Water, like gold, is where you find it and NASA’s Curiosity Mars rover has discovered water in the Martian soil in greater quantities than expected. The unmanned explorer’s analysis of the first soil samples taken in Gale Crater indicate that water is present globally and uniformly in the Martian topsoil, and isn't found just at the polar ice caps.
However much water may have been on Mars in its distant past, today it is a desiccated planet where one of the major objectives in the search for life is finding places outside of the polar ice caps and closer to the relatively warm equator where water may still exist.
According to the findings, which NASA published in a series of five papers in Science, Curiosity discovered water in the Martian topsoil in quantities of 1.5 to 3 percent by weight. However, this is not free water soaked into the soil, but water that is locked inside mineral compounds. The soil involved is the sand and dust that is found all over Mars thanks to millennia of planet-wide wind storms, which means that the results in Gale Crater apply to anywhere else on the Red Planet.
The analysis was made using the Sample Analysis at Mars (SAM) laboratory, the largest of Curiosity’s internal labs and the one that made the news recently due to its discovery that Mars has no methane in its atmosphere. SAM contains a gas chromatograph, a mass spectrometer, and a tunable laser spectrometer.
The sample was collected at the Rocknest area of Gale Crater, specifically the fifth scoop of soil to be run through SAM. This was sifted and then heated to 1,535° F (835° C) under a helium flow, and the gases given off were analyzed by SAM’s instruments. In addition to water, SAM also detected sulfur dioxide, carbon dioxide, and oxygen. Due to the high temperature needed to release the water, scientists believe that is is bound into the minerals of the soil.
The presence of water is of great scientific value, but NASA also believes that it has practical implications as well. Future robotic and manned missions to Mars may one day be able to bake the water out of the soil anywhere on the planet and use it for life support and even fuel.
Despite the discovery of water, the implications for the search for life are not as great as they may seem at first glance. The topsoil is still, for all practical purposes, utterly dry due to the lack of free water. Worse, scientists believe that organics can't survive in the surface soil, and that the indications of simple organic compounds that Curiosity have detected are probably from decomposed perchlorates reacting with terrestrial organics in SAM.
Perchlorates are molecules containing chlorine and oxygen. They’ve previously been found near the Martian north pole and can destroy organic carbon molecules. Their presence at Gale Crater indicates that they are much more widespread than previously thought and are an example of how active the Martian topsoil is.
Water is one of the most powerful solvents known, and on Earth it destroys many chemicals that are hazardous to organic molecules. The soil blown across Mars, on the other hand, is so dry and so bombarded with UV radiation on a daily basis that these chemicals are common enough that many scientists believe that life cannot exist on the surface. This is one reason why drilling missions are so popular with NASA and other space agencies that hope to find life in deeper protected layers.
"This work not only demonstrates that SAM is working beautifully on Mars, but also shows how SAM fits into Curiosity's powerful and comprehensive suite of scientific instruments," says Paul Mahaffy, principal investigator for SAM at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "By combining analyses of water and other volatiles from SAM with mineralogical, chemical and geological data from Curiosity's other instruments, we have the most comprehensive information ever obtained on Martian surface fines. These data greatly advance our understanding surface processes and the action of water on Mars."