Organisms cultured from the samples collected from Lake Whillans. Credit: LSU/Christner et. al. (2014)

Subglacial Life in Antarctica

Organisms cultured from the samples collected from Lake Whillans. Credit: LSU/Christner et. al. (2014)

Organisms cultured from the samples collected from Lake Whillans. Credit: LSU/Christner et. al. (2014)

Scientists have proven that microbial ecosystems exist in a subglacial lake in Antarctica. The researchers cultured microorganisms from samples of water and sediment that were collected from Lake Whillans, which lies 800 meters beneath the surface of the West Antarctic ice sheet.

Antarctica is thought to have more than 400 subglacial lakes and streams, potentially providing an extensive habitat for organisms like those found in Lake Whillans. The new study provides astrobiologists with a glimpse into these unique habitats for life, which have remained largely unexplored until now.

An image from the Whillans Ice Stream Subglacial Access Research Drilling project (WISSARD) borehole camera is shown. Credit: The Whillans Ice Stream Subglacial Access Research Drilling Project

An image from the Whillans Ice Stream Subglacial Access Research Drilling project (WISSARD) borehole camera is shown. Credit: The Whillans Ice Stream Subglacial Access Research Drilling Project

Astrobiologists have long been interested in Antarctica’s subglacial lakes as analog environments for icy worlds like Jupiter’s moon Europa. Beneath the icy surface of Europa lies a liquid water ocean, and studying ice covered lakes on Earth could provide clues about the potential for life beyond our planet.

Many of Antarctica’s lakes are thought to support habitats that are almost completely isolated from the surface environment. Organisms living in these lakes would have developed unique adaptations in order to survive in the dark, cold waters while being cut off from the rest of Earth’s biosphere for long periods of time. The evolution of these  ecosystems could serve as an example for how life might adapt to similarly isolated environments on other worlds in the Solar System.

Samples were collected during the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project. The article, “A microbial ecosystem beneath the West Antarctic ice sheet,” was published in the journal Nature under lead author Brent C. Christner.

 

Support for the project was provided by the National Science Foundation (NSF), NASA’s Cryospheric Sciences Program, the National Oceanic and Atmospheric Administration (NOAA), and the private Gordon and Betty Moore Foundation.

To read more about the research, including other results from the WISSARD project, visit the journal Nature at: http://www.nature.com/news/lakes-under-the-ice-antarctica-s-secret-garden-1.15729

The Voyager 2 spacecraft flew by Triton, a moon of Neptune, in the summer of 1989. Paul Schenk, a scientist at the Lunar and Planetary Institute in Houston, used Voyager data to construct the best-ever global color map of Triton. This map has a resolution of 1,970 feet (600 meters) per pixel. Image Credit: NASA/JPL-Caltech/Lunar & Planetary Institute

Triton: Oceans of the Outer Solar System

The Voyager 2 spacecraft flew by Triton, a moon of Neptune, in the summer of 1989. Paul Schenk, a scientist at the Lunar and Planetary Institute in Houston, used Voyager data to construct the best-ever global color map of Triton. This map has a resolution of 1,970 feet (600 meters) per pixel. Image Credit: NASA/JPL-Caltech/Lunar & Planetary Institute

The Voyager 2 spacecraft flew by Triton, a moon of Neptune, in the summer of 1989. Paul Schenk, a scientist at the Lunar and Planetary Institute in Houston, used Voyager data to construct the best-ever global color map of Triton. This map has a resolution of 1,970 feet (600 meters) per pixel. Image Credit: NASA/JPL-Caltech/Lunar & Planetary Institute

NASA recently released a new and highly detailed map of Neptune’s moon Triton. The map has a resolution of 600 meters per pixel and was created using ‘restored’ data from the Voyager 2 spacecraft’s 1989 encounter with Neptune. It is a beautiful example of the longevity of good data, and the value of using new technology and techniques to re-analyze archived data from past missions

The map of Triton provides a wealth of new information for comparative planetology and planetary geology studies, and scientists will use it to better-understand the diverse nature of solid bodies in the Solar System. But Triton also has some interesting things to teach astrobiologists.

Computer-generated montage of Triton and Neptune, using images from the Voyager 2 flyby. Image Credit: NASA/JPL/USGS

Computer-generated montage of Triton and Neptune, using images from the Voyager 2 flyby. Image Credit: NASA/JPL/USGS

When studying life’s potential beyond Earth, Triton doesn’t immediately spring to mind as a promising location for biology. Earth, the only inhabited planet yet known, is roughly 149,600,000 kilometers away from the Sun and sits within our star’s habitable zone. In this region of space, the planet receives just the right amount of energy for liquid water to persist at the surface. Triton (and its host planet Neptune) are more than 4,503,443,600 kilometers away from the Sun’s warmth, orbiting in the dark depths of the outer Solar System.

But a star’s habitable zone is not the only measure of habitability in a solar system. With data from missions like Voyager, astrobiologists have identified cold, dark moons of giant planets that may still have the potential to support life.

In a 2012 paper in the journal Icarus, Jodi Gaeman and colleagues outlined a possible scenario for a subsurface ocean on Triton. They found that after Triton was drawn into Neptune’s orbit, the moon could have experienced tidal heating in a way similar to Jupiter’s moon Europa. Like Europa, energy from this heating could have melted areas of Triton’s subsurface, creating an ocean of liquid water beneath the moon’s icy shell.

The researchers determined that Triton could have a thin layer of liquid water rich in ammonia (NH3) today – but only if Triton started its life as a Neptunain moon with a highly eccentric orbit that slowly circularized over time.

An illustration of Voyager 2 setting its sights on Neptune and Triton in 1989 from Issue 4 of the Astrobiology Program's graphic history of astrobiology. Available at: http://www.astrobio.net/nasa-astrobio-graphic-novels/ Credit: NASA Astrobiology Program, Artwork by Aaron L. Gronstal

An illustration of Voyager 2 setting its sights on Neptune and Triton in 1989 from Issue 4 of the Astrobiology Program’s graphic history of astrobiology. Available at: http://www.astrobio.net/nasa-astrobio-graphic-novels/ Credit: NASA Astrobiology Program, Artwork by Aaron L. Gronstal

Astrobiology Magazine asked Dr. Saswata Hier-Majumder, co-author of the 2012 study and Senior Lecturer in the Department of Earth Sciences at Royal Holloway University of London, if the new map of Triton could provide further clues about the moon’s subsurface.

“This high resolution map will be helpful in studying, among other geological features on Triton’s surface, the system of ridges in the Cantaloupe terrain and the smooth planes,” said Hier-Majumder. “Both of these features can provide clues regarding the presence of a subsurface ocean, and potential estimates of the thickness of Triton’s crust.”

In the case of Europa, images of the moon’s surface have been essential for identifying features that provide insights into what lies beneath the moon’s ice. The new, detailed map of Triton could  have similar applications. Dr. Hier-Majumder gave an example of the types of features he would look for:

“Given the young age of Triton’s surface (~100 Ma), cryovolcanic features on the surface would imply recent extrusion of fluid from the subsurface ocean. The mechanism by which such extrusions occur, however,  are still not completely clear.”


The Voyager 2 spacecraft flew by Triton, a moon of Neptune, on August 25, 1989. Paul Schenk, a scientist at the Lunar and Planetary Institute in Houston, used Voyager data to construct this video recreating that exciting encounter. Image Credit: NASA/JPL-Caltech/Lunar & Planetary Institute

Untitled

Rosetta: Landing site search narrows

Philae candidate landing sites. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Philae candidate landing sites. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Using detailed information collected by ESA’s Rosetta spacecraft during its first two weeks at Comet 67P/Churyumov-Gerasimenko, five locations have been identified as candidate sites to set down the Philae lander in November – the first time a landing on a comet has ever been attempted.

Before arrival, Comet 67P/Churyumov-Gerasimenko had never been seen close up and so the race to find a suitable landing site for the 100 kg lander could only begin when Rosetta rendezvoused with the comet on 6 August.

The landing is expected to take place in mid-November when the comet is about 450 million km from the Sun, before activity on the comet reaches levels that might jeopardise the safe and accurate deployment of Philae to the comet’s surface, and before surface material is modified by this activity.

The comet is on a 6.5-year orbit around the Sun and today is 522 million km from it. At their closest approach on 13 August 2015, just under a year from now, the comet and Rosetta will be 185 million km from the Sun, meaning an eightfold increase in the light received from the Sun.

While Rosetta and its scientific instruments will watch how the comet evolves as heating by the Sun increases, observing how its coma develops and how the surface changes over time, the lander Philae and its instruments will be tasked with making complementary in situ measurements at the comet’s surface. The lander and orbiter will also work together using the CONSERT experiment to send and detect radio waves through the comet’s interior, in order to characterise its internal structure.

Philae on the comet. Credit: ESA/ATG medialab

Philae on the comet. Credit: ESA/ATG medialab

Choosing the right landing site is a complex process. That site must balance the technical needs of the orbiter and lander during all phases of the separation, descent, and landing, and during operations on the surface with the scientific requirements of the 10 instruments on board Philae.

A key issue is that uncertainties in the navigation of the orbiter close to the comet mean that it is only possible to specify any given landing zone in terms of an ellipse – covering up to one square kilometre – within which Philae might land.

For each possible zone, important questions must be asked: Will the lander be able to maintain regular communications with Rosetta? How common are surface hazards such as large boulders, deep crevasses or steep slopes? Is there sufficient illumination for scientific operations and enough sunlight to recharge the lander’s batteries beyond its initial 64-hour lifetime, while not so much as to cause overheating?

To answer these questions, data acquired by Rosetta from about 100 km distance have been used, including high-resolution images of the surface, measurements of the comet’s surface temperature, and the pressure and density of gas around the nucleus. In addition, measurements of the comet’s orientation with respect to the Sun, its rotation, mass and surface gravity have been determined. All of these factors influence the technical feasibility of landing at any specific location on the comet.

This weekend, the Landing Site Selection Group (comprising engineers and scientists from Philae’s Science, Operations and Navigation Centre at CNES, the Lander Control Centre at DLR, scientists representing the Philae Lander instruments and ESA’s Rosetta team) met at CNES, Toulouse, to consider the available data and determine a shortlist of five candidate sites.

“This is the first time landing sites on a comet have been considered,” says Stephan Ulamec, Lander Manager at DLR.

“Based on the particular shape and the global topography of Comet 67P/ Churyumov-Gerasimenko, it is probably no surprise that many locations had to be ruled out. The candidate sites that we want to follow up for further analysis are thought to be technically feasible on the basis of a preliminary analysis of flight dynamics and other key issues – for example they all provide at least six hours of daylight per comet rotation and offer some flat terrain. Of course, every site has the potential for unique scientific discoveries.”

“The comet is very different to anything we’ve seen before, and exhibits spectacular features still to be understood,” says Jean-Pierre Bibring, a lead lander scientist and principal investigator of the CIVA instrument.

“The five chosen sites offer us the best chance to land and study the composition, internal structure and activity of the comet with the ten lander experiments.”

The sites were assigned a letter from an original pre-selection of 10 possible sites, which does not signify any ranking. Three sites (B, I and J) are located on the smaller of the two lobes of the comet and two sites (A and C) are located on the larger lobe.

Summary of the five candidate sites

Rosetta_OSIRIS_NAC_comet_67P_20140816_SiteA_625

Candidate landing site A

Site A is an interesting region located on the larger lobe, but with a good view of the smaller lobe. The terrain between the two lobes is likely the source of some outgassing. Higher-resolution imaging is needed to study potential surface hazards such as small depressions and slopes, while the illumination conditions also need to be considered further.

Candidate landing site B

Candidate landing site B

Site B, within the crater-like structure on the smaller lobe, has a flat terrain and is thus considered relatively safe for landing, but illumination conditions may pose a problem when considering the longer-term science planning of Philae. Higher-resolution imaging will be needed to assess the boulder hazards in more detail. In addition, the boulders are also thought to represent more recently processed material and therefore this site may not be as pristine as some of the others.

Candidate landing site C

Candidate landing site C

Site C is located on the larger lobe and hosts a range of surface features including some brighter material, depressions, cliffs, hills and smooth plains, but higher-resolution imaging is needed to assess the risk of some of these features. It is also well illuminated, which would benefit the long-term scientific planning for Philae.

Candidate landing site I

Candidate landing site I

Site I is a relatively flat area on the smaller lobe that may contain some fresh material, but higher-resolution imaging is needed to assess the extent of the rough terrain. The illumination conditions should also allow for longer-term science planning.

Candidate landing site J

Candidate landing site J

Site J is similar to site I, and also on the smaller lobe, offering interesting surface features and good illumination. It offers advantages for the CONSERT experiment compared with Site I, but higher-resolution imaging is needed to determine the details of the terrain, which shows some boulders and terracing.

The next step is a comprehensive analysis of each of the candidate sites, to determine possible orbital and operational strategies that could be used for Rosetta to deliver the lander to any of them. At the same time, Rosetta will move to within 50 km of the comet, allowing a more detailed study of the proposed landing sites.

By 14 September, the five candidate sites will have been assessed and ranked, leading to the selection of a primary landing site, for which a fully detailed strategy for the landing operations will be developed, along with a backup.

During this phase, Rosetta will move to within 20–30 km of the comet, allowing even more detailed maps of the boulder distributions at the primary and backup landing sites to be made. This information could be important in deciding whether to switch from primary to backup.

The Rosetta mission team are working towards a nominal landing date of 11 November, but confirmation of the primary landing site and the date will likely only come on 12 October. This will be followed by a formal Go/No Go from ESA, in agreement with the lander team, after a comprehensive readiness review on 14 October.

“The process of selecting a landing site is extremely complex and dynamic; as we get closer to the comet, we will see more and more details, which will influence the final decision on where and when we can land,” says Fred Jansen, ESA Rosetta mission manager.

“We had to complete our preliminary analysis on candidate sites very quickly after arriving at the comet, and now we have just a few more weeks to determine the primary site. The clock is ticking and we now have to meet the challenge to pick the best possible landing site.”

Untitled

NASA’s New Horizons Spacecraft Crosses Neptune Orbit En Route to Historic Pluto Encounter

During August 16 and 17, 1989, the Voyager 2 narrow-angle camera was used to photograph Neptune almost continuously, recording approximately two and one-half rotations of the planet. Image credit: NASA/JPL

During August 16 and 17, 1989, the Voyager 2 narrow-angle camera was used to photograph Neptune almost continuously, recording approximately two and one-half rotations of the planet. Image credit: NASA/JPL

NASA’s Pluto-bound New Horizons spacecraft has traversed the orbit of Neptune. This is its last major crossing en route to becoming the first probe to make a close encounter with distant Pluto on July 14, 2015.

The sophisticated piano-sized spacecraft, which launched in January 2006, reached Neptune’s orbit — nearly 2.75 billion miles from Earth — in a record eight years and eight months. New Horizons’ milestone matches precisely the 25th anniversary of the historic encounter of NASA’s Voyager 2 spacecraft with Neptune on Aug. 25, 1989.

“It’s a cosmic coincidence that connects one of NASA’s iconic past outer solar system explorers, with our next outer solar system explorer,” said Jim Green, director of NASA’s Planetary Science Division, NASA Headquarters in Washington. “Exactly 25 years ago at Neptune, Voyager 2 delivered our ‘first’ look at an unexplored planet. Now it will be New Horizons’ turn to reveal the unexplored Pluto and its moons in stunning detail next summer on its way into the vast outer reaches of the solar system.”

New Horizons now is about 2.48 billion miles from Neptune — nearly 27 times the distance between the Earth and our sun — as it crosses the giant planet’s orbit at 10:04 p.m. EDT Monday. Although the spacecraft will be much farther from the planet than Voyager 2’s closest approach, New Horizons’ telescopic camera was able to obtain several long-distance “approach” shots of Neptune on July 10.

NASA's Pluto-bound New Horizons spacecraft captured this view of the giant planet Neptune and its large moon Triton on July 10, 2014, from a distance of about 2.45 billion miles (3.96 billion kilometers) - more than 26 times the distance between the Earth and sun. Image Credit:  NASA/Johns Hopkins University Applied Physics Laboratory

NASA’s Pluto-bound New Horizons spacecraft captured this view of the giant planet Neptune and its large moon Triton on July 10, 2014, from a distance of about 2.45 billion miles (3.96 billion kilometers) – more than 26 times the distance between the Earth and sun. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory

NASA’s Voyager 1 and 2 explored the entire middle zone of the solar system where the giant planets orbit,” said Alan Stern, New Horizons principal investigator at the Southwest Research Institute in Boulder, Colorado. “Now we stand on Voyager’s broad shoulders to explore the even more distant and mysterious Pluto system.”

Several senior members of the New Horizons science team were young members of Voyager’s science team in 1989. Many remember how Voyager 2’s approach images of Neptune and its planet-sized moon Triton fueled anticipation of the discoveries to come. They share a similar, growing excitement as New Horizons begins its approach to Pluto.

“The feeling 25 years ago was that this was really cool, because we’re going to see Neptune and Triton up-close for the first time,” said Ralph McNutt of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, who leads the New Horizons energetic-particle investigation and served on the Voyager plasma-analysis team. “The same is happening for New Horizons. Even this summer, when we’re still a year out and our cameras can only spot Pluto and its largest moon as dots, we know we’re in for something incredible ahead.”

Voyager’s visit to the Neptune system revealed previously unseen features of Neptune itself, such as the Great Dark Spot, a massive storm similar to, but not as long-lived, as Jupiter’s Great Red Spot. Voyager also, for the first time, captured clear images of the ice giant’s ring system, too faint to be clearly viewed from Earth. “There were surprises at Neptune and there were surprises at Triton,” said Ed Stone, Voyager’s long-standing project scientist from the California Institute of Technology in Pasadena. “I’m sure that will continue at Pluto.”

Many researchers feel the 1989 Neptune flyby — Voyager’s final planetary encounter — might have offered a preview of what’s to come next summer. Scientists suggest that Triton, with its icy surface, bright poles, varied terrain and cryovolcanoes, is a Pluto-like object that Neptune pulled into orbit. Scientists recently restored Voyager’s footage of Triton and used it to construct the best global color map of that strange moon yet — further whetting appetites for a Pluto close-up.

“There is a lot of speculation over whether Pluto will look like Triton, and how well they’ll match up,” McNutt said. “That’s the great thing about first-time encounters like this — we don’t know exactly what we’ll see, but we know from decades of experience in first-time exploration of new planets that we will be very surprised.”

Similar to Voyager 1 and 2′s historic observations, New Horizons also is on a path toward potential discoveries in the Kuiper Belt, which is a disc-shaped region of icy objects past the orbit of Neptune, and other unexplored realms of the outer solar system and beyond.

“No country except the United States has the demonstrated capability to explore so far away,” said Stern. “The U.S. has led the exploration of the planets and space to a degree no other nation has, and continues to do so with New Horizons. We’re incredibly proud that New Horizons represents the nation again as NASA breaks records with its newest, farthest and very capable planetary exploration spacecraft.”

Voyager 1 and 2 were launched 16 days apart in 1977, and one of the spacecraft visited Jupiter, Saturn, Uranus and Neptune. Voyager 1 now is the most distant human-made object, about 12 billion miles (19 billion kilometers) away from the sun. In 2012, it became the first human-made object to venture into interstellar space. Voyager 2, the longest continuously operated spacecraft, is about 9 billion miles (15 billion kilometers) away from our sun.

New Horizons is the first mission in NASA’s New Frontiers program. APL manages the mission for NASA’s Science Mission Directorate at NASA Headquarters. APL also built and operates the New Horizons spacecraft.

The Voyager spacecraft were built and continue to be operated by NASA’s Jet Propulsion Laboratory in Pasadena, California. The Voyager missions are part of NASA’s Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate.

To view the Neptune images taken by New Horizons and learn more about the mission, visit:

http://www.nasa.gov/newhorizons

For more information about the Voyager spacecraft, visit:

http://www.nasa.gov/voyager

Untitled

Viruses take down massive algal blooms, with big implications for climate

Algae Bloom in Lake Erie. Credit: NASA Earth Observatory

Algae Bloom in Lake Erie. Credit: NASA Earth Observatory

Algae might seem easy to ignore, but they are the ultimate source of all organic matter that marine animals depend upon. Humans are increasingly dependent on algae, too, to suck up climate-warming carbon dioxide from the atmosphere and sink it to the bottom of the ocean.

Now, by using a combination of satellite imagery and laboratory experiments, researchers have evidence showing that viruses infecting those algae are driving the life-and-death dynamics of the algae’s blooms, even when all else stays essentially the same, and this has important implications for our climate.

According to results reported in the Cell Press journal Current Biology on August 21, a single North Atlantic algal bloom, about 30 kilometers in radius, converted 24,000 tons of carbon dioxide from the atmosphere into organic carbon via a process known as carbon fixation. Two-thirds of that carbon turned over within a week as that bloom grew at a very rapid rate and then quickly met its demise. A closer look at those algae revealed high levels of specific viruses infecting their cells.

To put it in perspective, Assaf Vardi of the Weizmann Institute of Science in Israel says that this patch of ocean fixes about as much carbon as an equivalent patch of rainforest and then almost immediately turns much of it over.

This is a location map.  (B) Map of surface chlorophyll from June 22, 2012 (day 174), emphasizing the phytoplankton patch as a distinct area of high chlorophyll concentration. Credit: Current Biology, Lehahn et al.

This is a location map. (B) Map of surface chlorophyll from June 22, 2012 (day 174), emphasizing the phytoplankton patch as a distinct area of high chlorophyll concentration. Credit: Current Biology, Lehahn et al.

“This is, of course, only one patch out of numerous co-occurring patches in other parts of the Atlantic Ocean,” adds Ilan Koren, also of the Weizmann Institute, not to mention those algal blooms that appear in other seasons and ecosystems.

“While the impact that viruses have on the entire ecosystem was previously estimated to be very large, we provide the first approach to quantify their immense impact on open ocean blooms.”

Important questions remain about the ultimate fate of all that carbon taken in by algal blooms, the researchers say. Much of it is probably recycled back to the atmosphere by bacteria. But it’s also possible that the virus-infected algae release sticky sugars and lipids, leading their cells and the carbon within them to sink faster to the ocean floor.

“If the latter scenario is true, it will have a profound impact [on] the efficiency of carbon dioxide ‘pumping’ from the atmosphere to the deep ocean,” Vardi says. “This carbon will then have a better chance [of being] buried in the ocean sediment.”

The findings will improve models that predict the future of algal blooms and their impact on climate. They also serve as a reminder that sometimes it really is the little things that matter.

“These interactions begin when one virus infects one cell, but they end up causing the collapse of massive blooms that span thousands of kilometers,” Koren says. “These life-and-death interactions on the micro scale have huge importance on the large scale and vice versa.”

Lakes are visible on the surface of Titan, Saturn's moon. Credit: Cassini Radar Mapper, JPL, USGS, ESA, NASA

How Titan’s Haze Help Us Understand Life’s Origins

Saturn's moon Titan appears as a hazy ball from a distance. Credit: NASA/JPL-Caltech/Space Science Institute

Saturn’s moon Titan appears as a hazy ball from a distance. Credit: NASA/JPL-Caltech/Space Science Institute

Where did life on Earth come from? There are several theories as to what might have happened. Maybe comets came bearing organic material, or life was transported from another planet such as Mars, or something happened in the chemistry of our planet that made life possible.

Luckily for researchers, there is a possible laboratory in our solar system to help us better understand the conditions on Earth before life arose — a situation sometimes referred to as a “prebiotic” environment. That location is Titan, the largest moon of Saturn.

The moon has fascinated researchers for decades, particularly after NASA’s Voyager 1 and Voyager 2 spacecraft flew by Saturn in the 1980s. The missions revealed a moon completely socked in with haze, which is a different experience to those used to gazing at Earth’s airless, cratered moon.

A closer look came in 2004, when the Cassini-Huygens mission arrived to study the system. Since then, the spacecraft has done hundreds of flybys of Titan and peered at its surface by penetrating the clouds with radar. The European Space Agency’s Huygens lander also made a soft landing on the moon in 2005.

One of the big research questions is the composition of the haze. A new study is trying to recreate substances in the atmosphere called tholins, organic aerosols which are produced when radiation bakes the nitrogen and methane-rich atmosphere. In some cases, organics are considered precursors to life.

“The study of organic chemistry on Titan’s surface would extend our understanding of the diversity of prebiotic chemistry, and perhaps life’s origin on Earth,” said Dr. Chao He, a chemist at the University of Houston (now moved to Johns Hopkins University) who led the study.

How tholins form in the upper atmosphere of Saturn's moon Titan. Credit: Southwest Research Institute

How tholins form in the upper atmosphere of Saturn’s moon Titan. Credit: Southwest Research Institute

The results were publishedas “Solubility and stability investigation of Titan aerosol analogs: New insight from NMR analysis” in the journal Icarus.

Dissolving tholins

According to He, the study of Titan’s tholins help scientists understand the basic properties of organic materials on Titan. Questions to consider include how they are structured, whether the aerosols can be dissolved in liquid in Titan’s surface or atmosphere, and how stable the organics could be. Titan’s tholins are thought to contain chemical precursors of life, and studying the molecule’s structure helps scientists better understand whether life’s possible precursors have formed on Titan. If they have formed, the solubility study helps to hint where to find them on Titan, and the stability study suggests the most capable detection methods.

The tholins were created by making a mix of methane (5 percent) and nitrogen (95 percent) in a reaction chamber at room temperature. The mixture was exposed to an electrical discharge for 72 hours, which then created a muddy substance — the tholin — on the walls of the vessel. The substances produced had a similar optical appearance to what Cassini observed in Titan’s atmosphere.

Researchers then investigated how well the tholins would dissolve in a solvent. Several solvents were investigated, including polar solvents (methanol, water, dimethyl sulfoxide and acetonitrile) and non-polar solvents (pentane, benzene and cyclohexane). Polar solvents usually have different electrical charges between atoms (such as positive-charged oxygen and negative-charged hydrogen, in water) while non-polar solvents have similar electrical charges between atoms. Generally, polar solvents dissolve polar compounds best and non-polar solvents dissolve non-polar compounds best.

The researchers found that the tholins preferentially dissolves in polar solvents, suggesting little or none of the substance would be dissolved in the lakes or oceans on Titan, which are consist of non-polar ethane/methane. Thus, the tholins should be on the surface of the land or at the bottom of the lakes and oceans, He noted.

“The tholin preferentially dissolves in polar solvents, alsosuggesting the tholins are composed of a large percentage of polar species,” Headded.

Picking future landing sites

The Huygens probe only survived on the surface of Titan for a few hours, but there are proposals out there to do extended missions. One example is a NASA Innovative Advanced Concepts proposal to send a submarine to explore Titan’s lakes. The proposal is at the first stage of investigation and would be decades away to launch, if funding is approved.

An artist's impression of the only spacecraft to land on Titan. Called Huygens, it separated from the Cassini spacecraft in 2005 and lasted on the surface for a few hours. Credit: European Space Agency

An artist’s impression of the only spacecraft to land on Titan. Called Huygens, it separated from the Cassini spacecraft in 2005 and lasted on the surface for a few hours. Credit: European Space Agency

If researchers were looking for tholins with a surface or underwater craft on Titan, He’s study could help narrow down the location. Tholins break down in hot temperatures, but this is not a problem for Titan’s surface, which sees an average surface temperature of -179 degrees Celsius (-290 degrees Fahrenheit). Future landing missions, however, might have to contend with avoiding heating the tholins to look at their structure, and instead should focus on nondestructive instruments and methods to accomplish this, He said. Possible methods of detecting organics could be liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance spectroscopy (NMR). Both methods can provide detailed structural information of organic mixtures nondestructively.

Greater search for life’s origins

In the midst of this analysis, He’s team developed a new method to study the solubility of tholins. They found several nitrogenated organic molecules in Titan tholins.

“Some of them are very important to the prebiotic chemistry and the origin of life,” He said.

While trying to understand what is happening on Titan, He is also interested in learning about the rest of the Solar System.

“My research focuses on the astrobiology on potential environments and objects,” He said. “Titan is an important one. This study helps to understand the basic properties of organics on Titan. It also provides the basis for the development of in situ analysis of methods and instruments for a Titan mission and other outer planet exploration.”

He plans to continue his study of organic chemistry on Titan, and then extend that understanding to other potentially interesting environments for life in the Solar System, such as Mars, Jupiter’s icy moon Europa or Saturn’s moon Enceladus, which has been recorded spouting water-rich plumes into the atmosphere.

Scientists’ understanding of Titan is constantly changing as the Cassini-Huygens mission beams back data from the distant moon. For example, in 2007 scientists discovered that the tholins form at much higher altitudes than previously believed, at greater than 1,000 kilometers (621 miles) as opposed to a few hundred kilometers above the ground.

The results also revealed an unexpected high number of ions (negatively charged atoms) among the clouds of the moon, as well as detecting benzene, an element that is required to put together the tholins.

Called Huygens, it separated from the Cassini spacecraft in 2005 and lasted on the surface for a few hours. Credit: European Space Agency

Called Huygens, it separated from the Cassini spacecraft in 2005 and lasted on the surface for a few hours. Credit: European Space Agency

“The negative ions were a complete surprise,” stated David Young, a scientist at the Southwest Research Institute in Texas, who led the Cassini Plasma Spectrometer (CAPS) investigation. “This suggests they may play an unexpected role in making tholins from carbon-nitrogen precursors.”

A more recent finding revealed that Titan’s atmosphere is likely older than that of Saturn. This suggests that the moon did not arise from the ringed gas giant, but instead was created separately in the gas and dust floating around the young Solar System while the Sun and planets were being formed.

Untitled

Alternate mechanism of species formation picks up support, thanks to a South American ant

A queen ant of the host species Mycocepurus goeldii. Credit: Christian Rabeling/University of Rochester

A queen ant of the host species Mycocepurus goeldii. Credit: Christian Rabeling/University of Rochester

A newly-discovered species of ant supports a controversial theory of species formation. The ant, only found in a single patch of eucalyptus trees on the São Paulo State University campus in Brazil, branched off from its original species while living in the same colony, something thought rare in current models of evolutionary development.

“Most new species come about in geographic isolation,” said Christian Rabeling, assistant professor of biology at the University of Rochester. “We now have evidence that speciation can take place within a single colony.”

The findings by Rabeling and the research team were published today in the journal Current Biology.

In discovering the parasitic Mycocepurus castrator, Rabeling and his colleagues uncovered an example of a still-controversial theory known as sympatric speciation, which occurs when a new species develops while sharing the same geographic area with its parent species, yet reproducing on its own.“While sympatric speciation is more difficult to prove,” said Rabeling, “we believe we are in the process of actually documenting a particular kind of evolution-in-progress.”

New species are formed when its members are no longer able to reproduce with members of the parent species. The commonly-accepted mechanism is called allopatric speciation, in which geographic barriers—such as mountains—separate members of a group, causing them to evolve independently.

“Since Darwin’s Origin of Species, evolutionary biologists have long debated whether two species can evolve from a common ancestor without being geographically isolated from each other,” said Ted Schultz, curator of ants at the Smithsonian’s National Museum of Natural History and co-author of the study. “With this study, we offer a compelling case for sympatric evolution that will open new conversations in the debate about speciation in these ants, social insects and evolutionary biology more generally.”

A queen ant of the parasitic species Mycocepurus castrator. Credit: Christian Rabeling/University of Rochester

A queen ant of the parasitic species Mycocepurus castrator. Credit: Christian Rabeling/University of Rochester

M. castrator is not simply another ant in the colony; it’s a parasite that lives with—and off of—its host, Mycocepurus goeldii. The host is a fungus-growing ant that cultivates fungus for its nutritional value, both for itself and, indirectly, for its parasite, which does not participate in the work of growing the fungus garden.

That led the researchers to study the genetic relationships of all fungus-growing ants in South America, including all five known and six newly discovered species of the genus Mycocepurus, to determine whether the parasite did evolve from its presumed host. They found that the parasitic ants were, indeed, genetically very close to M. goeldii, but not to the other ant species.

They also determined that the parasitic ants were no longer reproductively compatible with the host ants—making them a unique species—and had stopped reproducing with their host a mere 37,000 years ago—a very short period on the evolutionary scale.

A big clue for the research team was found by comparing the ants’ genes, both in the cell’s nucleus as well as in the mitochondria—the energy-producing structures in the cells. Genes are made of units called nucleotides, and Rabeling found that the sequencing of those nucleotides in the mitochondria is beginning to look different from what is found in the host ants, but that the genes in the nucleus still have traces of the relationship between host and parasite, leading him to conclude that M. castrator has begun to evolve away from its host.

Rabeling explained that just comparing some nuclear and mitochondrial genes may not be enough to demonstrate that the parasitic ants are a completely new species. “We are now sequencing the entire mitochondrial and nuclear genomes of these parasitic ants and their host in an effort to confirm speciation and the underlying genetic mechanism.”

The parasitic ants need to exercise discretion because taking advantage of the host species is considered taboo in ant society. Offending ants have been known to be killed by worker mobs. As a result, the parasitic queen of the new species has evolved into a smaller size, making them difficult to distinguish from a host worker.

Host queens and males reproduce in an aerial ceremony, in the wet tropics only during a particular season when it begins to rain. Rabeling found that the parasitic queens and males, needing to be more discreet about their reproductive activities, diverge from the host’s mating pattern. By needing to hide their parasitic identity, M. castrator males and females lost their special adaptations that allowed them to reproduce in flight, and mate inside the host nest, making it impossible for them to sexually interact with their host species.

Untitled

Electric Sparks May Alter Evolution of Lunar Soil

This illustration shows a permanently shadowed region of the moon undergoing subsurface sparking (the "lightning bolts"), which ejects vaporized material (the "clouds") from the surface. Subsurface sparking occurs at a depth of about one millimeter. Image not to scale. Image Credit: Andrew Jordan/UNH

This illustration shows a permanently shadowed region of the moon undergoing subsurface sparking (the “lightning bolts”), which ejects vaporized material (the “clouds”) from the surface. Subsurface sparking occurs at a depth of about one millimeter. Image not to scale. Image Credit: Andrew Jordan/UNH

The moon appears to be a tranquil place, but modeling done by University of New Hampshire (UNH) and NASA scientists suggests that, over the eons, periodic storms of solar energetic particles may have significantly altered the properties of the soil in the moon‘s coldest craters through the process of sparking—a finding that could change our understanding of the evolution of planetary surfaces in the solar system.

The study, published August 8 in the Journal of Geophysical Research-Planets, proposes that high-energy particles from uncommon, large solar storms penetrate the moon’s frigid, polar regions and electrically charge the soil. The charging may create sparking, or electrostatic breakdown, and this “breakdown weathering” process has possibly changed the very nature of the moon’s polar soil, suggesting that permanently shadowed regions, which hold clues to our solar system’s past, may be more active than previously thought.

“Decoding the history recorded within these cold, dark craters requires understanding what processes affect their soil,” said Andrew Jordan of the UNH Institute for the Study of Earth, Oceans, and Space and lead author of the paper. “To that end, we built a computer model to estimate how high-energy particles detected by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument on board NASA’s Lunar Reconnaissance Orbiter (LRO) can create significant electric fields in the top layer of lunar soil.”

The scientists also used data from the Electron, Proton, and Alpha Monitor (EPAM) on the Advanced Composition Explorer. CRaTER, which is led by scientists from UNH, and EPAM both detect high-energy particles, including solar energetic particles (SEPs). SEPs, after being created by solar storms, stream through space and bombard the moon. These particles can buildup electric charges faster than the soil can dissipate them and may cause sparking, particularly in the polar cold of permanently shadowed regions—unique lunar sites as cold as minus 240 degrees Celsius (minus 400 degrees Fahrenheit) that may contain water ice.

“Sparking is a process in which electrons, released from the soil grains by strong electric fields, race through the material so quickly that they vaporize little channels,” said Jordan. Repeated sparking with each large solar storm could gradually grow these channels large enough to fragment the grains, disintegrating the soil into smaller particles of distinct minerals, Jordan and colleagues hypothesize.

The next phase of this research will involve investigating whether other instruments aboard LRO could detect evidence for sparking in lunar soil, as well as improving the model to better understand the process and its consequences.

“If breakdown weathering occurs on the moon, then it has important implications for our understanding of the evolution of planetary surfaces in the solar system, especially in extremely cold regions that are exposed to harsh radiation from space,” said coauthor Timothy Stubbs of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Untitled

Voyager Map Details Neptune’s Strange Moon Triton

The Voyager 2 spacecraft flew by Triton, a moon of Neptune, in the summer of 1989. Image credit: NASA/JPL-Caltech/Lunar & Planetary Institute

The Voyager 2 spacecraft flew by Triton, a moon of Neptune, in the summer of 1989. Image credit: NASA/JPL-Caltech/Lunar & Planetary Institute

NASA’s Voyager 2 spacecraft gave humanity its first glimpse of Neptune and its moon Triton in the summer of 1989. Like an old film, Voyager’s historic footage of Triton has been “restored” and used to construct the best-ever global color map of that strange moon. The map, produced by Paul Schenk, a scientist at the Lunar and Planetary Institute in Houston, has also been used to make a movie recreating that historic Voyager encounter, which took place 25 years ago, on August 25, 1989.

The new Triton map has a resolution of 1,970 feet (600 meters) per pixel. The colors have been enhanced to bring out contrast but are a close approximation to Triton’s natural colors. Voyager’s “eyes” saw in colors slightly different from human eyes, and this map was produced using orange, green and blue filter images.

In 1989, most of the northern hemisphere was in darkness and unseen by Voyager. Because of the speed of Voyager’s visit and the slow rotation of Triton, only one hemisphere was seen clearly at close distance. The rest of the surface was either in darkness or seen as blurry markings.

The production of the new Triton map was inspired by anticipation of NASA’s New Horizons encounter with Pluto, coming up a little under a year from now. Among the improvements on the map are updates to the accuracy of feature locations, sharpening of feature details by removing some of the blurring effects of the camera, and improved color processing.

Triton has a sparsely cratered surface with smooth volcanic plains, mounds and round pits formed by icy lava flows.

Triton has a sparsely cratered surface with smooth volcanic plains, mounds and round pits formed by icy lava flows. Credit: NASA

Although Triton is a moon of a planet and Pluto is a dwarf planet, Triton serves as a preview of sorts for the upcoming Pluto encounter. Although both bodies originated in the outer solar system, Triton was captured by Neptune and has undergone a radically different thermal history than Pluto. Tidal heating has likely melted the interior of Triton, producing the volcanoes, fractures and other geological features that Voyager saw on that bitterly cold, icy surface.

Pluto is unlikely to be a copy of Triton, but some of the same types of features may be present. Triton is slightly larger than Pluto, has a very similar internal density and bulk composition, and has the same low-temperature volatiles frozen on its surface. The surface composition of both bodies includes carbon monoxide, carbon dioxide, methane and nitrogen ices.

Voyager also discovered atmospheric plumes on Triton, making it one of the known active bodies in the outer solar system, along with objects such as Jupiter’s moon Io and Saturn’s moon Enceladus. Scientists will be looking at Pluto next year to see if it will join this list. They will also be looking to see how Pluto and Triton compare and contrast, and how their different histories have shaped the surfaces we see.

Although a fast flyby, New Horizons’ Pluto encounter on July 14, 2015, will not be a replay of Voyager but more of a sequel and a reboot, with a new and more technologically advanced spacecraft and, more importantly, a new cast of characters. Those characters are Pluto and its family of five known moons, all of which will be seen up close for the first time next summer.

Triton may not be a perfect preview of coming attractions, but it serves as a prequel to the cosmic blockbuster expected when New Horizons arrives at Pluto next year.

The new Triton map and movie can be found at:

http://www.lpi.usra.edu/icy_moons/

In another historic milestone for the Voyager mission, Aug. 25 also marks the two-year anniversary of Voyager 1 reaching interstellar space.

ddd

Sunlight controls the fate of carbon released from thawing Arctic permafrost

Headwaters of the Sagavanirktok River, North Slope of the Brooks Range, Arctic Alaska. Image credit: George W. Kling

Headwaters of the Sagavanirktok River, North Slope of the Brooks Range, Arctic Alaska. Image credit: George W. Kling

Just how much Arctic permafrost will thaw in the future and how fast heat-trapping carbon dioxide will be released from those warming soils is a topic of lively debate among climate scientists.

To answer those questions, scientists need to understand the mechanisms that control the conversion of organic soil carbon into carbon dioxide gas. Until now, researchers believed that bacteria were largely responsible.

But in a study scheduled for online publication in Science on Aug. 21, University of Michigan researchers show for the first time that sunlight, not microbial activity, dominates the production of carbon dioxide in Arctic inland waters.

“Our results suggest that sunlight, rather than biological processes, controls the fate of carbon released from thawing permafrost soils into Arctic surface waters,” said aquatic geochemist Rose Cory, first author of the Science paper and an assistant professor in the U-M Department of Earth and Environmental Sciences.

University of Michigan aquatic geochemist Rose M. Cory collects water from the Sagavanirktok River, Arctic Alaska. Image credit: George W. Kling

University of Michigan aquatic geochemist Rose M. Cory collects water from the Sagavanirktok River, Arctic Alaska. Image credit: George W. Kling

Last year, the same team reported in the Proceeding of the National Academy of Sciences that recently exposed carbon from thawed Alaskan permafrost is extremely sensitive to sunlight and can quickly be converted to carbon dioxide. Taken together, the two studies suggest that “we’re likely to see more carbon dioxide released from thawing permafrost than people had previously believed,” Cory said.

“We’re able to say that because we now know that sunlight plays a key role and that carbon released from thawing permafrost is readily converted to carbon dioxide once it’s exposed to sunlight,” she said.

Worldwide, permafrost soils contain twice the amount of carbon that’s in the atmosphere. So thawing permafrost is a special concern for climate modelers trying to predict the timing and extent of future warming due to the ongoing buildup of carbon dioxide and other greenhouse gases.

But soil carbon does not instantly turn into carbon dioxide gas when permafrost thaws. It must be dissolved in water and chemically processed before it gets released into the atmosphere as carbon dioxide. Until now, scientists believed that bacteria were largely responsible for converting dissolved organic carbon into carbon dioxide gas in Arctic streams, lakes and rivers.

he Sagavanirktok River on the North Slope of Arctic Alaska. Image credit: George W. Kling

he Sagavanirktok River on the North Slope of Arctic Alaska. Image credit: George W. Kling

To test that assumption, Cory and her colleagues analyzed water samples collected from 135 lakes and 73 rivers on the North Slope of Alaska over a three-year period. They compared the levels of sunlight-induced carbon processing—also called photodegradation, photochemical oxidation or photochemical processing—to carbon conversion due to bacterial respiration.

They found that photodegradation of carbon exceeded bacterial respiration by up to 19-fold, accounting for 70-to-95 percent of the carbon processed in Arctic lakes and rivers. They determined that photochemical processing of soil carbon accounts for about one-third of all the carbon dioxide released from surface waters in the Arctic.

“Carbon in thawing permafrost soils may have global impacts on climate change, yet controls on its processing and fate have been poorly understood,” said study co-author George Kling, a professor in the U-M Department of Ecology and Evolutionary Biology. “Our study shows that photochemical processing of soil carbon is an important, newly measured component of the Arctic carbon budget.”

In last year’s PNAS paper, Cory and her colleagues reported on places in the Alaskan Arctic where permafrost is melting and is causing the overlying land surface to collapse, forming erosional holes and landslides and exposing long-buried soils.

Spring breakup of ice on the Kuparuk River, Alaska’s North Slope. Image credit: George W. Kling

Spring breakup of ice on the Kuparuk River, Alaska’s North Slope. Image credit: George W. Kling

Sunlight—and especially ultraviolet radiation, the wavelengths that cause sunburn—can degrade organic soil carbon directly to carbon dioxide gas. It can also alter the carbon to make it a better food for bacteria, which respire it to carbon dioxide in much the same way that people respire carbon in food and exhale carbon dioxide as a byproduct.

In PNAS, the team reported that sunlight increases bacterial conversion of exposed soil carbon into carbon dioxide gas by at least 40 percent compared to carbon that remains in the dark.

One reason scientists are so interested in all of this is that the thawing of Arctic permafrost creates the potential for what’s called a positive feedback loop: As the Earth warms due to the human-caused release of heat-trapping gases, frozen soils thaw and release carbon dioxide. The added carbon dioxide accelerates Earth’s warming, which speeds the thawing of Arctic soils and releases even more carbon dioxide.

Understanding how permafrost carbon is converted into carbon dioxide and incorporating photochemical processing into climate models “is critical for predictions of how the Arctic C [carbon] cycle will respond to and perhaps amplify climate change,” the authors of the Science paper conclude.

Untitled

Cause of global warming hiatus found deep in the Atlantic Ocean

Atlantic Ocean. Image credit: Wikipedia

Atlantic Ocean. Image credit: Wikipedia

Following rapid warming in the late 20th century, this century has so far seen surprisingly little increase in the average temperature at the Earth’s surface. At first this was a blip, then a trend, then a puzzle for the climate science community.

More than a dozen theories have now been proposed for the so-called global warming hiatus, ranging from air pollution to volcanoes to sunspots. New research from the University of Washington shows that the heat absent from the surface is plunging deep in the north and south Atlantic Ocean, and is part of a naturally occurring cycle. The study is published Aug. 22 in Science.

Subsurface ocean warming explains why global average air temperatures have flatlined since 1999, despite greenhouse gases trapping more solar heat at the Earth’s surface.

“Every week there’s a new explanation of the hiatus,” said corresponding author Ka-Kit Tung, a UW professor of applied mathematics and adjunct faculty member in atmospheric sciences. “Many of the earlier papers had necessarily focused on symptoms at the surface of the Earth, where we see many different and related phenomena. We looked at observations in the ocean to try to find the underlying cause.”

The results show that a slow-moving current in the Atlantic, which carries heat between the two poles, sped up earlier this century to draw heat down almost a mile (1,500 meters). Most of the previous studies focused on shorter-term variability or particles that could block incoming sunlight, but they could not explain the massive amount of heat missing for more than a decade.

“The finding is a surprise, since the current theories had pointed to the Pacific Ocean as the culprit for hiding heat,” Tung said. “But the data are quite convincing and they show otherwise.”

Tung and co-author Xianyao Chen of the Ocean University of China, who was a UW visiting professor last year, used recent observations of deep-sea temperatures from Argo floats that sample the water down to 6,500 feet (2,000 meters) depth. The data show an increase in heat sinking around 1999, when the rapid warming of the 20th century stopped.

(Top) Global average surface temperatures, where black dots are yearly averages. Two flat periods (hiatus) are separated by rapid warming from 1976-1999. (Middle) Observations of heat content, compared to the average, in the north Atlantic Ocean. (Bottom) Salinity of the seawater in the same part of the Atlantic. Higher salinity is seen to coincide with more ocean heat storage. K. Tung / Univ. of Washington

(Top) Global average surface temperatures, where black dots are yearly averages. Two flat periods (hiatus) are separated by rapid warming from 1976-1999. (Middle) Observations of heat content, compared to the average, in the north Atlantic Ocean. (Bottom) Salinity of the seawater in the same part of the Atlantic. Higher salinity is seen to coincide with more ocean heat storage. K. Tung / Univ. of Washington

“There are recurrent cycles that are salinity-driven that can store heat deep in the Atlantic and Southern oceans,” Tung said. “After 30 years of rapid warming in the warm phase, now it’s time for the cool phase.”

Rapid warming in the last three decades of the 20th century, they found, was roughly half due to global warming and half to the natural Atlantic Ocean cycle that kept more heat near the surface. When observations show the ocean cycle flipped, in about 2000, the current began to draw heat deeper into the ocean, working to counteract human-driven warming.

The cycle starts when saltier, denser water at the surface northern part of the Atlantic, near Iceland, causes the water to sink. This changes the speed of the huge current in the Atlantic Ocean that circulates heat throughout the planet.

“When it’s heavy water on top of light water, it just plunges very fast and takes heat with it,” Tung said. Recent observations at the surface in the North Atlantic show record-high saltiness, Tung said, while at the same time, deeper water in the North Atlantic shows increasing amounts of heat.

The oscillations have a natural switch. During the warm period, faster currents cause more tropical water to travel to the North Atlantic, warming both the surface and the deep water. At the surface this warming melts ice. This slowly makes the surface water there less dense and after a few decades puts the brakes on the circulation, setting off a 30-year cooling phase.

The authors dug up historical data to show that the cooling in the three decades between 1945 to 1975 – which caused people to worry about the start of an Ice Age – was during a cooling phase. (It was thought to have been caused by air pollution.) Earlier records in Central England show the 40- to 70-year cycle goes back centuries, and other records show it has existed for millennia.

Changes in Atlantic Ocean circulation historically meant roughly 30 warmer years followed by 30 cooler years. Now that it is happening on top of global warming, however, the trend looks more like a staircase.

This explanation implies that the current slowdown in global warming could last for another decade, or longer, and then rapid warming will return. But Tung emphasizes it’s hard to predict what will happen next.

A pool of freshwater from melting ice now sitting in the Arctic Ocean, for example, could overflow into the North Atlantic to upset the cycle.

“We are not talking about a normal situation because there are so many other things happening due to climate change,” Tung said.

Untitled

U.S. expedition finds life under Antarctic ice

The bottom of subglacial Lake Whillans. Credit: Alberto Behar, JPL/ASU

The bottom of subglacial Lake Whillans. Credit: Alberto Behar, JPL/ASU

The first breakthrough paper to come out of a massive U.S. expedition to one of Earth’s final frontiers shows that there’s life and an active ecosystem one-half mile below the surface of the West Antarctic Ice Sheet, specifically in a lake that hasn’t seen sunlight or felt a breath of wind for millions of years.

The life is in the form of microorganisms that live beneath the enormous Antarctic ice sheet and convert ammonium and methane into the energy required for growth. Many of the microbes are single-celled organisms known as Archaea, said Montana State University professor John Priscu, the chief scientist of the U.S. project called WISSARD that sampled the sub-ice environment. He is also co-author of the MSU author-dominated paper in the Aug. 21 issue of Nature, an international weekly journal for all fields of science and technology.

“We were able to prove unequivocally to the world that Antarctica is not a dead continent,” Priscu said, adding that data in the Nature paper is the first direct evidence that life is present in the subglacial environment beneath the Antarctic ice sheet.

The microorganisms that came out of Subglacial Lake Whillans were “incredibly diverse,” and the microbial cells came in a variety of shapes. The yellow arrow points to a rod-shaped cell as seen through a scanning electron microscope. (Image courtesy of WISSARD).

The microorganisms that came out of Subglacial Lake Whillans were “incredibly diverse,” and the microbial cells came in a variety of shapes. The yellow arrow points to a rod-shaped cell as seen through a scanning electron microscope. (Image courtesy of WISSARD).

Lead author Brent Christner said, “It’s the first definitive evidence that there’s not only life, but active ecosystems underneath the Antarctic ice sheet, something that we have been guessing about for decades. With this paper, we pound the table and say, ‘Yes, we were right.’”

Priscu said he wasn’t entirely surprised that the team found life after drilling through half a mile of ice to reach Subglacial Lake Whillans in January 2013. An internationally renowned polar biologist, Priscu researches both the South and North Poles. This fall will be his 30th field season in Antarctica, and he has long predicted the discovery.

More than a decade ago, he published two manuscripts in the journal Science describing for the first time that microbial life can thrive in and under Antarctic ice. Five years ago, he published a manuscript where he predicted that the Antarctic subglacial environment would be the planet’s largest wetland, one not dominated by the red-winged blackbirds and cattails of typical wetland regions in North America, but by microorganisms that mine minerals in rocks at subzero temperatures to obtain the energy that fuels their growth.

Following more than a decade of traveling the world presenting lectures describing what may lie beneath Antarctic ice, Priscu was instrumental in convincing U.S. national funding agencies that this research would transform the way we view the fifth largest continent on the planet.

Although he was not really surprised about the discovery, Priscu said he was excited by some of the details of the Antarctic find, particularly how the microbes function without sunlight at subzero temperatures and the fact that evidence from DNA sequencing revealed that the dominant organisms are archaea. Archaea is one of three domains of life, with the others being Bacteria and Eukaryote.

Montana State University graduate student Alex Michaud, left, and Brent Christner, associate professor of biological sciences at Lousianan State University, retrieve the first water sample from Subglacial Lake Whillans in January 2013 in West Antarctica. (Image courtesy of Reed Scherer).

Montana State University graduate student Alex Michaud, left, and Brent Christner, associate professor of biological sciences at Lousianan State University, retrieve the first water sample from Subglacial Lake Whillans in January 2013 in West Antarctica. (Image courtesy of Reed Scherer).

Many of the subglacial archaea use the energy in the chemical bonds of ammonium to fix carbon dioxide and drive other metabolic processes. Another group of microorganisms uses the energy and carbon in methane to make a living.

According to Priscu, the source of the ammonium and methane is most likely from the breakdown of organic matter that was deposited in the area hundreds of thousands of years ago when Antarctica was warmer and the sea inundated West Antarctica. He also noted that, as Antarctica continues to warm, vast amounts of methane, a potent greenhouse gas, will be liberated into the atmosphere enhancing climate warming.

The U.S. team also proved that the microorganisms originated in Lake Whillans and weren’t introduced by contaminated equipment, Priscu said. Skeptics of his previous studies of Antarctic ice have suggested that his group didn’t actually discover microorganisms, but recovered microbes they brought in themselves.

“We went to great extremes to ensure that we did not contaminate one of the most pristine environments on our planet while at the same time ensuring that our samples were of the highest integrity,” Priscu said.

Extensive tests were conducted at MSU two years ago on WISSARD’s borehole decontamination system to ensure that it worked, and Priscu led a publication in an international journal presenting results of these tests.

This decontamination system was mated to a one-of-a-kind hot water drill that was used to melt a borehole through the ice sheet, which provided a conduit to the subglacial environment for sampling.

Every day in Antarctica, he would tell his team to keep it simple, Priscu said. To prove that an ecosystem existed below the West Antarctic Ice Sheet, he wanted at least three lines of evidence. They had to see microorganisms under the microscope that came from Lake Whillans and not contaminated equipment. They then had to show that the microorganisms were alive and growing. They had to be identifiable by their DNA.

This aerial photo shows the drill and camp site for a massive U.S. expedition to discover an active ecosystem under the West Antarctic Ice Sheet. (Image courtesy of WISSARD).

This aerial photo shows the drill and camp site for a massive U.S. expedition to discover an active ecosystem under the West Antarctic Ice Sheet. (Image courtesy of WISSARD).

When the team found those things, he knew they had succeeded, Priscu said.

The Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project officially began in 2009 with a $10 million grant from the National Science Foundation. Now involving 13 principal investigators at eight U.S. institutions, the researchers drilled down to Subglacial Lake Whillans in January 2013. The microorganisms they discovered are still being analyzed at MSU and other collaborating institutions.

Christner said species are hard to determine in microbiology, but “We are looking at a water column that probably has about 4,000 things we call species. It’s incredibly diverse.”

Planning to drill again this austral summer in a new Antarctic location, Priscu said WISSARD was the first large-scale multidisciplinary effort to directly examine the biology of an Antarctic subglacial environment. The Antarctic Ice Sheet covers an area 1 ½ times the size of the United States and contains 70 percent of Earth’s freshwater, and any significant melting can drastically increase sea level.

Lake Whillans, one of more than 200 known lakes beneath the Antarctic Ice Sheet and the primary lake in the WISSARD study, fills and drains about every three years. The river that drains Lake Whillans flows under the Ross Ice Shelf, which is the size of France, and feeds the Southern Ocean, where it can provide nutrients for life and influence water circulation patterns.

The opportunity to explore the world under the West Antarctic Ice Sheet is an unparalleled opportunity for the U.S. team, as well as for several MSU-affiliated researchers who are part of that team and wrote or co-authored the Nature paper, Priscu said.

Christner, for one, was a postdoctoral researcher with Priscu and Mark Skidmore at MSU from 2002 through 2006. He is now associate professor of biological sciences at Louisiana State University. Jill Mikucki, now an assistant professor at the University of Tennessee in Knoxville, was one of Priscu’s doctoral students. Skidmore is a glacial geochemist in MSU’s Department of Earth Sciences. Andrew Mitchell, now at Aberystwyth University in the United Kingdom, was a postdoctoral researcher with MSU’s Center for Biofilm Engineering. Alex Michaud and Trista Vick-Majors are currently earning their doctorates in Priscu’s research group at MSU. Other MSU people on the team were Education and Outreach Coordinator Susan Kelly and Project Manager John Sherve.

Montana State University professor and polar ecologist John Priscu is the chief scientist for a U.S. project called WISSARD that discovered an active ecosystem one-half mile below the surface of the West Antarctic Ice Sheet. (MSU photo by Kelly Gorham).

Montana State University professor and polar ecologist John Priscu is the chief scientist for a U.S. project called WISSARD that discovered an active ecosystem one-half mile below the surface of the West Antarctic Ice Sheet. (MSU photo by Kelly Gorham).

The fact that MSU was so involved reflects the fact that it is pioneering a new field of science, Priscu said. MSU is the common ancestor of many scientists who study life in and under ice.

“I always tell my students when they come into the lab that ‘We are inventing this field of science. It’s working on life in ice and under ice. This field has never existed before. We thought it up. You are pioneers,’” Priscu said.

Appreciative of the opportunity to participate in WISSARD, Vick-Majors said she saw bacteria under the microscope within an hour after the first sample of water was pulled out of Subglacial Lake Whillans. Within days, she saw proof that the bacteria were active.

“It was very exciting. It will be hard to top,” she said.

She added that, “If you want to do microbial ecology in Antarctic subglacial environments, John is probably the person you want to work with. I feel very lucky to have gotten the opportunity.”

Agreeing, Michaud said, “Some of the graduate students joke, ‘How do we top this?’ We can’t.”

But the students can build on their WISSARD experience and gain a deeper understanding of Subglacial Lake Whillans and other subglacial habitats, he said. It’s not about going out and finding more novel habitats.

Christner said the team that wrote the paper in Nature is the dream team of polar biology. Besides the MSU-affiliated scientists, the co-authors include Amanda Achberger, a graduate student at Louisiana State University; Carlo Barbante, a geochemist at the University of Venice in Italy; Sasha Carter, a postdoctoral researcher at the University of California in San Diego; and Knut Christianson a postdoctoral researcher from St. Olaf College in Minnesota and New York University.

“I hope this exciting discovery will touch the lives (both young and old) of people throughout the world and inspire the next generation of polar scientists,” Priscu said.

Untitled

Ancient Earth, Alien Earths

Follow Johnny Bontemps on Twitter

Panelists discuss how research on early Earth could help guide our search for habitable planets orbiting other stars. Photo Credit: (NASA/Aubrey Gemignani)

Panelists of at the event “Ancient Earth, Alien Earths,” from left to right:  Dr. Christopher House, Dr. Phoebe Cohen, Dr. David Grinspoon, Dr. Timothy Lyons, Dr. Dawn Sumner, Dr. Shawn Domagal-Goldman. Photo Credit: (NASA/Aubrey Gemignani)

At a recent event held at NASA headquarters, titled “Ancient Earth, Alien Earths,” a panel of scientists discussed how our knowledge of ancient Earth can help guide our search for habitable planets around other stars.

“We live in a revolutionary time in terms of our knowledge of the universe–this is the time of the exoplanet revolution,” began the planetary scientist and panel moderator David Grinspoon. “We’re also in a time of rapid discovery about the origin and early evolution of life on Earth.”

The event was held on August 20, 2014 as the public portion of a two-parts workshop sponsored by NASA, the National Science Foundation, and the Smithsonian Institution, focusing on the habitability of the early Earth.

Our Earth was very much an alien world in its early days. Its atmosphere started out oxygen-free. Methane levels were higher. And yet, our planet was able to support the emergence and evolution of life relatively early on. But what counts as a potential biosignature as we study these ancient times? And how can we apply that knowledge to our search for life elsewhere?

The panelists covered a wide range of topics–including the history of liquid water on Earth and on Mars; signs of microbial life in ancient rocks; the rise of oxygen in Earth’s atmosphere; and the evolution of animal complexity.

“The early Earth is our great natural lab,” said the biogeochemist Timothy Lyons.

But they also emphasized the need to keep thinking outside our Earth-centric box, and to remain open to the possibility of life elsewhere being drastically different than here on Earth.

 

 

The discussion participants included:

  • Phoebe Cohen, Professor of Geosciences Williams College, Williamstown, Massachusetts.
  • Shawn Domagal-Goldman, research space scientist, NASA’s Goddard Space Flight Center, Greenbelt, Maryland.
  • Christopher House, Professor of Geosciences, Pennsylvania State University, University Park, Pennsylvania.
  • Timothy Lyons, Professor of Biogeochemistry, UC Riverside, Riverside, California.
  • Dawn Sumner, Professor of Geology, UC Davis, Davis, California.
  • David Grinspoon, senior scientist, Planetary Science Institute, Tucson, Ariz. and former Blumberg NASA-Library of Congress Chair in Astrobiology, Washington

 

Schematic cross section of the Earth’s interior highlighting the transition zone layer (light blue, 410-660 km depth), which has an anomalously high water storage capacity. The study by Schmandt and Jacobsen used seismic waves to detect magma generated near the top of the lower mantle at about 700 km depth. Dehydration melting at those conditions, also observed in the study’s high-pressure experiments, suggests the transition zone may be nearly saturated with H2O dissolved in high-pressure rock. Image Credit: Steve Jacobsen/Northwestern University

Scientists Detect Evidence of ‘Oceans Worth’ of Water in Earth’s Mantle

Schematic cross section of the Earth’s interior highlighting the transition zone layer (light blue, 410-660 km depth), which has an anomalously high water storage capacity. The study by Schmandt and Jacobsen used seismic waves to detect magma generated near the top of the lower mantle at about 700 km depth. Dehydration melting at those conditions, also observed in the study’s high-pressure experiments, suggests the transition zone may be nearly saturated with H2O dissolved in high-pressure rock. Image Credit: Steve Jacobsen/Northwestern University

Schematic cross section of the Earth’s interior highlighting the transition zone layer (light blue, 410-660 km depth), which has an anomalously high water storage capacity. The study by Schmandt and Jacobsen used seismic waves to detect magma generated near the top of the lower mantle at about 700 km depth. Dehydration melting at those conditions, also observed in the study’s high-pressure experiments, suggests the transition zone may be nearly saturated with H2O dissolved in high-pressure rock. Image Credit: Steve Jacobsen/Northwestern University

Researchers have found evidence of a potential “ocean’s worth” of water deep beneath the United States.

Although not present in a familiar form, the building blocks of water are bound up in rock located deep in the Earth’s mantle, and in quantities large enough to represent the largest water reservoir on the planet, according to the research.

For many years, scientists have attempted to establish exactly how much water may be cycling between the Earth’s surface and interior reservoirs through the action of plate tectonics. Northwestern University geophysicist Steve Jacobsen and University of New Mexico seismologist Brandon Schmandt have found deep pockets of magma around 400 miles beneath North America — a strong indicator of the presence of H₂O stored in the crystal structure of high-pressure minerals at these depths.

“The total H₂O content of the planet has long been among the most poorly constrained ‘geochemical parameters’ in Earth science. Our study has found evidence for widespread hydration of the mantle transition zone,” says Jacobsen.

For at least 20 years geologists have known from laboratory experiments that the Earth’s transition zone — a rocky layer of the Earth’s mantle located between the lower mantle and upper mantle, at depths between 250 and 410 miles — can, in theory, hold about 1 percent of its total weight as H₂O, bound up in minerals called wadsleyite and ringwoodite. However, as Schmandt explains, up until now it has been difficult to figure out whether that potential water reservoir is empty, as many have suggested, or not.

If there does turn out to be a substantial amount of H₂O in the transition zone, then recent laboratory experiments conducted by Jacobsen indicate there should be large quantities of what he calls “partial melt” in areas where mantle flows downward out of the zone. This water-rich silicate melt is molten rock that occurs at grain boundaries between solid mineral crystals and may account for about 1 percent of the volume of rocks.

Brandon Schmandt (University of New Mexico, left) and Steve Jacobsen (Northwestern University, right) combined seismic observations from the US-Array with laboratory experiments to detect dehydration melting of hydrous mantle material beneath North America at depths of 700-800 km. Credit: University of New Mexico/Northwestern University

Brandon Schmandt (University of New Mexico, left) and Steve Jacobsen (Northwestern University, right) combined seismic observations from the US-Array with laboratory experiments to detect dehydration melting of hydrous mantle material beneath North America at depths of 700-800 km. Credit: University of New Mexico/Northwestern University

“Melting occurs because hydrated rocks are carried from the transition zone, where the rocks can hold lots of H₂O, downward into the lower mantle, where the rocks cannot hold as much H₂O. Melting is the way to get rid of the H₂O that won’t fit in the crystal structure present in the lower mantle,” says Jacobsen.

He adds:

“When a rock starts to melt, whatever H₂O is bound in the rock will go into the melt right away. So the melt would have much higher H₂O concentration than the remaining solid. We’re not sure how it got there. Maybe it’s been stuck there since early in Earth’s history or maybe it’s constantly being recycled by plate tectonics.”

Seismic Waves

Melt strongly affects the speed of seismic waves — the acoustic-like waves of energy that travel through the Earth’s layers as a result of an earthquake or explosion. This is because stiff rocks, like the silicate-rich ones present in the mantle, propagate seismic waves very quickly. According to Schmandt, if just a little melt — even 1 percent or less — is added between the crystal grains of such a rock it causes it to become less stiff, meaning that elastic waves propagate more slowly.

“We were able to analyse seismic waves from earthquakes to look for melt in the mantle just beneath the transition zone,” says Schmandt.

“What we found beneath the U.S. is consistent with partial melt being present in areas of downward flow out of the transition zone. Without the presence of H₂O, it is very difficult to explain melting at these depths. This is a good hint that the transition zone H₂O reservoir is not empty, and even if it’s only partially filled that could correspond to about the same mass of H₂O as in Earth’s oceans,” he adds.

Jacobsen and Schmandt hope that their findings, published in the June issue of the journal Science, will help other scientists to understand how the Earth formed and what its current composition and inner workings are, as well as establish how much water is trapped in mantle rock.

“I think we are finally seeing evidence for a whole-Earth water cycle, which may help explain the vast amount of liquid water on the surface of our habitable planet. Scientists have been looking for this missing deep water for decades,” says Jacobsen

Mantle Rock Studies

The study combined Schmandt’s analysis of seismic data from the USArray, a network of over 2,000 seismometers across the U.S., with Jacobsen’s laboratory experiments, in which he examined the behaviour of mantle rock under conditions designed to simulate the high pressures and temperatures present at 400 miles below the Earth’s surface.

Schematic representation of seismometers placed in the US-Array between 2004 and 2014 and used in the study by Schmandt and Jacobsen to detect dehydration melting at the top of the lower mantle beneath North America. Image Credit: NSF-Earthscope

Schematic representation of seismometers placed in the US-Array between 2004 and 2014 and used in the study by Schmandt and Jacobsen to detect dehydration melting at the top of the lower mantle beneath North America. Image Credit: NSF-Earthscope

The USArray is part of Earthscope, a program sponsored by National Science Foundation. Jacobsen’s experiments were conducted at two Department of Energy user facilities, the Advanced Photon Source of Argonne National Laboratory and the National Synchrotron Light Source at Brookhaven National Laboratory.

Taken as a whole, their findings produced strong evidence that melting may occur about 400 miles deep in the Earth, with H₂O stored in mantle rocks, such as those containing the mineral ringwoodite, which is likely to be a dominant mineral at those depths.

Schmandt explains that he made this discovery after carrying out seismic imaging of the boundary between the transition zone and lower mantle. He found evidence that, in areas where “sharp transitions” like melt are present, some earthquake energy had converted from a compressional, or longitudinal wave, to a shear or S-wave. The phase of the converted S-waves in areas where the mantle is flowing down and out of the transition zone indicated a significantly lower velocity than surrounding mantle. The discovery suggests that water from the Earth’s surface can be driven to such great depths by plate tectonics, eventually resulting in the partial melting of the rocks found deep in the mantle.

“We used many seismic wave conversions to see that many areas beneath the U.S. may have some melt just beneath the transition zone. The next step was comparing these areas to the areas where mantle flow models predict downward flow out of the transition zone,” says Schmandt.

Ringwoodite

Schmandt and Jacobsen’s findings build on a discovery reported in March in the journal Nature in which scientists discovered a piece of the blue mineral ringwoodite inside a diamond brought up from a depth of 400 miles by a volcano in Brazil. That tiny piece of ringwoodite — the only sample we have from within the Earth — contained a surprising amount of water bound in solid form in the mineral.

“Not only was this the first terrestrial ringwoodite ever seen — all other natural ringwoodite examples came from shocked meteorites — but the tiny inclusion of ringwoodite was also full of H₂O, to about 1.5 percent of total weight,” says Jacobsen. “This is about the maximum amount of water that we are able to put into ringwoodite in laboratory experiments.”

Although the discovery provided direct evidence of water in the deep mantle at about 700 kilometers (434 miles) deep, the diamond sampled only one point of the mantle. Jacobsen explains that the paper expands the search to question how widespread hydration might be throughout the entire transition zone. This is important because the presence of H₂O in the large volumes of rock found at depths of between 410 to 660 kilometers (255 to 410 miles) would “significantly alter our understanding of the composition of the Earth.”

Crystals of laboratory-grown hydrous ringwoodite, a high-pressure polymorph of olivine that is stable from about 520-660 km depth in the Earth’s mantle. The ringwoodite pictured here contains around one weight percent of H2O, similar to what was inferred in the seismic observations made by Schmandt and Jacobsen. Image Credit: Steve Jacobsen/Northwestern University

Crystals of laboratory-grown hydrous ringwoodite, a high-pressure polymorph of olivine that is stable from about 520-660 km depth in the Earth’s mantle. The ringwoodite pictured here contains around one weight percent of H2O, similar to what was inferred in the seismic observations made by Schmandt and Jacobsen. Image Credit: Steve Jacobsen/Northwestern University

“It would double or triple the known amount of H₂O in the bulk Earth. Just 1 to 2 percent H₂O by weight in the transition zone would be equivalent to 2 to 3 times the amount of H₂O in the oceans,” adds Jacobsen.

Big Questions

Looking ahead, Jacobsen admits that some big questions remain. For example, if the transition zone is full of H₂O, what does this tell us about the origin of Earth’s water? And is the presence of ringwoodite in a planet’s mantle necessary for a planet to retain enough original water to form oceans? Moreover, how is the H₂O in the transition zone connected to the surface reservoirs? Is the transition zone, if it contains a geochemical reservoir of H₂O larger than the oceans, somehow buffering the amount of liquid water on the Earth’s surface?

“An analogy could be that of a sponge, which needs to be filled before liquid water can be supported on top. Was water in the transition zone added through plate tectonics early in Earth’s history, or did the oceans de-gas from the mantle until an equilibrium was reached between surface and interior reservoirs?” asks Jacobsen.

Either way, the research is likely to be of strong interest to astrobiologists largely because water is often so closely linked to the formation of biological life. Remote geochemical analysis could be one way of detecting if such processes occur elsewhere in the universe, and it is likely that such analysis would involve the use of gamma-ray, neutron, and x-ray spectrometers of the type used by the NASA MESSENGER spacecraft for the remote geochemical mapping of Mercury.

“On other hard to reach planets it’s not practical to apply the type of seismic imaging that I used. So my guess is that geochemical analysis of volcanic rocks from other planetary bodies may be our best way to test whether volatiles are stored in the planet’s interior,” says Schmandt.

Nakhla meteorite (BM1913,25) inside surfaces after breaking in 1998. NASA photo # S98-04014. Credit: NASA

Life on Mars? Implications of a newly discovered mineral-rich structure

Nakhla meteorite (BM1913,25) inside surfaces after breaking in 1998. NASA photo # S98-04014. Credit: NASA

Nakhla meteorite (BM1913,25) inside surfaces after breaking in 1998. NASA photo # S98-04014. Credit: NASA

A new ovoid structure discovered in the Nakhla Martian meteorite is made of nanocrystalline iron-rich clay, contains a variety of minerals, and shows evidence of undergoing a past shock event from impact, with resulting melting of the permafrost and mixing of surface and subsurface fluids. Based on the results of a broad range of analytical studies to determine the origin of this new structure, scientists present the competing hypotheses for how this ovoid formed, point to the most likely conclusion, and discuss how these findings impact the field of astrobiology in a fascinating article published in Astrobiology, a peer-reviewed journal from Mary Ann Liebert, Inc., publishers. The article is available Open Access on the Astrobiology website.

In the article, “A Conspicuous Clay Ovoid in Nakhla: Evidence for Subsurface Hydrothermal Alteration on Mars with Implications for Astrobiology,” Elias Chatzitheodoridis, National Technical University of Athens, Greece, and Sarah Haigh and Ian Lyon, the University of Manchester, UK, describe the use of tools including electron microscopy, x-ray, and spectroscopy to analyze the ovoid structure. While the authors do not believe the formation of this structure involved biological materials, that is a possible hypothesis, and they note that evidence exists supporting the presence of niche environments in the Martian subsurface that could support life.

NASA's Hubble Space Telescope took this close-up of the red planet Mars. Credit: NASA

NASA’s Hubble Space Telescope took this close-up of the red planet Mars. Credit: NASA

“This study illustrates the importance of correlating different types of datasets when attempting to discern whether something in rock is a biosignature indicative of life,” says Sherry L. Cady, PhD, Editor-in-Chief of Astrobiology and Chief Scientist at the Pacific Northwest National Laboratory. “Though the authors couldn’t prove definitively that the object of focus was evidence of life, their research strategy revealed a significant amount of information about the potential for life to inhabit the subsurface of Mars.”