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GEOCHEMISTRY
Martian crater lake could have supported life Curiosity rover data unveils geochemical history of Gale Crater, including redox layering of its ancient waters
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C&EN | CEN.ACS.ORG | JUNE 5, 2017
The Gale Crater on Mars was once a briny, habitable lake. we were able to reconstruct these aspects of Martian paleo-environment at such a high level of detail,” Hurowitz tells C&EN. For example, Curiosity data showed that the lake contained a number of habitable subenvironments for potential microbial life, he says. These environments could have nurtured microbes that thrive in oxidant-rich conditions, in oxidant-poor conditions, and at the interface between both. The team also deduced that as the lake gradually dried up, it became saltier, possibly forming the calcium sulfate veins that Curiosity found in the lake bed’s sediment. The work “provides interesting evidence for differing oxidation states in the lake,” says Jonathan I. Lunine, director of Cornell University’s Center for Astrophysics & Planetary Science. “That’s good for habitability,” he says, “but the interest is, I think, in the ability to get detailed geochemical information on a stratigraphic sequence on Mars.”—ELIZABETH WILSON
CREDIT: NASA/JPL-CALTECH/MSSS (ROBOT); NASA (CRATER)
The ancient Gale Crater on Mars, once filled been extended indefinitely, and scientists with water, could have been habitable during are now trying to pinpoint the times during Mars’s early history, with oxidant-rich and Martian history when microbial life may oxidant-poor layers that became saltier as have had the chance to develop. the lake dried up, according to a new study To that end, a team led by Joel Hurowitz, (Science 2017, DOI: 10.1126/science.aah6849). a geoscientist at Stony Brook University, reThe data, sent back to Earth from NASA’s constructed portions of the lake bed’s sevCuriosity rover, not only add to growing everal-billion-year history, using data from idence that ancient Martian environments Curiosity’s first 1,300 days of exploration. could have supported life but also demonThe effort involved sedimentologists, strate the abilities of sophisticated robotic geochemists, mineralogists, and instruinstruments to probe fine geological details ment scientists, who pored over data from of an extraterrestrial environment. multiple sources, including Curiosity’s X-ray Curiosity landed inside the 150-km-diamdiffraction instrument and its α-particle eter, 3.8 billion-year-old Gale Crater in 2012, X-ray spectrometer. and quickly accomplished, The team concluded that through its study of rock The Curiosity rover the ancient lake contained a chemistry, its original goals took this picture of mineral brew with a neutral to of investigating potential itself while collecting alkaline pH that could have sushabitability on Mars. samples from inside tained life between 3.8 billion The rover’s mission has Gale Crater. and 3.1 billion years ago. The geology that Curiosity explored showed that the lake was also geochemically layered, similar to Earth’s geology. At the top, where photochemically generated O2 from the atmosphere could mingle with surface water, oxidizing compounds helped form oxidized iron minerals and phyllosilicates in rocks with coarse-grained structures. At the lower regions, the water was devoid of oxidants and formed silica and mixed-valence iron minerals in rocks with fine-grained sediment. “It’s really exciting for us that
