posted 12-06-2006 12:28 PM               

NASA Images Suggest Water Still Flows in Brief Spurts on Mars

NASA photographs have revealed bright new deposits seen in two gullies on Mars that suggest water carried sediment through them sometime during the past seven years.

"These observations give the strongest evidence to date that water still flows occasionally on the surface of Mars," said Michael Meyer, lead scientist for NASA's Mars Exploration Program, Washington.

Liquid water, as opposed to the water ice and water vapor known to exist at Mars, is considered necessary for life. The new findings heighten intrigue about the potential for microbial life on Mars. The Mars Orbiter Camera on NASA's Mars Global Surveyor provided the new evidence of the deposits in images taken in 2004 and 2005.

"The shapes of these deposits are what you would expect to see if the material were carried by flowing water," said Michael Malin of Malin Space Science Systems, San Diego. "They have finger-like branches at the downhill end and easily diverted around small obstacles." Malin is principal investigator for the camera and lead author of a report about the findings published in the journal Science.

The atmosphere of Mars is so thin and the temperature so cold that liquid water cannot persist at the surface. It would rapidly evaporate or freeze. Researchers propose that water could remain liquid long enough, after breaking out from an underground source, to carry debris downslope before totally freezing. The two fresh deposits are each several hundred meters or yards long.

The light tone of the deposits could be from surface frost continuously replenished by ice within the body of the deposit. Another possibility is a salty crust, which would be a sign of water's effects in concentrating the salts. If the deposits had resulted from dry dust slipping down the slope, they would likely be dark, based on the dark tones of dust freshly disturbed by rover tracks, dust devils and fresh craters on Mars.

Mars Global Surveyor has discovered tens of thousands of gullies on slopes inside craters and other depressions on Mars. Most gullies are at latitudes of 30 degrees or higher. Malin and his team first reported the discovery of the gullies in 2000. To look for changes that might indicate present-day flow of water, his camera team repeatedly imaged hundreds of the sites. One pair of images showed a gully that appeared after mid-2002. That site was on a sand dune, and the gully-cutting process was interpreted as a dry flow of sand.

Today's announcement is the first to reveal newly deposited material apparently carried by fluids after earlier imaging of the same gullies. The two sites are inside craters in the Terra Sirenum and the Centauri Montes regions of southern Mars.

"These fresh deposits suggest that at some places and times on present-day Mars, liquid water is emerging from beneath the ground and briefly flowing down the slopes. This possibility raises questions about how the water would stay melted below ground, how widespread it might be, and whether there's a below-ground wet habitat conducive to life. Future missions may provide the answers," said Malin.

Besides looking for changes in gullies, the orbiter's camera team assessed the rate at which new impact craters appear. The camera photographed approximately 98 percent of Mars in 1999 and approximately 30 percent of the planet was photographed again in 2006. The newer images show 20 fresh impact craters, ranging in diameter from 7 feet (2 meters) to 486 feet (148 meters) that were not present approximately seven years earlier. These results have important implications for determining the ages of features on the surface of Mars. These results also approximately match predictions and imply that Martian terrain with few craters is truly young.

Mars Global Surveyor began orbiting Mars in 1997. The spacecraft is responsible for many important discoveries. NASA has not heard from the spacecraft since early November. Attempts to contact it continue. Its unprecedented longevity has allowed monitoring Mars for over several years past its projected lifetime.

posted 08-04-2011 02:07 PM               

NASA Spacecraft Data Suggest Water Flowing on Mars

Observations from NASA's Mars Reconnaissance Orbiter have revealed possible flowing water during the warmest months on Mars.

"NASA's Mars Exploration Program keeps bringing us closer to determining whether the Red Planet could harbor life in some form,” NASA Administrator Charles Bolden said, “and it reaffirms Mars as an important future destination for human exploration."

Dark, finger-like features appear and extend down some Martian slopes during late spring through summer, fade in winter, and return during the next spring. Repeated observations have tracked the seasonal changes in these recurring features on several steep slopes in the middle latitudes of Mars' southern hemisphere.

"The best explanation for these observations so far is the flow of briny water," said Alfred McEwen of the University of Arizona, Tucson. McEwen is the principal investigator for the orbiter's High Resolution Imaging Science Experiment (HiRISE) and lead author of a report about the recurring flows published in Thursday's edition of the journal Science. [continue reading]

posted 08-04-2011 10:30 PM               

The Mars Science Laboratory rover, scheduled to launch late this year, will not be able to help. Its landing site is far from any of the streaks, and it would not be able to navigate the steep slopes.

posted 08-05-2011 02:35 PM               

It would be great to confirm that flowing liquid water exists but I wondered if seasonal winds (aeolian activity) could be blowing dark silt from upper strata into the valleys/gullies and lower geographic features, with later (seasonal) dissipation. Despite the rarefied atmosphere on Mars and fractional pressures at work, could the patterns observed be explained by such an alternative?

I don't know enough here to even be dangerous so I'd be curious to hear from others who might. For the record, I prefer the idea of flowing water and wish them the best in conclusively proving the thesis.

Per McEwen's quote "It's a mystery now, but I think it's a solvable mystery with further observations and laboratory experiments". Hopefully those experiments will continue, and a bright spot in NASA activities amidst some of our shared gloom around the decline in manned missions.

posted 08-05-2011 03:02 PM               

Saltiness lowers the freezing temperature of water. Sites with active flows get warm enough, even in the shallow subsurface, to sustain liquid water that is about as salty as Earth's oceans, while pure water would freeze at the observed temperatures.

posted 09-28-2015 10:10 AM               

Images from the High Resolution Imaging Science Experiment (HiRISE), a camera aboard the Mars Reconnaissance Orbiter (MRO), have revealed thousands of narrow, dark streaks that appear on some of Mars's steep slopes during warmer seasons.

The streaks appear on equator-facing slopes in the mid-latitudes of the southern hemisphere, and can grow by as much as 20 metres a day. Temperatures in this part of the planet can rise as high as 27ºC during warm seasons. That's easily warm enough for water to exist, especially if it contains salts, which lower the melting temperature of ice. By winter, the streaks have faded or vanished.

HiRISE principal investigator Alfred McEwen, a planetary scientist at the University of Arizona in Tucson, thinks that the most likely explanation is that the streaks are formed by briny water oozing downhill in small, steep channels.

He says that the streaks are the strongest evidence yet for the existence of liquid water on Mars today. "This can focus the search for extant life on Mars," he says. He and his colleagues report their findings today in Science.

posted 09-28-2015 10:16 AM               

R.S.L.s are treated as special regions that NASA’s current robotic explorers are barred from because the rovers were not thoroughly sterilized, and NASA worries that they might be carrying microbial hitchhikers from Earth that could contaminate Mars.

Of the spacecraft NASA has sent to Mars, only the two Viking landers in 1976 were baked to temperatures hot enough to kill Earth microbes. NASA’s next Mars rover, scheduled to launch in 2020, will be no cleaner. Sterilizing spacecraft, which requires electronics and systems that can withstand the heat of baking, adds to the cost and complicates the design.

In selecting the landing site for the 2020 rover, the space agency is ruling out places that might be habitable, including those with R.S.L.s.

That prohibition may continue even though two candidate R.S.L.s have been identified on the mountain in Gale Crater that NASA’s Curiosity rover is now exploring, not very far from its current planned path.

NASA and the Curiosity team could decide to approach the streaks without driving onto them, or to simply observe from a distance. The rover still has at least several months of driving before it would pass them.

posted 09-28-2015 10:48 AM               

NASA Confirms Evidence That Liquid Water Flows on Today's Mars

New findings from NASA's Mars Reconnaissance Orbiter provide the strongest evidence yet that liquid water flows intermittently on present-day Mars.

Above: These dark, narrow, 100 meter-long streaks called recurring slope lineae flowing downhill on Mars are inferred to have been formed by contemporary flowing water. Recently, planetary scientists detected hydrated salts on these slopes at Hale crater, corroborating their original hypothesis that the streaks are indeed formed by liquid water.

The blue color seen upslope of the dark streaks are thought not to be related to their formation, but instead are from the presence of the mineral pyroxene. The image is produced by draping an orthorectified (Infrared-Red-Blue/Green (IRB)) false color image (ESP_030570_1440) on a Digital Terrain Model (DTM) of the same site produced by High Resolution Imaging Science Experiment (University of Arizona). Vertical exaggeration is 1.5. (NASA/JPL/University of Arizona)

Using an imaging spectrometer on MRO, researchers detected signatures of hydrated minerals on slopes where mysterious streaks are seen on the Red Planet. These darkish streaks appear to ebb and flow over time. They darken and appear to flow down steep slopes during warm seasons, and then fade in cooler seasons. They appear in several locations on Mars when temperatures are above minus 10 degrees Fahrenheit (minus 23 Celsius), and disappear at colder times.

"Our quest on Mars has been to 'follow the water,' in our search for life in the universe, and now we have convincing science that validates what we've long suspected," said John Grunsfeld, astronaut and associate administrator of NASA's Science Mission Directorate in Washington. "This is a significant development, as it appears to confirm that water — albeit briny — is flowing today on the surface of Mars."

These downhill flows, known as recurring slope lineae (RSL), often have been described as possibly related to liquid water. The new findings of hydrated salts on the slopes point to what that relationship may be to these dark features. The hydrated salts would lower the freezing point of a liquid brine, just as salt on roads here on Earth causes ice and snow to melt more rapidly. Scientists say it's likely a shallow subsurface flow, with enough water wicking to the surface to explain the darkening.

"We found the hydrated salts only when the seasonal features were widest, which suggests that either the dark streaks themselves or a process that forms them is the source of the hydration. In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks," said Lujendra Ojha of the Georgia Institute of Technology (Georgia Tech) in Atlanta, lead author of a report on these findings published Sept. 28 by Nature Geoscience.

Above: Dark narrow streaks called recurring slope lineae emanating out of the walls of Garni crater on Mars. The dark streaks here are up to few hundred meters in length. They are hypothesized to be formed by flow of briny liquid water on Mars. The image is produced by draping an orthorectified (RED) image (ESP_031059_1685) on a Digital Terrain Model (DTM) of the same site produced by High Resolution Imaging Science Experiment (University of Arizona). Vertical exaggeration is 1.5. (NASA/JPL/University of Arizona)

Ojha first noticed these puzzling features as a University of Arizona undergraduate student in 2010, using images from the MRO's High Resolution Imaging Science Experiment (HiRISE). HiRISE observations now have documented RSL at dozens of sites on Mars. The new study pairs HiRISE observations with mineral mapping by MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM).

The spectrometer observations show signatures of hydrated salts at multiple RSL locations, but only when the dark features were relatively wide. When the researchers looked at the same locations and RSL weren't as extensive, they detected no hydrated salt.

Ojha and his co-authors interpret the spectral signatures as caused by hydrated minerals called perchlorates. The hydrated salts most consistent with the chemical signatures are likely a mixture of magnesium perchlorate, magnesium chlorate and sodium perchlorate. Some perchlorates have been shown to keep liquids from freezing even when conditions are as cold as minus 94 degrees Fahrenheit (minus 70 Celsius). On Earth, naturally produced perchlorates are concentrated in deserts, and some types of perchlorates can be used as rocket propellant.

Perchlorates have previously been seen on Mars. NASA's Phoenix lander and Curiosity rover both found them in the planet's soil, and some scientists believe that the Viking missions in the 1970s measured signatures of these salts. However, this study of RSL detected perchlorates, now in hydrated form, in different areas than those explored by the landers. This also is the first time perchlorates have been identified from orbit.

MRO has been examining Mars since 2006 with its six science instruments.

"The ability of MRO to observe for multiple Mars years with a payload able to see the fine detail of these features has enabled findings such as these: first identifying the puzzling seasonal streaks and now making a big step towards explaining what they are," said Rich Zurek, MRO project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.

For Ojha, the new findings are more proof that the mysterious lines he first saw darkening Martian slopes five years ago are, indeed, present-day water.

"When most people talk about water on Mars, they're usually talking about ancient water or frozen water," he said. "Now we know there's more to the story. This is the first spectral detection that unambiguously supports our liquid water-formation hypotheses for RSL."

The discovery is the latest of many breakthroughs by NASA's Mars missions.

"It took multiple spacecraft over several years to solve this mystery, and now we know there is liquid water on the surface of this cold, desert planet," said Michael Meyer, lead scientist for NASA's Mars Exploration Program at the agency's headquarters in Washington. "It seems that the more we study Mars, the more we learn how life could be supported and where there are resources to support life in the future."

There are eight co-authors of the Nature Geoscience paper, including Mary Beth Wilhelm at NASA's Ames Research Center in Moffett Field, California and Georgia Tech; CRISM Principal Investigator Scott Murchie of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland; and HiRISE Principal Investigator Alfred McEwen of the University of Arizona Lunar and Planetary Laboratory in Tucson, Arizona. Others are at Georgia Tech, the Southwest Research Institute in Boulder, Colorado, and Laboratoire de Planétologie et Géodynamique in Nantes, France.

The agency's Jet Propulsion Laboratory (JPL) in Pasadena, California manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington. Lockheed Martin built the orbiter and collaborates with JPL to operate it.

posted 07-29-2016 10:45 AM               

Mars Gullies Likely Not Formed by Liquid Water

New findings using data from NASA's Mars Reconnaissance Orbiter show that gullies on modern Mars are likely not being formed by flowing liquid water. This new evidence will allow researchers to further narrow theories about how Martian gullies form, and reveal more details about Mars' recent geologic processes.

Scientists use the term "gully" for features on Mars that share three characteristics in their shape: an alcove at the top, a channel, and an apron of deposited material at the bottom. Gullies are distinct from another type of feature on Martian slopes, streaks called "recurring slope lineae," or RSL, which are distinguished by seasonal darkening and fading, rather than characteristics of how the ground is shaped. Water in the form of hydrated salt has been identified at RSL sites. The new study focuses on gullies and their formation process by adding composition information to previously acquired imaging.

Above: The highly incised Martian gullies resemble gullies on Earth that are carved by liquid water. However, when the gullies are observed with the addition of mineralogical information, no evidence for alteration by water appears.

Researchers from the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, examined high-resolution compositional data from more than 100 gully sites throughout Mars. These data, collected by the orbiter's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), were then correlated with images from the same spacecraft's High Resolution Imaging Science Experiment (HiRISE) camera and Context Camera (CTX).

The findings showed no mineralogical evidence for abundant liquid water or its by-products, thus pointing to mechanisms other than the flow of water -- such as the freeze and thaw of carbon dioxide frost -- as being the major drivers of recent gully evolution.

The findings were published in Geophysical Research Letters.

Gullies are a widespread and common feature on the Martian surface, mostly occurring between 30 and 50 degrees latitude in both the northern and southern hemispheres, generally on slopes that face toward the poles. On Earth, similar gullies are formed by flowing liquid water; however, under current conditions, liquid water is transient on the surface of Mars, and may occur only as small amounts of brine even at RSL streaks. The lack of sufficient water to carve gullies has resulted in a variety of theories for the gullies' creation, including different mechanisms involving evaporation of water and carbon dioxide frost.

"The HiRISE team and others had shown there was seasonal activity in gullies -- primarily in the southern hemisphere -- over the past couple of years, and carbon dioxide frost is the main mechanism they suspected of causing it. However, other researchers favored liquid water as the main mechanism," said Jorge Núñez of APL, the lead author of the paper. "What HiRISE and other imagers were not able to determine on their own was the composition of the material in gullies, because they are optical cameras. To bring another important piece in to help solve the puzzle, we used CRISM, an imaging spectrometer, to look at what kinds of minerals were present in the gullies and see if they could shed light on the main mechanism responsible."

Núñez and his colleagues took advantage of a new CRISM data product called Map-projected Targeted Reduced Data Records. It allowed them to more easily perform their analyses and then correlate the findings with HiRISE imagery.

"On Earth and on Mars, we know that the presence of phyllosilicates — clays — or other hydrated minerals indicates formation in liquid water," Núñez said. "In our study, we found no evidence for clays or other hydrated minerals in most of the gullies we studied, and when we did see them, they were erosional debris from ancient rocks, exposed and transported downslope, rather than altered in more recent flowing water. These gullies are carving into the terrain and exposing clays that likely formed billions of years ago when liquid water was more stable on the Martian surface."

Other researchers have created computer models that show how sublimation of seasonal carbon dioxide frost can create gullies similar to those observed on Mars, and how their shape can mimic the types of gullies that liquid water would create. The new study adds support to those models.

posted 11-20-2017 10:56 AM               

Recurring Martian Streaks: Flowing Sand, Not Water?

Dark features on Mars previously considered evidence for subsurface flowing of water are interpreted by new research as granular flows, where grains of sand and dust slip downhill to make dark streaks, rather than the ground being darkened by seeping water.

Continuing examination of these still-perplexing seasonal dark streaks with a powerful camera on NASA's Mars Reconnaissance Orbiter (MRO) shows they exist only on slopes steep enough for dry grains to descend the way they do on faces of active dunes.

Above: This inner slope of a Martian crater has several of the seasonal dark streaks called "recurrent slope lineae," or RSL, that a November 2017 report interprets as granular flows, rather than darkening due to flowing water. The image is from the HiRISE camera on NASA's Mars Reconnaissance Orbiter. (Credits: NASA/JPL-Caltech/UA/USGS)

The findings published today in Nature Geoscience argue against the presence of enough liquid water for microbial life to thrive at these sites. However, exactly how these numerous flows begin and gradually grow has not yet been explained. Authors of the report propose possibilities that include involvement of small amounts of water, indicated by detection of hydrated salts observed at some of the flow sites.

These features have evoked fascination and controversy since their 2011 discovery, as possible markers for unexpected liquid water or brine on an otherwise dry planet. They are dark streaks that extend gradually downhill in warm seasons, then fade away in winter and reappear the next year. On Earth, only seeping water is known to have these behaviors, but how they form in the dry Martian environment remains unclear.

Many thousands of these Martian features, collectively called "recurring slope lineae" or RSL, have been identified in more than 50 rocky-slope areas, from the equator to about halfway to the poles.

"We've thought of RSL as possible liquid water flows, but the slopes are more like what we expect for dry sand," said Colin Dundas of the U.S. Geological Survey's Astrogeology Science Center in Flagstaff, Arizona. "This new understanding of RSL supports other evidence that shows that Mars today is very dry."

Dundas is lead author of the report, which is based on observations with the High Resolution Imaging Science Experiment (HiRISE) camera on MRO. The data include 3-D models of slope steepness using pairs of images for stereo information. Dundas and co-authors examined 151 RSL features at 10 sites.

The RSL are almost all restricted to slopes steeper than 27 degrees. Each flow ends on a slope that matches the dynamic "angle of repose" seen in the slumping dry sand of dunes on Mars and Earth. A flow due to liquid water should readily extend to less steep slopes.

"The RSL don't flow onto shallower slopes, and the lengths of these are so closely correlated with the dynamic angle of repose, it can't be a coincidence," said HiRISE Principal Investigator Alfred McEwen at the University of Arizona, Tucson, a co-author of the new report.

The seasonal dark streaks have been thought of as possible evidence for biologically significant liquid water -- sufficient water for microbial life -- though explaining how so much liquid water could exist on the surface in Mars' modern environment would be challenging. A granular-flow explanation for RSL fits with the earlier understanding that the surface of modern Mars, exposed to a cold, thin atmosphere, lacks flowing water. A 2016 report also cast doubt on possible sources of underground water at RSL sites. Liquid water on today's Mars may be limited to traces of dissolved moisture from the atmosphere and thin films, which are challenging environments for life as we know it.

However, RSL remain puzzling. Traits with uncertain explanations include their gradual growth, their seasonal reappearance, their rapid fading when inactive, and the presence of hydrated salts, which have water molecules bound into their crystal stucture.

The new report describes possible connections between these traits and how RSL form. For example, salts can become hydrated by pulling water vapor from the atmosphere, and this process can form drops of salty water. Seasonal changes in hydration of salt-containing grains might result in some trigger mechanism for RSL grainflows, such as expansion, contraction, or release of some water. Darkening and fading might result from changes in hydration. If atmospheric water vapor is a trigger, then a question is why the RSL appear on some slopes but not others.

"RSL probably form by some mechanism that is unique to the environment of Mars," McEwen said, "so they represent an opportunity to learn about how Mars behaves, which is important for future surface exploration."

"Full understanding of RSL is likely to depend upon on-site investigation of these features," said MRO Project Scientist Rich Zurek of NASA's Jet Propulsion Laboratory, Pasadena, California. "While the new report suggests that RSL are not wet enough to favor microbial life, it is likely that on-site investigation of these sites will still require special procedures to guard against introducing microbes from Earth, at least until they are definitively characterized. In particular, a full explanation of how these enigmatic features darken and fade still eludes us. Remote sensing at different times of day could provide important clues."

posted 03-17-2021 08:10 AM               

There's never been much mystery surrounding the murder of Mars. Once a warm, wet world, Mars lost its magnetic field more than 4 billion years ago when its outer core cooled, shutting off the dynamo that kept the field in place. That exposed the planet to the solar wind, which clawed away at the atmosphere; and that in turn allowed the planet's water to sputter off into space. To look at Mars today is to see a desert world, stamped with the dry riverbeds, delicate deltas and deep ocean basins hinting at the water that is no more.

At least, that's the long-accepted view. But according to a study published Mar. 16 in Science by a team of researchers at the California Institute of Technology, that scenario might be all wrong. Mars is dry, alright — or at least it appears to be. But the researchers say much of its water — from 30% to a staggering 99% of it — is still there. It simply retreated into the martian rocks and clay rather than escaping into space.

posted 03-24-2021 09:28 PM            

quote:

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Originally posted by Cooper95:
I tried to find any proof of the existence of water on Mars and failed...

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posted 09-29-2022 09:36 PM               

New evidence for liquid water beneath the south polar ice cap of Mars

An international team of researchers has revealed new evidence for the possible existence of liquid water beneath the south polar ice cap of Mars.

The researchers, led by the University of Cambridge, used spacecraft laser-altimeter measurements of the shape of the upper surface of the ice cap to identify subtle patterns in its height. They then showed that these patterns match computer model predictions for how a body of water beneath the ice cap would affect the surface.

Their results agree with earlier ice-penetrating radar measurements that were originally interpreted to show a potential area of liquid water beneath the ice. There has been debate over the liquid water interpretation from the radar data alone, with some studies suggesting the radar signal is not due to liquid water.

The results, reported in the journal Nature Astronomy, provide the first independent line of evidence, using data other than radar, that there is liquid water beneath Mars' south polar ice cap.

"The combination of the new topographic evidence, our computer model results, and the radar data make it much more likely that at least one area of subglacial liquid water exists on Mars today, and that Mars must still be geothermally active in order to keep the water beneath the ice cap liquid," said Professor Neil Arnold from Cambridge's Scott Polar Research Institute, who led the research.

Like Earth, Mars has thick water ice caps at both poles, roughly equivalent in combined volume to the Greenland Ice Sheet. Unlike Earth's ice sheets however, which are underlain by water-filled channels and even large subglacial lakes, the polar ice caps on Mars have until recently been thought to be frozen solid all the way to their beds due to the cold Martian climate.

In 2018, evidence from the European Space Agency's Mars Express satellite challenged this assumption. The satellite has an ice-penetrating radar called MARSIS, which can see through Mars' southern ice cap. It revealed an area at the base of the ice that strongly reflected the radar signal, which was interpreted as an area of liquid water beneath the ice cap.

However, subsequent studies suggested that other types of dry materials, which exist elsewhere on Mars, could produce similar patterns of reflectance if they exist beneath the ice cap. Given the cold climate conditions, liquid water beneath the ice cap would require an additional heat source, such as geothermal heat from within the planet, at levels above those expected for present-day Mars. This left confirmation of the existence of this lake awaiting another, independent line of evidence.

On Earth, subglacial lakes affect the shape of the overlying ice sheet – its surface topography. The water in subglacial lakes lowers friction between the ice sheet and its bed, affecting the velocity of ice flow under gravity. This in turn affects the shape of the ice sheet surface above the lake, often creating a depression in the ice surface followed by a raised area further down-flow.

The team – which also included researchers from the University of Sheffield, the University of Nantes, University College, Dublin, and the Open University – used a range of techniques to examine data from NASA's Mars Global Surveyor satellite of the surface topography of the part of Mars' south polar ice cap where the radar signal was identified.

Their analysis revealed a 10-15 kilometre-long surface undulation comprising a depression and a corresponding raised area, both of which deviate from the surrounding ice surface by several metres. This is similar in scale to undulations over subglacial lakes here on Earth.

The team then tested whether the observed undulation on the surface of the ice could be explained by liquid water at the bed. They ran computer model simulations of ice flow, adapted to specific conditions on Mars. They then inserted a patch of reduced bed friction in the simulated ice sheet bed where water, if present, would allow the ice to slide and speed up. They also varied the amount of geothermal heat coming from inside the planet. These experiments generated undulations on the simulated ice surface that were similar in size and shape to those the team observed on the real ice cap surface.

The similarity between the model-produced topographic undulation and the actual spacecraft observations, together with the earlier ice-penetrating radar evidence suggest that there is an accumulation of liquid water beneath Mars' south polar ice cap, and that magmatic activity occurred relatively recently in the subsurface of Mars to enable the enhanced geothermal heating needed to keep the water in a liquid state.

"The quality of data coming back from Mars, from orbital satellites as well as from the landers, is such that we can use it answer really difficult questions about conditions on, and even under the planet's surface, using the same techniques we also use on Earth," said Arnold. "It's exciting to use these techniques to find out things about planets other than our own."

The research was supported in part by the European Research Council.

posted 03-17-2023 07:10 AM               

Remains of a Modern Glacier Found Near Mars' Equator Implies Water Ice Possibly Present at Low Latitudes on Mars Even Today

If there is still water ice preserved at shallow depths at a low latitude on Mars, there would be implications for science and human exploration

In a groundbreaking announcement at the 54th Lunar and Planetary Science Conference held in The Woodlands, Texas, scientists revealed the discovery of a relict glacier near Mars' equator. Located in Eastern Noctis Labyrinthus at coordinates 7 degrees 33 minutes S, 93 degrees 14 minutes W, this finding is significant as it implies the presence of surface water ice on Mars in recent times, even near the equator. This discovery raises the possibility that ice may still exist at shallow depths in the area, which could have significant implications for future human exploration.

Above: Figure 1: A Relict Glacier near Mars' Equator. (NASA MRO HiRISE and CRISM false color composite. Lee et al. 2023).

The surface feature identified as a "relict glacier" is one of many light-toned deposits (LTDs) found in the region. Typically, LTDs consist mainly of light-colored sulfate salts, but this deposit also shows many of the features of a glacier, including crevasse fields and moraine bands. The glacier is estimated to be 6 kilometers long and up to 4 kilometers wide, with a surface elevation ranging from +1.3 to +1.7 kilometers. This discovery suggests that Mars' recent history may have been more watery than previously thought, which could have implications for understanding the planet's habitability.

"What we've found is not ice, but a salt deposit with the detailed morphologic features of a glacier. What we think happened here is that salt formed on top of a glacier while preserving the shape of the ice below, down to details like crevasse fields and moraine bands," said Dr. Pascal Lee, a planetary scientist with the SETI Institute and the Mars Institute, and the lead author of the study.

The presence of volcanic materials blanketing the region hints of how the sulfate salts might have formed and preserved a glacier's imprint underneath. When freshly erupted pyroclastic materials (mixtures of volcanic ash, pumice, and hot lava blocks) come in contact with water ice, sulfate salts like the ones commonly making up Mars' light-toned deposits may form and build up into a hardened, crusty salt layer.

Above: Figure 2: Interpretation of the "Relict Glacier's" features. (Lee et al. 2023).

"This region of Mars has a history of volcanic activity. And where some of the volcanic materials came in contact with glacier ice, chemical reactions would have taken place at the boundary between the two to form a hardened layer of sulfate salts," explains Sourabh Shubham, a graduate student at the University of Maryland's Department of Geology, and a co-author of the study. "This is the most likely explanation for the hydrated and hydroxylated sulfates we observe in this light-toned deposit."

Over time, with erosion removing the blanketing volcanic materials, a crusty layer of sulfates mirroring the glacier ice underneath became exposed, which would explain how a salt deposit is now visible, presenting features unique to glaciers such as crevasses and moraine bands.

"Glaciers often present distinctive types of features, including marginal, splaying, and tic-tac-toe crevasse fields, and also thrust moraine bands and foliation. We are seeing analogous features in this light-toned deposit, in form, location, and scale. It's very intriguing," said John Schutt, a geologist at the Mars Institute, experienced icefield guide in the Arctic and Antarctica, and a co-author of this study.

The glacier's fine-scale features, its associated sulfate salts deposit, and the overlying volcanic materials are all very sparsely cratered by impacts and must be geologically young, likely Amazonian in age, the latest geologic period which includes modern Mars. "We've known about glacial activity on Mars at many locations, including near the equator in the more distant past. And we've known about recent glacial activity on Mars, but so far, only at higher latitudes. A relatively young relict glacier in this location tells us that Mars experienced surface ice in recent times, even near the equator, which is new," said Lee.

It remains to be seen whether water ice might still be preserved underneath the light-toned deposit or if it has disappeared entirely. "Water ice is, at present, not stable at the very surface of Mars near the equator at these elevations. So, it's not surprising that we're not detecting any water ice at the surface. It is possible that all the glacier's water ice has sublimated away by now. But there's also a chance that some of it might still be protected at shallow depth under the sulfate salts."

The study draws an analogy with the ancient ice islands on salt lakebeds, or salars, of the Altiplano in South America. There, old glacier ice has remained protected from melting, evaporation, and sublimation underneath blankets of bright salts. Lee and his co-authors hypothesize a similar situation to explain how sulfate salts on Mars might be able to offer protection to otherwise sublimation-vulnerable ice at low latitudes on the planet.

If there is still water ice preserved at shallow depths at a low latitude on Mars, there would be implications for science and human exploration. "The desire to land humans at a location where they might be able to extract water ice from the ground has been pushing mission planners to consider higher latitude sites. But the latter environments are typically colder and more challenging for humans and robots. If there were equatorial locations where ice might be found at shallow depth, then we'd have the best of both environments: warmer conditions for human exploration and still access to ice," said Lee.

But Lee cautions that more work still needs to be done: "We now have to determine if, and how much, water ice might actually be present in this relict glacier, and whether other light-toned deposits might also have, or have had, ice-rich substrates."