miércoles, 13 de marzo de 2013

NASA Rover Finds Conditions Once Suited for Ancient Life on Mars

March 12, 2013

PASADENA, Calif. -- An analysis of a rock sample collected by NASA's Curiosity rover shows ancient Mars could have supported living microbes

Scientists identified sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon -- some of the key chemical ingredients for life -- in the powder Curiosity drilled out of a sedimentary rock near an ancient stream bed in Gale Crater on the Red Planet last month. 

"A fundamental question for this mission is whether Mars could have supported a habitable environment," said Michael Meyer, lead scientist for NASA's Mars Exploration Program at the agency's headquarters in Washington. "From what we know now, the answer is yes.

Clues to this habitable environment come from data returned by the rover's Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin) instruments. The data indicate the Yellowknife Bay area the rover is exploring was the end of an ancient river system or an intermittently wet lake bed that could have provided chemical energy and other favorable conditions for microbes. The rock is made up of a fine-grained mudstone containing clay minerals, sulfate minerals and other chemicals. This ancient wet environment, unlike some others on Mars, was not harshly oxidizing, acidic or extremely salty. 

The patch of bedrock where Curiosity drilled for its first sample lies in an ancient network of stream channels descending from the rim of Gale Crater. The bedrock also is fine-grained mudstone and shows evidence of multiple periods of wet conditions, including nodules and veins. 

Curiosity's drill collected the sample at a site just a few hundred yards away from where the rover earlier found an ancient streambed in September 2012. 

"Clay minerals make up at least 20 percent of the composition of this sample," said David Blake, principal investigator for the CheMin instrument at NASA's Ames Research Center in Moffett Field, Calif. 

These clay minerals are a product of the reaction of relatively fresh water with igneous minerals, such as olivine, also present in the sediment. The reaction could have taken place within the sedimentary deposit, during transport of the sediment, or in the source region of the sediment. The presence of calcium sulfate along with the clay suggests the soil is neutral or mildly alkaline

Scientists were surprised to find a mixture of oxidized, less-oxidized, and even non-oxidized chemicals, providing an energy gradient of the sort many microbes on Earth exploit to live. This partial oxidation was first hinted at when the drill cuttings were revealed to be gray rather than red. 

"The range of chemical ingredients we have identified in the sample is impressive, and it suggests pairings such as sulfates and sulfides that indicate a possible chemical energy source for micro-organisms," said Paul Mahaffy, principal investigator of the SAM suite of instruments at NASA's Goddard Space Flight Center in Greenbelt, Md. 

An additional drilled sample will be used to help confirm these results for several of the trace gases analyzed by the SAM instrument. 

"We have characterized a very ancient, but strangely new 'gray Mars' where conditions once were favorable for life," said John Grotzinger, Mars Science Laboratory project scientist at the California Institute of Technology in Pasadena, Calif. "Curiosity is on a mission of discovery and exploration, and as a team we feel there are many more exciting discoveries ahead of us in the months and years to come.

Scientists plan to work with Curiosity in the "Yellowknife Bay" area for many more weeks before beginning a long drive to Gale Crater's central mound, Mount Sharp. Investigating the stack of layers exposed on Mount Sharp, where clay minerals and sulfate minerals have been identified from orbit, may add information about the duration and diversity of habitable conditions. 

NASA's Mars Science Laboratory Project has been using Curiosity to investigate whether an area within Mars' Gale Crater ever has offered an environment favorable for microbial life. Curiosity, carrying 10 science instruments, landed seven months ago to begin its two-year prime mission. NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the project for NASA's Science Mission Directorate in Washington. 

For more about the mission, visit: http://www.jpl.nasa.gov/msl , http://mars.jpl.nasa.gov/msl/ and http://www.nasa.gov/msl . You can follow the mission on Facebook and Twitter at: http://www.facebook.com/marscuriosity and http://www.twitter.com/marscuriosity

DC Agle 818-393-9011
Jet Propulsion Laboratory, Pasadena, Calif.

Dwayne Brown 202-358-1726
NASA Headquarters, Washington

Two Different Aqueous Environments
This set of images compares rocks seen by NASA's Opportunity rover and Curiosity rover at two different parts of Mars. On the left is " Wopmay" rock, in Endurance Crater, Meridiani Planum, as studied by the Opportunity rover. 

First Curiosity Drilling Sample in the Scoop. This image from NASA's Curiosity rover shows the first sample of powdered rock extracted by the rover's drill. Image credit: NASA/JPL-Caltech/MSSS 

Minerals at 'Rocknest' and 'John Klein' 
This side-by-side comparison shows the X-ray diffraction patterns of two different samples collected from the Martian surface by NASA's Curiosity rover. These images, made from data obtained by Curiosity's Chemistry and Mineralogy instrument (CheMin), show the patterns obtained from a drift of windblown dust and sand called "Rocknest" and from a powdered rock sample drilled from the "John Klein" bedrock.

The presence of abundant clay minerals in the John Klein drill powder and the lack of abundant salt suggest a fresh water environment. The presence of calcium sulfates rather than magnesium or iron sulfates (as found at Meridiani Planum by NASA's Mars Exploration Rover Opportunity) suggests a neutral to mildly alkaline pH environment. The Rocknest sand shadow mineralogy suggests a dry, aeolian (wind-shaped) environment with low water activity. The John Klein mineralogy suggests a lacustrine (lakebed) environment with high water activity.

As seen on the left, the Rocknest data reveal abundant plagioclase feldspar, pyroxene and olivine minerals. The data also indicate reveal small amounts of magnetite and anhydrite. In addition, the Rocknest sample contains 25 to 35 percent amorphous, or non-crystalline, material.

X-ray diffraction analysis of the John Klein drill powder reveals abundant phyllosilicate (a class of clay minerals called smectites that form by the action of relatively pure and neutral pH water on source minerals), plagioclase feldspar, pyroxene, magnetite and olivine. Alternatively, the clay minerals could have been transported by water from sources higher up the sediment fan to form the John Klein mineral assemblage. The region of the pattern indicating the phyllosilicates is labeled in the annotated version of this image. The data also show minor amounts of anhydrite and bassanite. The John Klein sample also contains about 20 percent amorphous material.

NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the project for NASA's Science Mission Directorate, Washington, and built Curiosity and CheMin.

An Earth Analog to Mars' Yellowknife Bay. This set of images shows a modern terrestrial analog to the "Yellowknife Bay" area that NASA's Curiosity rover is exploring. At left is a sampling pit exposing clay-bearing lake sediments, deposited in a basaltic basin in southern Australia. Image Credit: NASA/JPL-Caltech/Ames 

Location of John Klein Drill Site 

Studying Habitability in Ancient Martian Environments
This set of images shows the results from the rock abrasion tool from NASA's Mars Exploration Rover Opportunity (left) and the drill from NASA's Curiosity rover (right). Note how the rock grindings from Opportunity are brownish red, indicating the presence of hematite, a strongly oxidized iron-bearing mineral. Such minerals are less supportive of habitability and also may degrade organic compounds. The diameter of the abraded circle is 1.8 inches (4.5 centimeters). The image was cropped from an image
taken on Sol 35 (the 35th Martian day of Opportunity's operations, or Feb. 28, 2004, on Earth) by Opportunity's panoramic camera at a target called "Guadalupe" inside Eagle Crater.

On the right is the hole produced by Curiosity during the first drilling into a rock on Mars to collect a sample from inside the rock. In this case, the rock produced gray tailings -- not red -- suggesting the presence of iron that is less oxidized. One possibility is magnetite, which was determined to be present by Curiosity's Chemistry and Mineralogy instrument. Magnetite has less oxygen than hematite and would be more compatible with habitability and the preservation of organics, all other factors being equal. These other factors would include the primary concentration of organics in the sedimentary environment, in addition to later exposure of rock to surface radiation. The diameter of the hole is 0.63 inch (1.6 centimeters), which is approximately 1/3 of that on the left-hand image. The image was cropped fromPIA16726. It was taken on Sol 182 (the 182d Martian day of Curiosity's operations, or Feb. 8, 2013, on Earth) by the Mars Hand Lens Imager on Curiosity's arm after that day's drilling at a target rock called "John Klein."

JPL manages the Mars Science Laboratory/Curiosity for NASA's Science Mission Directorate in Washington. The rover was designed, developed and assembled at JPL, a division of the California Institute of Technology in Pasadena.

For more about NASA's Curiosity mission, visit: http://www.jpl.nasa.gov/msl, http://www.nasa.gov/mars, andhttp://mars.jpl.nasa.gov/msl.

Major Gases Released from Drilled Samples of the 'John Klein' Rock
An analysis of a drilled rock sample from NASA's Curiosity rover shows the presence of water, carbon dioxide, oxygen, sulfur dioxide, and hydrogen sulfide released on heating. The results analyzing the high temperature water release are consistent with smectite clay minerals.

Curiosity's Sample Analysis at Mars (SAM) instrument suite conducted the analysis. The first step in the analysis of a portion of this drilled sample was to heat the sample in a quartz oven to 1,535 degrees Farenheit (835 degrees Celsius) and analyze the gases as they were released using SAM's quadrupole mass spectrometer (QMS). The signatures of more than five hundred mass values were sampled during the heating of this drilled sample and analyzed by the QMS. Five are shown in the graph. These traces are diagnostic of water, carbon dioxide, oxygen, and two forms of sulfur (sulfur dioxide, the oxidized form, and hydrogen sulfide, the reduced form) measured by the QMS.

The second step in the analysis was to send a portion of the gas released from the sample to the tunable laser spectrometer (TLS) to measure isotopes of carbon, oxygen and hydrogen, in both water and carbon dioxide. The ratio of deuterium (a heavy form of hydrogen) to the lighter, more abundant form of hydrogen was lower than the deuterium-to-hydrogen ratio measured by SAM in more loosely bound water in the sample from the "Rocknest" drift. The high deuterium-to-hydrogen ratio in water in the Mars atmosphere is a signature of the lighter hydrogen more rapidly escaping to space over geological time. Therefore, measuring the deuterium-to-hydrogen in water released from rocks is one tool that can be used to explore ancient reservoirs of water on Mars.

The third step in the analysis was to inject gas trapped during the heating process into SAM's third instrument, the gas chromatograph. Individual compounds separate out in time in a long capillary column in this instrument and are then introduced into the QMS. The gas chromatograph mass spectrometer is a prime tool in the SAM search for organic compounds.

The ratio of reduced species to oxidized species released by the SAM ovens is significantly higher in this drilled bedrock than in the previously scooped dust samples. These results indicate a significant amount of available chemical energy because oxidized and less oxidized versions of molecules are present. This result, combined with suitable aqueous conditions at this site in the distant past, made this a potentially habitable environment.

The SAM analysis was conducted on Sol 200 (the 200th Martian day of Curosity's operations, which was Feb. 27, 2013, on Earth).

JPL manages the Mars Science Laboratory/Curiosity for NASA's Science Mission Directorate in Washington. The rover was designed, developed and assembled at JPL, a division of the California Institute of Technology in Pasadena.

For more about NASA's Curiosity mission, visit: http://www.jpl.nasa.gov/msl, http://www.nasa.gov/mars, andhttp://mars.jpl.nasa.gov/msl.

Chlorinated Forms of Methane at 'John Klein' Site
NASA's Curiosity rover has detected the simple carbon-containing compounds chloro- and dichloromethane from the powdered rock sample extracted from the "John Klein" rock on Mars. These species were detected by the gas chromatograph mass spectrometer (GCMS) on Curiosity's Sample Analysis at Mars instrument (SAM).

The blue peak on the left shows the presence of chloromethane and the two red peaks on the right show the presence of dichloromethane. The powdered rock sample from John Klein was heated and some of the gas released was injected into the capillary column of the GCMS. The time at which different compounds exited the gas chromatograph column and entered the mass spectrometer, and the patterns produced in the mass spectrometer indicated molecular identity.

This chart also indicates "blank runs," which were conducted on Mars prior to delivery of this drilled sample to SAM. The runs helped to insure that signals from the gases released from the John Klein sample were above background levels. Curiosity began drilling at John Klein in February 2013. The SAM analysis was conducted on Sol 200 (the 200th Martian day of Curosity's operations, which was Feb. 27, 2013, on Earth).

Both chloro- and dichloromethane were also detected earlier by SAM at the "Rocknest" drift. It is possible that these simple carbon-containing compounds were produced by the reaction between Martian carbon and chlorine released when this sample was heated in the SAM oven. However, analysis of an additional drilled sample is required to help scientists understand if instead any residual terrestrial carbon from the drill, or perhaps chlorine left over from the Rocknest sample, is responsible for the generation of some or all of these compounds. In any case, these detections demonstrate clearly that the SAM GCMS is performing as designed and ready to continue the search for organic compounds in Gale Crater.

JPL manages the Mars Science Laboratory/Curiosity for NASA's Science Mission Directorate in Washington. The rover was designed, developed and assembled at JPL, a division of the California Institute of Technology in Pasadena.

For more about NASA's Curiosity mission, visit: http://www.jpl.nasa.gov/msl, http://www.nasa.gov/mars, andhttp://mars.jpl.nasa.gov/msl.

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