March 9-24, 2018

Learning More about Mars

Yesterday, the journal Science published several articles about Curiosity's early findings on Mars. Assistant Professor James Wray (School of Earth and Atmospheric Sciences) is on the rover's science team.

Curiosity and the rust-colored landscape of Mars fill the cover of Science magazine this week. More importantly, rover results fill its pages, although in this case they are virtual pages, as there was so much to report that the full papers are available only online.

Save for one paper earlier this summer, today's five articles are the first peer-reviewed publications of what Curiosity has found in the surface rocks and soils of Gale crater. They tell the tale of "Jake_M," the first rock studied in detail with the rover's arm instruments, which was expected to be a chunk of typical (for Mars) basaltic lava; instead it has the highest concentrations of sodium and potassium ever seen in an igneous rock from Mars, implying distinct magma processes. Another paper describes what the rover has found by firing its mast-mounted laser at a range of soils along its traverse. Two papers describe the first-ever measurements made on Mars using x-ray diffraction, a mineralogist's favorite tool for characterizing materials, here applied to wind-blown sands at a site called "Rocknest."

Finally, the paper to which I contributed describes what happened when we heated Rocknest sands to temperatures above 1500 degrees Fahrenheit. In brief, a range of molecular species was vaporized, including soil-bound water and simple organic compounds. The organics observed were chlorinated, implying the presence of highly reactive chlorine compounds indigenous to Mars. But whether the organic carbon itself predates Curiosity's arrival in Gale crater, or was instead a chemical stowaway from Earth, remains unresolved. Certainly we brought some carbon with us, but we cannot rule out a Martian component.

Much of this may sound like "old news," first reported to the public and the broader scientific community in late 2012. Today's papers do not yet address what Curiosity later found upon drilling the first holes into Martian rocks: clay-rich sediments deposited in an ancient lake.  

The pace of scientific peer review is slower than that of rover operations or press releases, as it should be: the rover is a precious asset that we must fully utilize every day, supported by a public that deserves regular updates on its return on investment. But the journal articles must stand the test of time, and the rigorous scrutiny to which these rock and soil measurements have now been subjected will allow them to serve as robust baselines as the rover continues to explore Gale crater's record of habitable environments on early Mars.

Photo: View From Curiosity's Arm-Mounted Camera After a Long Drive (NASA/JPL-Caltech/MSSS)


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Georgia Tech's James Wray, who's on the Mars Curiosity rover's science team, talks about their first findings.