So while the mudstone indicates the existence of an ancient lake—and a habitable environment some time in the planet's distant past—neither crater counting nor potassium-argon dating can directly determine exactly when this was.To provide an answer for how the geology of Yellowknife Bay has changed over time, Farley and his colleagues also designed an experiment using a method called surface exposure dating.However, shortly before the rover left Earth in 2011, NASA's participating scientist program asked researchers from all over the world to submit new ideas for experiments that could be performed with the MSL's already-designed instruments. Findings from the first such experiment on the Red Planet—published by Farley and coworkers this week in a collection of Curiosity papers in the journal —provide the first age determinations performed on another planet.The paper is one of six appearing in the journal that reports results from the analysis of data and observations obtained during Curiosity's exploration at Yellowknife Bay—an expanse of bare bedrock in Gale Crater about 500 meters from the rover's landing site.That is probably the most remarkable thing I've ever seen as a scientist, given the difficulty of the analyses," Farley says.This also helps researchers looking for evidence of past life on Mars.The work, led by geochemist Ken Farley of the California Institute of Technology (Caltech), could not only help in understanding the geologic history of Mars but also aid in the search for evidence of ancient life on the planet.
Farley had the idea of performing the experiment on Mars using the SAM instrument."The surface of Mars, the surface of Earth, and basically all surfaces in the solar system are being bombarded by cosmic rays," explains Farley, and when these rays—very high-energy protons—blast into an atom, the atom's nucleus shatters, creating isotopes of other elements.Cosmic rays can only penetrate about two to three meters below the surface, so the abundance of cosmic-ray-debris isotopes in rock indicates how long that rock has been on the surface.The exposure of rock in Yellowknife Bay has been caused by wind erosion.Over time, as wind blows sand against the small cliffs, or scarps, that bound the Yellowknife outcrop, the scarps erode back, revealing new rock that previously was not exposed to cosmic rays."Imagine that you are in this site a hundred million years ago; the area that we drilled in was covered by at least a few meters of rock.