Untitled

A better way to learn if alien planets have the right stuff

(Illustration by Michael S. Helfenbein / Yale University)

(Illustration by Michael S. Helfenbein / Yale University)

A new method for analyzing the chemical composition of stars may help scientists winnow the search for Earth 2.0.

Yale University researchers Debra Fischer and John Michael Brewer, in a new study that will appear in the Astrophysical Journal, describe a computational modeling technique that gives a clearer sense of the chemistry of stars, revealing the conditions present when their planets formed. The system creates a new way to assess the habitability and biological evolution possibilities of planets outside our solar system.

“This is a very useful, easy diagnostic to tell whether that pale blue dot you see is more similar to Venus or the Earth,” said Fischer, a Yale professor of astronomy. “Our field is very focused on finding Earth 2.0, and anything we can do to narrow the search is helpful.”

Lead author Brewer, a postdoctoral researcher at Yale, has used the technique previously to determine temperature, surface gravity, rotational speed, and chemical composition information for 1,600 stars, based on 15 elements found within those stars. The new study looks at roughly 800 stars, focusing on their ratio of carbon to oxygen, and magnesium to silicon.

Brewer explained that understanding the makeup of stars helps researchers understand the planets in orbit around them. “We’re getting a look at the primordial materials that made these planets,” he said. “Knowing what materials they started with leads to so much else.”

For instance, the new study shows that in many cases, carbon isn’t the driving force in planetary composition. Brewer found that if a star has a carbon/oxygen ratio similar to or lower than that of our own Sun, its planets have mineralogy dominated by the magnesium/silicon ratio. About 60% of the stars in the study have magnesium/silicon ratios that would produce Earth-like compositions; 40% of the stars have silicate-heavy interiors.

“This will have a profound impact on determining habitability,” Brewer said. “It will help us make better inferences about which planets will be ones where life like ours can form.”

In addition to helping identify planets more like Earth, the study sheds light on the occurrence of “diamond” planets — planets with a high carbon-to-oxygen abundance. Brewer and Fischer found that it is “exceedingly rare” to find a star with a carbon/oxygen ratio high enough to produce a diamond planet. In fact, the new data reveals that the star of the much discussed diamond planet, 55 Cancri e, does not have a high enough carbon/oxygen ratio to support its nickname.

“They’re even more rare than we thought a few years ago,” Fischer said. “Diamond planets truly are the most precious.”

Untitled

Planet Found in Habitable Zone Around Nearest Star

This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface. Credit: ESO/M. Kornmesser

This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface. Credit: ESO/M. Kornmesser

Astronomers using ESO telescopes and other facilities have found clear evidence of a planet orbiting the closest star to Earth, Proxima Centauri. The long-sought world, designated Proxima b, orbits its cool red parent star every 11 days and has a temperature suitable for liquid water to exist on its surface. This rocky world is a little more massive than the Earth and is the closest exoplanet to us — and it may also be the closest possible abode for life outside the Solar System. A paper describing this milestone finding will be published in the journal Nature on 25 August 2016.

Just over four light-years from the Solar System lies a red dwarf star that has been named Proxima Centauri as it is the closest star to Earth apart from the Sun. This cool star in the constellation of Centaurus is too faint to be seen with the unaided eye and lies near to the much brighter pair of stars known as Alpha Centauri AB.

During the first half of 2016 Proxima Centauri was regularly observed with the HARPS spectrograph on the ESO 3.6-metre telescope at La Silla in Chile and simultaneously monitored by other telescopes around the world. This was the Pale Red Dot campaign, in which a team of astronomers led by Guillem Anglada-Escudé, from Queen Mary University of London, was looking for the tiny back and forth wobble of the star that would be caused by the gravitational pull of a possible orbiting planet.

This picture combines a view of the southern skies over the ESO 3.6-metre telescope at the La Silla Observatory in Chile with images of the stars Proxima Centauri (lower-right) and the double star Alpha Centauri AB (lower-left) from the NASA/ESA Hubble Space Telescope. Credit: Y. Beletsky (LCO)/ESO/ESA/NASA/M. Zamani

This picture combines a view of the southern skies over the ESO 3.6-metre telescope at the La Silla Observatory in Chile with images of the stars Proxima Centauri (lower-right) and the double star Alpha Centauri AB (lower-left) from the NASA/ESA Hubble Space Telescope. Credit: Y. Beletsky (LCO)/ESO/ESA/NASA/M. Zamani

As this was a topic with very wide public interest, the progress of the campaign between mid-January and April 2016 was shared publicly as it happened on the Pale Red Dot website and via social media. The reports were accompanied by numerous outreach articles written by specialists around the world.

Guillem Anglada-Escudé explains the background to this unique search: “The first hints of a possible planet were spotted back in 2013, but the detection was not convincing. Since then we have worked hard to get further observations off the ground with help from ESO and others. The recent Pale Red Dot campaign has been about two years in the planning.”

The Pale Red Dot data, when combined with earlier observations made at ESO observatories and elsewhere, revealed the clear signal of a truly exciting result. At times Proxima Centauri is approaching Earth at about 5 kilometres per hour — normal human walking pace — and at times receding at the same speed. This regular pattern of changing radial velocities repeats with a period of 11.2 days. Careful analysis of the resulting tiny Doppler shifts showed that they indicated the presence of a planet with a mass at least 1.3 times that of the Earth, orbiting about 7 million kilometres from Proxima Centauri — only 5% of the Earth-Sun distance.

Guillem Anglada-Escudé comments on the excitement of the last few months: “I kept checking the consistency of the signal every single day during the 60 nights of the Pale Red Dot campaign. The first 10 were promising, the first 20 were consistent with expectations, and at 30 days the result was pretty much definitive, so we started drafting the paper!”

Artist's impression of the planet orbiting Proxima Centauri. Credit: ESO/M. Kornmesser

Artist’s impression of the planet orbiting Proxima Centauri. Credit:
ESO/M. Kornmesser

Red dwarfs like Proxima Centauri are active stars and can vary in ways that would mimic the presence of a planet. To exclude this possibility the team also monitored the changing brightness of the star very carefully during the campaign using the ASH2 telescope at the San Pedro de Atacama Celestial Explorations Observatory in Chile and the Las Cumbres Observatory telescope network. Radial velocity data taken when the star was flaring were excluded from the final analysis.

Although Proxima b orbits much closer to its star than Mercury does to the Sun in the Solar System, the star itself is far fainter than the Sun. As a result Proxima b lies well within the habitable zone around the star and has an estimated surface temperature that would allow the presence of liquid water. Despite the temperate orbit of Proxima b, the conditions on the surface may be strongly affected by the ultraviolet and X-ray flares from the star — far more intense than the Earth experiences from the Sun.

Two separate papers discuss the habitability of Proxima b and its climate. They find that the existence of liquid water on the planet today cannot be ruled out and, in such case, it may be present over the surface of the planet only in the sunniest regions, either in an area in the hemisphere of the planet facing the star (synchronous rotation) or in a tropical belt (3:2 resonance rotation). Proxima b’s rotation, the strong radiation from its star and the formation history of the planet makes its climate quite different from that of the Earth, and it is unlikely that Proxima b has seasons.

This discovery will be the beginning of extensive further observations, both with current instruments and with the next generation of giant telescopes such as the European Extremely Large Telescope (E-ELT). Proxima b will be a prime target for the hunt for evidence of life elsewhere in the Universe. Indeed, the Alpha Centauri system is also the target of humankind’s first attempt to travel to another star system, the StarShot project.

Guillem Anglada-Escudé concludes: “Many exoplanets have been found and many more will be found, but searching for the closest potential Earth-analogue and succeeding has been the experience of a lifetime for all of us. Many people’s stories and efforts have converged on this discovery. The result is also a tribute to all of them. The search for life on Proxima b comes next…”

1

Fossilised rivers suggest warm, wet ancient Mars

Perspective view of Aram Dorsum, an inverted channel on Mars and candidate landing site for the ExoMars rover (credit: NASA/JPL/MSSS)

Perspective view of Aram Dorsum, an inverted channel on Mars and candidate landing site for the ExoMars rover (credit: NASA/JPL/MSSS)

Extensive systems of fossilised riverbeds have been discovered on an ancient region of the Martian surface, supporting the idea that the now cold and dry Red Planet had a warm and wet climate about four billion years ago, according to UCL-led research.

The study, published in Geology and funded by the Science & Technology Facilities Council and the UK Space Agency, identified over 17,000km of former river channels on a northern plain called Arabia Terra, providing further evidence of water once flowing on Mars.

“Climate models of early Mars predict rain in Arabia Terra and until now there was little geological evidence on the surface to support this theory. This led some to believe that Mars was never warm and wet but was a largely frozen planet, covered in ice-sheets and glaciers. We’ve now found evidence of extensive river systems in the area which supports the idea that Mars was warm and wet, providing a more favourable environment for life than a cold, dry planet,” explained lead author, Joel Davis (UCL Earth Sciences).

Topographic map of Mars. Arabia Terra is an ancient region that connects the southern highlands and the northern lowlands (credit: NASA/JPL/MOLA Science Team)

Topographic map of Mars. Arabia Terra is an ancient region that connects the southern highlands and the northern lowlands (credit: NASA/JPL/MOLA Science Team)

Since the 1970s, scientists have identified valleys and channels on Mars which they think were carved out and eroded by rain and surface runoff, just like on Earth. Similar structures had not been seen on Arabia Terra until the team analysed high resolution imagery from NASA’s Mars Reconnaissance Orbiter (MRO) spacecraft.

The new study examined images covering an area roughly the size of Brazil at a much higher resolution than was previously possible – six metres per pixel compared to 100 metres per pixel. While a few valleys were identified, the team revealed the existence of many systems of fossilised riverbeds which are visible as inverted channels spread across the Arabia Terra plain.

The inverted channels are similar to those found elsewhere on Mars and Earth. They are made of sand and gravel deposited by a river and when the river becomes dry, the channels are left upstanding as the surrounding material erodes. On Earth, inverted channels often occur in dry, desert environments like Oman, Egypt, or Utah, where erosion rates are low – in most other environments, the channels are worn away before they can become inverted.

Aerial view of inverted channels on the Earth, south-west of the Green River, Utah (credit: Rebecca Williams, Planetary Science Institute, Arizona, USA)

Aerial view of inverted channels on the Earth, south-west of the Green River, Utah (credit: Rebecca Williams, Planetary Science Institute, Arizona, USA)

“The networks of inverted channels in Arabia Terra are about 30m high and up to 1–2km wide, so we think they are probably the remains of giant rivers that flowed billions of years ago. Arabia Terra was essentially one massive flood plain bordering the highlands and lowlands of Mars. We think the rivers were active 3.9–3.7 billion years ago, but gradually dried up before being rapidly buried and protected for billions of years, potentially preserving any ancient biological material that might have been present,” added Joel Davis.

“These ancient Martian flood plains would be great places to explore to search for evidence of past life. In fact, one of these inverted channels called Aram Dorsum is a candidate landing site for the European Space Agency’s ExoMars Rover mission, which will launch in 2020,” said Dr Matthew Balme, Senior Lecturer at The Open University and co-author of the study.

The researchers now plan on studying the inverted channels in greater detail, using higher-resolution data from MRO’s HiRISE camera.

Untitled

Test for Damp Ground at Mars’ Seasonal Streaks Finds None

Blue dots on this map indicate sites of recurring slope lineae (RSL) in part of the Valles Marineris canyon network on Mars. RSL are seasonal dark streaks that may be indicators of liquid water. The area mapped here has the highest density of known RSL on Mars. Image Credit: NASA/JPL-Caltech/Univ. of Arizona

Blue dots on this map indicate sites of recurring slope lineae (RSL) in part of the Valles Marineris canyon network on Mars. RSL are seasonal dark streaks that may be indicators of liquid water. The area mapped here has the highest density of known RSL on Mars. Image Credit: NASA/JPL-Caltech/Univ. of Arizona

Seasonal dark streaks on Mars that have become one of the hottest topics in interplanetary research don’t hold much water, according to the latest findings from a NASA spacecraft orbiting Mars.

The new results from NASA’s Mars Odyssey mission rely on ground temperature, measured by infrared imaging using the spacecraft’s Thermal Emission Imaging System (THEMIS). They do not contradict last year’s identification of hydrated salt at these flows, which since their 2011 discovery have been regarded as possible markers for the presence of liquid water on modern Mars. However, the temperature measurements now identify an upper limit on how much water is present at these darkened streaks: about as much as in the driest desert sands on Earth.

When water is present in the spaces between particles of soil or grains of sand, it affects how quickly a patch of ground heats up during the day and cools off at night.

“We used a very sensitive technique to quantify the amount of water associated with these features,” said Christopher Edwards of Northern Arizona University, Flagstaff. “The results are consistent with no moisture at all and set an upper limit at three percent water.”

The features, called recurring slope lineae or RSL, have been identified at dozens of sites on Mars. A darkening of the ground extends downhill in fingerlike flows during spring or summer, fades away in fall and winter, then repeats the pattern in another year at the same location. The process that causes the streaks to appear is still a puzzle.

“Some type of water-related activity at the uphill end still might be a factor in triggering RSL, but the darkness of the ground is not associated with large amounts of water, either liquid or frozen,” Edwards said. “Totally dry mechanisms for explaining RSL should not be ruled out.”

He and Sylvain Piqueux of NASA’s Jet Propulsion Laboratory, Pasadena, California, analyzed several years of THEMIS infrared observations of a crater-wall region within the large Valles Marineris canyon system on Mars. Numerous RSL features sit close together in some parts of the study region. Edwards and Piqueux compared nighttime temperatures of patches of ground averaging about 44 percent RSL features, in the area, to temperatures of nearby slopes with no RSL. They found no detectable difference, even during seasons when RSL were actively growing.

The report of these findings by Edwards and Piqueux has been accepted by the peer-reviewed Geophysical Research Letters and is available online.

There is some margin of error in assessing ground temperatures with the multiple THEMIS observations used in this study, enough to leave the possibility that the RSL sites differed undetectably from non-RSL sites by as much as 1.8 degrees Fahrenheit (1 Celsius degree). The researchers used that largest possible difference to calculate the maximum possible amount of water — either liquid or frozen — in the surface material.

How deeply moisture reaches beneath the surface, as well as the amount of water present right at the surface, affects how quickly the surface loses heat. The new study calculates that if RSL have only a wafer-thin layer of water-containing soil, that layer contains no more than about an ounce of water per two pounds of soil (3 grams water per kilogram of soil). That is about the same concentration of water as in the surface material of the Atacama Desert and Antarctic Dry Valleys, the driest places on Earth. If the water-containing layer at RSL is thicker, the amount of water per pound or kilogram of soil would need to be even less, to stay consistent with the temperature measurements.

Research published last year identified hydrated salts in the surface composition of RSL sites, with an increase during the season when streaks are active. Hydrated salts hold water molecules affecting the crystalline structure of the salt.

“Our findings are consistent with the presence of hydrated salts, because you can have hydrated salt without having enough for the water to start filling pore spaces between particles,” Edwards said. “Salts can become hydrated by pulling water vapor from the atmosphere, with no need for an underground source of the water.”

“Through additional data and studies, we are learning more about these puzzling seasonal features — narrowing the range of possible explanations,” said Michael Meyer. “It just shows us that we still have much to learn about Mars and its potential as a habitat for life.”

The new study touches on additional factors that add to understanding of RSL.

— If RSL were seasonal flows of briny water followed by evaporation, annual buildup of crust-forming salt should affect temperature properties. So the lack of a temperature difference between RSL and non-RSL sites is evidence against evaporating brines.

— Lack of a temperature difference is also evidence against RSL being cascades of dry material with different thermal properties than the pre-existing slope material, such as would be the case with annual avalanching of powdery dust that accumulates from dusty air.

1

Spotlight on Schiaparelli’s Landing Site

Mars Express image of Schiaparelli’s landing site – with ellipse. Credit: ESA

Mars Express image of Schiaparelli’s landing site – with ellipse. Credit: ESA

Schiaparelli, the Entry, Descent and Landing Demonstrator Module of the joint ESA/Roscosmos ExoMars 2016 mission, will target the Meridiani Planum region for its October landing, as seen in this mosaic created from Mars Express images.

The landing ellipse, measuring 100 x 15 km, is located close to the equator, in the southern highlands of Mars. The region was chosen based on its relatively flat and smooth characteristics, as indicated in the topography map, in order to satisfy landing safety requirements for Schiaparelli.

NASA’s Opportunity rover also landed within this ellipse near Endurance crater in Meridiani Planum, in 2004, and has been exploring the 22 km-wide Endeavour crater for the last five years. Endeavour lies just outside the south-eastern extent of Schiaparelli’s landing ellipse.

Meridiani Planum in context. Credit: ESA

Meridiani Planum in context. Credit: ESA

The region has also been well studied from orbit and is shown to host clay sediments and sulphates that were likely formed in the presence of water. Indeed, a number of water-carved channels are also clearly visible, in particular in the southern portion of the image.

Dune fields are seen inside a number of the craters in the region, and along with the dark deposits surrounding them, are likely shaped by wind and dust storms.

Although Schiaparelli’s main task is to demonstrate technologies needed to safely land on Mars, its small suite of scientific instruments will also record the wind speed, humidity, pressure and temperature at its landing site.

It will also obtain the first measurements of electric fields on the surface of Mars that, combined with measurements of the concentration of atmospheric dust, will provide new insights into the role of electric forces in dust lifting, the trigger for dust storms.

Perspective view in Meridiani Planum – with Schiaparelli landing ellipse. Credit: ESA

Perspective view in Meridiani Planum – with Schiaparelli landing ellipse. Credit: ESA

Schiaparelli is riding to Mars on board the ExoMars Trace Gas Orbiter. The mission launched on a Proton rocket from Baikonur on 14 March, and is on course for a 19 October rendezvous with the Red Planet.

Schiaparelli will separate from its mothership on 16 October; three days later, it will use a combination of a heat shield, a parachute, a propulsion system and a crushable structure to slow down during its six-minute descent to the surface of Mars.

ESA’s Mars Express, which has been in orbit at the Red Planet since 2003, is among the fleet of orbiters that will act as a data relay during Schiaparelli’s short battery-powered mission on the surface.

Images acquired with the Mars Express High Resolution Stereo Camera on 23, 26 and 29 August 2005, and 1 August 2010, were used to compile the four-image colour mosaic featured in this release.

Untitled1

Earth’s Viral Diversity

DOE JGI researchers utilized the largest collection of assembled metagenomic datasets from around the world to uncover over 125,000 partial and complete viral genomes, the majority of them infecting microbes. (Graphic by Zosia Rostomian, Berkeley Lab)

DOE JGI researchers utilized the largest collection of assembled metagenomic datasets from around the world to uncover over 125,000 partial and complete viral genomes, the majority of them infecting microbes. (Graphic by Zosia Rostomian, Berkeley Lab)

The number of microbes in, on, and around the planet – on the order of a nonillion, or 1030 – is estimated to outnumber the stars in the Milky Way. Microbes are known to play crucial roles in regulating carbon fixation, as well as maintaining global cycles involving nitrogen, sulfur, and phosphorus and other nutrients, but the majority of them remain uncultured and unknown. The U.S. Department of Energy (DOE) is targeting this “microbial dark matter” to better understand the planet’s microbial diversity and glean from nature lessons that can be applied toward energy and environmental challenges.

Plumbing the Earth’s microbial diversity, though, requires learning more about the poorly-studied relationships between microbes and the viruses that infect them, viruses that impact the microbes’ abilities to regulate global cycles. Although the number of viruses is estimated to be at least two orders of magnitude more than the microbial cells on the planet, there are currently less than 2,200 sequenced DNA virus genomes, compared to the approximately 50,000 bacterial genomes, in sequence databases.

In a study published online August 17, 2016 in Nature, researchers at the DOE Joint Genome Institute (JGI), a DOE Office of Science User Facility at Lawrence Berkeley National Laboratory, utilized the largest collection of assembled metagenomic datasets from around the world to uncover over 125,000 partial and complete viral genomes, the majority of them infecting microbes. This single effort increases the number of known viral genes by a factor of 16, and provides researchers with a unique resource of viral sequence information.

“It is the first time that someone has looked systematically across all habitats and across such a large compendium of data,” said study senior author and DOE JGI Prokaryote Super Program head Nikos Kyrpides. “A key to uncover all these novel viruses was the sensitive computational approach we have developed along this work.”

A key to uncover novel viruses

That approach, explained first author and postdoctoral fellow David Paez-Espino, involved using a non-targeted metagenomic approach, referencing both isolate viruses and manually curated viral protein models, and what he described as “the largest and most diverse dataset to date.” The team analyzed over 5 trillion bases (Terabases or Tb) of sequence available in the DOE JGI’s Integrated Microbial Genomes with Microbiome Samples (IMG/M) system collected from 3,042 samples around the world from 10 different habitat types. Their efforts to sift through the veritable haystack of datasets yielded over 125,000 viral sequences containing 2.79 million proteins.

The team matched viral sequences against multiple samples in multiple habitats. For example, one viral group they identified was found in 95 percent of all samples in the ocean’s twilight zone – a region located between 200 and 1,000 meters below the ocean surface where insufficient sunlight penetrates for microorganisms to perform photosynthesis.

By analyzing a CRISPR-Cas system – an immune mechanism in bacteria that confers resistance to foreign genetic elements by incorporating short sequences from infecting viruses and phages – the team was able to generate a database of 3.5 million spacer sequences in IMG. These spacers, fragments of phage genetic sequences retained by the host, can then be used to explore viral and phage metagenomes for where the fragments may have originally come from.

Also, using mainly this approach, the team computationally identified the host for nearly 10,000 viruses. “The majority of these connections were previously unknown, and include the identification of organisms serving as viral hosts from 16 prokaryotic phyla for which no viruses have previously been identified,” they reported.

Beacons for CRISPR-Cas proteins

Jan-Fang Cheng, head of the DOE JGI’s Functional Genomics group, said the work being done by Kyrpides’ group in identifying new viral sequences will help the Synthetic Biology group develop novel promoters that can work in many bacterial hosts. “We are constantly searching for regulatory DNA parts that will work across many different phyla, and that would allow us to build genes and pathways that can express in many different hosts.”

Cheng also anticipated that the expanded viral sequence space generated by Kyrpides’ team will allow researchers to look for other genetic sequences known as proto-spacer adjacent motifs (PAMs). These sequences lie next to spacer sequencers in phages and are used as beacons by CRISPR-Cas proteins, triggering actions such as editing or regulating a gene. “People are looking for new PAM sequences and new Cas9s, and with this new information, if you can map the spacer sequence back to the same phage and align them and see what’s in common in neighboring sequences, then you could ID new PAM sequences.”

“We believe that the finding of many large phages including the longest phage genome reported thus far points to the limitations of conventional virome enrichment and sequencing strategies which may bias the studies against the highly novel viruses with unusual properties”, said Natalia Ivanova, group lead in the Super Program and co-author of this study.

“One of the most important aspects of this study is that we did not focus on a single habitat type. Instead, we explored the global virome and examined the flow of viruses across all ecosystems,” said Kyrpides.

“We have increased the number of viral sequences by 50x, and 99 percent of the virus families identified are not closely related to any previously sequenced virus. This provides an enormous amount of new data that would be studied in more detail in the years to come. We have more than doubled the number of microbial phyla that serve as hosts to viruses, and have created the first global viral distribution map. The amount of analysis and discoveries that we anticipate will follow this dataset cannot be overstated.”

Untitled1

Venus-like Exoplanet Might Have Oxygen Atmosphere, But Not Life

This artist's conception shows the rocky exoplanet GJ 1132b, located 39 light-years from Earth. New research shows that it might possess a thin, oxygen atmosphere - but no life due to its extreme heat. Dana Berry / Skyworks Digital / CfA

This artist’s conception shows the rocky exoplanet GJ 1132b, located 39 light-years from Earth. New research shows that it might possess a thin, oxygen atmosphere – but no life due to its extreme heat. Dana Berry / Skyworks Digital / CfA

The distant planet GJ 1132b intrigued astronomers when it was discovered last year. Located just 39 light-years from Earth, it might have an atmosphere despite being baked to a temperature of around 450 degrees Fahrenheit. But would that atmosphere be thick and soupy or thin and wispy? New research suggests the latter is much more likely.

Harvard astronomer Laura Schaefer (Harvard-Smithsonian Center for Astrophysics, or CfA) and her colleagues examined the question of what would happen to GJ 1132b over time if it began with a steamy, water-rich atmosphere.

Orbiting so close to its star, at a distance of just 1.4 million miles, the planet is flooded with ultraviolet or UV light. UV light breaks apart water molecules into hydrogen and oxygen, both of which then can be lost into space. However, since hydrogen is lighter it escapes more readily, while oxygen lingers behind.

“On cooler planets, oxygen could be a sign of alien life and habitability. But on a hot planet like GJ 1132b, it’s a sign of the exact opposite – a planet that’s being baked and sterilized,” said Schaefer.

Since water vapor is a greenhouse gas, the planet would have a strong greenhouse effect, amplifying the star’s already intense heat. As a result, its surface could stay molten for millions of years.

A “magma ocean” would interact with the atmosphere, absorbing some of the oxygen, but how much? Only about one-tenth, according to the model created by Schaefer and her colleagues. Most of the remaining 90 percent of leftover oxygen streams off into space, however some might linger.

“This planet might be the first time we detect oxygen on a rocky planet outside the solar system,” said co-author Robin Wordsworth (Harvard Paulson School of Engineering and Applied Sciences).

If any oxygen does still cling to GJ 1132b, next-generation telescopes like the Giant Magellan Telescope and James Webb Space Telescope may be able to detect and analyze it.

The magma ocean-atmosphere model could help scientists solve the puzzle of how Venus evolved over time. Venus probably began with Earthlike amounts of water, which would have been broken apart by sunlight. Yet it shows few signs of lingering oxygen. The missing oxygen problem continues to baffle astronomers.

Schaefer predicts that their model also will provide insights into other, similar exoplanets. For example, the system TRAPPIST-1 contains three planets that may lie in the habitable zone. Since they are cooler than GJ 1132b, they have a better chance of retaining an atmosphere.

This work has been accepted for publication in The Astrophysical Journal and is available online. The journal paper is authored by Laura Schaefer , Robin Wordsworth, Zachory Berta-Thompson (University of Colorado, Boulder), and Dimitar Sasselov (CfA).

Untitled

New technique may help detect Martian life

Mars’ Valles Marineris canyon, pictured, spans as much as 600 kilometers across and delves as much as 8 kilometers deep. The image was created from over 100 images of Mars taken by Viking Orbiters in the 1970s. Image: NASA

Mars’ Valles Marineris canyon, pictured, spans as much as 600 kilometers across and delves as much as 8 kilometers deep. The image was created from over 100 images of Mars taken by Viking Orbiters in the 1970s. Image: NASA

In 2020, NASA plans to launch a new Mars rover that will be tasked with probing a region of the planet scientists believe could hold remnants of ancient microbial life. The rover will collect samples of rocks and soil, and store them on the Martian surface; the samples would be returned to Earth sometime in the distant future so that scientists can meticulously analyze the samples for signs of present or former extraterrestrial life.

Now, as reported in the journal Carbon, MIT scientists have developed a technique that will help the rover quickly and non-invasively identify sediments that are relatively unaltered, and that maintain much of their original composition. Such “pristine” samples give scientists the best chance for identifying signs of former life, if they exist, as opposed to rocks whose histories have been wiped clean by geological processes such as excessive heating or radiation damage.

Spectroscopy on Mars

The team’s technique centers on a new way to interpret the results of Raman spectroscopy, a common, non-destructive process that geologists use to identify the chemical composition of ancient rocks. Among its suite of scientific tools, the 2020 Mars rover includes SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals), an instrument that will acquire Raman spectra from samples on or just below the Martian surface. SHERLOC will be pivotal in determining whether life ever existed on Mars.

Raman spectroscopy measures the minute vibrations of atoms within the molecules of a given material. For example, graphite is composed of a very orderly arrangement of carbon atoms. The bonds between these carbon atoms vibrate naturally, at a frequency that scientists can measure when they focus a laser beam on graphite’s surface.

As atoms and molecules vibrate at various frequencies depending on what they are bound to, Raman spectroscopy enables scientists to identify key aspects of a sample’s chemical composition. More importantly, the technique can determine whether a sample contains carbonaceous matter — a first clue that the sample may also harbor signs of life.

But Roger Summons, professor of earth, atmospheric, and planetary sciences at MIT, says the chemical picture that scientists have so far been able to discern using Raman spectroscopy has been somewhat fuzzy. For example, a Raman spectrum acquired from a piece of coal on Earth might look very similar to that of an organic particle in a meteorite that was originally made in space.

“We don’t have a way to confidently distinguish between organic matter that was once biological in origin, versus organic matter that came from some other chemical process,” Summons says.

However, Nicola Ferralis, a research scientist in MIT’s Department of Materials Science and Engineering, discovered hidden features in Raman spectra that can give a more informed picture of a sample’s chemical makeup. Specifically, the researchers were able to estimate the ratio of hydrogen to carbon atoms from the substructure of the peaks in Raman spectra. This is important because the more heating any rock has experienced, the more the organic matter becomes altered, specifically through the loss of hydrogen in the form of methane.

The improved technique enables scientists to more accurately interpret the meaning of existing Raman spectra, and quickly evaluate the ratio of hydrogen to carbon — thereby identifying the most pristine, ancient samples of rocks for further study. Summons says this may also help scientists and engineers working with the SHERLOC instrument on the 2020 Mars rover to zero in on ideal Martian samples.

“This may help in deciding what samples the 2020 rover will archive,” Summons says. “It will be looking for organic matter preserved in sediments, and this will allow a more informed selection of samples for potential return to Earth.”

Credit: NASA

Credit: NASA

Seeing the hidden peaks

A Raman spectrum represents the vibration of a molecule or atom, in response to laser light. A typical spectrum for a sample containing organic matter appears as a curve with two main peaks — one wide peak, and a sharper, more narrow peak. Researchers have previously labeled the wide peak as the D (disordered) band, as vibrations in this region correlate with carbon atoms that have a disordered makeup, bound to any number of other elements. The second, more narrow peak is the G (graphite) band, which is typically related to more ordered arrangements of carbon, such as is found in graphitic materials.

Ferralis, working with ancient sediment samples being investigated in the Summons’ lab, identified substructures within the main D band that are directly related to the amount of hydrogen in a sample. That is, the higher these sub-peaks, the more hydrogen is present — an indication that the sample has been relatively less altered, and its original chemical makeup better preserved.

To test this new interpretation, the team sought to apply Raman spectroscopy, and their analytic technique, to samples of sediments whose chemical composition was already known. They obtained additional samples of ancient kerogen — fragments of organic matter in sedimentary rocks — from a team based at the University of California at Los Angeles, who in the 1980s had used meticulous, painstaking chemical methods to accurately determine the ratio of hydrogen to carbon.

The team quickly estimated the same ratio, first using Raman spectroscopy to generate spectra of the various kerogen samples, then using their method to interpret the peaks in each spectrum. The team’s ratios of hydrogen to carbon closely matched the original ratios.

“This means our method is sound, and we don’t need to do an insane or impossible amount of chemical purification to get a precise answer,” Summons says.

Mapping a fossil

Going a step further, the researchers wondered whether they could use their technique to map the chemical composition of a microscopic fossil, which ordinarily would contain so little carbon that it would be undetectable by traditional chemistry techniques.

“We were wondering, could we map across a single microscopic fossil and see if any chemical differences were preserved?” Summons says.

To answer that question, the team obtained a microscopic fossil of a protist — an ancient, single-celled organism that could represent a simple alga or its predator. Scientists deduce that such fossils were once biological in origin, simply from their appearance and their similarity to hundreds of other patterns in the fossil record.

The team used Raman spectroscopy to measure the atomic vibrations throughout the fossil, at a sub-micron resolution, and then analyzed the resulting spectra using their new analytic technique. They then created a chemical map based on their analysis.

“The fossil has seen the same thermal history throughout, and yet we found the cell wall and cell contents have higher hydrogen than the cell’s matrix or its exterior,” Summons says. “That to me is evidence of biology. It might not convince everybody, but it’s a significant improvement than what we had before.”

Ultimately, Summons says that, in addition to identifying promising samples on Mars, the group’s technique will help paleontologists understand Earth’s own biological evolution.

“We’re interested in the oldest organic matter preserved on the planet that might tell us something about the physiologies of Earth’s earliest forms of cellular life,” Summons says. “We’re hoping to understand, for example, when did the biological carbon cycle that we have on the Earth today first appear? How did it evolve over time? This technique will ultimately help us to find organic matter that is minimally altered, to help us learn more about what organisms were made of, and how they worked.”

Untitled

New Antarctic ice discovery aids future climate predictions

View of Sheldon Glacier with Mount Barre in the background, seen from Ryder Bay near Rothera Research Station, Adelaide Island, Antarctica. Image credit: British Antarctic Survey

View of Sheldon Glacier with Mount Barre in the background, seen from Ryder Bay near Rothera Research Station, Adelaide Island, Antarctica. Image credit: British Antarctic Survey

A team of British climate scientists comparing today’s environment with the warm period before the last ice age has discovered a 65% reduction of Antarctic sea ice around 128,000 years ago. The finding is an important contribution towards the challenge of making robust predictions about the Earth’s future climate.

Reporting this week in the journal Nature Communications scientists describe how by reconstructing the Earth’s climate history through analysis of Antarctic ice cores they can determine what environmental conditions were like during ice ages and past warm periods. This study focussed on sea ice conditions during the most recent warm period – known as the last interglacial – when global temperatures were similar to today.

Sea ice in the Arctic and around Antarctica regulates climate as, in summer vast areas of whiteness reflect heat from the sun back into the atmosphere, whilst in winter, sea ice prevents heat from escaping from the warm ocean to the air. Current climate models forecast a reduction in Antarctic sea ice of up to about 60% by the end of the next century. Finding a 65% reduction in the climate record during a time when global climate conditions were similar to the present day is especially relevant.

The research team from British Antarctic Survey (BAS) and from the Universities of Bristol, Reading, Leeds and Cambridge studied data from ice cores drilled on the East Antarctic Ice Sheet. A climate model was then used in the analysis of these data. The ice core data and climate model simulations were combined using advanced statistical techniques to determine the state of Antarctic sea ice 128,000 years ago.

Lead author Max Holloway of British Antarctic Survey explains,

“We know that the Earth’s climate is changing and that climate models predict a warmer world. What we are not yet sure about is the precise magnitude of future change or the timeline. This is where looking into the past can help. We used a number of analytical techniques to quantify change in sea ice extent around Antarctica during this important past warm period.

“We were expecting to see a relationship between warm temperatures around 128,000 years ago and a past collapse of the West Antarctic Ice Sheet. Surprisingly, we found that a major retreat of Antarctic sea ice is a more likely explanation. Our analysis suggests that a collapse of the West Antarctic Ice Sheet occurred later during the last interglacial. Something that our team will be looking at in more detail through another collaborative UK-US project.”

Today researchers observe differences between sea ice changes at both poles. This is largely due to different geography – the Arctic being a frozen sea surrounded by land and the Antarctic being a frozen landmass surrounded by sea. Whilst a rapid sea ice retreat has been recorded in the Arctic in recent decades, sea ice extent around some parts of the Antarctic have grown. Understanding the similarities and differences between hemispheres has been the subject of intense study by the international polar research community.

Research group leader, Dr Louise Sime, of BAS, said:

“The current rapid retreat of sea ice in the Arctic Sea is of critical importance to Arctic ecosystems and global climate. By uncovering, for the first time, a huge retreat around Antarctica we have established that sea ice in the Southern Hemisphere is also susceptible to major climate changes. This discovery will help us understand whether similar sea ice retreat events are likely in a future high-CO2 world.

“Although Arctic sea ice has diminished during the past 30 years, little change has been observed around Antarctica. This discovery in the ice core record of a massive loss of sea ice provides evidence that Antarctic sea ice can also undergo similar major reductions. This may give vital clues to what might happen by the end of the next century.”

Untitled

Brown Dwarfs Reveal Exoplanets’ Secrets

Image credit: NASA

Image credit: NASA

Brown dwarfs are smaller than stars, but more massive than giant planets. As such, they provide a natural link between astronomy and planetary science. However, they also show incredible variation when it comes to size, temperature, chemistry, and more, which makes them difficult to understand, too.

New work led by Carnegie’s Jacqueline Faherty surveyed various properties of 152 suspected young brown dwarfs in order to categorize their diversity and found that atmospheric properties may be behind much of their differences, a discovery that may apply to planets outside the solar system as well. The work is published by The Astrophysical Journal Supplement Series.

Scientists are very interested in brown dwarfs, which hold promise for explaining not just planetary evolution, but also stellar formation. These objects are tougher to spot than more-massive and brighter stars, but they vastly outnumber stars like our Sun.  They represent the smallest and lightest objects that can form like stars do in the Galaxy so they are an important “book end” in Astronomy.

For the moment, data on brown dwarfs can be used as a stand-in for contemplating extrasolar worlds we hope to study with future instruments like the James Webb Space Telescope.

“Brown dwarfs are far easier to study than planets, because they aren’t overwhelmed by the brightness of a host star,” Faherty explained.

But the tremendous diversity we see in the properties of the brown dwarf population means that there is still so much about them that remains unknown or poorly understood.

Brown dwarfs are too small to sustain the hydrogen fusion process that fuels stars, so after formation they slowly cool and contract over time and their surface gravity increases. This means that their temperatures can range from nearly as hot as a star to as cool as a planet, which is thought to influence their atmospheric conditions, too. What’s more, their masses also range between star-like and giant planet-like and they demonstrate great diversity in age and chemical composition.

By quantifying the observable properties of so many young brown dwarf candidates, Faherty and her team—including Carnegie’s Jonathan Gagné and Alycia Weinberger—were able to show that these objects have vast diversity of color, spectral features, and more. Identifying the cause of this range was at the heart of Faherty’s work.  By locating the birth homes of many of the brown dwarfs, Faherty was able to eliminate age and chemical composition differences as the underlying reason for this great variation.  This left atmospheric conditions—meaning weather phenomena or differences in cloud composition and structure—as the primary suspect for what drives the extreme differences between objects of similar origin.

All of the brown dwarf birthplaces identified in this work are regions also host exoplanets, so these same findings hold for giant planets orbiting nearby stars.

“I consider these young brown dwarfs to be siblings of giant exoplanets.  As close family members, we can use them to investigate how the planetary aging process works,” Faherty said.

Untitled

Specialized Life Forms Abound at Arctic Methane Seeps

Chemosymbiotic worm (Siboglinidae) from Bjørnøyrenna crater field. Emmelie Åström/CAGE

Chemosymbiotic worm (Siboglinidae) from Bjørnøyrenna crater field. Emmelie Åström/CAGE

Cold seeps are places where hydrocarbons, mostly methane, emanate from the sea floor. Unlike the hydrothermal vents, the fluids and bubbles are no hotter than the surrounding seawater, thus the name.

But like the hydrothermal vents, cold seeps can support high densities of specialized life forms through a process called chemosynthesis.

These seeps can dramatically influence many aspects of the overall seabed community, even in the frigid and dark Arctic Ocean, new study featured in Marine Ecology Progress Series shows.

“For the first time, we have documented that methane seepage clearly influences faunal communities on the bottom of the ocean in high Arctic areas around Svalbard Archipelago.” says CAGE PhD candidate Emmelie Åström who is the lead author of the study.

Plenty but not diverse

Many cold seeps have recently been discovered and mapped on the Arctic shelf of Western Svalbard and Barents Sea. These are connected to melting of methane hydrate, an ice-like substance that forms, and is stable, under the sea floor in cold temperatures and under high pressure.

The study found that methane seeps have a strong localized influence on the abundance and diversity of benthic organisms. The total biomass at seepage sites was significantly higher around the cold seeps compared to non-seepage sites nearby.

“However even though there was a lot of life around those seeps, most of it was comprised of a few species that are highly tolerant of the difficult, methane-rich environments, or even more specially adapted to thrive on methane as an energy source. This led to a substantially lower diversity of species at the cold seeps”, says Åström

Illustration: Maja Sojtaric/CAGE

Illustration: Maja Sojtaric/CAGE

Chemosynthesis – A successful life strategy

Åström and colleagues discovered dense fields of chemosymbiotic worms, so-called Siboglinids, around the cold seeps. These are cousins to the dramatic and huge hydrothermal vent worms.

The siboglinids are dependent on microbes for their nutrition. This successful symbiosis relies on the microbes to convert the methane to organic material that provides energy for the worms

”Our study shows that the effect of these Arctic methane seeps on life at the sea bottom can be strong but is highly localized, reflecting strong gradients associated to the focused methane emission. This means that the environment changes quickly. The organisms living here have to be flexible and tolerate large changes.” Emmelie Åström points out.

Cold seeps can be difficult to spot in contrast to dramatic black smokers of hydrothermal vents. But the observations of specialized – life forms surrounding them may give scientists an indication on location and the amount of methane release.

“This study gives us key observations in a high Arctic location that is likely to be affected by warming ocean temperatures. This in turn may lead to increased methane release from gas hydrates under the sea floor. How biological communities react and consume this methane is extremely important to understand.” Åström states.

 

Untitled

NASA Climate Modeling Suggests Venus May Have Been Habitable

Observations suggest Venus may have had water oceans in its distant past. A land-ocean pattern like that above was used in a climate model to show how storm clouds could have shielded ancient Venus from strong sunlight and made the planet habitable. Credits: NASA

Observations suggest Venus may have had water oceans in its distant past. A land-ocean pattern like that above was used in a climate model to show how storm clouds could have shielded ancient Venus from strong sunlight and made the planet habitable. Credits: NASA

Venus may have had a shallow liquid-water ocean and habitable surface temperatures for up to 2 billion years of its early history, according to computer modeling of the planet’s ancient climate by scientists at NASA’s Goddard Institute for Space Studies (GISS) in New York.

The findings, published this week in the journal Geophysical Research Letters, were obtained with a model similar to the type used to predict future climate change on Earth.

“Many of the same tools we use to model climate change on Earth can be adapted to study climates on other planets, both past and present,” said Michael Way, a researcher at GISS and the paper’s lead author. “These results show ancient Venus may have been a very different place than it is today.”

Venus today is a hellish world. It has a crushing carbon dioxide atmosphere 90 times as thick as Earth’s. There is almost no water vapor. Temperatures reach 864 degrees Fahrenheit (462 degrees Celsius) at its surface.

Scientists long have theorized that Venus formed out of ingredients similar to Earth’s, but followed a different evolutionary path. Measurements by NASA’s Pioneer mission to Venus in the 1980s first suggested Venus originally may have had an ocean. However, Venus is closer to the sun than Earth and receives far more sunlight. As a result, the planet’s early ocean evaporated, water-vapor molecules were broken apart by ultraviolet radiation, and hydrogen escaped to space. With no water left on the surface, carbon dioxide built up in the atmosphere, leading to a so-called runaway greenhouse effect that created present conditions.

Previous studies have shown that how fast a planet spins on its axis affects whether it has a habitable climate. A day on Venus is 117 Earth days. Until recently, it was assumed that a thick atmosphere like that of modern Venus was required for the planet to have today’s slow rotation rate. However, newer research has shown that a thin atmosphere like that of modern Earth could have produced the same result. That means an ancient Venus with an Earth-like atmosphere could have had the same rotation rate it has today.

Another factor that impacts a planet’s climate is topography. The GISS team postulated ancient Venus had more dry land overall than Earth, especially in the tropics. That limits the amount of water evaporated from the oceans and, as a result, the greenhouse effect by water vapor. This type of surface appears ideal for making a planet habitable; there seems to have been enough water to support abundant life, with sufficient land to reduce the planet’s sensitivity to changes from incoming sunlight.

Way and his GISS colleagues simulated conditions of a hypothetical early Venus with an atmosphere similar to Earth’s, a day as long as Venus’ current day, and a shallow ocean consistent with early data from the Pioneer spacecraft. The researchers added information about Venus’ topography from radar measurements taken by NASA’s Magellan mission in the 1990s, and filled the lowlands with water, leaving the highlands exposed as Venusian continents. The study also factored in an ancient sun that was up to 30 percent dimmer. Even so, ancient Venus still received about 40 percent more sunlight than Earth does today.

“In the GISS model’s simulation, Venus’ slow spin exposes its dayside to the sun for almost two months at a time,” co-author and fellow GISS scientist Anthony Del Genio said. “This warms the surface and produces rain that creates a thick layer of clouds, which acts like an umbrella to shield the surface from much of the solar heating. The result is mean climate temperatures that are actually a few degrees cooler than Earth’s today.”

The research was done as part of NASA’s Planetary Science Astrobiology program through the Nexus for Exoplanet System Science (NExSS) program, which seeks to accelerate the search for life on planets orbiting other stars, or exoplanets, by combining insights from the fields of astrophysics, planetary science, heliophysics, and Earth science. The findings have direct implications for future NASA missions, such as the Transiting Exoplanet Survey Satellite and James Webb Space Telescope, which will try to detect possible habitable planets and characterize their atmospheres.

Untitled1

Cassini Finds Flooded Canyons on Titan

NASA's Cassini spacecraft pinged the surface of Titan with microwaves, finding that some channels are deep, steep-sided canyons filled with liquid hydrocarbons. One such feature is Vid Flumina, the branching network of narrow lines in the upper-left quadrant of the image. Credits: NASA/JPL-Caltech/ASI

NASA’s Cassini spacecraft pinged the surface of Titan with microwaves, finding that some channels are deep, steep-sided canyons filled with liquid hydrocarbons. One such feature is Vid Flumina, the branching network of narrow lines in the upper-left quadrant of the image. Credits: NASA/JPL-Caltech/ASI

NASA’s Cassini spacecraft has found deep, steep-sided canyons on Saturn’s moon Titan that are flooded with liquid hydrocarbons. The finding represents the first direct evidence of the presence of liquid-filled channels on Titan, as well as the first observation of canyons hundreds of meters deep.

The canyons of Vid Flumina are seen in this view from Cassini's radar mapper. Credits: NASA/JPL-Caltech/ASI

The canyons of Vid Flumina are seen in this view from Cassini’s radar mapper. Credits: NASA/JPL-Caltech/ASI

A new paper in the journal Geophysical Research Letters describes how scientists analyzed Cassini data from a close pass the spacecraft made over Titan in May 2013. During the flyby, Cassini’s radar instrument focused on channels that branch out from the large, northern sea Ligeia Mare.

The Cassini observations reveal that the channels — in particular, a network of them named Vid Flumina — are narrow canyons, generally less than half a mile (a bit less than a kilometer) wide, with slopes steeper than 40 degrees. The canyons also are quite deep — those measured are 790 to 1,870 feet (240 to 570 meters) from top to bottom.

The branching channels appear dark in radar images, much like Titan’s methane-rich seas. This suggested to scientists that the channels might also be filled with liquid, but a direct detection had not been made until now. Previously it wasn’t clear if the dark material was liquid or merely saturated sediment — which at Titan’s frigid temperatures would be made of ice, not rock.

Cassini’s radar is often used as an imager, providing a window to peer through the dense haze that surrounds Titan to reveal the surface below. But during this pass, the radar was used as an altimeter, sending pings of radio waves to the moon’s surface to measure the height of features there. The researchers combined the altimetry data with previous radar images of the region to make their discovery.

Key to understanding the nature of the channels was the way Cassini’s radar signal reflected off the bottoms of the features. The radar instrument observed a glint, indicating an extremely smooth surface like that observed from Titan’s hydrocarbon seas. The timing of the radar echoes, as they bounced off the canyons’ edges and floors, provided a direct measure of their depths.

The presence of such deep cuts in the landscape indicates that whatever process created them was active for a long time or eroded down much faster than other areas on Titan’s surface. The researchers’ proposed scenarios include uplift of the terrain and changes in sea level, or perhaps both.

“It’s likely that a combination of these forces contributed to the formation of the deep canyons, but at present it’s not clear to what degree each was involved. What is clear is that any description of Titan’s geological evolution needs to be able to explain how the canyons got there,” said Valerio Poggiali of the University of Rome, a Cassini radar team associate and lead author of the study.

Earthly examples of both of these types of canyon-carving processes are found along the Colorado River in Arizona. An example of uplift powering erosion is the Grand Canyon, where the terrain’s rising altitude caused the river to cut deeply downward into the landscape over the course of several million years. For canyon formation driven by variations in water level, look to Lake Powell. When the water level in the reservoir drops, it increases the river’s rate of erosion.

“Earth is warm and rocky, with rivers of water, while Titan is cold and icy, with rivers of methane. And yet it’s remarkable that we find such similar features on both worlds,” said Alex Hayes, a Cassini radar team associate at Cornell University, Ithaca, New York, and a co-author of the study.

While the altimeter data also showed that the liquid in some of the canyons around Ligeia Mare is at sea level — the same altitude as the liquid in the sea itself — in others it sits tens to hundreds of feet (tens of meters) higher in elevation. The researchers interpret the latter to be tributaries that drain into the main channels below.

Future work will extend the methods used in this study to all other channels Cassini’s radar altimeter has observed on Titan. The researchers expect their continued work to produce a more comprehensive understanding of forces that have shaped the Saturnian moon’s landscape.

Untitled1

Bacteria Could Aid Search for Creatures On Other Planets

Massive composite stromatolites from Carbla Province.Photo: Erica Suosaari

Massive composite stromatolites from Carbla Province.Photo: Erica Suosaari

Could there be a way to find bacterial structures on another planet? And if so, how important might these bacteria be in making a planet life-friendly? These are some of the questions that could be answered through studies on stromatolites, which are mounds of calcium-carbonate rock that are built up through lime-secreting cyanobacteria (bacteria that use photosynthesis for energy).

The research into the life-giving potential of these “living fossils” is based on small microbes in Australia, but the results could help us identify fossil evidence of life on other planets, in particular Mars, said Erica Suosaari, a science fellow for Bush Heritage Australia, a non-profit conservation and land management organization. Suosaari is based at Hamelin Station Reserve, Western Australia, a 500,000 acre property that borders one of the world’s most diverse and abundant examples of marine stromatolites, the Hamelin Pool Marine Nature Reserve.

“Looking for evidence of life in the rocks is like finding a needle in the haystack,” wrote Suosaari in an e-mail. “If stromatolites have definitive bio-signatures — such as self organized morphologies that are indicative of life processes — then it may be possible to look for that ‘signature’ in rocks on the surface of other planets and significantly reduce the size of that haystack.”

Bands of seif stromatolites at low tide located in Booldah Province on the southwestern margin of Hamelin Pool. Photo: Pamela Reid

Bands of seif stromatolites at low tide located in Booldah Province on the southwestern margin of Hamelin Pool. Photo: Pamela Reid

A paper based on Suosaari’s research at Hamelin Pool entitled “New multi-scale perspectives on the stromatolites of Shark Bay, Western Australia,” was published in the journal Scientific Reports earlier this year.

Funding for the collaborative research was provided by a consortium of oil companies (Chevron, Shell, Repsol and BP) who are interested in modern microbial carbonate environments to develop models for subsurface reservoirs and source rocks. Additional support for genomics analyses was provided by the Exobiology and Evolutionary Biology element of the NASA Astrobiology Program

Composite stromatolites from Carbla Province. Photo: Pamela Reid

Composite stromatolites from Carbla Province. Photo: Pamela Reid

Learning more about ancient structures

On Earth, microbial communities responsible for creating stromatolites were essential in making the planet life-friendly. These stromatolite-forming cyanobacteria were the first living organisms to generate energy from the Sun using photosynthesis while creating oxygen as a byproduct. Over billions of years, cyanobacteria have changed Earth’s atmosphere from 1 percent oxygen to more than 20 percent oxygen, a composition that has allowed complex life evolve.

Suosaari’s research zeroes in on the stromatolites of Hamelin Pool, the most abundant and diverse modern assemblage of these microbial structures, which dominate nearly the entire 135 km of the coastline. Previous research into stromatolites identified them by the types of microbial mats colonizing the surface of the structure, a direct response of where the stromatolite resides in the tidal zone. Each lamination recorded in the stromatolite is thereby a record of a former surface mat. Her team instead classified stromatolites by their shape, revealing that certain shapes prefer to cluster in certain areas of the pool. Their investigation also showed that modern stromatolites have more in common with ancient stromatolites than previously thought.

“Modern marine stromatolites are often regarded as poor analogs of ancient stromatolites as a result of their grainy internal textures, which contrast with the fine grained nature of most ancient stromatolites,” Suosaari said.

Elongate nested stromatolites colonized by pustular mat in the Spaven Province on the western margin of Hamelin Pool. Photo: Pamela Reid

Elongate nested stromatolites colonized by pustular mat in the Spaven Province on the western margin of Hamelin Pool. Photo: Pamela Reid

By contrast, her team found out that in Hamelin Pool, the microbial communities commonly produce a fine-grained limestone known as micrite (microcrystalline calcite) creating stromatolite structures that are similar to the ancient stromatolites seen in the fossil record.

Furthermore, the stromatolite types in Hamelin Pool are dominated by a coccoid cyanobacterium that traces its lineage back 2 billion years to an ancient form of this cyanobacteria, called Eoentophysalis. This provides yet another similarity back to ancient times, Suosaari said. This means that standing along the shorelines of Hamelin Pool and gazing out onto the stromatolites, we are essentially looking through a window to early Earth at microbes of the same ancient lineage, pumping out oxygen and continuing to undertake processes that have been happening for billenia. There is not another place on the planet where this can be observed at such a scale.

Elongate nested stromatolites colonized by smooth mat in the Spaven Province on the western margin of Hamelin Pool.  Taken from the boat on a flat-calm day.  Photo: Erica Suosaari

Elongate nested stromatolites colonized by smooth mat in the Spaven Province on the western margin of Hamelin Pool. Taken from the boat on a flat-calm day. Photo: Erica Suosaari

Applications for Mars

The stromatolites studied were in a small region of Australia, but Suosaari said that as a whole, similar microbial communities could potentially be exported to other places — such as Mars — to make other locations in the Solar System more life-friendly to humans.

Suosaari said she thought of stromatolites when reading about SpaceX founder Elon Musk’s plans to bring life to the planet Mars. She suggested that because these stromatolite-building microbial communities produce oxygen, they could potentially make the Red Planet more life-friendly.

“Obviously with Elon Musk’s plans, we don’t have billions of years to shape the atmosphere if he is planning to move life there in the coming years, and Mars has less than 1 percent of the atmosphere of Earth,” she acknowledged. “But I begin to think about photosynthesizing microbial mats and how they have prevailed for billions of years; it’s a kind of resilience and longevity that our species hasn’t yet achieved. Perhaps we should look to these microbial communities to generate oxygen on the Red Planet at a small scale.”

Untitled1

Astronomers make first accurate measurement of oxygen in distant galaxy

UCLA astronomy graduate student Ryan Sanders discovered a way to precisely measure oxygen in distant galaxies like COSMOS-1908, indicated by the arrow. Credit: Ryan Sanders and the CANDELS team

UCLA astronomy graduate student Ryan Sanders discovered a way to precisely measure oxygen in distant galaxies like COSMOS-1908, indicated by the arrow. Credit: Ryan Sanders and the CANDELS team

UCLA astronomers have made the first accurate measurement of the abundance of oxygen in a distant galaxy. Oxygen, the third-most abundant chemical element in the universe, is created inside stars and released into interstellar gas when stars die. Quantifying the amount of oxygen is key to understanding how matter cycles in and out of galaxies.

This research is published online in the Astrophysical Journal Letters, and is based on data collected at the W. M. Keck Observatory on Mauna Kea, in Hawaii.

“This is by far the most distant galaxy for which the oxygen abundance has actually been measured,” said Alice Shapley, a UCLA professor of astronomy, and co-author of the study. “We’re looking back in time at this galaxy as it appeared 12 billion years ago.”

Knowing the abundance of oxygen in the galaxy called COSMOS-1908 is an important stepping stone toward allowing astronomers to better understand the population of faint, distant galaxies observed when the universe was only a few billion years old and galaxy evolution, Shapley said.

COSMOS-1908, contains approximately 1 billion stars. In contrast, the Milky Way contains approximately 100 billion stars; some galaxies in the universe contain many more, while others contain many fewer. Furthermore, COSMOS-1908 contains approximately only 20 percent the abundance of oxygen that is observed in the sun.

Typically, astronomers rely on extremely indirect and imprecise techniques for estimating oxygen abundance for the vast majority of distant galaxies. But in this case, UCLA researchers used a direct measurement, said Ryan Sanders, astronomy graduate student and the study’s lead author.

“Close galaxies are much brighter, and we have a very good method of determining the amount of oxygen in nearby galaxies,” Sanders said. In faint, distant galaxies, the task is dramatically more difficult, but COSMOS-1908 was one case for which Sanders was able to apply the “robust” method commonly applied to nearby galaxies. “We hope this will be the first of many,” he said.

Shapley said that prior to Sanders’ discovery researchers didn’t know if they could measure how much oxygen there was in these distant galaxies.

“Ryan’s discovery shows we can measure the oxygen and compare these observations with models of how galaxies form and what their history of star formation is,” Shapley said.

The amount of oxygen in a galaxy is determined primarily by three factors: how much oxygen comes from large stars that end their lives violently in supernova explosions — a ubiquitous phenomenon in the early universe, when the rate of stellar births was dramatically higher than the rate in the universe today; how much of that oxygen gets ejected from the galaxy by so-called “super winds,” which propel oxygen and other interstellar gases out of galaxies at hundreds of thousands of miles per hour; and how much pristine gas enters the galaxy from the intergalactic medium, which doesn’t contain much oxygen.

“If we can measure how much oxygen is in a galaxy, it will tell us about all these processes,” said Shapley, who, along with Sanders, is interested in learning how galaxies form and evolve, why galaxies have different structures, and how galaxies exchange material with their intergalactic environments.

Shapley expects the measurements of oxygen will reveal that super winds are very important in how galaxies evolved. “Measuring the oxygen content of galaxies over cosmic time is one of the key methods we have for understanding how galaxies grow, as well as how they spew out gas into the intergalactic medium,” she said.

The researchers used an extremely advanced and sophisticated instrument called MOSFIRE (Multi-Object Spectrometer for Infra-Red Exploration) installed on the Keck I telescope at the Keck Observatory. This five-ton instrument was designed to study the most distant, faintest galaxies, said UCLA physics and astronomy professor Ian McLean, project leader on MOSFIRE and director of UCLA’s Infrared Laboratory for Astrophysics. McLean built the instrument with colleagues from UCLA, the California Institute of Technology and UC Santa Cruz and industrial sub-contractors.

MOSFIRE collects visible-light photons from objects billions of light years away whose wavelengths have been stretched or “redshifted” to the infrared by the expansion of the universe. Due to the finite speed of light, MOSFIRE is providing a view of these galaxies as they existed billions of years ago, when the light first started traveling to Earth.

MOSFIRE is a type of instrument known as a “spectrograph,” which spreads the light from astronomical objects out into a spectrum of separate wavelengths (colors), indicating the specific amount of energy emitted at each wavelength. Spectrographs enable astronomers to determine the chemical contents of galaxies, because different chemical elements — such as oxygen, carbon, iron or hydrogen — each provide a unique spectral fingerprint, emitting light at specific wavelengths.

To characterize the chemical contents of COSMOS-1908, Sanders analyzed a particular wavelength in the MOSFIRE spectrum of this galaxy that is sensitive to the amount of oxygen. “MOSFIRE made Ryan’s measurement possible,” said Shapley, who described it as an “amazing instrument.”