Observations of a new stabilizing effect for polar water ice on Mars

TL;DR

This study reveals a new seasonal stabilizing effect of water ice on Mars, where the outer ice mound in Louth crater is replenished from surrounding regolith, influencing ice stability and distribution.

Contribution

It introduces the observation of a previously unknown stabilizing effect of water ice in Martian polar regions, linked to seasonal replenishment from regolith.

Findings

Outer ice mound is seasonally replenished with water ice.

Transport distance of water migration is approximately 4 km.

Explains absence of water ice mounds in craters smaller than 9 km.

Abstract

Using the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), we map the temporal variability of water ice absorption bands over the near-polar ice mound in Louth crater, Mars. The absorption band depth of water ice at 1.5 microns can be used as a proxy for ice grain size and so sudden reductions can time any switches from ablation to condensation. A short period of deposition on the outer edge of the ice mound during late spring coincides with the disappearance of seasonal water frost from the surrounding regolith suggesting that this deposition is locally sourced. The outer unit at Louth ice mound differs from its central regions by being rough, finely layered, and lacking wind-blown sastrugi. This suggests we are observing a new stabilizing effect wherein the outer unit is being seasonally replenished with water ice from the surrounding regolith during spring. We observe the transport distance for water migration at Louth crater to be ~4km, and we use this new finding to address why no water ice mounds are observed in craters <9km in diameter.