Multiple Episodes of Fluid Alteration in Jezero Crater Indicated by MIST Mineral Identifications in PIXL XRF Data

The Mineral Identification by Stoichiometry (MIST) algorithm can identify mineral species in geochemical data sets. MIST is applied to X-ray fluorescence chemical analyses from the Planetary Instrument for X-ray Lithochemistry (PIXL) on the Mars 2020 Perseverance rover to identify mineral phases in abraded rock targets at Jezero crater.

We used a Monte Carlo (MC) error propagation technique to assess confidence in the results. Our study reports 24 high-confidence mineral phases from the first 1100 sols of Perseverance’s traverse. Primary mineral groups include plagioclase, pyroxene, and olivine, in agreement with previously published results, and support an (ultra)mafic rock source.

Additionally, MIST identified a range of phyllosilicate minerals, including nontronite, saponite, hisingerite, greenalite, minnesotaite, and sepiolite; identification of such alteration phases is essential for constraining the aqueous alteration history of Jezero’s rocks.

An initial survey of the reported phases suggests multiple, distinct stages of fluid alteration in Jezero’s history: high temperature and acidic, moderate temperature and circumneutral, and later stage ambient alkaline conditions.

MIST results from PIXL data help determine rocks of interest on Mars’ surface for investigation by Perseverance and will also be important for informing analysis of samples when returned to Earth.

Overview of Planetary Instrument for X-ray Lithochemistry (PIXL) scans on WATSON images of abrasion patches through sol 1100. The names of each abrasion patch are displayed above the image, and the color of the label indicates which campaign the scan occurred within (see Figure 1). Green indicates the Crater Floor campaign, orange indicates the Fan Front campaign, blue shows the Upper Fan campaign, gray indicates boulders, and pink represents the Margin Unit campaign. An asterisk (*) next to the name indicates a sample (or two) was obtained from the outcrop. The dagger (†) indicates that an atmospheric sample was obtained when the rover was parked at the outcrop. Each PIXL map or line scan outline is labeled with the sol number on which the PIXL scan occurred (Table 1). Abrasions are 5 cm in diameter, and the scale bar on each image is 1 cm. — Journal of Geophysical Research: Planets

Multiple Episodes of Fluid Alteration in Jezero Crater Indicated by MIST Mineral Identifications in PIXL XRF Data From the First 1100 Sols of the Mars 2020 Mission, Journal of Geophysical Research: Planets (open access)

Astrobiology,