Evidence of mud volcanism due to the rapid compaction of martian tsunami deposits in southeastern Acidalia Planitia, Mars

摘要

Thumbprint terrain was first recognized in Viking Orbiter data and described as sets of alternating continuous parallel ridges and depressions up to several tens of kilometres in length, with high and low albedo respectively. We performed a geomorphological analysis of these features using both Context Camera and High Resolution Imaging Science Experiment images, as well as topographic profiles based on Mars Orbiter Laser Altimeter data, with the aim to provide an origin for thumbprint terrain and constrain the geological evolution of southeastern Acidalia Planitia. The identification of runup lobate deposits, coupled with the putative presence of a Late Hesperian ocean in the northern lowlands, led to speculations that evidence of tsunamis may be present in the geologic record of the area. There are several hypotheses that have been proposed previously to explain the origin of thumbprint terrain and include ice-related, volcanic-related, liquefaction and mud-volcanism driven processes. However, a tsunami-related origin provides a strong geological framework for the energy required for the associated lobes to flow uphill and leaving peripheral termination ridges as a result of viscosity. Numerical simulations indicate that - prior to their emplacement - the lobes sustained high velocities, thereby lending further support to the tsunami hypothesis and their origin from the Lomonosov crater impact. Wave interference patterns, formed during the propagation of the tsunamis over and around prominent topography, likely explain the thumbprint terrain spatial arrangement. The thumbprint terrain sedimentary cones are, herein, considered mud volcanoes related to a tsunami that occurred in southeastern Acidalia Planitia.