Assessing the mineralogy of the watershed and fan deposits of the Jezero crater paleolake system, Mars

Abstract

We present results from geomorphic mapping and visible to near-infrared spectral analyses of the Jezero crater paleolake basin and its associated watershed. The goal of this study is to understand the provenance of the sedimentary deposits within this open-basin lake using a source-to-sink approach. Two fan deposits located within the basin have distinct visible to near-infrared mineralogic signatures measured by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). The northern fan is spectrally characterized by a mixture of Mg-rich carbonate and olivine, while the western fan is characterized by Fe/Mg-smectite (e.g., saponite or nontronite) with variable amounts of Mg-rich carbonate and olivine in isolated exposures. The watersheds of these deposits contain a variety of geomorphic units that are likely to have supplied sediment to the Jezero crater paleolake, as the fluvial valleys that fed the basin incise these units. The geomorphic units include exposures of Fe/Mg-smectite-, olivine-, and Mg-rich carbonate-bearing terrain. We show that the difference in fan deposit mineralogy is a function of the areal exposure of the major geomorphic units within their watersheds. This indicates that the spectrally dominant aqueous alteration minerals in the fan deposits are primarily detrital, or transported, in nature and did not form in situ. We conclude that the aqueous alteration of the units in the watershed occurred prior to the fluvial activity that carved the valleys of the Jezero crater paleolake system, and that the two periods of aqueous activity are not genetically related.

Areally Extensive Surface Bedrock Exposures on Mars: Many Are Clastic Rocks, Not Lavas

“…There, the geologic context would support a sedimentary origin, as suggested by Goudge et al (2015). There, the geologic context would support a sedimentary origin, as suggested by Goudge et al (2015).…”

Wind in Jezero Crater, Mars

“…We refer to geologic units mapped by Goudge et al (2015) for context associations with aeolian features. We refer to geologic units mapped by Goudge et al (2015) for context associations with aeolian features.…”

Olivine‐Carbonate Mineralogy of the Jezero Crater Region

“…Buffered crater counts of inflowing valley networks indicate that this system ceased fluvial activity by approximately the Noachian‐Hesperian boundary (Fassett & Head, ), similar to the timing of other large valley network systems on Mars (Fassett & Head, ; Hoke & Hynek, ). Jezero crater contains two well‐exposed fluvio‐lacustrine delta deposits (Ehlmann et al, ; Fassett & Head, ; Goudge et al, , ; Schon et al, ) as well as large exposures of both phyllosilicate minerals and carbonates (Ehlmann et al, ; Ehlmann, Mustard, Fassett, et al, ; Ehlmann, Mustard, Murchie, et al, ; Goudge et al, , ). In situ exploration of this region could provide novel insights into the fluvial sedimentary record, the timing of the valley networks, and the aqueous alteration history of early Mars.…”

“…The two delta deposits within Jezero contain Mg/Fe‐phyllosilicate and carbonate in varying proportions, with the northern fan dominated by carbonate and the western fan dominated by phyllosilicate (Goudge et al, ). The provenance of the phyllosilicate and carbonate within the Jezero crater deltas can be traced to mineralogically similar protolith units within the watershed, which provides strong evidence that the alteration minerals were primarily emplaced by fluvial transport (Goudge et al, ).…”

“…The provenance of the phyllosilicate and carbonate within the Jezero crater deltas can be traced to mineralogically similar protolith units within the watershed, which provides strong evidence that the alteration minerals were primarily emplaced by fluvial transport (Goudge et al, ). These deposits therefore have bulk compositions that integrate heavily altered Martian crust of the Nili Fossae region (Ehlmann et al, ; Goudge et al, ; Mustard et al, ) and offer an opportunity to examine a diverse array of alteration minerals. Furthermore, Jezero crater contains large exposures of olivine‐ and carbonate‐bearing units on the floor of the crater, underlying the deltaic deposits and draping the interior rim of the crater (Ehlmann et al, ; Ehlmann, Mustard, Murchie, et al, ; Goudge et al, ).…”