The ChemCam Instrument Suite on the Mars Science Laboratory Rover Curiosity: Remote Sensing by Laser-Induced Plasmas

Figure 1. Concept drawing of the rover Curiosity on the Martian surface firing the ChemCam laser. Drawing by J.-L. Lacour of CEA France who helped develop the ChemCam.

Title: The ChemCam Instrument Suite on the Mars Science Laboratory Rover Curiosity: Remote Sensing by Laser-Induced Plasmas

Authors: Wiens, R. C., S. Maurice, and the ChemCam Team

Journal: Geochemical News

Affiliations: Los Alamos National Laboratory (USA), Institute de Recherche en Astrophysique et Planetologie (France)

Take Home Importance According to Authors: The ChemCam is the first laser-induced breakdown spectrometer to be used in space, and will provide ground scientists with rapid stand-off elemental analysis of target materials on the Martian surface.

Take Home Importance According to Blogger: The ChemCam is a fascinating  analytical tool which can function in a hostile environment. It provokes interesting questions about how the chemistry of beyond-Earth environments can be studied.

Summary: This past Saturday a rocket screeched skyward from Cape Canaveral, Florida and sent NASA’s newest rover Curiosity on a 354 million mile trek through space to Mars. We talk about this here because of the incredible suite of analytical instruments on board Curiosity which will provide detailed chemical information about the Martian surface – all crucial in NASA’s quest to determine if life ever could have existed on Mars. Here we will discuss one of these analytical tools, the ChemCam.

The ChemCam is in essence an atomic emission spectrometer. Remember those flame-test experiments you may have done in high school chemistry where the flame color indicated which elements were present? This is just like that…except with 240 – 850 nm spectral sensitivity, ppm detection limits for some elements, a laser with a 10 megawatt / square millimeter intensity for atomic excitation, and a 0.2 to 0.5 mm analysis spot size up to 3 meters away.

Specifically, a mast-mounted high resolution camera will first permit scientists back on Earth to identify targets for analysis. These targets may be rocks or soil away from the rover. After a target is chosen the Nd laser takes over, first cleaning away the dust layer by using more gentle bursts of light. With the surface cleaned, the power is dialed up to and the target irradiated with multiple short (5 ns long) pulses to excite the atoms present into a plasma. As the excited atoms relax by emitting photons, a telescope on Curiosity’s mast will collect the emitted light and feed it via a fiber optic cable to the spectrometer buried inside the rover. By repeatedly blasting the same point the elemental composition at different depths (a depth profile) of the target can be constructed – this capability will be particularly useful for determining if the rock surface chemistry was modified by a past environment, say a watery one. The ChemCam spectrometer is reported to be particularly sensitive to light elements normally outside the reach of X-ray techniques (techniques which are also present on the rover): H, Li, Be, B, C, N, and O. The rover will convert the acquired spectra into percent elemental abundance by means of an on-board calibration target. All in all, a pretty nifty analysis tool for doing stand-off analysis of the Martian surface. The rover will land* in August 2012, so stay tuned for some interesting reports on the chemistry of Mars!

*this isn’t chemistry related, but the Curiosity landing sequence is amazing. Watch NASA’s animation of it here.


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