The Chemcam LIBS and Imaging Instrument Suite on the Curiosity Mars Rover, and Terrestrial Field Testing of LIBS

Abstract:

The Curiosity rover that landed on Mars in 2012 includes an instrument suite consisting of a laser-induced breakdown spectrometer (LIBS) and a remote micro-imager (RMI). The LIBS is effectively the first Mars microprobe, as its interrogation region is 0.35-0.5 mm in diameter; it can access targets up to 7 m from the rover. The LIBS pulsed laser excites atoms and ions from the target, creating a plasma that emits light at characteristic wavelengths. When calibrated, LIBS provides quantitative elemental abundances. The elements observed on Mars include H, Li, O, F, Na, Mg, Al, Si, S, Cl, Ca, Ti, Cr, Mn, Fe, Zn, Rb, Sr, Ba. The first few laser shots clear the surface of dust, allowing unobscured analyses of the targets. Within the first two years of operation ChemCam has returned > 150,000 spectra from > 4,000 locations along the rover traverse. The RMI is the highest resolution (0.04 mrad) remote imager on the rover and provides context before/after images of the LIBS targets as well as long-distance stand-alone imagery.

The ChemCam LIBS instrument concept was developed based on laboratory LIBS instrumentation. For terrestrial field work ChemCam’s design with its unshielded laser beam is an eye safety hazard. However, hand-held devices with closed laser-beam designs have been developed. In order to provide a realistic field test prior to the launch of the rover the ChemCam team fielded a backpack LIBS system featuring a shielded laser beam. The system was calibrated using the same 66 geological standards used by the ChemCam instrument prior to flight. During the field test, data was sent remotely to a team back at Los Alamos, effectively imitating operations on Mars and data analysis on the ground. The ground team successfully reported accurate results, identifying the site as rich in kaolinite clay soils.