Mars  

Although they did not detect the actual salty brines, researchers looking at data from the Mars Curiosity rover are now confident there are small amounts of liquid water just beneath the surface of the red planet.

The weather on Mars, combined with soil conditions in the prescence of a type of salt NASA's Curiosity rover has identified in Martian soil, mean a liquid salty brine may exist on the red planet, just under the surface.

Perchlorate identified in Martian soil by the Curiosity mission, and previously by NASA's Phoenix Mars Lander mission, has properties of absorbing water vapor from the atmosphere and lowering the freezing temperature of water. This has been proposed for years as a mechanism for possible existence of transient liquid brines at higher latitudes on modern Mars, despite the Red Planet's cold and dry conditions.

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New calculations were based on more than a full Mars year of temperature and humidity measurements by Curiosity. They indicate that conditions at the rover's near-equatorial location were favorable for small quantities of brine to form during some nights throughout the year, drying out again after sunrise. Conditions should be even more favorable at higher latitudes, where colder temperatures and more water vapor can result in higher relative humidity more often.

"Liquid water is a requirement for life as we know it, and a target for Mars exploration missions," said the report's lead author, Javier Martin-Torres of the Spanish Research Council, Spain, and Lulea University of Technology, Sweden, and a member of Curiosity's science team that published their findings in the journal Nature Geoscience. "Conditions near the surface of present-day Mars are hardly favorable for microbial life as we know it, but the possibility for liquid brines on Mars has wider implications for habitability and geological water-related processes."

The weather data in the report published today in Nature Geosciences come from the Cuirosity's Rover Environmental Monitoring Station (REMS), which was provided by Spain and includes a relative-humidity sensor and a ground-temperature sensor. NASA's Mars Science Laboratory Project is using Curiosity to investigate both ancient and modern environmental conditions in Mars' Gale Crater region. The report also draws on measurements of hydrogen in the ground by the rover's Dynamic Albedo of Neutrons (DAN) instrument, from Russia.

"We have not detected brines, but calculating the possibility that they might exist in Gale Crater during some nights testifies to the value of the round-the-clock and year-round measurements REMS is providing," said Curiosity Project Scientist Ashwin Vasavada of NASA's Jet Propulsion Laboratory, Pasadena, California, one of the new report's co-authors.

"Conditions near the surface of present-day Mars are hardly favorable for microbial life as we know it, but the possibility for liquid brines on Mars has wider implications for habitability and geological water-related processes."

Curiosity is the first mission to measure relative humidity in the Martian atmosphere close to the surface and ground temperature through all times of day and all seasons of the Martian year. Relative humidity depends on the temperature of the air, as well as the amount of water vapor in it. Curiosity's measurements of relative humidity range from about five percent on summer afternoons to 100 percent on autumn and winter nights.

Air filling pores in the soil interacts with air just above the ground. When its relative humidity gets above a threshold level, salts can absorb enough water molecules to become dissolved in liquid, a process called deliquescence. Perchlorate salts are especially good at this. Since perchlorate has been identified both at near-polar and near-equatorial sites, it may be present in soils all over the planet.

Scientists using the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter have in recent years documented numerous sites on Mars where dark flows appear and extend on slopes during warm seasons. These features are called recurring slope lineae, or RSL. A leading hypothesis for how they occur involves brines formed by deliquesence.

"Gale Crater is one of the least likely places on Mars to have conditions for brines to form, compared to sites at higher latitudes or with more shading. So if brines can exist there, that strengthens the case they could form and persist even longer at many other locations, perhaps enough to explain RSL activity," said HiRISE Principal Investigator Alfred McEwen of the University of Arizona, Tucson, also a co-author of the new report.

In the year following its August 2012 landing, Curiosity found evidence for ancient streambeds and a lakebed environment more than 3 billion years ago that offered conditions favorable for microbial life. Now, the rover is examining a layered mountain inside Gale Crater for evidence about how ancient environmental conditions evolved.


SOURCE  Jet Propulsion Laboratory

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 Mars  

The first scoop of soil analyzed by the SAM instrument of NASA's Curiosity rover reveals that fine materials on the surface of the planet contain two percent water by weight. The discovery reveals new insights into the conditions on Mars and the planet's ability to support life.

NASA has announced that the Mars Curiosity rover has successfully found water in a sample of soil taken from a digging site known as "Rocknest." This isn't the first proof of water on Mars, but it could be the proof NASA needs to start realistically considering sending people to the Red Planet.

The announcement supports research from the Mars Reconnaissance Orbiter (MRO), a NASA probe, say they've observed seasonally varying features on the surface of the Red Planet that could be carved by briny water.

Previously ice has been found on Mars at the planet's poles, inside some craters and sitting beneath the surface across vast swaths of the middle latitudes. Also, there is ample evidence that liquid water formed vast oceans on Mars in the distant past, carving valleys and other surface features.

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With a handful of exceptions, water is necessary for life as we know it. Not only is most of Earth's life water-based, but most scientists think life wouldn't have arisen in the first place if not for the watery "primordial soup" that covered the young Earth. Water makes it easier for organic molecules to swirl around and bump into each other to form interesting compounds.

"One of the most exciting results from this very first solid sample ingested by Curiosity is the high percentage of water in the soil," said Laurie Leshin, lead author of one paper and dean of the School Science at Rensselaer Polytechnic Institute. "About 2 percent of the soil on the surface of Mars is made up of water, which is a great resource, and interesting scientifically." The sample also released significant carbon dioxide, oxygen and sulfur compounds when heated.

According to NASA, each cubic foot of Martian soil contains around two pints of liquid water, though the molecules are not freely accessible; they are bound to other minerals in the soil.

Sample Analysis at Mars instrument suite

The Curiosity rover has been on Mars for a little over a year now, landing in an area near the equator of the planet known as Gale Crater. Its target is to circle and climb Mount Sharp, which is near the center of the crater, a five kilometer high mound of layered rock that will help scientists unravel the history of the planet.

Now, NASA scientists published a series of five papers in the journal Science, which detail the experiments carried out by the various scientific instruments aboard Curiosity in its first four months on the martian surface. Though highlights from the year-long mission have been released at conferences and press conferences, these are the first set of formal, peer-reviewed results from the Curiosity mission.

One of those instruments was employed in the current research: the Sample Analysis at Mars (SAM) instrument suite, which includes a gas chromatograph, a mass spectrometer and a tunable laser spectrometer. These tools enable SAM to identify a wide range of chemical compounds and determine the ratios of different isotopes of key elements.

"We tend to think of Mars as this dry place – to find water fairly easy to get out of the soil at the surface was exciting to me," said Laurie Leshin, dean of science at Rensselaer Polytechnic Institute and lead author on the Science paper which confirmed the existence of water in the soil. "If you took about a cubic foot of the dirt and heated it up, you'd get a couple of pints of water out of that – a couple of water bottles' worth that you would take to the gym."

About 2% of the soil, by weight, was water. Curiosity made the measurement by scooping up a sample of the Martian dirt under its wheels, sieving it and dropping tiny samples into an oven in its belly, an instrument called Sample Analysis at Mars. "We heat [the soil] up to 835C and drive off all the volatiles and measure them," said Leshin. "We have a very sensitive way to sniff those and we can detect the water and other things that are released."

Aside from water, the heated soil released sulphur dioxide, carbon dioxide and oxygen as the various minerals within it were decomposed as they warmed up.

Along with discoveries of organic chemicals on Mars, the existence of ample water on the planet further strengthens the impetus for humans to explore and eventually colonize Mars.


SOURCE  NASA

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