end of the day, a substantial amount of anthropogenic or life-made methane that doesn’t emanate from oceans or swamps comes the way people choose to live upon this planet.

Given the goal of finding advanced life, methane raises an important question. Here on Earth, the many origins of methane include seafloor bacteria, swamp gas, the digestive emissions of animal herds and the 4-range stovetops of the human race. Looking outward to many light years away, is there any way to know if methane signatures are coming from lifeless crystal ice sculptures, single-celled organisms or gas burners?

The answer is: maybe. Earlier this year, scientists from the University of New South Wales and University College London figured out how to distinguish the spectroscopic lines of hot methane from cooler forms of the same chemical. Their paper describes more than 10 billion spectroscopic lines for methane: an improvement of 2000 times over the previously known number of methane lines.

“Current models of methane are incomplete, leading to a severe underestimation of methane levels on planets,” said study co-author Jonathan Tennyson from the UCL Department of Physics and Astronomy. “We anticipate our new model will have a big impact on the future study of planets and ‘cool’ stars external to our solar system, potentially helping scientists identify signs of extraterrestrial life.”

Artistic Rendition of Extrasolar Planet HD189733b Rises From Behind Its Star Credit: ESA

Artistic Rendition of Extrasolar Planet HD189733b Rises From Behind Its Star. Credit: ESA

Since life forms from the bacterial to the bovine to the human being pump it out as part of their normal daily activities, searching for methane lines makes sense. In the specific search for highly evolved life, however, something even better may be on the horizon – something that would tell us that not only is life flourishing, but fabricating.

Proof of (Un)Intelligent Life in the Universe

If industrialized alien civilizations exist, Harvard Smithsonian scientists Henry Lin, Gonzalo Abad and Abraham Loeb contend that the best way to look for them may be in signs of environmental destruction that mirror our own.

According to Loeb, this method of detecting extraterrestrial life via environmental pollution is more efficient than SETI, because, for SETI to detect a signal, the other civilization has to be broadcasting.

“You have to assume that they are producing signals that are detectable at great distances,” Loeb told astrobio.net, “For over 50 years we have adopted that approach. The problem with that is that it’s like searching for a needle in a haystack. You are making assumptions for what the signal might be, and then looking for it, but there is no guarantee that you will find anything.”

Humans have been monitoring the skies for radio and laser signals from other species for a while. However, success in that particular mission depends to a certain extent on those races knowing that we exist – or at least wanting to make contact with another planet. Also, they would have to possess the tendency and technology to make transmissions. Searching for industrial pollution obviates these specific needs.

“If you have a civilization that tends to communicate, for example, by cable instead of radio, they will nevertheless pollute their atmospheres,” said Loeb.

So rather than wait for a signal that may or may not be coming in a form we may or may not be prepared to detect, Loeb, Abad and Lin suggest that we look for the effects alien civilizations are having on their home planets’ atmospheres.

There are a number of advantages to this approach. First, we are already searching exoplanet atmospheres for signs of life like methane. “It  doesn’t take too much extra effort,” Lin told astrobio.net, “to also look for signs of intelligent life.”

The specific signs Lin has in mind are chlorofluorocarbons (CFCs). As the key ingredient in many mass- produced products, CFCs are notorious on Earth for everything from holding hair in place to eating holes in our ozone layer. In 2012, a group at the Blue Marble Space Institute of Science hypothesized that CFCs would  be a great way to look for alien races. Sanjoy Som of the  Blue Marble Space Institute of Science told astrobio.net that, “We are about a decade away from being able to measure detailed compositions of the atmospheres of extrasolar planets.”

Advances in exoplanet spectroscopy  combined with better detection of the CFCs tetrafluoromethane (CF4) and trichlorofluoromethane (CCl3F) shrunk that decade down to less than 48 months. Abad’s expertise in tracing molecules like CF4 resulted in a map of those molecules in Earth’s atmosphere. That map combined with Lin and Loeb’s astrophysical model lead to this concrete proposal for possibly tracing civilizations by their CFC production.

A detailed spectrum of the Earth in the wavelengths that JWST can detect.  The pink and red lines are the signatures from CFCs, possibly detectable on other worlds around white dwarfs with ~1.2 days of observation. Credit: H. Lin, G. Abad and A. Loeb. Harvard Smithsonian Astrophysical Institute. Used with permission.

A detailed spectrum of the Earth in the wavelengths that JWST can detect. The pink and red lines are the signatures from CFCs, possibly detectable on other worlds around white dwarfs with ~1.2 days of observation. Credit: H. Lin, G. Abad and A. Loeb. Harvard Smithsonian Astrophysical Institute. Used with permission.

In addition to needing no new instruments to find them, CF4 and CCl3F have another advantage: both are sensitive as well as specific for industrialized life. If found in an alien atmosphere, there’s pretty much only one way that they got there.

“These molecules are basically only produced by human[-like] activities,” Abad told astrobio.net. “Whereas methane will be everywhere regardless of whether you are polluting or not. These markers target civilizations with advanced industry.”

While primitive forms of life have their own biomarkers – like oxygen and methane – these molecules are too complicated for nature to, as Loeb put it, “do this on its own.” However, at least for the moment, we can’t rush off and start looking for aliens by their hairspray.

“One thing that should be noted,” said Loeb, “Is that the transits that we are observing right now are not suitable for finding these molecules. An Earth-like planet moving around a sun-like star  would produce a very small imprint in the spectrum of the star because it covers a tiny bit of the surface area of the star.”

If an advanced alien civilization is looking for us by the spectral lines of our pollution in our passage in front of the Sun, we would be very difficult to detect. The area of the Earth is 10,000 times smaller than the area of the Sun. In addition, our atmosphere itself is a very tiny amount of our area. To make the job of finding alien civilizations easier, for now, Loeb et al suggest that we focus on white dwarfs.

“White dwarfs have a size comparable to the size of the Earth, and therefore you get a much bigger effect,” said Loeb.

Artist’s conception of a newly found planet. Credit: NASA

Artist’s conception of a newly found planet. Credit: NASA

We don’t necessarily expect life to be a common phenomenon near white dwarfs. White dwarfs are 100 times smaller than the Sun, so the habitable zone is a 100 times closer. Our own Sun will become a white dwarf someday, but only after becoming a red giant and consuming the inner planets. However, according to Loeb, a few potential candidate planets around white dwarfs have already been detected.  With the James Webb space telescope (JWST) coming in 2018, if we start surveying the nearest 300 light years for white dwarfs and focus in on them, many more may be found.

“We expect to find maybe one or two Earth-like planets that transit white dwarfs, and are observable with JWST, *if* such planets at all exist around white dwarfs,” said Dan Maoz from Tel-Aviv University, a collaborator of Loeb’s on a paper about detecting life on white dwarfs.

It won’t be easy to find an Earth-like planet around a white dwarf transiting at just the right angle, but once we do, Lin said, “We should check for crazy amounts of pollution.”

With this model and a survey of white dwarfs in hand, when the JWST takes to the skies in 2018 we can begin an earnest quest for life as brilliantly self-destructive as we are. Until then, we continue to find more exoplanets whose atmospheric methane may hold the key to finding life sleeping on ocean floors or cooking over fires from millions of light years away.

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Voyager spacecraft might not have reached interstellar space

This artist’s concept shows the Voyager 1 spacecraft entering the space between stars. The Voyager mission team announced in 2012 that the Voyager 1 spacecraft had passed into interstellar space, but some scientists say it is still within the heliosphere – the region of space domininated by the Sun and its wind of energetic particles. In a new study, two Voyager team scientists are proposing a test that they say could prove once and for all of Voyager 1 has crossed the boundary. Credit: NASA/JPL-Caltech

This artist’s concept shows the Voyager 1 spacecraft entering the space between stars. Credit: NASA/JPL-Caltech

In 2012, the Voyager mission team announced that the Voyager 1 spacecraft had passed into interstellar space, traveling further from Earth than any other manmade object.

But, in the nearly two years since that historic announcement, and despite subsequent observations backing it up, uncertainty about whether Voyager 1 really crossed the threshold continues. There are some scientists who say that the spacecraft is still within the heliosphere – the region of space dominated by the Sun and its wind of energetic particles – and has not yet reached the space between the stars.

Now, two Voyager team scientists have developed a test that they say could prove once and for all if Voyager 1 has crossed the boundary. The new test is outlined in a study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

The scientists predict that, in the next two years, Voyager 1 will cross the current sheet – the sprawling surface within the heliosphere where the polarity of the sun’s magnetic field changes from plus to minus. The spacecraft will detect a reversal in the magnetic field, proving that it is still within the heliosphere. But, if the magnetic field reversal doesn’t happen in the next year or two as expected, that is confirmation that Voyager 1 has already passed into interstellar space.

“The proof is in the pudding,” said George Gloeckler, a professor in atmospheric, oceanic and space sciences at the University of Michigan in Ann Arbor and lead author of the new study.

Gloeckler has worked on the Voyager mission since 1972 and has been a vocal opponent of the view that Voyager 1 has entered interstellar space. He said that, although the spacecraft has observed many of the signs indicating it may have reached interstellar space, like cosmic rays, Voyager 1 did not see a change in magnetic field that many were expecting.

“This controversy will continue until it is resolved by measurements,” Gloeckler said.

If the new prediction is right, “this will be the highlight of my life,” he said. “There is nothing more gratifying than when you have a vision or an idea and you make a prediction and it comes true.”

The heliosphere, in which the Sun and planets reside, is a large bubble inflated from the inside by the high-speed solar wind blowing out from the Sun. Pressure from the solar wind, along with pressure from the surrounding interstellar medium, determines the size and shape of the heliosphere. The supersonic flow of solar wind abruptly slows at the termination shock, the innermost boundary of the solar system. The edge of the solar system is the heliopause. The bow shock pushes ahead through the interstellar medium as the heliosphere plows through the galaxy. Credit: Southwest Research Institute

The heliosphere, in which the Sun and planets reside, is a large bubble inflated from the inside by the high-speed solar wind blowing out from the Sun. Pressure from the solar wind, along with pressure from the surrounding interstellar medium, determines the size and shape of the heliosphere. The supersonic flow of solar wind abruptly slows at the termination shock, the innermost boundary of the solar system. The edge of the solar system is the heliopause. The bow shock pushes ahead through the interstellar medium as the heliosphere plows through the galaxy. Credit: Southwest Research Institute

The Voyager 1 and 2 spacecraft were launched in 1977 to study Jupiter and Saturn. The mission has since been extended to explore the outermost limits of the Sun’s influence and beyond. Voyager 2, which also flew by Uranus and Neptune, is on its way to interstellar space.

Gloeckler and co-author, Len Fisk, also a professor in atmospheric, oceanic and space sciences at the University of Michigan, are basing their new test on a model they developed and published earlier this year in The Astrophysical Journal. The model assumes that the solar wind is slowing down and, as a result, that the solar wind can be compressed. Based on this assumption, the study says Voyager 1 is moving faster than the outward flow of the solar wind and will encounter current sheets where the polarity of the magnetic field will reverse, proving that the spacecraft has not yet left the heliosphere. The scientists predict this reversal will most likely happen during 2015, based on observations made by Voyager 1.

“If that happens, I think if anyone still believes Voyager 1 is in the interstellar medium, they will really have something to explain,” Gloeckler said. “It is a signature that can’t be missed.”

Ed Stone of the California Institute of Technology in Pasadena and NASA’s Voyager Project Scientist said in a statement that “It is the nature of the scientific process that alternative theories are developed in order to account for new observations. This paper differs from other models of the solar wind and the heliosphere and is among the new models that the Voyager team will be studying as more data are acquired by Voyager.”

Alan Cummings, a senior research scientist at California Institute of Technology in Pasadena and a co-investigator on the Voyager mission, believes Voyager 1 has most likely crossed into interstellar space, but he said there is a possibility that Gloeckler and Fisk are right and the spacecraft is still in the heliosphere. He said that if Voyager 1 experiences a current sheet crossing like the one being proposed in the new study, it could also mean that the heliosphere is expanding and crossed the spacecraft again.

This artist's concept shows the general locations of NASA's two Voyager spacecraft. Voyager 1 (top) has sailed beyond our solar bubble into interstellar space, the space between stars. Its environment still feels the solar influence. Voyager 2 (bottom) is still exploring the outer layer of the solar bubble. Image Credit: NASA

This artist’s concept shows the general locations of NASA’s two Voyager spacecraft. Voyager 1 (top) may have sailed beyond our solar bubble into interstellar space, the space between stars. Its environment still feels the solar influence. Voyager 2 (bottom) is still exploring the outer layer of the solar bubble. Image Credit: NASA

“If the magnetic field had cooperated, I don’t think we’d be having this discussion,” Cummings said. “This is a puzzle. It is very reasonable to explore alternate explanations. We don’t understand everything that happened out there.”

Stephen Fuselier, director of the space science department at the Southwest Research Institute in San Antonio, Texas, who is not involved with the research and is not on the Voyager 1 team, said the scientists have come up with a good test to prove once and for all if Voyager 1 has crossed into interstellar space. However, he does not agree with the assumption that the paper is making about the how fast the solar wind is moving. But, he said there is no way to measure this flow velocity, and if Gloeckler and Fisk’s assumptions are correct, the model makes sense and Voyager 1 could still be inside the heliosphere.

“I applaud them for coming out with a bold prediction,” said Fuselier, who works on the Interstellar Boundary Explorer mission that is examining the boundary between the solar wind and the interstellar medium. “If they are right, they are heroes. If they are wrong, though, it is important for the community to understand why … If they are wrong, then that must mean that one or more of their assumptions is incorrect, and we as a community have to understand which it is.”

Fuselier, who believes Voyager 1 has entered interstellar space, said he will reserve judgment on whether Gloecker and Fisk are correct until 2016. He said there is a sizeable fraction of the space community that is skeptical that Voyager 1 has entered interstellar space, but the new proposed test could help end that debate. Another good test will come when Voyager 2 crosses into interstellar space in the coming years, Fuselier and Cummings said.

“If you go back 10 years and talk to the Voyager people, they would have told you 10 years ago that what they would see upon exiting the heliosphere is very, very different from what they are seeing now,” Fuselier said. “We are just loaded down with surprises and this might be one of them.”

SEM-FISH images obtained from a bacterial cluster bound to the minerals in one of the cores. Credit: Victor Parro and Elena González-Toril (CAB)

Biomarkers of the Deep

A view of the “Peña de Hierro” lake. It is a small lake left after mining activities. Pyrite stockwork outcrops (light gray) can be seen in the walls. MARTE drillings were performed on top of the hill, passed through the 90 m to the phreatic level and went to 166 m depth. Credit: Victor Parro (CAB-INTA-CSIC)

A view of the “Peña de Hierro” lake. It is a small lake left after mining activities. Pyrite stockwork outcrops (light gray) can be seen in the walls. MARTE drillings were performed on top of the hill, passed through the 90 m to the phreatic level and went to 166 m depth. Credit: Victor Parro (CAB-INTA-CSIC)

Tucked away in the southwest corner of Spain is a unique geological site that has fascinated astrobiologists for decades. The Iberian Pyrite Belt (IPB) in Spain’s Río Tinto area is the largest known deposit of sulfide on Earth, and for decades it has been a field-site for scientists studying chemolithotrophic microbes.

Many of these unique organisms are thought to survive independently of the Sun and instead gather the energy they need to live from the chemical imbalance of minerals. Organisms with this ability could stand the best chance of surviving in environments on other worlds, like the deep subsurface of Mars.

“The Río Tinto mineralogy is dominated mainly by iron and sulfur minerals such as hematite and jarosite, both already discovered on Mars,” said Victor Parro Garcia, head of the Molecular Evolution Department at the Centro de Astrobiología (CAB) (INTA-CSIC) in Spain. “These minerals are the consequence of the pyrite (FeS2) oxidation, a process highly accelerated by iron oxidizing microbes to obtain energy for their metabolisms.”

In the Rio Tinto, these microorganisms don’t need the Sun to survive. To grow, all they need is iron, carbon and nitrogen CO2 and N2 in the atmosphere, and some salts from the water for growth.

“They have very simple nutrient requirements,” said Parro Garcia, a co-author on the recent study. “In summary, the Iberian Pyrite Belt subsurface is an excellent analogue for a potential Martian subsurface habitat because of its mineralogy and the variety of anaerobic metabolisms that can occur there.”

The Red River

Legend has it that the region surrounding Spain’s Río Tinto River was once the location of King Solomon’s mines. Today, the region is still famous for its mining history, but astrobiolgists have also found a treasure-trove of data that explain the limits to habitability on Earth. Due to its incredibly high iron content, the acidic river flows like red wine through a multicolored and rocky landscape that at sometimes resembles an alien world.

The Río Tinto has an average pH of 2.3, which is acidic enough to eat metal. For years, scientists believed that industrial pollution from 5,000 years of mining in the region was responsible for this harsh environment. However, when astrobiologists began searching for life in the river, they found that microorganisms also played a role in maintaining the acidity through a process known as acid rock drainage. This naturally produces acid runoff when microbes interact with sulfide from the IPB.

“The water table and the high temperatures all year around favor the growth of chemolithotrophic bacteria, which exist in high amounts in the river and probably in underground waters,” explained Ricardo Amils in a 2002 interview with Astrobiology Magazine.

Red waters of the Rio Tinto in Spain. Image credit: Leslie Mullen

Red waters of the Rio Tinto in Spain. Image credit: Leslie Mullen

Amils has been studying the Tinto river for decades as director of the laboratory of applied microbiology at the Center for Molecular Biology (CBM) at the Autonomous University in Madrid.

“The most important characteristics of the system — sulfuric acid and high concentrations of ferric iron — are products of chemolithotrophic activity using pyrite and other sulfidic minerals.”

In the early 2000’s, NASA joined with CAB to explore habitats for life beneath the Earth in the region of the Rio Tinto. The project was known as the Mars Analog Research and Technology Experiment (MARTE), and for more than a decade the project has been using the Rio Tinto as an analog site for testing equipment that could be used on future Mars missions. This includes remote drilling techniques that provide scientists with access to the deep subsurface. Previous studies were mostly focused on testing the equipment, but now a team of scientists has performed a thorough investigation of the microorganisms collected in the cores.

The team drilled into the ground in different locations and to depths ranging from just 5 meters down to over 166 meters. Every time the drill bit moved one meter, a sample was collected and multiple tests were performed, including: DNA extraction, cultivation, ATP activity, Microscopic analysis, or Geochemistry analysis.

“In total, more than 200 samples were collected for biology,” said Parro Garcia.

Previous work identified specific species of organisms that survive in the subsurface at Rio Tinto. The new study focuses on deeper drill cores collected by the MARTE project, and paints a more complete picture of the diversity and interaction of microorganisms that thrive in this acid-stained earth.

Spitting out Acid Underground

The deep subsurface may be one of the best environments in which to study life’s potential on other rocky worlds in the Solar System. Deep below ground, specific types of microorganisms have access to resources that allow them to live independently of light from the Sun or the rest of the biosphere at the surface. The thick layers of rock and soil also provide protection from environmental stresses like temperature, pressure and radiation that could otherwise kill them. The deep subsurface of the Rio Tinto is particularly interesting, because can create the acidic niches that pushes life even closer to the limit of habitability, and because is the responsible for the acidic waters of the river.

The team looked at sections of a drill core that started at 90 meters below the surface and continued down to 164 meters. They were particularly interested in the biological processes happening in sections of the core where conditions were anaerobic (meaning oxygen is not present).

A second view of the walls surrounding “Peña de Hierro” lake. Credit: Victor Parro (CAB-INTA-CSIC)

A second view of the walls surrounding “Peña de Hierro” lake. Credit: Victor Parro (CAB-INTA-CSIC)

Samples of rock were collected from inside the drill cores and either analyzed immediately on site or frozen and brought into the lab. In their analysis, the team used a wide range of methods and equipment to study the geochemistry of samples, detect complex organic matter, and identify microbial communities.

In terms of the geochemistry, they focused on anions that can be used in microbial metabolism (think vitamins in your bathroom cupboard). This included things like nitrate, sulfate, iron and organic acids like acetate and formate. The concentrations of all these biologically-important anions throughout the length of the core helped them determine which microbes were living at different levels in the subsurface, and how the communities were interacting with each other.

To identify the microbes, the team collected and analyzed DNA from samples throughout the length of the core. They also used life detection chips that contain individual antibodies that react with specific biomolecules.

An example of an extracted cores  from around 120 meters depth. It can be seen that the rock contains bright material (pyrite crystals) and some reddish spots likely from oxidized iron. Credit: Victor Parro (CAB-INTA-CSIC)

An example of an extracted cores from around 120 meters depth. It can be seen that the rock contains bright material (pyrite crystals) and some reddish spots likely from oxidized iron. Credit: Victor Parro (CAB-INTA-CSIC)

“At least 40 of the samples were also analyzed by a Life Detector Chip (LDChip) containing 200 antibodies,” Parro told Astrobiology Magazine.

By exposing a sample to each of the antibodies, you can test the types of molecules that are present simply by looking at the antibodies that react. Then, you can check and see which organisms match up with which biomolecules.

The team also stained samples with different types of DNA and RNA-binding dyes that help determine whether or not the cells are actually alive and working, or if they are just left-over material from cells that died long ago.

In the samples, there was evidence for numerous types of microorganisms, including methanogens, iron-respiring bacteria, ferric iron reducers, methane oxidizers and denitrifying bacteria. In some parts of the core, aerobic microorganisms were also found (e.g. microbes that live in the presence of oxygen). This showed that not all of the deep subsurface environments were anaerobic.

All of the data from the microbe tests was then correlated with the geochemical data to create a model of the IPB subsurface ecosystem that was broken into three parts.

The first section is a zone where some oxygen is present in small pockets. Here, organisms get the energy to survive by oxidizing methane, iron and sulfur. Outside of the oxygen-rich areas, anaerobic organisms perform denitrification and methanogenesis..

The second zone is completely anaerobic, and the ecosystem thrives in a similar fashion to the aerobic areas higher up.

The third and deepest zone contains fractured rock that allows more water to flow into the system, increasing the availability of oxygen once again. This influx of resources means that communities are more metabolically active. Like zone one, pockets of both aerobic and anaerobic environments exist, allowing for the various types of metabolism to occur.

“These results, together with measures of the geochemical parameters in the borehole, allowed us to create a preliminary scheme of the biogeochemical processes that could be operating in the deep subsurface of the Iberian Pyrite Belt, including microbial metabolisms such as sulfate reduction, methanogenesis and anaerobic methane oxidation,” the researchers concluded in their paper.

All together, the team showed that the deep subsurface at the Rio Tinto contains a very diverse community of microorganisms, heterogeneously distributed in multiple microniches, some of them acidic and other at circumneutral pH.

“I did not expect such diversity in such a hard rocky cores,” said Parro. “One realizes that life is really tough and colonizes any accessible niche.”

Next, the team will drill even deeper below ground and add tests for even more types of microbial metabolism that could be occurring. In a new effort, they have already drilled down to 612 meters as part of the Iberian Pyrite Subsurface Life experiment (IPBSL), led by professor Ricardo Amils at Centro de Astrobiología (INTA-CSIC), and funded by a European Research Council Advanced Grant.

As the study goes deeper, environments with oxygen will likely become less and less available, favoring anaerobic metabolism. Studying these samples will not only provide an opportunity to better-explain the Rio Tinto environment, but could also bring astrobiologists closer to understanding possible survival strategies for life on Mars.

“Other anaerobic metabolisms do not need inputs from the exterior (that is organic matter from photosynthesis), such as acetogenesis (the production of acetic acid instead of methane), nitrate reduction or methane consumption by certain anaerobic microbes,” said Parro. “These are highly relevant for a potential Martian biota.”

Hunting for Exo-biomarkers

Another outcome of the study is in showing that some of the techniques used to detect the signatures of microbial life in the Rio Tinto subsurface could be useful in future exploration beyond Earth. The multiple techniques provide redundancy, and none of them require microbes to be cultured in a laboratory. Samples can be collected in the field and immediately analyzed, and the study could help scientist integrate these techniques into automated robotic missions.

SEM-FISH images obtained from a bacterial cluster bound to the minerals in one of the cores. In (A), bacterial were stained with DAPI, a stain that bind to DNA. In (B), cells were stained with a specific fluorescent DNA sequence that binds to ribosomes (which means that cells are alive). The bottom images are electron microscopy pictures showing polymeric material (C) and cells bound to the minerals (D). Credit: Victor Parro and Elena González-Toril (CAB)

SEM-FISH images obtained from a bacterial cluster bound to the minerals in one of the cores. In (A), bacterial were stained with DAPI, a stain that bind to DNA. In (B), cells were stained with a specific fluorescent DNA sequence that binds to ribosomes (which means that cells are alive). The bottom images are electron microscopy pictures showing polymeric material (C) and cells bound to the minerals (D). Credit: Victor Parro and Elena González-Toril (CAB)

One such instrument is the Sings Of Life Detector (SOLID) in development at CAB. This automated system could collect samples of dust, regolith or rock on Mars, and then extract organic matter, suspend it in solution, filter it, and expose it to a life detection chip full of antibodies to identify biomolecules.

The more we learn about microbial metabolism in the subsurface, and the multitude of ways that organisms are able to eek out a living on the limited resources available there, the closer we get to finding molecules that we could search for in order to identify life in the Solar System. Parro already has an idea of what he would hunt for in the subsurface of Mars.

“I would search for biomolecules (peptides, nucleic acids, polysaccharides) and cell or biofilm debris in subsurface samples with our Life Detector Chip immunosensor and the SOLID (Signs Of Life Detector) instrument.”

MARTE project is a joint project between NASA and CAB with partial funding from the Astrobiology Science and Technology for Exploring Planets (ASTEP) element of the NASA Astrobiology Program.

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Transiting Exoplanet with Longest Known Year

An artist's conception of Kepler-421b. Credit:  David A. Aguilar (CfA)

An artist’s conception of Kepler-421b. Credit: David A. Aguilar (CfA)

Astronomers have discovered a transiting exoplanet with the longest known year. Kepler-421b circles its star once every 704 days. In comparison, Mars orbits our Sun once every 780 days. Most of the 1,800-plus exoplanets discovered to date are much closer to their stars and have much shorter orbital periods.

“Finding Kepler-421b was a stroke of luck,” says lead author David Kipping of the Harvard-Smithsonian Center for Astrophysics (CfA). “The farther a planet is from its star, the less likely it is to transit the star from Earth’s point of view. It has to line up just right.”

Kepler-421b orbits an orange, type K star that is cooler and dimmer than our Sun. It circles the star at a distance of about 110 million miles. As a result, this Uranus-sized planet is chilled to a temperature of -135° Fahrenheit.

As the name implies, Kepler-421b was discovered using data from NASA’s Kepler spacecraft. Kepler was uniquely suited to make this discovery. The spacecraft stared at the same patch of sky for 4 years, watching for stars that dim as planets cross in front of them. No other existing or planned mission shows such long-term, dedicated focus. Despite its patience, Kepler only detected two transits of Kepler-421b due to that world’s extremely long orbital period.

The planet’s orbit places it beyond the “snow line” – the dividing line between rocky and gas planets. Outside of the snow line, water condenses into ice grains that stick together to build gas giant planets.

“The snow line is a crucial distance in planet formation theory. We think all gas giants must have formed beyond this distance,” explains Kipping.

Since gas giant planets can be found extremely close to their stars, in orbits lasting days or even hours, theorists believe that many exoplanets migrate inward early in their history.

Kepler-421b shows that such migration isn’t necessary. It could have formed right where we see it now.

“This is the first example of a potentially non-migrating gas giant in a transiting system that we’ve found,” adds Kipping.

The host star, Kepler-421, is located about 1,000 light-years from Earth in the direction of the constellation Lyra.

This research has been accepted for publication in The Astrophysical Journal and is available online. Additional information can be found at https://www.cfa.harvard.edu/~dkipping/kepler421.html