Mars loses water to space during warm, stormy seasons

All kinds of geological formations on Mars, alluvial fans, dry lake beds and eroded river valleys, suggest the Red Planet once hosted an abundance of water. Today, the water is mostly gone. What's left is largely locked up in the planet's polar ice caps. Scientists have been trying to figure out where all the water went and how fast it disappeared. New research, published this week in the journal Science, suggests Mars' seasonality may have dictated the rate at which water vapor was able to escape from the atmosphere and into space. In addition to the water trapped in the Red Planet's ice caps, trace amounts of water vapor persist in the Martian atmosphere. If these tiny water crystals rise high enough into the atmosphere, they can dissipate into space. To better understand this mechanism of water loss, scientists used data collected by the NASA spacecraft ExoMars Trace Gas Orbiter to produce vertical distribution of water in the Martian atmosphere. "TGO uses solar occultation method," researcher Anna Fedorova, an astrophysicist at the Space Research Institute in Moscow, told UPI in an email. "The presence of water vapor and their amount are determined using the spectroscopic signatures near 1.38 micrometer [infrared bands] by the NIR/ACS spectrometer." In other words, TGO studies how sunlight is absorbed as it passes through the Martian atmosphere in order to detect the presence of H2O. "The results were obtained using the analysis of absorption features of H2O and CO2 gases," Fedorova said. "For each occultation we have the vertical profiles of H2O density and temperature from CO2."

Scientists surveyed the data for links between temperature and water distribution and found the Martian atmosphere became supersaturated during the warmest portions of its orbit. Their findings suggest water is more likely to rise into the upper atmosphere and escape to space when Mars is warmer and wetter.

Authors of the new study suspect their findings will improve a variety of Martian climate models.

"Saturation is one of the key points in the water transport on Mars," Fedorova told UPI. "The climate models have to be updated to predict such levels of supersaturation and perform the necessary adjustments."

So far, TGO has only collected water vapor distribution data during Mars warm season, so there isn't enough data to understand the full picture of seasonal water distribution on Mars.

"We don't have information that the cold aphelion season is less supersaturated," Fedorova said.

That data will be available soon, and when it is, scientists will have more analysis to do.

Mars Express Detects Liquid Water Hidden Under Planet's South Pole

Evidence for the Red Planet's watery past is prevalent across its surface in the form of vast dried-out river valley networks and gigantic outflow channels clearly imaged by orbiting spacecraft. Orbiters, together with landers and rovers exploring the Martian surface, also discovered minerals that can only form in the presence of liquid water. But the climate has changed significantly over the course of the planet's 4.6-billion-year history and liquid water cannot exist on the surface today, so scientists are looking underground. Early results from the 15-year-old Mars Express spacecraft already found that water ice exists at the planet's poles and is also buried in layers interspersed with dust. The presence of liquid water at the base of the polar ice caps has long been suspected; after all, from studies on Earth, it is well known that the melting point of water decreases under the pressure of an overlying glacier. Moreover, the presence of salts on Mars could further reduce the melting point of water and keep the water liquid even at below-freezing temperatures. But until now evidence from the Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument, MARSIS, the first radar sounder ever to orbit another planet, remained inconclusive. It has taken the persistence of scientists working with this subsurface-probing instrument to develop new techniques in order to collect as much high-resolution data as possible to confirm their exciting conclusion.

Ground-penetrating radar uses the method of sending radar pulses towards the surface and timing how long it takes for them to be reflected back to the spacecraft, and with what strength. The properties of the material that lies between influences the returned signal, which can be used to map the subsurface topography.

The radar investigation shows that south polar region of Mars is made of many layers of ice and dust down to a depth of about 1.5 km in the 200-km-wide area analyzed in this study. A particularly bright radar reflection underneath the layered deposits is identified within a 20-km-wide zone.

Analyzing the properties of the reflected radar signals and considering the composition of the layered deposits and expected temperature profile below the surface, the scientists interpret the bright feature as an interface between the ice and a stable body of liquid water, which could be laden with salty, saturated sediments. For MARSIS to be able to detect such a patch of water, it would need to be at least several tens of centimeters thick.

"This subsurface anomaly on Mars has radar properties matching water or water-rich sediments," says Roberto Orosei, principal investigator of the MARSIS experiment and lead author of the paper published in the journal Science.

"This is just one small study area; it is an exciting prospect to think there could be more of these underground pockets of water elsewhere, yet to be discovered."

"We'd seen hints of interesting subsurface features for years but we couldn't reproduce the result from orbit to orbit, because the sampling rates and resolution of our data was previously too low," adds Andrea Cicchetti, MARSIS operations manager and a co-author on the new paper.

"We had to come up with a new operating mode to bypass some onboard processing and trigger a higher sampling rate and thus improve the resolution of the footprint of our dataset: now we see things that simply were not possible before."

The finding is somewhat reminiscent of Lake Vostok, discovered some 4 km below the ice in Antarctica on Earth. Some forms of microbial life are known to thrive in Earth's subglacial environments, but could underground pockets of salty, sediment-rich liquid water on Mars also provide a suitable habitat, either now or in the past? Whether life has ever existed on Mars remains an open question, and is one that Mars missions, including the current European-Russian ExoMars orbiter and future rover, will continue to explore.

"The long duration of Mars Express, and the exhausting effort made by the radar team to overcome many analytical challenges, enabled this much-awaited result, demonstrating that the mission and its payload still have a great science potential," says Dmitri Titov, ESA's Mars Express project scientist.

"This thrilling discovery is a highlight for planetary science and will contribute to our understanding of the evolution of Mars, the history of water on our neighbor planet and its habitability."

Mars Express launched 2 June 2003 and celebrates 15 years in orbit on 25 December this year.

SwRI scientist helps characterize water on lunar surface

A Southwest Research Institute scientist with expertise in how water reacts with lunar soil contributed to a new study that indicates water and/or hydroxyl may be more prevalent on the Moon's surface than previously thought."Water on the Moon is of intense interest for many reasons," said SwRI's Dr. Michael Poston, a coauthor of the paper, "Widespread Distribution of OH/ H2O on the Lunar Surface Inferred from Spectral Data," published in Nature Geoscience online. Water has been the focus of many lunar missions, largely because it is a critical resource for a Moon habitat. "When you split water molecules, you end up with oxygen and hydrogen, critical components for breathable air and rocket fuel. Hydroxyl (OH) is a more reactive relative to water and not as attractive as water in terms of supporting a lunar station." Up until the last decade or so, scientists thought negligible amounts of water were present on the Moon, perhaps existing mainly as ice in the permanently shaded craters near the poles. However, in 2009, NASA's Moon Minerology Mapper spectrometer onboard India's Chandrayaan-1 spacecraft and two other NASA flight spectrometers detected signatures interpreted as water in sunlight reflected from the Moon's surface.

These data, along with measurements from NASA's Lunar Reconnaissance Orbiter (LRO), also indicated the amount of water on the surface could vary diurnally ? a cycle based on the time of day ? and be more common at higher latitudes. One of these measurements came from the Lyman Alpha Mapping Project (LAMP), built and managed by SwRI.

"This research is a great example of how multiple instruments and investigations allow you to do more than what you could do with one instrument alone," added the paper's lead author Dr. Josh Bandfield, of the Space Science Institute in Boulder, Colorado. "As new data about the temperature environment on the Moon emerged, it became apparent that we needed to recalibrate our spectral datasets."

The Moon produces a mixture of reflected and emitted light. It glows in the infrared when heated by the Sun, and its surface reflects infrared light from the Sun. Using detailed surface temperature maps from the Diviner Lunar Radiometer Experiment on LRO and thermophysics modeling, Bandfield could subtract the right amount of Moon glow from the reflected sunlight to better characterize the inferred measurements of water.

Poston has conducted extensive experiments with water and lunar samples collected by the Apollo missions that revealed the amount of energy needed to remove water molecules from lunar rock. This helps scientists understand how tightly water is bound to surface materials.

Based on the team's results, it appears that OH/H2O is present on lunar surfaces under much more wide-ranging conditions than previously understood. The OH/H2O, either in a steady state or actually static, does not appear to be daily migrating about the lunar surface in significant quantities. This limits the amount of OH/H2O that would land in dark polar craters and be trapped there for millennia.

"The next step is to determine whether it's water, hydroxyl, or a mixture of the two - and where it came from," Poston said. "Is it from external sources, delivered by comet or asteroid impacts? Is it from internal processes on the Moon itself, such as ancient volcanism? Or could it be an ongoing process of the solar wind reacting with lunar materials to create OH or HH2O?"

"Some of these scientific problems are very, very difficult, and it's only by drawing on multiple resources from different missions that we are able to hone in on an answer," said LRO project scientist John Keller of NASA's Goddard Space Flight Center in Greenbelt, Maryland.