news of the week CURIOSITY FINDS A HOSPITABLE MARS
ity’s ovens, gave off CO2. Mission scientists say the CO2 was produced during either a reaction with carbon or by the decomposition of a carbonate in the sample. Finally, the analysis also detected a possible microbial food source in the form of sulfur dioxide and hydrogen PLANETARY SCIENCE: Rock dust shows sulfide. These compounds can serve as a chemical batwatery minerals, neutral pH, and an tery, facilitating a flow of electrons for microbes known unusual energy source for microbes as chemolithoautotrophs. Such organisms, which get energy by oxidizing inorganic compounds and use CO2 as a carbon source, live on Earth in exotic habitats such HE PLANET MARS was hospitable to microbial as deep-sea vents. life at some point in its history. That’s the conThe significance of the simple organics found in the clusion from analyses of martian rock samples martian sample remains complicated, the team mempulverized by instruments aboard the NASA rover Cubers noted. Curiosity’s gas chromatograph/mass specriosity seven months after it landed on the Red Planet. trometer detected dichloromethane and chloromethane Curiosity’s analyses of the first sample of rock ever in the recently analyzed rock sample. Both compounds drilled on another planet have yielded strong evidence were also detected in earlier test samples from Curiosthat microbes could have thrived on Mars several ity’s wanderings (C&EN, Dec. 10, 2012, page 44). But billion years ago. in each case, it’s NASA scientists anpossible that the nounced the results compounds were at a March 12 press generated by reacconference. tions with contamiScientists have nants in Curiosity’s known that Mars instruments. The has a watery past— team plans to repeat many spacecraft the experiment, with have discovered greater controls, water-laden minerwith another rock als and geographic sample. features altered by Despite its initial water. But never success, Curiosity before has a chemistill has more work cal examination to do. In April, Mars provided so many will be on the oplines of evidence for posite side of the habitability. sun from Earth, and The rover’s suite so the rover will be TOUCHDOWN Curiosity collected rock samples on Mars of analytical instruincommunicado. near its landing site in an ancient lake bed. ments revealed that But in May, it will 20 to 30% of the drill another rock gray-green rock powder it analyzed is composed of the sample. It will then begin wending its way toward an clay mineral smectite, which forms in water. The rock intriguing location known as Mount Sharp, which has also contains calcium sulfate, which has a neutral—and more clay and sulfate minerals. therefore organism-friendly—pH. This contrasts with Samuel Kounaves, a chemistry professor at Tufts the more acidic martian environments containing magUniversity who was lead scientist for the Wet Chemisnesium and iron sulfates detected elsewhere on the plan- try Lab on NASA’s Mars Phoenix Lander mission, tells et by the long-lived NASA rovers Spirit and Opportunity. C&EN the discovery of organic chemicals could make “We have found a habitable environment that is so the case for habitability even stronger. “Even though benign and supportive of life that if you were around, organisms such as chemolithoautotrophs could survive you would have been able to drink” the water, John P. without an organic carbon source, finding organics Grotzinger, Curiosity project scientist, said at the press would bolster the habitability for more complex miconference. crobial life, especially photosynthetic organisms,” he Portions of the rock sample, when heated in Curiossays.—ELIZABETH WILSON
NASA/JPL-CALTECH/MSSS (BOTH)
MARCH 18, 2013 EDITED BY WILLIAM G. SCHULZ & NADER HEIDARI
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MARCH 18, 2013
Analyses of rock sample drilled by Curiosity show a once-habitable environment.
