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Impact Crater or Supervolcano Caldera?

Siloe Patera. Credit: ESA/DLR/FU Berlin

Siloe Patera. Credit: ESA/DLR/FU Berlin

At first glance, the region covered by this latest Mars Express image release appears to be pockmarked with impact craters. But the largest structure among them may hold a rather explosive secret: it could be remains of an ancient supervolcano.

The images presented here were taken by the high-resolution stereo camera on ESA’s Mars Express on 26 November 2014, and focus on the Siloe Patera feature in the Arabia Terra region of Mars.

Siloe Patera comprises two large nested craters, close to the centre of the main colour image. The outer rim measures about 40 x 30 km and, at its deepest point, the crater dips as low as 1750 m below the surrounding plains.

Some scientists believe that Siloe Patera and a number of similar features in Arabia Terra are calderas, the collapsed centres of volcanoes. But not just any volcanoes: these are thought to be martian supervolcanoes.

Siloe Patera in context. Credit: NASA MGS MOLA Science Team

Siloe Patera in context. Credit: NASA MGS MOLA Science Team

On Earth, a supervolcano is defined as a volcano that can produce at least 1000 cubic kilometres of volcanic materials in an eruption – thousands of times larger than ‘normal’ volcanic eruptions and powerful enough to alter global climate. An example is the Yellowstone caldera in the United States.

Supervolcanoes occur when magma is trapped below the surface, leading to a huge built up in pressure. They erupt suddenly in violent explosions and thus do not ‘grow’ sloping mountains like Olympus Mons. That makes them hard to identify, especially millions or billions of years later.

But a number of irregularly shaped craters have been detected in the Arabia Terra region that could represent a family of ancient supervolcano calderas.

Siloe Patera is one such example. It is characterised by two depressions with steep-sided walls, collapse features and low topographic relief. The two depressions could even represent two different eruptive episodes due to collapse as the underlying magma pressure was released, or as the magma chamber migrated below the surface.

By comparison, impact craters include features such as a central peak, uplifted crater rims and ejecta blankets surrounding them. Indeed, impact craters are widespread in this scene: textbook examples can be found in the two side-by-side craters just above Siloe Patera, and in the large crater at the far right of the scene. These craters each exhibit a central peak, terraced crater walls and a surrounding ejecta blanket.

An impact crater with depth to diameter ratio comparable to Siloe Patera would be expected to show these features – unless perhaps the crater had undergone extensive erosion or modification – but it does not.

Perspective view of Siloe Patera. Credit: ESA/DLR/FU Berlin

Perspective view of Siloe Patera. Credit: ESA/DLR/FU Berlin

Looking in more detail at Siloe Patera, as shown in the perspective view, numerous small channels and gullies are seen, cut into the walls and partly flowing into the depression. A prominent valley-like feature is present in the foreground, which cuts into the depression on one side.

The valley, along with numerous other small channels in the immediate vicinity, appears to cut through material to the lower left of the craters that could be either ejecta from an impact or volcanic flow.

If it is impact ejecta, then its asymmetric distribution could be explained either by an oblique meteoroid impact or by selective erosion of the blanket. Alternatively, it could be the product of lava flow from this part of the caldera.

Arabia Terra is already known to comprise plains of fine-grained, layered sulphate- and clay-bearing materials. The source of the material has been much debated, but lava and dust from eruptions could be the explanation.

Without any doubt, more data and high-resolution coverage – and even in situ sampling – would be necessary to resolve this mystery. And since the gases released in supervolcano eruptions could have had significant effects on the martian climate, this is a topic of great interest.

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Ceres Bright Spots Seen Closer Than Ever

This image of Ceres is part of a sequence taken by NASA's Dawn spacecraft on May 16, 2015, from a distance of 4,500 miles (7,200 kilometers). Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

This image of Ceres is part of a sequence taken by NASA’s Dawn spacecraft on May 16, 2015, from a distance of 4,500 miles (7,200 kilometers). Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

NASA’s Dawn mission captured a sequence of images, taken for navigation purposes, of dwarf planet Ceres on May 16, 2015. The image showcases the group of the brightest spots on Ceres, which continue to mystify scientists. It was taken from a distance of 4,500 miles (7,200 kilometers) and has a resolution of 2,250 feet (700 meters) per pixel.

“Dawn scientists can now conclude that the intense brightness of these spots is due to the reflection of sunlight by highly reflective material on the surface, possibly ice,” Christopher Russell, principal investigator for the Dawn mission from the University of California, Los Angeles, said recently.

Dawn arrived at Ceres on March 6, marking the first time a spacecraft has orbited a dwarf planet. Previously, the spacecraft explored giant asteroid Vesta for 14 months from 2011 to 2012. Dawn has the distinction of being the only spacecraft to orbit two extraterrestrial targets.

The spacecraft has been using its ion propulsion system to maneuver to its second mapping orbit at Ceres, which it will reach on June 6. The spacecraft will remain at a distance of 2,700 miles (4,400 kilometers) from the dwarf planet until June 30. Afterward, it will make its way to lower orbits.

Credit: NASA

Credit: NASA

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Could ‘Green Rust’ Be A Catalyst For Martian Life?

NASA's Curiosity rover is among those machines that have discovered signs of ancient water on Mars. Credit: NASA/JPL-Caltech/Univ. of Arizona

NASA’s Curiosity rover is among those machines that have discovered signs of ancient water on Mars. Credit: NASA/JPL-Caltech/Univ. of Arizona

Mars is a large enough planet that astrobiologists looking for life need to narrow the parameters of the search to those environments most conducive to habitability.

NASA’s Mars Curiosity mission is exploring such a spot right now at its landing site around Gale Crater, where the rover has found extensive evidence of past water and is gathering information on methane in the atmosphere, a possible signature of microbial activity.

But where would life most likely gain energy from its surroundings? One possibility is in an environment that includes “green rust,” a partially oxidized iron mineral. A fully oxidized iron “rust” — one exposed to oxidation for long enough — turns orangey-red, similar to the color of Mars’ regolith. When oxidization is incomplete, however, the iron rust is greenish.

This means that there are two different “redox states,” or types of iron with different numbers of electrons in the same mineral. This difference between the two iron redox states could allow the mineral to take in or give up electrons and thus act as a catalyst, said Laurie Barge, a planetary scientist at NASA’s Jet Propulsion Laboratory. She studies hydrothermal vents, an area where chemical contrasts also fuel life.

“From an environmental science perspective, green rust can absorb and concentrate nutrients, and can also accept and donate electrons for life,” said Barge.

She is the lead author of related work that was presented at the American Geophysical Union’s Joint Assembly meeting in May 2015. Funding for this work comes from the Jet Propulsion Laboratory’s Icy Worlds team as part of the NASA Astrobiology Institute (NAI) element of the Astrobiology Program at NASA.

Digging deep

One major challenge in the search for life on Mars is that its surface is highly oxidized. On Earth, green rust generated in Barge’s lab oxidizes quickly when exposed to air, and its composition is changed in only an hour. However, the lack of oxygen on Mars makes this a slower process. It is likely that green rust occurs beneath the oxidized surface, perhaps only a centimeter or half-inch deep as revealed by Curiosity.

NASA's InSight lander, set to launch in 2016, will include a drill to search below the surface. Credit: NASA

NASA’s InSight lander, set to launch in 2016, will include a drill to search below the surface. Credit: NASA

There are more probes on the way to Mars that will include drills. One of those will be NASA’s InSight lander, which is set to go to the Red Planet in 2016. Another is the European Space Agency’s ExoMars rover, expected to launch in 2018.

A major focus of current NASA missions on Mars is finding out where water has flowed in the past. NASA’s Curiosity, Opportunity and Spirit rovers have all found rocks that form in the presence of water, such as the red iron oxide mineral hematite, as well as select sulfates and clays. Further, several orbiting spacecraft have seen signs, such as the presence of gullies, in which water is thought to have once flowed on the surface.

Barge knows from her experiments that green rust forms when two contrasting solutions – one containing iron and one containing hydroxide – are mixed. On Earth, green rust has been found in such environments as non-oxygenated wet sediments and steel pipes that corrode in sea water.

Probing by laser

To detect green rust, Barge suggests using laser Raman spectroscopy, a technique which will be included on ESA’s ExoMars and NASA’s Mars 2020 missions. The technique involves directing a laser beam at a sample and then collecting and analyzing the light that is scattered from the spot to identify its molecular composition and structure. The scattered light contains fingerprint spectral features that allow us to determine the molecular makeup and mineralogy of the sample.

Barge has teamed up with Pablo Sobron, a research scientist at the SETI Institute, an expert in laser-based spectroscopy applied to Mars exploration, to adapt the Raman technique for the detection and analysis of green rust.

Michael Russell and Laurie Barge of NASA's Jet Propulsion Laboratory, who are trying to learn more about a mineral called “green rust” that could exist on Mars. Credit: NASA/JPL-Caltech

Michael Russell and Laurie Barge of NASA’s Jet Propulsion Laboratory, who are trying to learn more about a mineral called “green rust” that could exist on Mars. Credit: NASA/JPL-Caltech

But first, there needs to be a better understanding of where green rust will occur and how it can support habitability. The JPL Icy Worlds team (led by the Jet Propulsion Laboratory’s Isik Kanik) recently received a second five-year NASA Astrobiology Institute grant to study the habitability of icy worlds, including an investigation into how green rust might drive prebiotic chemistry, or chemistry that is a precursor to life.

“There’s a theory proposed by Michael Russell at JPL that green rust could have acted as a proto-enzyme to convert energy currencies on early Earth,” Barge said, referring to how lifeforms convert proton and electron gradients into chemical energy to drive metabolism and, thereby, life.

Green rust is especially interesting in this regard because it is a double layered hydroxide that can sandwich all sorts of interesting components relevant to life in between these layers, Barge added. These include phosphates, DNA, amino acids and proteins.

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NASA’s Webb ‘Strutting its Stuff’ in New ‘Behind the Webb’ Video

The newest video in the “Behind the Webb” series, called “Strutting its Stuff,” provides a look at three “struts” or poles that fold and unfold the secondary mirror on the James Webb Space Telescope.

The video series takes viewers behind the scenes to understand more about the Webb telescope, the world’s next-generation space observatory and successor to NASA’s Hubble Space Telescope. Designed to be the most powerful space telescope ever built, Webb will observe the most distant objects in the universe, provide images of the first galaxies formed and study unexplored planets around distant stars.


Credits: Space Telescope Science Institute
In “Strutting its Stuff,” Andy Carpenter, one of the mechanical integration engineers at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, talks about how the mirrors will unfold. “We deploy three struts that are much like a tripod, and the secondary mirror will sit above the backplane.”

Because the Webb telescope is too large to fit into a rocket in its final shape, engineers have designed it to unfold like origami after its launch. That unfolding, or deployment, includes the mirrors on the observatory, too. The segmented primary mirror collects light from the cosmos and directs it to the secondary mirror, which sends it additional smaller mirrors before it reaches the cameras and spectrographs.

This test model of James Webb Space Telescope components shows a trio of struts supporting a placeholder secondary mirror prior to testing in a massive vacuum chamber at NASA's Johnson Space Center in Houston. Credits: NASA/Chris Gunn

This test model of James Webb Space Telescope components shows a trio of struts supporting a placeholder secondary mirror prior to testing in a massive vacuum chamber at NASA’s Johnson Space Center in Houston.
Credits: NASA/Chris Gunn

The three struts are almost 25 feet long, yet are very strong and light-weight. They are hollow composite tubes, and the material is about 40-thousandths of an inch (about 1 millimeter) thick. They are built to withstand the temperature extremes of space.

During the video, viewers see a test of the struts being deployed in an environment that replicates the zero gravity of deep space.

The Webb telescope is a joint project of NASA, the European Space Agency and the Canadian Space Agency.

The 3 minute and 32 second video was produced at the Space Telescope Science Institute (STScI) in Baltimore, which conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy Inc. in Washington. The “Behind the Webb” video series is available in HQ, large and small Quicktime formats, HD, large and small WMV formats, and HD, large and small Xvid formats.

For more information about the Webb telescope, visit:

http://www.nasa.gov/webb or http://www.jwst.nasa.gov/

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Driest Place on Earth Hosts Life

María Elena South: Mars on Earth in the Atacama Desert, Chile. Photo courtesy: Armando Azua-Bustos

María Elena South: Mars on Earth in the Atacama Desert, Chile. Photo courtesy: Armando Azua-Bustos

Researchers have pinpointed the driest location on Earth in the Atacama Desert, a region in Chile already recognised as the most arid in the world. They have also found evidence of life at the site, a discovery that could have far-reaching implications for the search for life on Mars.

For more than a decade, the Yungay region has been established as the driest area of the hyper-arid Atacama desert, with conditions close to the so-called “dry limit” for life on Earth. Several academic papers have been published reporting on the extraordinary characteristics of the site and its relevance to astrobiologists as an analogue of conditions on Mars. However, following a more systematic search of the desert, a Chilean research team has now found a new site, María Elena South (MES), which it describes as “much drier” than Yungay.

Lead author Armando Azua-Bustos, an environmental biologist and research scientist at the Blue Marble Space Institute of Science in Seattle, says the team discovered that MES has a mean atmospheric relative humidity (RH) of 17.3 percent and a soil RH of a constant 14 percent at a depth of one meter. This soil value matches the lowest RH measurements taken by the Mars Science Laboratory at Gale Crater on Mars, establishing the fact that conditions at the site are as dry as those found recently on the Martian surface.

“Remarkably, we found a number of viable bacterial species in the soil profile at MES using a combination of molecular dependent and independent methods, unveiling the presence of life in the driest place on the Atacama Desert reported to date,” Azua-Bustos says.

Microsensors

The team used microsensors, including atmospheric temperature and relative humidity loggers, to take detailed measurements of the microenvironmental conditions at the MES site. It also characterized the geochemical composition of the soils at the site to unveil the presence and type of microbial species able to survive under these conditions. The results are presented in the paper, “Discovery and microbial content of the driest site of the hyperarid Atacama Desert, Chile,” published in March in the journal Environmental Microbiology Reports.

Digging for soil samples at María Elena South. Photo courtesy: Armando Azua-Bustos

Digging for soil samples at María Elena South. Photo courtesy: Armando Azua-Bustos

Azua-Bustos has spent the last 12 years studying the Atacama Desert and developing the field of astrobiology in Chile, and in so doing earned the nickname “astrobiologist of the desert.” He first became interested in the region after reading what he describes as a “pivotal paper” published in the journal Science in 2003 by a research team led by Chris McKay, a planetary scientist at NASA Ames Research Center.

The paper proposed the Yungay region in the Atacama as a “pertinent Mars analogue model,” mainly due to its extreme dryness, the characteristics of its soils, the presence of organic species at trace levels and extremely low levels of culturable bacteria.

However, based on his experience as a native of the Atacama who was born and raised in the desert, Azua-Bustos was convinced that there were drier places than Yungay, so he decided to set RH sensors in several places that were potentially drier.

“We found at least three such places, the driest of which we describe in this paper,” he says.

Implications for Astrobiology

For Azua-Bustos, the fact that the conditions at MES site, in terms of dryness, are the closest to Mars as it is possible to get means that it is one of the best analogue models on Earth to understand and investigate the potential existence, and type of, microbial life in the Martian subsurface.

“This also implies that if you want to test the next generation of robots, instruments and other detection techniques and technologies in a Mars-like environment, this is one of the best you can find as it possesses many of the key characteristics that you will find on the Red Planet,” he says.

Dr.  Armando Azua-Bustos, corresponding author.

Dr. Armando Azua-Bustos, corresponding author.

The site could also be used to conduct experiments that might inform future work carried out by the Mars Science Laboratory (MSL) at Gale Crater in its search for extant life on Mars. In Azua-Bustos’ view, one interesting experiment would be to test the same instruments being used by MSL at the MES site to compare results with the Martian data and to “further detail how similar both sites may be in terms of habitability, having the advantage of this new site in the Atacama as a positive control.”

For Azua-Bustos, the fact that we already know that there is life in the soil at María Elena South means that it would also be interesting to test if the sample analysis at Mars (SAM) instrument (a suite of three instruments, including a mass spectrometer, gas chromatograph, and tuneable laser spectrometer carried onboard the MSL rover), as well as similar detection instruments scheduled to be sent to Mars, are also able to detect life at a similarly dry terrestrial site.

“[K]nowing the amount, location in the subsoil and type of microbial life present in María Elena South, it would be of interest to test the SAM instruments here, in order to test its sensitivity in a site which you know is inhabited. In other words, if SAM or any other instrument were not able to detect life in Maria Elena soils, one could argue that SAM would not be sensitive enough to detect life on Mars,” he adds.

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It’s the Final Act for Larsen B Ice Shelf, NASA Finds

Antarctica's Larsen B Ice Shelf is likely to shatter into hundreds of icebergs like this one before the end of the decade, according to a new NASA study. Image credit: NSIDC/Ted Scambos

Antarctica’s Larsen B Ice Shelf is likely to shatter into hundreds of icebergs like this one before the end of the decade, according to a new NASA study. Image credit: NSIDC/Ted Scambos

A new NASA study finds the last remaining section of Antarctica’s Larsen B Ice Shelf, which partially collapsed in 2002, is quickly weakening and is likely to disintegrate completely before the end of the decade.

A team led by Ala Khazendar of NASA’s Jet Propulsion Laboratory in Pasadena, California, found the remnant of the Larsen B Ice Shelf is flowing faster, becoming increasingly fragmented and developing large cracks. Two of its tributary glaciers also are flowing faster and thinning rapidly.

“These are warning signs that the remnant is disintegrating,” Khazendar said. “Although it’s fascinating scientifically to have a front-row seat to watch the ice shelf becoming unstable and breaking up, it’s bad news for our planet. This ice shelf has existed for at least 10,000 years, and soon it will be gone.”

Ice shelves are the gatekeepers for glaciers flowing from Antarctica toward the ocean. Without them, glacial ice enters the ocean faster and accelerates the pace of global sea level rise. This study, the first to look comprehensively at the health of the Larsen B remnant and the glaciers that flow into it, has been published online in the journal Earth and Planetary Science Letters.

Khazendar’s team used data on ice surface elevations and bedrock depths from instrumented aircraft participating in NASA’s Operation IceBridge, a multiyear airborne survey campaign that provides unprecedented documentation annually of Antarctica’s glaciers, ice shelves and ice sheets. Data on flow speeds came from spaceborne synthetic aperture radars operating since 1997.

Khazendar noted his estimate of the remnant’s remaining life span was based on the likely scenario that a huge, widening rift that has formed near the ice shelf’s grounding line will eventually crack all the way across. The free-floating remnant will shatter into hundreds of icebergs that will drift away, and the glaciers will rev up for their unhindered move to the sea.

Located on the coast of the Antarctic Peninsula, the Larsen B remnant is about 625 square miles (1,600 square kilometers) in area and about 1,640 feet (500 meters) thick at its thickest point. Its three major tributary glaciers are fed by their own tributaries farther inland.

“What is really surprising about Larsen B is how quickly the changes are taking place,” Khazendar said. “Change has been relentless.”

The remnant’s main tributary glaciers are named Leppard, Flask and Starbuck — the latter two after characters in the novel Moby Dick. The glaciers’ thicknesses and flow speeds changed only slightly in the first couple of years following the 2002 collapse, leading researchers to assume they remained stable. The new study revealed, however, that Leppard and Flask glaciers have thinned by 65-72 feet (20-22 meters) and accelerated considerably in the intervening years. The fastest-moving part of Flask Glacier had accelerated 36 percent by 2012 to a flow speed of 2,300 feet (700 meters) a year — comparable to a car accelerating from 55 to 75 mph.

Flask’s acceleration, while the remnant has been weakening, may be just a preview of what will happen when the remnant breaks up completely. After the 2002 Larsen B collapse, the glaciers behind the collapsed part of the shelf accelerated as much as eightfold — comparable to a car accelerating from 55 to 440 mph.

The third and smallest glacier, Starbuck, has changed little. Starbuck’s channel is narrow compared with those of the other glaciers, and the small glacier is strongly anchored to the bedrock, which, according to authors of the study, explains its comparative stability.

“This study of the Antarctic Peninsula glaciers provides insights about how ice shelves farther south, which hold much more land ice, will react to a warming climate,” said JPL glaciologist Eric Rignot, a coauthor of the paper.

The research team included scientists from JPL; the University of California, Irvine; and the University Centre in Svalbard, Norway. The paper is online at: http://go.nasa.gov/1bbpfsC

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Researchers hone technique for finding signs of life on the Red Planet

Image credit: NASA / USGS

Image credit: NASA / USGS

For centuries, people have imagined the possibility of life on Mars. But long-held dreams that Martians could be invaders of Earth, or little green men, or civilized superbeings, all have been undercut by missions to our neighboring planet that have, so far, uncovered no life at all.

Yet visits to the Red Planet by unmanned probes from NASA and the European Space Agency have found evidence that a prime condition for life once may have existed: water.

“There has been a tremendous amount of very exciting findings this year that Mars once contained actively flowing, low-saline, near-neutral-pH water — pretty much the type of water where you find life on Earth today,” said Alison Olcott Marshall, assistant professor of geology at the University of Kansas. “This has made people think that it’s possible that life could have existed on Mars, although most researchers agree it’s unlikely to exist today — at least on the surface — as conditions on the surface of Mars are incredibly harsh.”

Olcott Marshall is working with her colleague and husband, Craig Marshall, associate professor of geology at KU, to improve the way scientists detect condensed aromatic carbon, thought to be a chemical signature of astrobiology.

“If we’re going to identify life on Mars, it will likely be the fossil remnants of the chemicals once synthesized by life, and we hope our research helps strengthen the ability to evaluate the evidence collected on Mars,” Craig Marshall said.

Craig Marshall is an expert in using Raman spectroscopy to look for carbonaceous materials, while Alison Olcott Marshall is a paleontologist interested in how the record of life gets preserved on Earth, especially when there is no bone or shell or tooth or other hard part to fossilize.

The pair is known recently for overturning the idea that 3.5 billion-year-old specks found in rocks in Australia were the oldest examples of life on Earth. (Rather than ancient bacteria fossils, the researchers showed the shapes were nothing more than tiny gaps in the rock that are packed with minerals.)

If traces if ancient biology are detected in Mars, the KU researchers want to make sure the evidence is more conclusive.

According to a recent paper by the Marshalls in the peer-reviewed Philosophical Transactions of the Royal Society, by itself Raman spectroscopy is able to screen for carbonaceous material, but it can’t determine its source — thus the technology needs to be supplemented in order to determine if life exists on Mars.

“Raman spectroscopy works by impinging a laser on a sample so the molecules within that sample vibrate at diagnostic frequencies,” Craig Marshall said. “Measuring those frequencies allows the identification of inorganic and organic materials. It’s insufficient because however the carbonaceous material is made, it will be the same chemically and structurally, and thus Raman spectroscopy cannot determine the origin.”

The Marshalls call for the use of gas chromatography/mass spectroscopy to supplement Raman spectroscopy and develop more conclusive evidence of ancient extraterrestrial life.

“Much like the search for ancient life on Earth, though, one strand of evidence is not, and should not be, conclusive,” said Alison Olcott Marshall. “This is a vast puzzle, and we want to make sure we are examining as many different pieces as we can.”

Currently, the KU researchers are extending this line of investigation by using Raman spectroscopy to analyze rocks from Earth that are similar to those on Mars. They hope to publish their findings in the near future.

“If you were to pick up a typical rock on Mars it would look quite different, chemically, from a typical rock here on Earth, not to mention the fact that it would be covered in rusty dust,” Alison Olcott Marshall said. “Previous research into how Raman spectroscopy would fare on Mars was mainly done on pure salts and minerals, often ones synthesized in a lab. We identified field sites on the Kansas-Oklahoma border with a chemical content more like what could be found on Mars, right down to the rusty dust, and we’ve been exploring how Raman spectroscopy fares in such an environment.”

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Kepler’s Six Years In Science (and Counting): By The Numbers

The artistic concept shows NASA's planet-hunting Kepler spacecraft operating in a new mission profile called K2. Using publicly available data, astronomers may have confirmed K2's first discovery of star with more than one planet. Image Credit: NASA Ames/JPL-Caltech/T Pyle

The artistic concept shows NASA’s planet-hunting Kepler spacecraft operating in a new mission profile called K2. Using publicly available data, astronomers may have confirmed K2’s first discovery of star with more than one planet. Image Credit: NASA Ames/JPL-Caltech/T Pyle

NASA’s Kepler spacecraft began hunting for planets outside our solar system on May 12, 2009. From the trove of data collected, we have learned that planets are common, that most sun-like stars have at least one planet and that nature makes planets with unimaginable diversity.

Kepler launched on March 6, 2009. Its mission was to survey a portion of our galaxy to determine what fraction of stars might harbor potentially habitable, Earth-sized exoplanets, or planets that orbit other stars. Of particular interest are exoplanets orbiting in the habitable zone — the range of distance from a star in which the surface temperature of an orbiting planet might sustain liquid water. For life as we know it, liquid water is a necessary ingredient.

Of the more than 1,000 confirmed planets found by Kepler, eight are less than twice the size of Earth and are in their stars’ habitable zone. All eight orbit stars cooler and smaller than our sun.

During its four-year prime mission, Kepler simultaneously and continuously measured the brightness of more than 150,000 stars, looking for the telltale dimming that would indicate the presence of an orbiting planet. From these dimmings, or transits, and information about the parent star, researchers can determine a planet’s size (radius), the time it takes to orbit its star and the amount of energy received from the host star.

NASA's Kepler: Six Years of Science. Image Credit: NASA/JPL-Caltech

NASA’s Kepler: Six Years of Science. Image Credit: NASA/JPL-Caltech

Kepler’s exquisitely precise photometer, or light sensor, was designed to detect minute changes in brightness, in order to infer the presence of an Earth-sized planet. For a remote observer, Earth transiting the sun would dim its light by less than 1/100th of one percent, or the equivalent of the amount of light blocked by a gnat crawling across a car’s headlight viewed from several miles away.

In May 2014, the Kepler spacecraft began a new mission, K2, to observe parts of the sky along the ecliptic plane, the orbital path of = Earth about the sun, where the familiar constellations of the zodiac lie. This new mission provides scientists with an opportunity to search for even more exoplanets, as well as opportunities to observe notable star clusters, young and old stars, active galaxies and supernovae. The spacecraft continues to collect data in its new mission.

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Mystery Methane on Mars: The Saga Continues

A scientist has raised questions about the latest detection of methane on Mars, suggesting that NASA’s rover could be responsible for the mysterious burp. Highly unlikely, but not impossible, says the Curiosity team.

NASA’s Curiosity rover has detected methane on Mars. Could the gas be coming from the rover itself? Credit: NASA/JPL

NASA’s Curiosity rover has detected methane on Mars. Could the gas be coming from the rover itself? Credit: NASA/JPL

 

Is the Red Planet giving off methane?

The question has taunted scientists for nearly 50 years, ever since the Mariner 7 spacecraft detected a whiff of the gas near Mars’ south pole. Researchers retracted the finding a month later after realizing that the signal was in fact coming from carbon dioxide ice.

Then in 2003 and 2004, earthbound telescopes and orbiting spacecraft rekindled the mystery with reports of large methane clouds in Mars’ atmosphere. Most of Earth’s methane comes from living organisms, though a small fraction can form when rocks and hot water interact. A burp of methane on Mars would indicate that the planet might be more alive than previously thought—whether biologically or geologically. But the “plumes” mysteriously vanished a few years later, sparking intense debate over whether they might have been seasonal, or the results of flawed measurements.

NASA’s Curiosity rover would resolve the matter, everyone hoped. The rover sampled Mars’ atmosphere six times for methane between October 2012 and June 2013—and detected none. But the case for Martian methane remained far from settled. A few months later, Curiosity detected a sudden burst of the gas in four measurements over a period of two months.

Working hard to rule out potential anomalies and monitor the evolution of the burst over time, the Curiosity team waited an entire year before announcing the new results at a meeting of the American Geophysical Union in December 2014. A paper was published in the journal Science in January 2015. Whether microbes hid below the Martian surface or geology was at play, the Red Planet could well be alive in some way after all.

And yet, a researcher remains skeptical. Kevin Zahnle, a scientist at NASA Ames Researcher Center who was not involved with the discovery, voiced his concerns last month in a seminar hosted by the NASA Astrobiology Institute’s Virtual Planetary Lab.

“I am convinced that they really are seeing methane,” he said. “But I’m thinking that it has to be coming from the rover.”

Methane From Earth

Zahnle, who was also critical of the 2003 and 2004 methane reports, said that it wouldn’t take much from the rover to lead scientists astray. After all, the rover contains within a chamber some methane at a concentration 1,000 times higher than the puff supposedly found in Mars’ atmosphere. That methane had come from Earth.

Upon landing in Gale Crater, the rover’s tunable laser spectrometer gave off an unusually high reading for methane. The scientists on the team quickly realized that some terrestrial air had leaked into the instrument while the rover was sitting on the launch pad at Cape Canaveral. They pumped out most of that methane, keeping a small amount in the antechamber to the sample cell for calibration purposes.

The Tunable Laser Spectrometer on NASA's Curiosity Mars Rover. The foreoptics chamber contains a small amount of methane for calibration purpose. Credit: NASA/JPL

The Tunable Laser Spectrometer on NASA’s Curiosity Mars Rover. The foreoptics chamber contains a small amount of methane for calibration purpose. Credit: NASA/JPL

But Curiosity’s team insists that this known source hasn’t interfered with the discovery.

“We are continuously monitoring that methane amount and there hasn’t been evidence of any leakage during the entire mission,” says Chris Webster, a senior research scientist at NASA’s Jet Propulsion Laboratory and lead author of the study. “And while it’s true that the concentration of methane in that chamber is 1,000 times higher than in Mars’s atmosphere, the comparison is actually misleading.”

“You have to look at the amount of methane, not the concentration,” he explains. The concentration of methane on the rover may seem high, but the actual amount is very small because the chamber is very small. To produce the amount we detected in Mars’s atmosphere, you’d need a gas bottle of pure methane leaking from the rover. And we simply don’t have it.”

Unknown Sources?

Zahnle also contends that the terrestrial air could have infiltrated other areas on the rover.

“Ruling out the rover entirely as a cause is a hard thing to do,” he says. “You’d have to know about every place where methane could be stored.”

Chris McKay, a researcher at NASA Ames and co-author on the January paper, thinks that Zanhle’s concerns are valid. “I think the possibility of a methane source aboard should still be considered until completely ruled out,” he says.

But Paul Mahaffy, the principal investigator on the Sample Analysis at Mars (SAM) suite of instruments, doubts that the rover could be a possible source. “It seems unlikely that after more than a year on the surface of Mars a sudden source of methane from the spacecraft would appear, persist for 60 days and then disappear,” he says. “Methane is a very volatile gas and any residual methane brought to Mars should be long gone.”

Webster agrees that an unknown source on the rover seems highly unlikely, but he says it’s not impossible.

“There are a few areas that are sealed,” he says. “They could, in theory, be a source if some methane had made its way into them and was then leaking out, but we’ve looked very hard for other sources and we haven’t identified any.”

What’s Next?

Curiosity is gearing up for new measurements later this year around the holiday season, which is when the mysterious burst was detected in 2013, one Mars year ago. “If the methane comes back around that time, that will tell us that something seasonal is going on,” Webster says. “That would be a huge discovery, and would put to rest the questions about the rover being a potential source.”

Daybreak at Gale Crater. Credit: NASA/JPL

Daybreak at Gale Crater. Credit: NASA/JPL

Meanwhile, McKay is exploring another possibility—namely, that a meteorite may have recently fallen within the vicinity of the rover. Carbonaceous meteorites contain a small amount of organic materials, which can give off a plume of methane when broken down by ultraviolet radiation.

“It’s probabilistically unlikely, but those events do happen,” McKay says. “If the rover had been in the town of Murchison when the meteorite fell in 1969, it would have detected a pulse of methane.”

The Curiosity team has searched for fresh craters near the rover by looking at images taken from orbit. They haven’t found any. However, McKay noted that, unlike stony-iron meteorites, carbonaceous meteorites don’t leave craters. Instead, they typically break apart in the atmosphere and fall into a rain of small organic fragments. McKay is currently working with a meteorite expert to determine the size of a potential object that could have produce the methane spike detected by Curiosity.

The ExoMars Trace Gas Orbiter, a new mission led by the European Space Agency and planned for 2016, will also scan the Martian atmosphere for trace amounts of methane and other exotic gases. India’s Mars mission currently in orbit may also soon report its methane findings. Both will survey an area much greater than covered by Curiosity, which will spend its lifetime in Gale Crater. Will they finally resolve the mystery behind Mars’s capricious methane plumes? Time will tell.

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Water Was Plentiful in the Early Universe

Credit: NASA/JPL

Credit: NASA/JPL

Astronomers have long held that water — two hydrogen atoms and an oxygen atom — was a relative latecomer to the universe. They believed that any element heavier than helium had to have been formed in the cores of stars and not by the Big Bang itself. Since the earliest stars would have taken some time to form, mature, and die, it was presumed that it took billions of years for oxygen atoms to disperse throughout the universe and attach to hydrogen to produce the first interstellar “water.”

New research poised for publication in Astrophysical Journal Letters by Tel Aviv University and Harvard University researchers reveals that the universe’s first reservoirs of water may have formed much earlier than previously thought — less than a billion years after the Big Bang, when the universe was only 5 percent of its current age.

According to the study, led by PhD student Shmuel Bialy and his advisor Prof. Amiel Sternberg of the Department of Astrophysics at TAU’s School of Physics and Astronomy, in collaboration with Prof. Avi Loeb of Harvard’s Astronomy Department, the timing of the formation of water in the universe bears important implications for the question of when life itself originated.

“Our theoretical model predicts that significant amounts of water vapor could form in molecular clouds in young galaxies, even though these clouds bear thousands of times less oxygen than that in our own galaxy today,” said Bialy, the lead author of the study. “This was very surprising and raises important questions about the habitability of the first planets, because water is the key component of life as we know it.”

For the purpose of the study, the researchers examined chemical reactions that led to the formation of water within the oxygen-poor environment of early molecular clouds. They found that at temperatures around 80 degrees Fahrenheit, the formation process became very efficient, and in the gas phase abundant water could form despite the relative lack of raw materials.

“The universe then was warmer than today and gas clouds were unable to cool effectively,” said Prof. Sternberg. “Indeed the glow of the cosmic microwave background was hotter, and gas densities were higher,” said Prof. Loeb, who also holds a Sackler Senior Professorship by special appointment in the School of Physics and Astronomy at TAU.

Because ultraviolet light from stars breaks down water molecules, an equilibrium between water formation and destruction could only be reached after hundreds of millions of years. The team found that the equilibrium in the early universe was similar to that measured in the universe today.

“We found that it is possible to build up significant quantities of water in the gas phase without much enrichment in heavy elements,” said Bialy. “In this current work, we calculated how much water could exist in the gas phase within molecular clouds that would form later generations of stars and planets. In future research we intend to address questions such as how much water could have existed as interstellar ice, as in our own galaxy, and what fraction of all the water might actually be incorporated into newly-forming planetary systems.”

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NASA’s New Horizons Spots Pluto’s Faintest Known Moons

Credit: NASA

Credit: NASA

It’s a complete Pluto family photo – or at least a photo of the family members we’ve already met.

For the first time, NASA’s New Horizons spacecraft has photographed Kerberos and Styx – the smallest and faintest of Pluto’s five known moons. Following the spacecraft’s detection of Pluto’s giant moon Charon in July 2013, and Pluto’s smaller moons Hydra and Nix in July 2014 and January 2015, respectively, New Horizons is now within sight of all the known members of the Pluto system.

“New Horizons is now on the threshold of discovery,” said mission science team member John Spencer, of the Southwest Research Institute in Boulder, Colorado. “If the spacecraft observes any additional moons as we get closer to Pluto, they will be worlds that no one has seen before.”

Drawing ever closer to Pluto in mid-May, New Horizons will begin its first search for new moons or rings that might threaten the spacecraft on its passage through the Pluto system. The images of faint Styx and Kerberos shown here are allowing the search team to refine the techniques they will use to analyze those data, which will push the sensitivity limits even deeper.

Kerberos and Styx were discovered in 2011 and 2012, respectively, by New Horizons team members using the Hubble Space Telescope. Styx, circling Pluto every 20 days between the orbits of Charon and Nix, is likely just 4 to 13 miles (approximately 7 to 21 kilometers) in diameter, and Kerberos, orbiting between Nix and Hydra with a 32-day period, is just 6 to 20 miles (approximately 10 to 30 kilometers) in diameter. Each is 20 to 30 times fainter than Nix and Hydra.

The images detecting Kerberos and Styx shown here were taken with New Horizons’ most sensitive camera, the Long Range Reconnaissance Imager (LORRI), from April 25-May 1. Each observation consists of five 10-second exposures that have been added together to make the image in the left panel. Images were extensively processed to reduce the bright glare of Pluto and Charon and largely remove the dense field of background stars (center and right panels). This reveals the faint satellites, whose positions and orbits – along with those of brighter moons Nix and Hydra –  are given in the right panel.

“Detecting these tiny moons from a distance of more than 55 million miles is amazing, and a credit to the team that built our LORRI long-range camera and John Spencer’s team of moon and ring hunters,” added New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute.

Kerberos is visible in all of the images, though is partially obscured in the second image. Styx is not visible in the first image, only in subsequent ones; on April 25 it was obscured by electronic artifacts in the camera – the black and white streaks extending to the right of the extremely overexposed images of Pluto and Charon in the center of the frame. These artifacts point in different directions in different images due to the varying orientation of the spacecraft. Other unlabeled features in the processed images include the imperfectly removed images of background stars and other residual artifacts.

Although Styx and Kerberos are more visible in some frames than others, perhaps due to brightness fluctuations as they rotate on their axes, their identity is confirmed by their positions being exactly where they are predicted to be (in the center of the circles in the right panel).

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NASA Research Reveals Europa’s Mystery Dark Material Could Be Sea Salt

A "Europa-in-a-can" laboratory setup at NASA-JPL mimics conditions of temperature, near vacuum and heavy radiation on the surface of Jupiter's icy moon. Image credit: NASA/JPL-Caltech

A “Europa-in-a-can” laboratory setup at NASA-JPL mimics conditions of temperature, near vacuum and heavy radiation on the surface of Jupiter’s icy moon. Image credit: NASA/JPL-Caltech

NASA laboratory experiments suggest the dark material coating some geological features of Jupiter’s moon Europa is likely sea salt from a subsurface ocean, discolored by exposure to radiation. The presence of sea salt on Europa’s surface suggests the ocean is interacting with its rocky seafloor — an important consideration in determining whether the icy moon could support life.

The study is accepted for publication in the journal Geophysical Research Letters and is available online.

“We have many questions about Europa, the most important and most difficult to answer being is there life? Research like this is important because it focuses on questions we can definitively answer, like whether or not Europa is inhabitable,” said Curt Niebur, Outer Planets Program scientist at NASA Headquarters in Washington. “Once we have those answers, we can tackle the bigger question about life in the ocean beneath Europa’s ice shell.”

For more than a decade, scientists have wondered about the nature of the dark material that coats long, linear fractures and other relatively young geological features on Europa’s surface. Its association with young terrains suggests the material has erupted from within Europa, but with limited data available, the material’s chemical composition has remained elusive.

“If it’s just salt from the ocean below, that would be a simple and elegant solution for what the dark, mysterious material is,” said research lead Kevin Hand, a planetary scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California.

A salt sample inside a JPL test chamber is bathed in an eerie blue glow as an electron beam scans across it many times each second, delivering a powerful dose of radiation. Image credit: NASA/JPL-Caltech

A salt sample inside a JPL test chamber is bathed in an eerie blue glow as an electron beam scans across it many times each second, delivering a powerful dose of radiation. Image credit: NASA/JPL-Caltech

One certainty is that Europa is bathed in radiation created by Jupiter’s powerful magnetic field. Electrons and ions slam into the moon’s surface with the intensity of a particle accelerator. Theories proposed to explain the nature of the dark material include this radiation as a likely part of the process that creates it.

Previous studies using data from NASA’s Galileo spacecraft, and various telescopes, attributed the discolorations on Europa’s surface to compounds containing sulfur and magnesium. While radiation-processed sulfur accounts for some of the colors on Europa, the new experiments reveal that irradiated salts could explain the color within the youngest regions of the moon’s surface.

To identify the dark material, Hand and his co-author Robert Carlson, also at JPL, created a simulated patch of Europa’s surface in a laboratory test apparatus for testing possible candidate substances. For each material, they collected spectra — which are like chemical fingerprints — encoded in the light reflected by the compounds.

“We call it our ‘Europa in a can,'” Hand said. “The lab setup mimics conditions on Europa’s surface in terms of temperature, pressure and radiation exposure. The spectra of these materials can then be compared to those collected by spacecraft and telescopes.”

A close-up of salt grains discolored by radiation following exposure in a "Europa-in-a-can" test setup at JPL. Image credit: NASA/JPL-Caltech

A close-up of salt grains discolored by radiation following exposure in a “Europa-in-a-can” test setup at JPL. Image credit: NASA/JPL-Caltech

For this particular research, the scientists tested samples of common salt — sodium chloride — along with mixtures of salt and water, in their vacuum chamber at Europa’s chilly surface temperature of minus 280 degrees Fahrenheit (minus 173 Celsius). They then bombarded the salty samples with an electron beam to simulate the intense radiation on the moon’s surface.

After a few tens of hours of exposure to this harsh environment, which corresponds to as long as a century on Europa, the salt samples, which were initially white just like table salt, turned a yellowish-brown color similar to features on the icy moon. The researchers found the color of these samples, as measured in their spectra, showed a strong resemblance to the color within fractures on Europa that were imaged by NASA’s Galileo mission.

“This work tells us the chemical signature of radiation-baked sodium chloride is a compelling match to spacecraft data for Europa’s mystery material,” Hand said.

Additionally, the longer the samples were exposed to radiation, the darker the resulting color. Hand thinks scientists could use this type of color variation to help determine the ages of geologic features and material ejected from any plumes that might exist on Europa.

Previous telescope observations have shown tantalizing hints of the spectral features seen by the researchers in their irradiated salts. But no telescope on or near Earth can observe Europa with sufficiently high resolving power to identify the features with certainty. The researchers suggest this could be accomplished by future observations with a spacecraft visiting Europa.

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Cloudy Mornings & Hot Afternoons on Alien Worlds

Artist's interpretation of a cloudy exoplanet. Image Credit: Courtesy Space Telescope Science Instutute

Artist’s interpretation of a cloudy exoplanet. Image Credit: Courtesy Space Telescope Science Instutute

We may complain a lot about the weather on earth but perhaps we are much better off here than on some alien worlds, where the daily forecast is cloudy, overcast skies in the morning and scorching heat in the afternoon.

A team of international astronomers including York University scientist Professor Ray Jayawardhana have uncovered evidence of daily weather cycles on six extra-solar planets using sensitive observations from the Kepler space telescope.

“Despite the discovery of thousands of extra-solar planets, what these far-off worlds look like is still shrouded in mystery,” says lead author Lisa Esteves, graduate student at the University of Toronto.

In their paper entitled “Changing Phases of Alien Worlds: Probing Atmospheres of Kepler Planets with High-Precision Photometry” published today in the Astrophysical Journal, the team analyzed all 14 Kepler planets known to exhibit phase variations, and found indications of cloudy mornings on four and hot, clear afternoons on two others.

Most of the worlds examined in the study were very hot and large, with temperatures greater than 1600 degrees Celsius and sizes comparable to Jupiter. These conditions are far from hospitable to life, but excellent for phase measurements, the authors note.

“We are getting to know these exotic alien planets as dynamic, three-dimensional worlds through remote sensing across vast distances. Someday soon we hope to provide similar weather reports for worlds not much bigger than the Earth,” says study co-author Jayawardhana, who adds that upcoming space missions such as TESS (2017) and PLATO (2024) should reveal many small planets around bright stars, making great targets for detailed studies.

For the study, the researchers determined weather on these alien worlds by measuring phase changes as the planets circle their host stars. Similar to the Moon in the solar system, an exoplanet going through a cycle of phases can be traced, from fully lit to completely dark, when different portions of the planet are illuminated by its star.

“The detection of the light from these far-away planets, some of which took thousands of years to reach us, is in itself remarkable,” says co-author Ernst de Mooij of Queen’s University Belfast, UK. “But when we consider that phase cycle variations can be up to 100,000 times fainter than the host star, these detections become truly astonishing.”

The Kepler space telescope was the ideal instrument for the study of exoplanet phase variations, according to the researchers. The telescope’s very precise measurements and the vast amount of data it collected over its initial four-year mission allowed astronomers to beat the noise and measure the tiny signals from these distant worlds.

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Ether Compounds Could Work like DNA On Oily Worlds

Sunlight glints off of hydrocarbon seas on Saturn's moon Titan, as seen here in near-infrared light by the Cassini spacecraft. Credit: NASA/JPL-Caltech/Univ. Arizona/Univ. Idaho

Sunlight glints off of hydrocarbon seas on Saturn’s moon Titan, as seen here in near-infrared light by the Cassini spacecraft. Credit: NASA/JPL-Caltech/Univ. Arizona/Univ. Idaho

In the search for life beyond Earth, scientists have justifiably focused on water because all biology as we know it requires this fluid. A wild card, however, is whether alternative liquids can also suffice as life-enablers. For example, Saturn’s frigid moon Titan is awash in inky seas of the hydrocarbon methane.

Here on warm, watery Earth, the molecules DNA and RNA serve as the blueprints of life, containing creatures’ genetic instruction manuals. An immense family of proteins carries out these instructions.

Yet in a hydrocarbon medium on Titan, these molecules could never perform their profound chemical duties. Other molecules must therefore step up to the plate if non-water-based, alien life is to operate and evolve in a Darwinian sense, with genetic changes leading to diversity and complexity.

A new study proposes that molecules called ethers, not used in any genetic molecules on Earth, could fulfill the role of DNA and RNA on worlds with hydrocarbon oceans. These worlds must be a good deal toastier though than Titan, the study found, for plausibly life-like chemistry to take place.

“The genetic molecules we have proposed could perform on ‘warm Titans’,” said paper lead author Steven Benner, a distinguished fellow at the Foundation for Applied Molecular Evolution, a private scientific research organization based in Alachua, Florida.

Bigger molecular cousins to Titan’s methane, such as the octane that helps fuel our vehicles, would also make for far more suitable solvents. Although no “warm Titans” close-in to their host stars have turned up so far in exoplanet exploration, Benner is hopeful there are worlds aplenty that fit the bill.

“Within our own solar system, we do not have a planet big enough, close enough to the Sun, and with the right temperature to support warm hydrocarbon oceans on its surface,” said Benner. “But each week, astronomers are discovering new solar systems other than our own.”

The new paper appeared in the March issue of the journal Astrobiology and was funded in part by the Exobiology & Evolutionary Biology element of the NASA Astrobiology Program.

A molecular sketch of life on Earth

On a fundamental level, the development of life on Earth has been a push-and-pull between molecules changing and staying the same. For an organism to reproduce and make copies of itself, the vast majority of its genetic information must be conserved if the offspring are to survive and still carry life forward. But if life does not change and adapt to inconstant environmental conditions, it will die out. The environmental curve balls to life include temperature swings and varying water and nutrient availability.

DNA and RNA allow for a biological version of the axiom “the more things change, the more they stay the same.” Individual “letters,” or nucleobases, in the four-letter code of DNA and RNA can mutate without destroying the molecule’s overall form and function.

A schematic of a DNA molecule. The four nucleobases – A, T, C and G – are shown at right. Note the repeating backbone of oxygen, carbon and phosphorus throughout the double helix structure of DNA. Credit: Zephyris/Wikipedia

A schematic of a DNA molecule. The four nucleobases – A, T, C and G – are shown at right. Note the repeating backbone of oxygen, carbon and phosphorus throughout the double helix structure of DNA. Credit: Zephyris/Wikipedia

These nucleobase changes can produce novel proteins. These proteins in turn let life chemically interact with its environment in new ways to promote survival. Brand new species arise in this manner, as fresh traits take hold in contrasting conditions and locations. (In the mid-1800s, Charles Darwin famously intuited this overarching concept of the origin of species, though the biomolecular nitty-gritty was not fathomed until many decades hence.)

The general structure, and therefore the general behavior, of DNA and RNA remains the same because of repeating elements in the chemical’s backbone, or main scaffolding. The molecules possess an outwardly negative charge that repeat along their backbones, which allows DNA and RNA to dissolve and float freely in water. In this fluid medium, the DNA and RNA can interact with other biomolecules, leading to complexity in biological systems.

“This is the central point of the ‘polyelectrolyte theory of gene,’ which holds that any genetic biopolymer able to support Darwinian evolution operating in water must have an ever-repeating backbone charge,” explained Benner. “The repeating charges so dominate the physical behavior of the genetic molecule that any changes in the nucleobases that influence genetic information have essentially no significant impact on the molecule’s overall physical properties.”

All of which is well and good for us water-based organisms. The trouble is, for waterless worlds like Titan where hydrocarbons reign, molecules like DNA and RNA would never cut it. These biomolecules cannot dissolve, as required, in hydrocarbons to allow for life’s microscopic bump-and-grind.

“None of these molecules have any chance of dissolving in a hydrocarbon ocean like on Titan or on a warm Titan,” said Benner.

More bothersome still, molecules with any sort of outward charge goop up in hydrocarbons. The blueprints of life on Earth as contained in DNA and RNA cannot translate to hydrocarbon-logged worlds.

Enter the ether

Is life, at least as we can conceive of it, impossible amidst hydrocarbons? Benner and colleagues think not. Compounds called ethers, when strung together form complex “polyethers,” can likely perform in a manner that stays faithful to the polyelectrolyte theory of gene.

An artist's impression of the low-lit surface of Titan under the moon's thick, orange haze, with liquid hydrocarbons pooling and eroding the surface much like water on Earth. Credit: Steven Hobbs (Brisbane, Queensland, Australia).

An artist’s impression of the low-lit surface of Titan under the moon’s thick, orange haze, with liquid hydrocarbons pooling and eroding the surface much like water on Earth. Credit: Steven Hobbs (Brisbane, Queensland, Australia).

Ethers, like DNA and DNA, have simple, repeating backbones, in their case of carbon and oxygen. Structurally, ethers do not have an outward charge, like DNA and RNA. But ethers do possess internal charge repulsions that open up useful “spaces” within the molecules, wherein small elemental chunks can go that work like the DNA’s and RNA’s nucleobases.

Following from this insight, Benner and colleagues tested out how well polyethers would dissolve in various hydrocarbons. The researchers further ran experiments at temperatures expected of Titan-esque worlds at different distances from host stars.

Hydrocarbons, like water, can be solids liquids or gases, depending on temperature and pressure. As with the astrobiological hunts for water-based life, the liquid phase of hydrocarbons is the one of interest, because in solids (like ice), biomolecules cannot interact, and in gases (water vapor), the medium is too thin to support enough interaction.

As a rule, the temperature range at which a hydrocarbon is a liquid goes up as the hydrocarbon becomes longer. Methane, the simplest, shortest hydrocarbon with a single carbon atom linked to four hydrogen atoms, has a very narrow liquid range—between about -300 and -280 degrees Fahrenheit. Inconveniently, the solubility of ethers plummets when getting down into these Titanian chills.

According to Benner’s study, and to the disappointment of many scientists, Titan looks like a very unlikely abode for aliens.

“We have shown that the methane oceans at Titan are likely to be too cold to hold any genetic biopolymer,” said Benner.

(Puzzling readings of less hydrogen and acetylene than expected at Titan’s surface have, however, hinted previously at a form of microbial life.)

Degrees of degrees

Habitable zones beyond the conventional one for water might exist for solvents such as hydrocarbons. Credit: NASA/JPL-Caltech

Habitable zones beyond the conventional one for water might exist for solvents such as hydrocarbons. Credit: NASA/JPL-Caltech

A better bet for life than methane-ocean worlds are those instead covered by propane. This hydrocarbon has three carbon atoms to methane’s one, and is another household name here on Earth as a gaseous fuel. It can stay liquid over a much broader and more suitable-for-chemistry range of -300 to -40 degrees Fahrenheit. Still better than propane is octane. This eight-carbon molecule does not freeze until about -70 degrees Fahrenheit, nor does it turn into a gas until reaching a quite-hot 257 degrees Fahrenheit.

That broad a range with sufficient ether solubility suggests that warm Titans could harbor a truly alien biochemistry capable of evolving complexity in a Darwinian manner. These worlds could be found in a fairly wide hydrocarbon “habitable zone” around other stars. The hydrocarbon habitable zone is akin to the familiar water-based zone, wherein a planet is neither too close nor too far from its star to have its water completely boil or freeze away.

Hydrocarbon worlds of interest need not be Titan-like, after all, in that they do not have to be moons of gas giants. Warm Titans could actually be more like oily Earths or super-Earths, drenched in octane.

As research continues, new and exotic solvents other than water and hydrocarbons could yet emerge as plausible milieus for life’s dealings.

“Virtually every star has a habitable zone for every solvent,” said Benner.

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Institute for Pale Blue Dots renamed in honor of Carl Sagan

Credit: Cornell University

Credit: Cornell University

Carl Sagan longed to explore other worlds, to learn if they, too, contain life. A research institution devoted to the pursuit of this challenge, the Carl Sagan Institute: Pale Blue Dot and Beyond, was unveiled May 9 at Cornell University, Sagan’s teaching and research home for most of his career. The inauguration event, “(un)Discovered Worlds,” featured a day of public talks given by leading scientists and renowned astronomy pioneers.

The Carl Sagan Institute (founded in 2014 as the Institute for Pale Blue Dots) is embedded in a rich environment of interdisciplinary cooperation at Cornell, bringing together astrophysicists, engineers, geologists, biologists and Earth scientists to find the fingerprints of life in the cosmos. The institute’s team members have wide-ranging backgrounds in both science and engineering. Their research focuses on other planets as well as our own; their collective experience includes numerous space missions, including Viking, Voyager, Rosetta and Cassini.

Emmy and Peabody award-winning writer/producer Ann Druyan announced the institute’s name at the May 9 inauguration event. Sagan and Druyan collaborated on numerous books, articles and speeches during their 20 years together; they co-created and produced the motion picture “Contact.” Druyan was co-writer of the original “Cosmos” TV series starring her late husband, as well as lead executive producer, co-writer and a director of “Cosmos: A Spacetime Odyssey.” She served as creative director of NASA’s legendary Voyager Interstellar Message Project, which Sagan chaired, and as program director on humanity’s first two solar sailing spacecraft missions.

Carl Sagan in 2005. Credit: Cornell University Photography

Carl Sagan in 2005. Credit: Cornell University Photography

“There’s a meta quality to this day,” Druyan said. “Honoring Carl by empowering interdisciplinary scientists to search for the answers to his most passionate scientific questioning, seeking to share that understanding with the public, and finding in that knowledge applications to life-threatening dangers here on Earth – that’s a multi-leveled and highly accurate reflection of who Carl was. That this new institute’s home is where he chose to work and live adds yet another meaningful dimension. From the moment I first met astrophysicist Lisa Kaltenegger, the Carl Sagan Institute’s founding director, I recognized one of Carl’s kindred. It’s thanks to her that his legacy is being given such vibrant expression here at Cornell.”

“We are grateful to have the opportunity to honor Professor Sagan’s legacy at Cornell through this new institute,” said Cornell President David Skorton.

“Cornellians have been searching the sky with telescopes for generations, and it’s exciting to see that same passion and promise reflected in the scientists now searching the universe for exoplanets and extraterrestrial life.”

“Are we alone in the universe? And how different or similar are other worlds to our own? These questions fascinated such inspirational pioneers as Carl Sagan, and for the first time in history, we have the technology to find out,” said Kaltenegger. “We’re truly standing on the shoulders of giants, especially here at Cornell, where Carl Sagan was looking at our own ‘pale blue dot’ to identify signs of life we can look for on other worlds.”

The institute hosts the newly created Color Catalog, a database containing color signatures of more than 100 different biota that for the first time give scientists a way to identify a wide range of signatures of life on other worlds. Researchers at the institute also have identified new targets in the search for potentially life-bearing worlds and are investigating the effects of UV radiation on their surfaces in connection with the origins of life, among a wide range of other topics.

This important research not only looks for other worlds like ours, it helps us understand and safeguard our own pale blue dot better,” said Kaltenegger. “Finding other, older worlds can also give us a first glimpse into our potential future. This is an exciting time, with the next generation of telescopes that can detect such worlds soon to be available, and the interdisciplinary team here at the Carl Sagan Institute exploring the essential questions in this search, together.”

For more information, visit instituteforpalebluedots.com.