Analysis of potential surface coatings in Jezero crater by SuperCam on the Perseverance rover
Abstract
The NASA Perseverance Mars rover has been exploring Jezero crater since February 2021. During that time, several rocks with potential coatings were observed. Rock coatings can record the interactions of rock surfaces with atmosphere, regolith, and water, and are important targets for understanding environmental conditions. The SuperCam instrument uses multiple analytical techniques including Laser-Induced Breakdown Spectroscopy (LIBS), a microphone for obtaining acoustic data from the LIBS shockwave, remote micro-imagery (RMI), visible-near infrared (VISIR), Raman, and luminescence spectroscopy. On sols 75-83, SuperCam analyzed a flat paver rock called Nataani that appeared to have a dusty surface with shiny, dark-toned material underneath and ~cm-sized spots of splotchy coating. An initial 10-point LIBS raster with 30 laser pulses per point indicated a potential systematic change in composition with depth, a known signature of coatings and thin layers. To investigate this further, the team conducted two depth profile LIBS rasters consisting of 5-point LIBS rasters with 150 laser pulses per location to sample deeper into the rock. Two additional locations were analyzed with co-located LIBS, Raman, and VISIR. Acoustics data were also collected during the LIBS depth profile analyses. LIBS chemistry data indicate the surface may be relatively enriched in Mg, Mn, Cr, and possibly H, whereas the interior was relatively enriched in Si, Al, and Sr. Notably, the acoustic data did not show a systematic change in amplitude with depth; this suggests that the surface and interior materials had similar material properties, i.e. hardness, optical, and thermal properties. Raman spectra suggested the presence of amorphous silica but due to SuperCams long optical fiber, which also produces a weak signature of amorphous silica, this feature could not be clearly attributed to Nataani. VISIR spectra exhibit a feature attributable to H2O at 1.9 microns, similar to other targets in Jezero. Due to their larger spot sizes relative to LIBS, the fields of view for both Raman and VISIR may contain some signal from dust and/or uncoated rock. Efforts to better understand these signatures, including collection of additional LIBS and acoustics data on similar martian rocks and terrestrial analogs, are ongoing.