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jueves, 26 de septiembre de 2013

MARS : Science Benefits from Diverse Landing Area of NASA Mars Rover

SAM before installation on Curiosity
The Sample Analysis at Mars instrument suite, prior to its installation on the Curiosity rover.
Image Credit: NASA Goddard
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trenches dug by Curiosity in 2012 to collect soil samples
The Sample Analysis at Mars instrument suite found water in the dust, dirt and fine soil from the Rocknest site on Mars. (This file photo shows trenches Curiosity dug in October 2012.)
Image Credit: NASA/JPL-Caltech/MSSS
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Mosaic image of Curiosity.
Image Credit: NASA/JPL-Caltech/Malin Space Science Systems
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The first scoop of soil analyzed by the analytical suite in the belly of NASA's Curiosity rover reveals that fine materials on the surface of the planet contain several percent water by weight. The results were published today in Science as one article in a five-paper special section on the Curiosity mission.

"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.
Curiosity landed in Gale Crater on the surface of Mars on Aug. 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: 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.
"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 Greenbelt, Md. "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."
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"—the dust, dirt and fine soil—were heated to 1,535 degrees F (835 C).
Baking the sample also revealed a compound containing chlorine and oxygen, likely chlorate or perchlorate, previously found near the north pole on Mars. Finding such compounds at Curiosity's equatorial site suggests they could be distributed more globally. 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 some isotopes in the soil is similar to the ratio found in atmospheric samples analyzed earlier, 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.
SAM can also search for trace levels of organic compounds. Although several simple organic compounds were detected in the experiments at Rocknest, they aren't clearly Martian in origin. Instead, it is likely that they formed during the high-temperature experiments, when the heat decomposed perchlorates in the Rocknest samples, releasing oxygen and chlorine that then reacted with terrestrial organics already present in the SAM instrument.
A related paper, published in the Journal of Geophysical Research-Planets, details the findings of perchlorates and other chlorine-bearing compounds in the Rocknest sample. This paper is led by Daniel Glavin, a Mars Science Laboratory Science Team member at Goddard.
Glavin notes that SAM has the ability to perform another kind of experiment to address the question of whether organic molecules are present in the Martian samples. The SAM suite includes nine fluid-filled cups which hold chemicals that can react with organic molecules if present in the soil samples. "Because these reactions occur at low temperatures, the presence of perchlorates will not inhibit the detection of Martian organic compounds," said Glavin.
The combined results shed light on the composition of the planet's surface, while offering direction for future research.
"Mars has kind of a global layer, a layer of surface soil that has been mixed and distributed by frequent dust storms. So a scoop of this stuff is basically a microscopic Mars rock collection," said Leshin. "If you mix many grains of it together, you probably have an accurate picture of typical Martian crust. By learning about it in any one place you're learning about the entire planet."
Nancy Neal-Jones and Elizabeth Zubritsky
NASA's Goddard Space Flight Center, Greenbelt, Md.
301-286-0039 / 301-614-5438
nancy.n.jones@nasa.gov / elizabeth.a.zubritsky@nasa.gov
Guy Webster
NASA's Jet Propulsion Laboratory, Pasadena, Calif.
Science Benefits from Diverse Landing Area of NASA Mars Rover
NASA's Curiosity rover is revealing a great deal about Mars, from long-ago processes in its interior to the current interaction between the Martian surface and atmosphere.
Examination of loose rocks, sand and dust has provided new understanding of the local and global processes on Mars. Analysis of observations and measurements by the rover's science instruments during the first four months after the August 2012 landing are detailed in five reports in this week's edition of the journal Science.
A key finding is water molecules are bound to fine-grained soil particles, accounting for about 2 percent of the particles' weight at Gale Crater where Curiosity landed. This result has global implications, because these materials are likely distributed around the Red Planet.
Curiosity also has completed the first comprehensive mineralogical analysis on another planet using a standard laboratory method for identifying minerals on Earth. The findings about both crystalline and non-crystalline components in soil provide clues to the planet's volcanic history.
Information about the evolution of the Martian crust and deeper regions within the planet comes from Curiosity's mineralogical analysis of a football-size igneous rock called "Jake M." Igneous rocks form by cooling molten material that originated well beneath the crust. The chemical compositions of the rocks can be used to infer the thermal, pressure and chemical conditions under which they crystallized.
"No other Martian rock is so similar to terrestrial igneous rocks," said Edward Stolper of the California Institute of Technology, lead author of a report about this analysis. "This is surprising because previously studied igneous rocks from Mars differ substantially from terrestrial rocks and from Jake M."
The other four reports include analysis of the composition and formation process of a windblown drift of sand and dust, by David Blake of NASA's Ames Research Center at Moffett Field, Calif., and co-authors.
Curiosity examined this drift, called Rocknest, with five instruments, preforming an onboard laboratory analysis of samples scooped up from the Martian surface. The drift has a complex history and includes sand particles with local origins, as well as finer particles that sample windblown Martian dust distributed regionally or even globally.
The rover is equipped with a laser instrument to determine material compositions from some distance away. This instrument found that the fine-particle component in the Rocknest drift matches the composition of windblown dust and contains water molecules. The rover tested 139 soil targets at Rocknest and elsewhere during the mission's first three months and detected hydrogen -- interpreted as water -- every time the laser hit fine-particle material.
"The fine-grain component of the soil has a similar composition to the dust distributed all around Mars, and now we know more about its hydration and composition than ever before," said Pierre-Yves Meslin of the Institut de Recherche en Astrophysique et Planétologie in Toulouse, France, lead author of a report about the laser instrument results.
A laboratory inside Curiosity used X-rays to determine the composition of Rocknest samples. This technique, discovered in 1912, is a laboratory standard for mineral identification on Earth. The equipment was miniaturized to fit on the spacecraft that carried Curiosity to Mars, and this has yielded spinoff benefits for similar portable devices used on Earth. David Bish of Indiana University in Bloomington co-authored a report about how this technique was used and its results at Rocknest.
X-ray analysis not only identified 10 distinct minerals, but also found an unexpectedly large portion of the Rocknest composition is amorphous ingredients, rather than crystalline minerals. Amorphous materials, similar to glassy substances, are a component of some volcanic deposits on Earth.
Another laboratory instrument identified chemicals and isotopes in gases released by heating the Rocknest soil in a tiny oven. Isotopes are variants of the same element with different atomic weights. These tests found water makes up about 2 percent of the soil, and the water molecules are bound to the amorphous materials in the soil.
"The ratio of hydrogen isotopes in water released from baked samples of Rocknest soil indicates the water molecules attached to soil particles come from interaction with the modern atmosphere," said Laurie Leshin of Rensselaer Polytechnic Institute in Troy, N.Y., lead author of a report about analysis with the baking instrument.
Baking and analyzing the Rocknest sample also revealed a compound with chlorine and oxygen, likely chlorate or perchlorate, which previously was known to exist on Mars only at one high-latitude site. This finding at Curiosity's equatorial site suggests more global distribution.
Data obtained from Curiosity since the first four months of the rover's mission on Mars are still being analyzed. NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the mission for NASA's Science Mission Directorate in Washington. The mission draws upon international collaboration, including key instrument contributions from Canada, Spain, Russia and France.
For more information about the mission, visit:
Guillermo Gonzalo Sánchez Achutegui

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