NASA's treasure map for water ice on Mars

Mars illustration (stock image).

NASA has big plans for returning astronauts to the Moon in 2024, a stepping stone on the path to sending humans to Mars. But where should the first people on the Red Planet land?

A new paper published in Geophysical Research Letters will help by providing a map of water ice believed to be as little as an inch (2.5 centimeters) below the surface.

Water ice will be a key consideration for any potential landing site. With little room to spare aboard a spacecraft, any human missions to Mars will have to harvest what's already available for drinking water and making rocket fuel.

NASA calls this concept "in situ resource utilization," and it's an important factor in selecting human landing sites on Mars. Satellites orbiting Mars are essential in helping scientists determine the best places for building the first Martian research station. The authors of the new paper make use of data from two of those spacecraft, NASA's Mars Reconnaissance Orbiter (MRO) and Mars Odyssey orbiter, to locate water ice that could potentially be within reach of astronauts on the Red Planet.

"You wouldn't need a backhoe to dig up this ice. You could use a shovel," said the paper's lead author, Sylvain Piqueux of NASA's Jet Propulsion Laboratory in Pasadena, California. "We're continuing to collect data on buried ice on Mars, zeroing in on the best places for astronauts to land."

Buried Treasure on Mars

Liquid water can't last in the thin air of Mars; with so little air pressure, it evaporates from a solid to a gas when exposed to the atmosphere.

Martian water ice is locked away underground throughout the planet's mid-latitudes. These regions near the poles have been studied by NASA's Phoenix lander, which scraped up ice, and MRO, which has taken many images from space of meteor impacts that have excavated this ice. To find ice that astronauts could easily dig up, the study's authors relied on two heat-sensitive instruments: MRO's Mars Climate Sounder and the Thermal Emission Imaging System (THEMIS) camera on Mars Odyssey.

Why use heat-sensitive instruments when looking for ice? Buried water ice changes the temperature of the Martian surface. The study's authors cross-referenced temperatures suggestive of ice with other data, such as reservoirs of ice detected by radar or seen after meteor impacts. Data from Odyssey's Gamma Ray Spectrometer, which is tailor-made for mapping water ice deposits, were also useful.

As expected, all these data suggest a trove of water ice throughout the Martian poles and mid-latitudes. But the map reveals particularly shallow deposits that future mission planners may want to study further.

Picking a Landing Site

While there are lots of places on Mars scientists would like to visit, few would make practical landing sites for astronauts. Most scientists have homed in on the northern and southern mid-latitudes, which have more plentiful sunlight and warmer temperatures than the poles. But there's a heavy preference for landing in the northern hemisphere, which is generally lower in elevation and provides more atmosphere to slow a landing spacecraft.

A large portion of a region called Arcadia Planitia is the most tempting target in the northern hemisphere. The map shows lots of blue and purple in this region, representing water ice less than one foot (30 centimeters) below the surface; warm colors are over two feet (60 centimeters) deep. Sprawling black zones on the map represent areas where a landing spacecraft would sink into fine dust.

What's Next?

Piqueux is planning a comprehensive campaign to continue studying buried ice across different seasons, watching how the abundance of this resource changes over time.

The more we look for near-surface ice, the more we find," said MRO Deputy Project Scientist Leslie Tamppari of JPL. "Observing Mars with multiple spacecraft over the course of years continues to provide us with new ways of discovering this ice."

JPL manages the MRO and Mars Odyssey missions for NASA's Science Mission Directorate in Washington. Lockheed Martin Space in Denver built both orbiters. JPL built and operates the Mars Climate Sounder instrument. THEMIS was built and is operated by Arizona State University in Tempe. The Gamma Ray Spectrometer was built and is operated by the University of Arizona in Tucson.

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NASA's treasure map for water ice on Mars

Mars illustration

NASA has big plans for returning astronauts to the Moon in 2024, a stepping stone on the path to sending humans to Mars. But where should the first people on the Red Planet land?

A new paper published in Geophysical Research Letters will help by providing a map of water ice believed to be as little as an inch (2.5 centimeters) below the surface.

Water ice will be a key consideration for any potential landing site. With little room to spare aboard a spacecraft, any human missions to Mars will have to harvest what's already available for drinking water and making rocket fuel.

NASA calls this concept "in situ resource utilization," and it's an important factor in selecting human landing sites on Mars. Satellites orbiting Mars are essential in helping scientists determine the best places for building the first Martian research station. The authors of the new paper make use of data from two of those spacecraft, NASA's Mars Reconnaissance Orbiter (MRO) and Mars Odyssey orbiter, to locate water ice that could potentially be within reach of astronauts on the Red Planet.

"You wouldn't need a backhoe to dig up this ice. You could use a shovel," said the paper's lead author, Sylvain Piqueux of NASA's Jet Propulsion Laboratory in Pasadena, California. "We're continuing to collect data on buried ice on Mars, zeroing in on the best places for astronauts to land."

Buried Treasure on Mars

Liquid water can't last in the thin air of Mars; with so little air pressure, it evaporates from a solid to a gas when exposed to the atmosphere.

Martian water ice is locked away underground throughout the planet's mid-latitudes. These regions near the poles have been studied by NASA's Phoenix lander, which scraped up ice, and MRO, which has taken many images from space of meteor impacts that have excavated this ice. To find ice that astronauts could easily dig up, the study's authors relied on two heat-sensitive instruments: MRO's Mars Climate Sounder and the Thermal Emission Imaging System (THEMIS) camera on Mars Odyssey.

Why use heat-sensitive instruments when looking for ice? Buried water ice changes the temperature of the Martian surface. The study's authors cross-referenced temperatures suggestive of ice with other data, such as reservoirs of ice detected by radar or seen after meteor impacts. Data from Odyssey's Gamma Ray Spectrometer, which is tailor-made for mapping water ice deposits, were also useful.

As expected, all these data suggest a trove of water ice throughout the Martian poles and mid-latitudes. But the map reveals particularly shallow deposits that future mission planners may want to study further.

Picking a Landing Site

While there are lots of places on Mars scientists would like to visit, few would make practical landing sites for astronauts. Most scientists have homed in on the northern and southern mid-latitudes, which have more plentiful sunlight and warmer temperatures than the poles. But there's a heavy preference for landing in the northern hemisphere, which is generally lower in elevation and provides more atmosphere to slow a landing spacecraft.

A large portion of a region called Arcadia Planitia is the most tempting target in the northern hemisphere. The map shows lots of blue and purple in this region, representing water ice less than one foot (30 centimeters) below the surface; warm colors are over two feet (60 centimeters) deep. Sprawling black zones on the map represent areas where a landing spacecraft would sink into fine dust.

What's Next?

Piqueux is planning a comprehensive campaign to continue studying buried ice across different seasons, watching how the abundance of this resource changes over time.

The more we look for near-surface ice, the more we find," said MRO Deputy Project Scientist Leslie Tamppari of JPL. "Observing Mars with multiple spacecraft over the course of years continues to provide us with new ways of discovering this ice."

JPL manages the MRO and Mars Odyssey missions for NASA's Science Mission Directorate in Washington. Lockheed Martin Space in Denver built both orbiters. JPL built and operates the Mars Climate Sounder instrument. THEMIS was built and is operated by Arizona State University in Tempe. The Gamma Ray Spectrometer was built and is operated by the University of Arizona in Tucson.

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NASA's treasure map for water ice on Mars

Mars illustration

NASA has big plans for returning astronauts to the Moon in 2024, a stepping stone on the path to sending humans to Mars. But where should the first people on the Red Planet land?

A new paper published in Geophysical Research Letters will help by providing a map of water ice believed to be as little as an inch (2.5 centimeters) below the surface.

Water ice will be a key consideration for any potential landing site. With little room to spare aboard a spacecraft, any human missions to Mars will have to harvest what's already available for drinking water and making rocket fuel.

NASA calls this concept "in situ resource utilization," and it's an important factor in selecting human landing sites on Mars. Satellites orbiting Mars are essential in helping scientists determine the best places for building the first Martian research station. The authors of the new paper make use of data from two of those spacecraft, NASA's Mars Reconnaissance Orbiter (MRO) and Mars Odyssey orbiter, to locate water ice that could potentially be within reach of astronauts on the Red Planet.

"You wouldn't need a backhoe to dig up this ice. You could use a shovel," said the paper's lead author, Sylvain Piqueux of NASA's Jet Propulsion Laboratory in Pasadena, California. "We're continuing to collect data on buried ice on Mars, zeroing in on the best places for astronauts to land."

Buried Treasure on Mars

Liquid water can't last in the thin air of Mars; with so little air pressure, it evaporates from a solid to a gas when exposed to the atmosphere.

Martian water ice is locked away underground throughout the planet's mid-latitudes. These regions near the poles have been studied by NASA's Phoenix lander, which scraped up ice, and MRO, which has taken many images from space of meteor impacts that have excavated this ice. To find ice that astronauts could easily dig up, the study's authors relied on two heat-sensitive instruments: MRO's Mars Climate Sounder and the Thermal Emission Imaging System (THEMIS) camera on Mars Odyssey.

Why use heat-sensitive instruments when looking for ice? Buried water ice changes the temperature of the Martian surface. The study's authors cross-referenced temperatures suggestive of ice with other data, such as reservoirs of ice detected by radar or seen after meteor impacts. Data from Odyssey's Gamma Ray Spectrometer, which is tailor-made for mapping water ice deposits, were also useful.

As expected, all these data suggest a trove of water ice throughout the Martian poles and mid-latitudes. But the map reveals particularly shallow deposits that future mission planners may want to study further.

Picking a Landing Site

While there are lots of places on Mars scientists would like to visit, few would make practical landing sites for astronauts. Most scientists have homed in on the northern and southern mid-latitudes, which have more plentiful sunlight and warmer temperatures than the poles. But there's a heavy preference for landing in the northern hemisphere, which is generally lower in elevation and provides more atmosphere to slow a landing spacecraft.

A large portion of a region called Arcadia Planitia is the most tempting target in the northern hemisphere. The map shows lots of blue and purple in this region, representing water ice less than one foot (30 centimeters) below the surface; warm colors are over two feet (60 centimeters) deep. Sprawling black zones on the map represent areas where a landing spacecraft would sink into fine dust.

What's Next?

Piqueux is planning a comprehensive campaign to continue studying buried ice across different seasons, watching how the abundance of this resource changes over time.

The more we look for near-surface ice, the more we find," said MRO Deputy Project Scientist Leslie Tamppari of JPL. "Observing Mars with multiple spacecraft over the course of years continues to provide us with new ways of discovering this ice."

JPL manages the MRO and Mars Odyssey missions for NASA's Science Mission Directorate in Washington. Lockheed Martin Space in Denver built both orbiters. JPL built and operates the Mars Climate Sounder instrument. THEMIS was built and is operated by Arizona State University in Tempe. The Gamma Ray Spectrometer was built and is operated by the University of Arizona in Tucson.

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Mars once had salt lakes similar to those on Earth

Salt flat in Bolivia

Mars once had salt lakes that are similar to those on Earth and has gone through wet and dry periods, according to an international team of scientists that includes a Texas A&M University College of Geosciences researcher.

Marion Nachon, a postdoctoral research associate in the Department of Geology and Geophysics at Texas A&M, and colleagues have had their work published in the current issue of Nature Geoscience.

The team examined Mars' geological terrains from Gale Crater, an immense 95-mile-wide rocky basin that is being explored with the NASA Curiosity rover since 2012 as part of the MSL (Mars Science Laboratory) mission.

The results show that the lake that was present in Gale Crater over 3 billion years ago underwent a drying episode, potentially linked to the global drying of Mars.

Gale Crater formed about 3.6 billion years ago when a meteor hit Mars and created its large impact crater.

"Since then, its geological terrains have recorded the history of Mars, and studies have shown Gale Crater reveals signs that liquid water was present over its history, which is a key ingredient of microbial life as we know it," Nachon said. "During these drying periods, salt ponds eventually formed. It is difficult to say exactly how large these ponds were, but the lake in Gale Crater was present for long periods of time -- from at least hundreds of years to perhaps tens of thousands of years," Nachon said.

So what happened to these salt lakes?

Nachon said that Mars probably became dryer over time, and the planet lost its planetary magnetic field, which left the atmosphere exposed to be stripped by solar wind and radiation over millions of years.

"With an atmosphere becoming thinner, the pressure at the surface became lesser, and the conditions for liquid water to be stable at the surface were not fulfilled anymore," Nachon said. "So liquid water became unsustainable and evaporated."

The salt ponds on Mars are believed to be similar to some found on Earth, especially those in a region called Altiplano, which is near the Bolivia-Peru border.

Nachon said the Altiplano is an arid, high-altitude plateau where rivers and streams from mountain ranges "do not flow to the sea but lead to closed basins, similar to what used to happen at Gale Crater on Mars," she said. "This hydrology creates lakes with water levels heavily influenced by climate. During the arid periods Altiplano lakes become shallow due to evaporation, and some even dry up entirely. The fact that the Atliplano is mostly vegetation free makes the region look even more like Mars," she said."

Nachon added that the study shows that the ancient lake in Gale Crater underwent at least one episode of drying before "recovering." It's also possible that the lake was segmented into separate ponds, where some of the ponds could have undergone more evaporation.

Because up to now only one location along the rover's path shows such a drying history, Nachon said it might give clues about how many drying episodes the lake underwent before Mars's climate became as dry as it is currently.

"It could indicate that Mars's climate 'dried out' over the long term, on a way that still allowed for the cyclical presence of a lake," Nachon said. "These results indicate a past Mars climate that fluctuated between wetter and drier periods. They also tell us about the types of chemical elements (in this case sulphur, a key ingredient for life) that were available in the liquid water present at the surface at the time, and about the type of environmental fluctuations Mars life would have had to cope with, if it ever existed."

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Materials provided by Texas A&M University. Original written by Keith Randall. Note: Content may be edited for style and length.

With Mars methane mystery unsolved, Curiosity serves scientists a new one: Oxygen

Curiosity serves scientists a new one: Oxygen

For the first time in the history of space exploration, scientists have measured the seasonal changes in the gases that fill the air directly above the surface of Gale Crater on Mars. As a result, they noticed something baffling: oxygen, the gas many Earth creatures use to breathe, behaves in a way that so far scientists cannot explain through any known chemical processes.

Over the course of three Mars years (or nearly six Earth years) an instrument in the Sample Analysis at Mars (SAM) portable chemistry lab inside the belly of NASA's Curiosity rover inhaled the air of Gale Crater and analyzed its composition. The results SAM spit out confirmed the makeup of the Martian atmosphere at the surface: 95% by volume of carbon dioxide (CO2), 2.6% molecular nitrogen (N2), 1.9% argon (Ar), 0.16% molecular oxygen (O2), and 0.06% carbon monoxide (CO). They also revealed how the molecules in the Martian air mix and circulate with the changes in air pressure throughout the year. These changes are caused when CO2 gas freezes over the poles in the winter, thereby lowering the air pressure across the planet following redistribution of air to maintain pressure equilibrium. When CO2 evaporates in the spring and summer and mixes across Mars, it raises the air pressure.

Within this environment, scientists found that nitrogen and argon follow a predictable seasonal pattern, waxing and waning in concentration in Gale Crater throughout the year relative to how much CO2 is in the air. They expected oxygen to do the same. But it didn't. Instead, the amount of the gas in the air rose throughout spring and summer by as much as 30%, and then dropped back to levels predicted by known chemistry in fall. This pattern repeated each spring, though the amount of oxygen added to the atmosphere varied, implying that something was producing it and then taking it away.

"The first time we saw that, it was just mind boggling," said Sushil Atreya, professor of climate and space sciences at the University of Michigan in Ann Arbor. Atreya is a co-author of a paper on this topic published on November 12 in the Journal of Geophysical Research: Planets.

As soon as scientists discovered the oxygen enigma, Mars experts set to work trying to explain it. They first double- and triple-checked the accuracy of the SAM instrument they used to measure the gases: the Quadrupole Mass Spectrometer. The instrument was fine. They considered the possibility that CO2 or water (H2O) molecules could have released oxygen when they broke apart in the atmosphere, leading to the short-lived rise. But it would take five times more water above Mars to produce the extra oxygen, and CO2 breaks up too slowly to generate it over such a short time. What about the oxygen decrease? Could solar radiation have broken up oxygen molecules into two atoms that blew away into space? No, scientists concluded, since it would take at least 10 years for the oxygen to disappear through this process.

"We're struggling to explain this," said Melissa Trainer, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland who led this research. "The fact that the oxygen behavior isn't perfectly repeatable every season makes us think that it's not an issue that has to do with atmospheric dynamics. It has to be some chemical source and sink that we can't yet account for."

To scientists who study Mars, the oxygen story is curiously similar to that of methane. Methane is constantly in the air inside Gale Crater in such small quantities (0.00000004% on average) that it's barely discernable even by the most sensitive instruments on Mars. Still, it's been measured by SAM's Tunable Laser Spectrometer. The instrument revealed that while methane rises and falls seasonally, it increases in abundance by about 60% in summer months for inexplicable reasons. (In fact, methane also spikes randomly and dramatically. Scientists are trying to figure out why.)

With the new oxygen findings in hand, Trainer's team is wondering if chemistry similar to what's driving methane's natural seasonal variations may also drive oxygen's. At least occasionally, the two gases appear to fluctuate in tandem.

"We're beginning to see this tantalizing correlation between methane and oxygen for a good part of the Mars year," Atreya said. "I think there's something to it. I just don't have the answers yet. Nobody does."

Oxygen and methane can be produced both biologically (from microbes, for instance) and abiotically (from chemistry related to water and rocks). Scientists are considering all options, although they don't have any convincing evidence of biological activity on Mars. Curiosity doesn't have instruments that can definitively say whether the source of the methane or oxygen on Mars is biological or geological. Scientists expect that non-biological explanations are more likely and are working diligently to fully understand them.

Trainer's team considered Martian soil as a source of the extra springtime oxygen. After all, it's known to be rich in the element, in the form of compounds such as hydrogen peroxide and perchlorates. One experiment on the Viking landers showed decades ago that heat and humidity could release oxygen from Martian soil. But that experiment took place in conditions quite different from the Martian spring environment, and it doesn't explain the oxygen drop, among other problems. Other possible explanations also don't quite add up for now. For example, high-energy radiation of the soil could produce extra O2 in the air, but it would take a million years to accumulate enough oxygen in the soil to account for the boost measured in only one spring, the researchers report in their paper.

"We have not been able to come up with one process yet that produces the amount of oxygen we need, but we think it has to be something in the surface soil that changes seasonally because there aren't enough available oxygen atoms in the atmosphere to create the behavior we see," said Timothy McConnochie, assistant research scientist at the University of Maryland in College Park and another co-author of the paper.

The only previous spacecraft with instruments capable of measuring the composition of the Martian air near the ground were NASA's twin Viking landers, which arrived on the planet in 1976. The Viking experiments covered only a few Martian days, though, so they couldn't reveal seasonal patterns of the different gases. The new SAM measurements are the first to do so. The SAM team will continue to measure atmospheric gases so scientists can gather more detailed data throughout each season. In the meantime, Trainer and her team hope that other Mars experts will work to solve the oxygen mystery.

"This is the first time where we're seeing this interesting behavior over multiple years. We don't totally understand it," Trainer said. "For me, this is an open call to all the smart people out there who are interested in this: See what you can come up with."

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NASA's Mars 2020 will hunt for microscopic fossils

Lighter colors represent higher elevation in this image of Jezero Crater on Mars, the landing site for NASA's Mars 2020 mission. The oval indicates the landing ellipse, where the rover will be touching down on Mars.

Credit: NASA/JPL-Caltech/MSSS/JHU-APL/ESA

Scientists with NASA's Mars 2020 rover have discovered what may be one of the best places to look for signs of ancient life in Jezero Crater, where the rover will land on Feb. 18, 2021.

A paper published in the journal Icarus identifies distinct deposits of minerals called carbonates along the inner rim of Jezero, the site of a lake more than 3.5 billion years ago. On Earth, carbonates help form structures that are hardy enough to survive in fossil form for billions of years, including seashells, coral and some stromatolites -- rocks formed on this planet by ancient microbial life along ancient shorelines, where sunlight and water were plentiful.

The possibility of stromatolite-like structures existing on Mars is why the concentration of carbonates tracing Jezero's shoreline like a bathtub ring makes the area a prime scientific hunting ground.

Mars 2020 is NASA's next-generation mission with a focus on astrobiology, or the study of life throughout the universe. Equipped with a new suite of scientific instruments, it aims to build on the discoveries of NASA's Curiosity, which found that parts of Mars could have supported microbial life billions of years ago. Mars 2020 will search for actual signs of past microbial life, taking rock core samples that will be deposited in metal tubes on the Martian surface. Future missions could return these samples to Earth for deeper study.

In addition to preserving signs of ancient life, carbonates can teach us more about how Mars transitioned from having liquid water and a thicker atmosphere to being the freezing desert it is today. Carbonate minerals formed from interactions between carbon dioxide and water, recording subtle changes in these interactions over time. In that sense, they act as time capsules that scientists can study to learn when -- and how -- the Red Planet began drying out.

Measuring 28 miles (45 kilometers) wide, Jezero Crater was also once home to an ancient river delta. The "arms" of this delta can be seen reaching across the crater floor in images taken from space by satellite missions like NASA's Mars Reconnaissance Orbiter. The orbiter's Compact Reconnaissance Imaging Spectrometer for Mars instrument, or CRISM, helped produce colorful mineral maps of the "bathtub ring" detailed in the new paper.

Scientists from NASA's Mars 2020 mission and the European Space Agency-Roscosmos ExoMars mission are in the Australian Outback to hone research techniques before their missions launch to the Red Planet in summer 2020. They are hoping to better understand how to search for signs of ancient life on Mars. The Pilbara region of North West Australia is home to "stromatolites," the oldest confirmed fossilized lifeforms on Earth.

"CRISM spotted carbonates here years ago, but we only recently noticed how concentrated they are right where a lakeshore would be," said the paper's lead author, Briony Horgan of Purdue University in West Lafayette, Indiana. "We're going to encounter carbonate deposits in many locations throughout the mission, but the bathtub ring will be one of the most exciting places to visit."

It isn't guaranteed that the shoreline carbonates were formed in the lake; they could have been deposited before the lake was present. But their identification makes the site's western rim, called "the marginal carbonate-bearing region," one of the richest troves of these minerals anywhere in the crater.

The Mars 2020 team expects to explore both the crater floor and delta during the rover's two-year prime mission. Horgan said the team hopes to reach the crater's rim and its carbonates near the end of that period.

"The possibility that the 'marginal carbonates' formed in the lake environment was one of the most exciting features that led us to our Jezero landing site. Carbonate chemistry on an ancient lakeshore is a fantastic recipe for preserving records of ancient life and climate," said Mars 2020 Deputy Project Scientist Ken Williford of NASA's Jet Propulsion Laboratory in Pasadena, California. JPL leads the 2020 mission. "We're eager to get to the surface and discover how these carbonates formed."

Jezero's former lake shoreline isn't the only place scientists are excited to visit. A new study in Geophysical Research Letters points to a rich deposit of hydrated silica on the edge of the ancient river delta. Like carbonates, this mineral excels at preserving signs of ancient life. If this location proves to be the bottom layer of the delta, it will be an especially good place to look for buried microbial fossils.

The Mars 2020 rover will launch in July or August 2020 from Cape Canaveral, Florida. The Mars 2020 Project at JPL manages rover development for the Science Mission Directorate at NASA Headquarters in Washington. NASA's Launch Services Program, based at the agency's Kennedy Space Center in Florida, is responsible for launch management.

Mars 2020 is part of a larger program that includes missions to the Moon as a way to prepare for human exploration of the Red Planet. Charged with returning astronauts to the Moon by 2024, NASA will establish a sustained human presence on and around the Moon by 2028 through NASA's Artemis lunar exploration plans.

The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, leads MRO's CRISM investigation.

For more information about Mars 2020, go to:

• https://mars.nasa.gov/mars2020/
• https://www.nasa.gov/mars2020

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