Mineralogy, morphology, and emplacement history of the Maaz formation on
the Jezero crater floor from orbital and rover observations
Abstract
The first samples collected by the Perseverance rover on the Mars 2020
mission were from the Maaz formation, a lava plain that covers most of
the floor of Jezero crater. Laboratory analysis of these samples back on
Earth will provide important constraints on the petrologic history,
aqueous processes, and timing of key events in Jezero. However,
interpreting these samples will require a detailed understanding of the
emplacement and modification history of the Maaz formation. Here we
synthesize rover and orbital remote sensing data to link outcrop-scale
interpretations to the broader history of the crater, including
Mastcam-Z mosaics and multispectral images, SuperCam chemistry and
reflectance point spectra, RIMFAX ground penetrating radar, and orbital
hyperspectral reflectance and high-resolution images. We show that the
Maaz formation is composed of a series of distinct members corresponding
to basaltic to basaltic andesite lava flows. The members exhibit
variable spectral signatures dominated by high-Ca pyroxene, Fe-bearing
feldspar, and hematite, which can be tied directly to igneous grains and
altered matrix in abrasion patches. Spectral variations correlate with
morphological variations, from recessive layers that produce a regolith
lag in lower Maaz, to weathered polygonally fractured paleosurfaces and
crater-retaining massive blocky hummocks in upper Maaz. The Maaz members
were likely separated by one or more extended periods of time, and were
subjected to variable erosion, burial, exhumation, weathering, and
tectonic modification. The two unique samples from the Maaz formation
are representative of this diversity, and together will provide an
important geochronological framework for the history of Jezero crater.