Earth-like Soils on Mars Suggest Microbial Life

Rover image from Gale Crater reveals soil features similar to paleosols (ancient fossilized soils) on Earth / University of Oregon
Janet Fang 17 Jul 2014, 19:55

Mars was a much warmer, wetter place once. Based on new images captured by the rover Curiosity, some geologists are saying there might be Earth-like soils on the red planet. Ancient fossilized soils deep in an impact crater, to be exact, and these suggest the presence of microbial life. 

Many images of Martian landscapes show a scattering of loose rocks from impacts and ancient, catastrophic floods. What we don’t often see are smooth contours of soil that soften the terrain, like we see here. But looking at mineral and chemical data from Curiosity, Gregory Retallack from the University of Oregon discovered soils that resemble ours.

The soil profiles from Gale Crater, which date to 3.7 billion years ago, appear to have cracked surfaces lined with sulfate and vesicular hollows (or rounded holes) -- which are both features of desert soils on Earth. Furthermore, the concentrations of sulfate are comparable with Antarctic Dry Valleys and Chile's Atacama Desert.

"The pictures were the first clue, but then all the data really nailed it," Retallack says in a news release. "The new data show clear chemical weathering trends, and clay accumulation at the expense of the mineral olivine, as expected in soils on Earth.” 

He adds: “Phosphorus depletion within the profiles is especially tantalizing, because it attributed to microbial activity on Earth."  His work was published in Geology this week. 

The newly discovered soils offer more benign and habitable conditions than previously found on Mars. And their dating to 3.7 billion years ago, according to Retallack, puts them into a transitional time, from "an early benign water cycle on Mars to the acidic and arid Mars of today." Life on Earth is believed to have begun diversifying at about that time.

Curiosity is now exploring topographically higher and geologically younger layers within the crater, and these soils appear less conducive to life. 

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