Degradation of Endeavour Crater Based on Orbital and Rover‐Based Observations in Combination With Landscape Evolution Modeling

Abstract

Exploration of Endeavour crater's Shoemaker formation rim rocks by the Opportunity rover, combined with extensive observations from the Mars Express and Mars Reconnaissance Orbiters, provides unique and quantitative insights into the processes that have degraded this 22‐km diameter Noachian age impact crater. These insights are informed by comparisons between Endeavour and the relatively young, and morphologically fresh appearing, 19‐km diameter Bopolu crater located 65 km to the southwest. Analyses of rover and orbiter data, combined with landscape evolution modeling using Bopolu topography as a starting point, demonstrate that significant weathering and fluvial degradation of Endeavour occurred during the Noachian Period, with ~0.3 km of vertical rim removal, ~0.9‐km backwasting of the rim, and deposition of ~0.5 km of fluvial‐deltaic‐lacustrine sediments on the crater floor, sourced from rim erosion. Pediments formed on external rim segments, with characteristic thin regolith covers over graded bedrock. Late Noachian to Early Hesperian age Grasberg formation draping sediments, and Burns formation sulfate‐rich sandstones, subsequently embayed all but high standing Shoemaker formation rocks. Burns formation strata accumulated in the crater interior up to a depth of ~0.8 km. Subsequent wind erosion of the interior deposits is indicated by an interior mound and moat, together with yardangs carved into Shoemaker formation rocks, and graded topographic profiles from Grasberg and Burns formation rocks up and through the interior rim Shoemaker formation outcrops. Up to ~0.4 km of Burns formation rocks were exhumed from within the crater by wind erosion to produce the mound and moat.

Geology and Geochemistry of Noachian Bedrock and Alteration Events, Meridiani Planum, Mars: MER Opportunity Observations

“…Endeavour crater is Noachian in age, and thus, the upper Shoemaker unit might also be part of the subdued cratered unit. The degradation of Endeavour crater rim took place when surface waters were actively modifying surface morphology (Hughes et al., 2019), which is characteristic of the subdued crater unit (Hynek & Di Achille, 2017). However, the differences in alteration styles recorded in the upper Shoemaker versus lower Shoemaker and Matijevic formation indicate that the former was deposited after a substantial time gap.…”

“…Grant et al. (2016) concluded that the Endeavour rim was degraded in part by fluvial processes and this is also indicated by modeling of Endeavour crater degradation (Hughes et al., 2019). Fluvial erosional and depositional processes were important in modifying subdued cratered unit surfaces, but not on the overlying Noachian cratered unit (Hynek & Di Achille, 2017).…”

“…Post‐impact erosion has degraded the Endeavour crater rim into a series of rim segments (Grant et al., 2016; Hughes et al., 2019). Opportunity reached the rim at the ∼700 m long Cape York segment that rises ∼10 m above the surrounding plains (Figure 1b) (Grant et al., 2016).…”

Morphodynamic Preservation of Fluvial Channel Belts

“…The topographic relief associated with the morphodynamic preservation of channel belts is present, and even exaggerated, in subaqueous settings (Jobe et al, 2020) and perhaps even across planets. Fluvial channel belts exposed at the surface of Mars can be mapped for 10s and even 100s of km (Davis et al, 2019;Hughes et al, 2019;Williams et al, 2013), likely due to the extent of their initial preservation followed by the relative gentleness of their exhumation (Burr et al, 2009;. In outcrops at Aeolis Dorsa, Mars, with depositional settings interpreted as coastal, stacking and shingling at the channel belt and lobe scales are common DiBiase et al, 2013;Hughes et al, 2019).…”

“…Fluvial channel belts exposed at the surface of Mars can be mapped for 10s and even 100s of km (Davis et al, 2019;Hughes et al, 2019;Williams et al, 2013), likely due to the extent of their initial preservation followed by the relative gentleness of their exhumation (Burr et al, 2009;. In outcrops at Aeolis Dorsa, Mars, with depositional settings interpreted as coastal, stacking and shingling at the channel belt and lobe scales are common DiBiase et al, 2013;Hughes et al, 2019). In the Hellas basin on Mars, exposures may have an architecture more consistent with reworking, with highly amalgamated fluvial strata (Salese et al, 2020).…”