ChemCam's mega blast: Martian rock succumbs

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  • Published: Sep 1, 2012
  • Author: David Bradley
  • Channels: UV/Vis Spectroscopy
thumbnail image: ChemCam's mega blast: Martian rock succumbs

Curious about Mars

The ChemCam instrument aboard NASA's Curiosity rover recorded its first spectra on Mars in mid-August, giving the systems a little target practice but also demonstrating that the device is working as it should by providing a sneak preview of rocky spectra. Credit: NASA 

The ChemCam instrument aboard NASA's Curiosity rover recorded its first spectra on Mars in mid-August, giving the systems a little target practice but also demonstrating that the device is working as it should by providing a sneak preview of rocky spectra.

On the 19th August 2012, a couple of weeks after NASA's Mars rover Curiosity landed in the Red Planet's Gale Crater, it fired its laser for the first time at a fist-size rock known as "Coronation." The Chemistry and Camera instrument, or ChemCam, flashed the rock with thirty pulses of laser light over a 10-second time period with each pulse blasting the Martian rock with a megawatt of power for just five nanoseconds.

The laser flash excites the rock at the atomic level generating a localised plasma cloud and the ChemCam detectors catch the light emitted for spectroscopic investigation with three instruments that can reveal elemental facts about the composition of the rock. Intensities are recorded in the ultraviolet, visible and infrared light regions of the electromagnetic spectrum.

"We got a great spectrum of Coronation - lots of signal," explains ChemCam Principal Investigator Roger Wiens of Los Alamos National Laboratory, in New Mexico. "Our team is both thrilled and working hard, looking at the results. After eight years building the instrument, it's payoff time!"

The team was not only calibrating the instruments in this initial blast but hoped to see whether or not the rocky composition changed with each successive laser pulse. Any such changes might hint at the displacement of superficial material, dust, and the penetration of the rock to deeper layers within.

"It's surprising that the data are even better than we ever had during tests on Earth, in signal-to-noise ratio," explains Deputy Project Scientist Sylvestre Maurice of the Institut de Recherche en Astrophysique et Planetologie (IRAP) in Toulouse, France. "It's so rich, we can expect great science from investigating what might be thousands of targets with ChemCam in the next two years."

Liberated

ChemCam exploits LIBS, laser-induced breakdown spectroscopy, a technique previously used to determine the composition of target materials in extreme environments here on Earth, such as the interior of nuclear reactors and on the deep sea bed. It has also been used in experimental applications for environmental monitoring and cancer detection. The investigation of the Coronation rock on Mars is, however, its first use in interplanetary exploration.

ChemCam also carries with it a Remote Micro-Imager (RMI) alongside the LIBS instrumentation. The LIBS data gives the scientists the elemental composition of materials on the Martian surface, while the RMI images put those analyses in their Martian context. The NASA team and its collaborators hope that working together both of these instruments will help them to determine which rock and soil targets close to Curiosity should be subjected to the direct contact and other analytical instruments on board. The fact that LIBS need not come into direct contact with a sample to be tested gives it the edge over other tests for scanning many more sample, more frequently, albeit with less data obtainable overall. Such scanning could be used to gain information about inaccessible material as well as allowing a picture of how surface materials might be changing over time to be built up.

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Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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