The first scoop of soil analyzed by the analytical suite in the belly of NASA’s Curiosity rover revealed that fine materials on the surface of the planet contain several percent water by weight. The results were published in Science as one article in a five-paper special section on the Curiosity mission. Rensselaer Dean of Science Laurie Leshin is the study’s lead author.
NASA's Curiosity rover found evidence for an ancient, flowing stream on Mars at a few sites, including the rock outcrop pictured here, which the science team has named "Hottah" after Hottah Lake in Canada’s Northwest Territories. Image credit: NASA/JPL-Caltech/MSSS
This set of images compares the Link outcrop of rocks on Mars (left) with similar rocks seen on Earth (right). Image credit: NASA/JPL-Caltech/MSSS and PSI
“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 Leshin. “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.
“One of the most exciting results from this very first solid sample ingested by Curiosity is the high percentage of water in the soil.”
Curiosity landed in Gale Crater on the surface of Mars on August 6, 2012, charged with answering the question “Could Mars have once harbored life?” To do that, Curiosity is the first rover on Mars to carry equipment for gathering and processing samples of rock and soil. One of those instruments was employed in the current research: Sample Analysis at Mars (SAM) includes a gas chromotograph, a mass spectrometer, and a tunable laser spectrometer enabling it to identify a wide range of chemical compounds and determine the ratios of different isotopes of key elements.
“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,” said Paul Mahaffy, principal investigator for SAM at NASA’s Goddard Space Flight Center in 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 of surface processes and the action of water on Mars.”
“This is the first solid sample that we’ve analyzed with the instruments on Curiosity. It’s the very first scoop of stuff that’s been fed into the analytical suite. Although this is only the beginning of the story, what we’ve learned is substantial,” said Leshin, who co-wrote the article, titled “Volatile, Isotope and Organic Analysis of Martian Fines with the Mars Curiosity Rover.” Thirty-four researchers, all members of the Mars Science Laboratory Science Team, contributed to the paper.
In this study, scientists used the rover’s scoop to collect dust, dirt, and finely grained soil from a sandy patch known as “Rocknest.” Researchers fed portions of the fifth scoop into SAM. Inside SAM, the “fines”—as the dust, dirt, and fine soil is known—were heated to 835 degrees Celsius.
Baking the sample also revealed a compound containing chlorine and oxygen, likely chlorate or perchlorate, previously known only from high-latitude locations on Mars. This finding at Curiosity’s equatorial site suggests more global distribution. The analysis also suggests the presence of carbonate materials, which form in the presence of water.
In addition to determining the amount of the major gases released, SAM also analyzed ratios of isotopes of hydrogen and carbon in the released water and carbon dioxide. Isotopes are variants of the same chemical element with different numbers of neutrons, and therefore different atomic weights. SAM found that the ratio of isotopes in the soil is similar to that found in the atmosphere analyzed earlier by Curiosity, indicating that the surface soil has interacted heavily with the atmosphere.
“The isotopic ratios, including hydrogen-to-deuterium ratios and carbon isotopes, tend to support the idea that as the dust is moving around the planet, it’s reacting with some of the gases from the atmosphere,” Leshin said.
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