Abstract
Perseverance landed at the Octavia E. Butler landing site next to
the Séítah dune region in Jezero crater on 18 February 2021, in
close proximity to the largest exposed carbonate deposit on Mars. These
carbonate signatures have been shown to be associated with the strongest
olivine signatures at Jezero crater (Goudge+ 2015, Brown+ 2020).
Alteration of olivine can lead to carbonate+H2 production, an energy
source for microbes (Mayhew+, 2013). The question of the origin of the
olivine-carbonate unit represents both an opportunity and a challenge
for the rover mission and future sample return efforts. Carbonate The
landing site is not near the region of carbonate detections (Figure 1),
however the rover’s westward traverse will take us over the carbonates
on approach to the crater rim. No reliable indications of the 2.5 μm
carbonate band have yet been convincingly detected by the SCAM VISIR
instrument. Olivine Studies of the olivine-carbonate unit concluded the
olivine is relatively Fe-rich and coarse grained (mm: Poulet+ 2007,
Clenet+ 2013). The strongest in-situ olivine signatures are found in
dune material analysed by LIBS/VISIR (Beyssac+ Mandon+ this conf). This
grain size characterization work may be used to investigate the
interaction of olivine with water and CO2 (Escamilla-Roa+ 2020). These
surface-gas processes are enhanced when olivine is in fine grain form.
Ash dispersal modeling is ongoing (Ravanis+ this conf) to determine the
range different sized ash particles could have traveled on ancient Mars.
We cannot directly compare the 1 μm band for CRISM and VISIR, so we
developed a new method that measures the curvature of three points on
the absorption bands to assess their relative Fo# shifts and applied it
to both datasets. Lab spectroscopy will be used to assess spectral
variations with composition versus grain size. Two key factors driving
the Fo# are mantle composition and melt temperature. Brown+ (2020)
estimated a range of Fo44-65 for the most redshifted olivine observed by
CRISM. McGetchin+Smythe (1978) showed that an Fe-rich mantle composition
would produce highly viscous lavas and suggested an upper bound of Fo70
for olivine. Understanding the astrobiological potential of the
olivine-carbonate unit is a priority of M2020 (Farley+ 2020) and we will
speculate on potential formation models in this contribution.