  A well-preserved, ancient delta deposit, in combination with ample exposures
of Mg-carbonate rich materials, make Jezero Crater in Nili Fossae a compelling
astrobiological site and a top candidate for future landed missions to Mars. We
use CRISM observations to characterize the surface mineralogy of the crater and
surrounding watershed. We have identified a three- endmember sequence of
olivine-bearing lithologies that we hypothesize are distinguished by their Mg
content. We find that Mg-carbonates are consistently identified in association
with one of the olivine-bearing lithologies, although that lithology is not
fully carbonatized. Surprisingly, this lithology contains relatively Fe-rich
olivine. We address a range of formation scenarios, including the possibility
that these olivine and carbonate associations are indicators of
serpentinization on early Mars. These deposits provide an opportunity for
deepening our understanding of early Mars by revealing the thermal history of
the martian interior and potentially changes in its tectonic regime with time.
