Episodic and Recent Glaciation in the Protonilus Mensae Region During the Amazonian

Amazonian modification of Moreux crater: Record of recent and episodic glaciation in the Protonilus Mensae region of Mars

Authors:

Sinha et al

Abstract:

Morphologic characteristics of ice-rich landforms in the martian mid-latitudes record evidence for significant modification of the landscape in response to spin–axis/orbital parameter-driven shifts in the Late Amazonian climate. These landforms are spatially distributed across the mid-latitudes and their co-existing presence has so far not been observed from a single crater to infer how exactly a terrain has been modified while Mars was undergoing major–moderate–minor shifts in its Late Amazonian climate. We have therefore carried out an in-depth investigation of Moreux crater (∼135 km, centered at 41.66°N, 44.44°E in the Protonilus Mensae region) for identification of features associated with recent and episodic glacial events and for emphasizing the role played by these glacial events in the modification of the crater. Evidence for extensive modification of the surfaces over crater rim/wall and around central peak by emplacement of multiple scales of ice-rich landforms that represents large history of glacial activities was found. From our results we document phases of major–moderate–minor glacial activities within the crater as: (1) piedmont lobes/lobate debris aprons/linear valley fills (∼1 Ga–100 Ma), (2) viscous flow features (∼30–0.1 Ma) and (3) gullies/thermal contraction crack polygons (∼2.1–0.4 Ma). The form and distribution of the random valleys observed within Moreux suggests their formation by pressure-induced melting and flow occurring beneath an extensive layer of ice. We also suggest that central peak of Moreux probably acted as the locus for accumulation of ice/snow and the diversity of glacial/periglacial features within the crater was possibly controlled by differences in the amount of accumulated ice/snow and the rate at which the terrain responded to the shifts in climate during subsequent periods of obliquity changes. Taken together, these ice-rich deposits within Moreux suggest that sequential modification of the crater surfaces over the rim/wall and around central peak has occurred over the last tens of millions of years of martian history. This new evidence thus adds another well-documented case to rapidly accumulating evidences for widespread glacial activity in the middle latitudes of Mars in recent martian history.