POSSIBLE HYDROLOGICAL ACTIVITY IN A LARGE IMPACT CRATER IN NILOSYRTIS MENSAE, MARS. A geomorphological and chronostratigraphical analysis.

Abstract

The arid and freezing landscapes of planet Mars cannot sustain liquid water during its present conditions. However, geomorphological and geochemical evidence suggest a ‘wetter and warmer’ climate in the early history of the planet. In this study, a geomorphological map was produced of an impact crater on Mars with the aim to uncover the spatiotemporal evolution of possible fluvial activity in the region. The study area is situated around 30°N, adjacent to the Nilosyrtis Mensae region. Landforms and structures were mapped by using data from The Context Camera [CTX] mosaic, raw imagery & DEM products (5-6 m/px) and High Resolution Imaging Science Experiment [HiRISE] (0.3-0.25m/px) imagery and DEM products. Interpretations were also supported by Thermal Emission Imaging System [THEMIS] Day and Night IR mosaics (100m/px) as well as the High Resolution Stereo Camera [HRSC] DEM product (50m/px).

This study identified multiple possible spatiotemporal events of geomorphology related to fluvial and glacial activity. The map classification uncovered the presence of fan shapes, valley networks, streamlined plains, streamlined mounds, eroded valley systems and viscous flow features. An absolute age estimation was performed on one fan shape using crates size frequency distribution measurements. The estimated age correlates with fluvial activity which occurred around 3.7 billion years ago. This also correlates with age estimations of other well known Martian impact craters with similar fan shaped fluvial geomorphology, supporting the hypothesis that the global climate was different on early Mars. The study found evidence of multiple events of fluvial activity. The northern impact crater floor showed geomorphology related to an outwash channel system, while the southern impact crater floor exhibited geomorphology related to possible lacustrine environments. The diversity, degradation and sedimentation of the impact crater suggest a long geological history with multiple events of fluvial activity. The fluvial activity would have occurred both integrated and/or separated through time and space due to local responses, driven by climate variability which affected the surrounding impact crater environment. The study could not confirm nor refute the impact crater as a lacustrine or marine environment. Further investigations by using geochemical data from Compact Reconnaissance Imaging Spectrometer [CRISM] could be used to cross-validate the fluvial geomorphological map classifications in this study.