Geomorfologisk studie av Jezerokraterns kant (Mars)

Sammanfattning

Over the last 30 years scientists have studied the morphological and mineralogical proofs of past aqueous activity on Mars. NASA’s latest flagship mission, the Mars 2020 mission with its Perseverance rover, landed in Jezero crater in 2021. Perseverance is tasked with investigating the wet history that has partially formed today’s Mars, and more specifically, find specific indicators for potential past life. Jezero is a 45 km wide impact structure with an uplifted rim and a lower standing relatively flat crater floor. This site is particularly interesting for investigating the aqueous history of Mars because Jezero once hosted a lake. Today Jezero preserves two deltas with inlet valleys and one outflow channel. While these features have been of focus in many publications, less scientific attention has been devoted to the large-scale structural features of Jezero crater. Presently, the crater rim is highly fluctuating in topographic relief and the northern rim is almost not possible to identify because of its low relief. Earlier studies means that the lower topographic relief of the northern rim is because of fluvial erosion. The present study uses topographic data and high-resolution orbital images and is aimed at investigating different mechanisms, including fluvial erosion, to explain the current expression of the Jezero crater rim. With the help of orbital data, in the form of satellite pictures and topographic data, a geological map was made. The mapping was based on topographic morphology (topographic variation and slope angles in and out of the crater) and texture (such as, ruggedness, knobs, rockiness). The map showed that the southwestern parts of the crater rim was characterized by more rugged rocky units and the northeastern parts held more smooth units. Mechanisms discussed to explain this expression of the crater rim was crater rim uplift, fluvial erosion and pre-impact factors (target rock properties). Possible evidence for a similar crater rim uplift in the northeastern parts as in the southwestern parts was found. This could indicate that crater rim uplift is not a driving factor in the different topographic expressions of the Jezero crater rim. The findings further indicate evidence for pre-impact factors, which would have influenced the erosional resistance of the crater rim, and fluvial erosion as mechanisms behind the present expression of the Jezero crater rim. The eastern rim of the crater was found to have a constant slope, with landslide-like features and potential lava flows preserved on the inside of the rim. These could originate from the high-standing feature Jezero Mons, a potential volcanic edifice, although further investigations are needed to exclude other possible mechanisms for the topography.