Bio-preservation Potential of Sediment in Eberswalde crater, Mars

Within Eberswalde crater, Mars, is one of the most well-preserved river delta deposits identified within Mars’ rock record, and visually traceable from the deposit, is the partially-intact watershed that fed the paleo-lake that once resided within the crater basin. Aqueous alteration minerals, smectite clays and opaline silica, have been previously identified within the deposit, however the origin of those minerals is not well understood. Through analysis of topographic and hyperspectral data, we seek to ascertain the origin and provenance of these minerals to better understand their formative conditions and formation age. We will also assess Eberswalde crater’s potential as a site to explore for preserved evidence of past life on planet Mars. Using hyperspectral data to compare the minima positions of particular absorption features (e.g., ~2.3 µm for metal-OH absorptions in smectite clays) from multiple regions, including the river delta deposit, the watershed, the adjacent Northwest Noachis Terra plateau, we test the hypothesis that the smectites found within the Eberswalde crater deposit are fluvial detritus transported there during the Hesperian age (i.e., 3.5-2.0 Ga). We find that the spectra from these three regions are consistent with each other, and most consistent with lab spectra of Fe/Mg smectite clays, namely nontronite and saponite. The similar CRISM signature, and the fluvial relationship between the rocks within the watershed and the preserved putative delta stratigraphy point to a detrital origin for the smectite clays observed within Eberswalde crater. A detrital origin indicates that the clays formed prior to transport during the late Noachian (i.e., 4.0-3.5 Ga), and possibly within the subsurface, which previous studies indicate may have been the time period and location most amenable to the preservation of evidence of past life on Mars. Furthermore, the presence of detrital clays within the deposit indicate that, during the period when a lake existed within Eberswalde crater and a river delta was forming therein (i.e., during the late Hesperian and/or early Amazonian), the lake was ~neutral-pH and a habitable environment. Taken together, these observations indicate that: (1) within Eberswalde crater is a river delta deposit that formed in a habitable environment, (2) that deposit is made up of layers of sediment composed of minerals that formed during the most habitable period in Mars’ ancient history, and (3) those minerals formed in an environment thought to be most likely to preserve evidence of past life. Furthermore, this high concentration of high-biosignature preservation features are within a small rover-accessible locale, so Eberswalde crater represents a strong candidate for consideration for future missions exploring Mars for past habitability. And, the similarities between the Eberswalde crater fluvial system and the Jezero crater system make it a compelling site as a standard of comparison for analyses by the upcoming NASA Perseverance rover mission