“Whites River” is the name of the Martian rock 12 m from the Perseverance rover on which the SuperCam instrument fired its 500,000th shot. The event took place on February 18, 4 years to the day after the rover's landing on the Red Planet, and just a few months after the millionth shot fired by ChemCam, the Curiosity rover's instrument. This target was chosen to check for the presence of clays in the stratum above the rover, which is currently in the Shallow Bay region on the rim of the Jezero crater.

A better understanding of the rocks of Mars

4 years ago, Perseverance, the Mars 2020 rover developed and operated by the Jet Propulsion Laboratory (Caltech-NASA), landed on Mars. Its mission: to study the planet's geological diversity, search for areas likely to have preserved traces of past life (known as 'bio-signatures') and, finally, collect samples to be sent back to Earth on subsequent missions. Installed at the top of the rover's mast, the instrument with French contribution SuperCam, worthy heir of ChemCam on Curiosity, contributes to these objectives by studying the landing site and the context of the samples collected.

This instrumental suite combines five different measurement techniques for remote rock analysis. It comprises three spectrometers (LIBS, Raman and infrared), a camera and a microphone. The LIBS technique provides information on the chemical composition of rocks, while Raman provides information on their mineralogy, i.e. how the elements are structured together. Both techniques use the same laser, developed by Thales. This laser has already been used 500,000 times. 

Five different measurement technologies

When a target is analyzed with LIBS, the instrument performs between 5 and 10 analysis points, each point representing a succession of 30 shots. Occasionally, in-depth analyses are carried out. In this case, 250 shots are fired at the same point. The signal is collected for each laser shot in LIBS mode. The Raman technique is generally coupled with LIBS, the difference being that only four points per target are shot, so that more shots - typically 400 per point - can be fired to obtain a better signal. To date, 1031 geological targets have been analyzed with this laser, representing 291,769 LIBS laser shots and 208,320 Raman laser shots.  

The infrared method, camera and microphone do not use the laser, but are also widely exploited, with 150 image mosaics (in addition to LIBS and Raman targets), 1,320 visible and infrared observations, and 35 hours of recording. Each of these techniques provides complementary information on rocks and the atmosphere. 

So SuperCam is doing just fine, and that's great news for the analysis of Martian rocks!