A billion or more years of possible periglacial/glacial cycling in Protonilus Mensae, Mars

TL;DR

This study investigates ancient periglacial landforms in Protonilus Mensae on Mars, suggesting possible cyclic glacial-periglacial periods over hundreds of millions of years based on geological and crater analysis.

Contribution

It provides the first detailed evaluation of potential periglacial structures in Protonilus Mensae, indicating long-term glacial cycles in Mars' history.

Findings

Dark-toned terrain contains structures similar to Earth's cryoturbation features.

Crater analysis suggests the landforms are between 100 million and 1 billion years old.

Candidate cryoturbation features are among the oldest on Mars.

Abstract

The long-term cyclicity and temporal succession of glacial-periglacial (or deglacial) periods or epochs are keynotes of Quaternary geology on Earth. Relatively recent work has begun to explore the histories of the mid- to higher-latitudinal terrain of Mars, especially in the northern hemisphere, for evidence of similar cyclicity and succession in the Mid to Late Amazonian Epoch. Here, we carry on with this work by focusing on Protonilus Mensae [PM] (43-490 N, 37-590 E). More specifically, we discuss, describe and evaluate an area within PM that straddles a geological contact between two ancient units: [HNt], a Noachian-Hesperian Epoch transition unit; and [eHT] an early Hesperian Epoch transition unit. Dark-toned terrain within the eHt unit (HiRISE image ESP_028457_2255) shows continuous coverage by structures akin to clastically-sorted circles [CSCs]. The latter are observed in permafrost regions on Earth where the freeze-thaw cycling of surface and/or near-surface water is commonplace and cryoturbation is not exceptional. The crater-size frequency distribution of the dark-toned terrain suggests a minimum age of ~100 Ma and a maximum age of ~1 Ga. The age estimates of the candidate CSCs fall within this dispersion. Geochronologically, this places the candidate CSCs amongst the oldest periglacial landforms identified on Mars so far.