March 20, 2013
Laser Blasts Help Find Patterns In Martian Rocks
Lee Rannals for redOrbit.com - Your Universe Online
Los Alamos National Laboratory postdoctoral researcher Nina Lanza announced at the 44th Annual Lunar and Planetary Science Conference in The Woodlands, Texas that Curiosity's ChemCam laser could be offering some detailed inside information about the Red Planet's surface.
NASA's Curiosity rover has a laser-shooting instrument onboard known as the ChemCam, which is used to vaporize a pinpoint of rock surface. The instrument is able to read the chemical composition of the vaporized sample with a spectrometer. The laser fires multiple pulses in the same spot, helping to provide scientists with ample opportunity to investigate the rock sample.
Lanza said during the poster session that Curiosity has shown what appears to be a common feature on the surface of some very different Martian rocks during these ChemCam tests. Rocks are zapped 30 to 50 times in a single location, and sometimes even up to 600 times. Scientists on the ChemCam team generally discard results from the first five laser blasts because they believe the laser has penetrated the rock to a depth that provides a true representative sample of rock chemistry.
Nina took notice of the pattern of taking five laser blasts to get to the depth of the rock necessary, and found that these shots had chemical similarities regardless of the rock type being shot at. After these five shots, the spectrum from the vaporized rock stabilized into a representative sample of the rock type below.
The researcher suggests that if the first blast is dusting off the rocks, the remaining four blasts could be showing that Martian rocks are all coated by a substance, similar in structure if not composition, to the dark rock varnish that appears on Earth rocks in arid locations.
“The thing about rock varnishes is the mechanism behind why they form is not clearly understood,” Lanza said in a recent statement. “Some people believe that rock varnish results from an interaction of small amounts of water from humidity in the air with the surface of rocks–a chemical reaction that forms a coating. Others think there could be a biological component to the formation of rock varnishes, such as bacteria or fungi that interact with dust on the rocks and excrete varnish components onto the surface.”
She says the first five blasts on the rock could be entirely surface dust, or it could be a rock coating or a rind formed by natural weathering processes. Lanza says she hopes to integrate other instruments on Curiosity to help rule out unknowns like surface dust.
“If we can find a reason for this widespread alteration of the surface of Martian rocks, it will tell us something about the Martian environment and the amount of water present there,” Lanza said. “It will also allow us to make the argument that what we´re seeing is the result of some kind of current geological process, which could give us insight into extraterrestrial geology or even terrestrial geology if what we´re seeing is a coating similar to what we find here on Earth.”
So far, ChemCam has helped fire more than 40,000 laser blasts at more than a thousand different locations on Mars. The ChemCam team also presented findings from the Martian rock blasts while at the Lunar and Planetary Science Conference.