Sen— Analysis of a rock sample collected by NASA's Curiosity rover shows ancient Mars could have supported living microbes.
Scientists identified some of the key chemical ingredients for life - sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon - in powder Curiosity drilled out of a sedimentary rock near an ancient stream bed in Gale Crater. The sample comes from a site just a few hundred yards away from where the rover earlier found an ancient streambed in September 2012.
False colour map showing the area in Gale Crater where Curiosity rover landed in 2012 and the location where Curiosity collected its first drilled sample at the "John Klein" rock. Image credit: NASA/JPL-Caltech/MSSS
"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."
Data returned by the rover's Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin) instruments indicate the Yellowknife Bay area the rover has been 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.
Side-by-side comparison shows the X-ray diffraction patterns of two different samples collected from the Martian surface by NASA's Curiosity rover. Image credit: NASA/JPL-Caltech/Ames
The rock is made up of a fine-grained mudstone containing clay minerals, sulfate minerals and other chemicals. Unlike some others on Mars, this ancient wet environment, was not harshly oxidizing, acidic or extremely salty. The bedrock also is fine-grained mudstone and shows evidence of multiple periods of wet conditions, including nodules and veins.
These clay minerals are a product of the reaction of relatively fresh water with igneous minerals, like olivine, also present in the sediment. This 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.
The mixture of oxidized, less-oxidized, and even non-oxidized chemicals, provide an energy gradient that 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.
An analysis of drilled rock sample from Curiosity shows the presence of water, carbon dioxide, oxygen, sulfur dioxide, and hydrogen sulfide released on heating. The results are consistent with smectite clay minerals.
"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, Maryland.
"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, California. "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."
Curiosity is on an initial two year mission (one Martian year) to find evidence if Gale Crater was ever suitable for microbial life. The rover has ten scientific instruments as its disposal.
NASA's Mars Science Laboratory, also known as Curiosity, landed on Mars on August 6 (UTC). NASA's Jet Propulsion Laboratory (JPL), based in Pasadena, California, a division of the California Institute of Technology, manages the Mars Science Laboratory mission for NASA.