Wind‐Eroded Crater Floors and Intercrater Plains, Terra Sabaea, Mars

Abstract

Ancient impact craters with wind‐eroded layering on their floors provide a record of resurfacing materials and processes on early Mars. In a 54 km Noachian crater in Terra Sabaea (20.2°S, 42.6°E), eolian deflation of a friable, dark‐toned layer up to tens of meters thick has exposed more resistant, underlying light‐toned material. These layers differ significantly from strata of similar tone described in other regions of Mars. The light‐toned material has no apparent internal stratification, and visible/near‐infrared spectral analysis suggests that it is rich in feldspar. Its origin is ambiguous, as we cannot confidently reject igneous, pyroclastic, or clastic alternatives. The overlying dark‐toned layer is probably a basaltic siltstone or sandstone that was emplaced mostly by wind, although its weak cementation and inverted fluvial paleochannels indicate some modification by water. Negative‐relief channels are not found on the crater floor, and fluvial erosion is otherwise weakly expressed in the study area. Small impacts onto this crater's floor have exposed deeper friable materials that appear to contain goethite. Bedrock outcrops on the crater walls are phyllosilicate bearing. The intercrater plains contain remnants of a post‐Noachian thin, widespread, likely eolian mantle with an indurated surface. Plains near Hellas‐concentric escarpments to the north are more consistent with volcanic resurfacing. A 48 km crater nearby contains similar dark‐over‐light outcrops but no paleochannels. Our findings indicate that dark‐over‐light stratigraphy has diverse origins across Mars and that some dark‐toned plains with mafic mineralogy are not of igneous origin.

Ancient Stratigraphy Preserving a Wet‐to‐Dry, Fluvio‐Lacustrine to Aeolian Transition Near Barth Crater, Arabia Terra, Mars

“…The morphology and geographic extent of the interpreted paleo‐dune field indicates that paleo‐sediment‐transport direction was from the southeast, perhaps sourced from eroding highlands in Terra Sabaea (Irwin et al, ). Southeast to northwest sediment transport follows the continental‐scale topographic gradient from highland toward lowland terrain on modern Mars, and the dune strata in this area may preserve evidence of an aeolian transport corridor that brought sediment to the northern lowlands.…”

Mapping and Characterization of Martian Intercrater Bedrock Plains: Insights Into Resurfacing Processes in the Martian Cratered Highlands

“…Surrounding materials have a relatively uniform composition and likely represent a mixture of impact ejecta, regolith and other unconsolidated materials (Tanaka et al, 1988). Bedrock plains are spectrally diverse and commonly contain multiple spectrally and morphologically distinctive subunits (Edwards et al, 2014;Irwin et al, 2018;Rogers et al, 2009;Wray et al, 2013). Orbital thermal infrared (TIR) and visible/near-infrared (VNIR) spectroscopy indicates many bedrock plain host olivine-enriched or olivine-and pyroxene-enriched surfaces (Edwards et al, 2014;Loizeau et al, 2012;Ody et al, 2013;Rogers & Fergason, 2011).…”

“…The spectral, morphological, and thermophysical properties of bedrock plains led to effusive volcanism and/or exposed mafic intrusions being favored as the petrogenic origin of bedrock materials (Edwards et al, ; Rogers & Nazarian, ). However, several newer observations suggest this interpretation is incorrect for many bedrock plains (Irwin et al, ; Rogers et al, ). A study of five heavily degraded Noachian‐aged craters hosting intracrater bedrock plains indicates that bedrock materials are friable, inconsistent with an effusive or intrusive igneous origin (Irwin et al, ).…”

Evolution of Escarpments, Pediments, and Plains in the Noachian Highlands of Mars

“…Low-viscosity lava flows have resurfaced some crater floors (e.g., Gusev crater as described by Arvidson et al, 2006), but the extent of this flooding is debated on the basis of crater floor morphology and spectroscopy (e.g., Edwards et al, 2014;Irwin et al, 2018;Rogers et al, 2018). Carr (1981) observed that intercrater plains are "intrinsically difficult to interpret" because their surfaces have been reworked through time, removing most diagnostic landforms.…”