162-10 Longitudinal Variations of Ice Coverage in Prometheus Basin, Mars

Session: Planetary Geologic Mapping Across the Solar System

Presenting Author:

Authors:

Abstract:

The south polar region of Mars contains massive deposits of ice that include both perennial and seasonal components. The perennial ice cap is made up of the water ice-rich South Polar Layered Deposits (SPLD) and the CO₂ ice-rich South Polar Residual Cap (SPRC). The seasonal component is an extensive CO₂ frost layer that undergoes significant accumulation and removal throughout a martian year and can cover from the pole to 50ºS at its maximum extent. Some areas of the polar cap display “cryptic” behavior, wherein the seasonal cap develops an anomalously low albedo even at cold temperatures, and is proposed to be related to the presence of CO₂ slab ice. In addition to modern ice sheets, the SPLD partially sits atop the Dorsa Argentea Formation (DAF), which is hypothesized to be the remnant of an ancient Hesperian-aged ice sheet. Both the cryptic terrain and the DAF overlap in extent within the Prometheus Basin, an ancient basin that is largely covered by the SPLD and partially filled by the DAF. In fact, Prometheus Basin is the only location where all three of these ice-rich units are exposed together.

To examine the nature of this combination of active cryptic terrain and ancient DAF, we mapped boundaries of ice-rich layers within Prometheus Basin. We selected 6 rectangular regions of interest (ROIs) within the basin and mapped layer boundaries at a 1:25,000 digitizing scale in the CTX global mosaic, which has a resolution of ~5 m/px.

We find a longitudinal variation, rather than a latitudinal one, in the icy layer coverage within the basin. Icy layered materials are prevalent and cover the entirety of the basin floor near 60ºE, but east of ~85ºE the presence of this material is restricted to sheltered topographic lows like small craters. Similar longitudinal trends are present in other datasets including SHARAD surface reflectivity, which captures geologic variations in the top ~10m of the surface. We will continue to investigate the composition of this material through analysis of CRSIM spectra to assess the water ice variation throughout the basin. Identifying local variations in DAF terrain (ice thickness, ice content, DAF thickness) can help to constrain active polar processes and their part in the evolutionary history of some of the most ancient deposits on Mars.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10757

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