Identification and interpretation of morphological evidence associated with fluvial-marine environments on Mars

Abstract

<p>Mars is the most Earth-like planet in the Solar System, due to its formation, structure and composition, but also due to the characteristics of its surface. These particularities point to the fact that, some time in its geological past, the planet was potentially habitable. Two such indicators are the morphological evidence that reveals an active hydrosphere with liquid water flow and the probable ocean existence. The deltaic lobes record possible interactions between watercourses and a potential giant water body on Mars. The goal of this study is to identify and characterize erosion and deposition processes, dominated by watercourses and littoral dynamics, through high-resolution imaging to characterize the shapes on the surface.  Through its morphological features the environmental behaviour of the Borealis Ocean at its interface with the coast was determined, establishing the parallelism with the dynamics observed on Earth.</p><p>Based on the literature review, a region of interest was selected that brought together fluvial phenomena and was in a strong dichotomous line. Two geographically close deltas were selected (Abus Vallis and Isara Vallis) that exhibit similar morphological characteristics, revealing that they were formed in the same environment. Abus Vallis appears to be of extreme importance, given its easy dating, as it is covered by units dating to the Late Hesperian (3.6 - 3.3 million years) permitting to temporally locate the Isara delta, which is given special focus. Subsequently, spectral images were used, obtained through the equipment orbiting Mars, specifically Mars Express- ESA, which has an instrument for storing high-resolution images and topographic data (HRSC). To identify and characterize the erosion and deposition processes, the high-resolution images were processed in GIS environment, and the morphology of the study area was identified, characterized and mapped. The results show that the Isara delta is located at the boundary between the northern lowlands and the southern highlands (potential ocean-continent boundary) in the Memnonia. There are two giant promontories (Amazonis Mensae and Gordii Dorsum) with a northwest - southeast orientation in the area, which may have been formed by massive flood events that filled the Amazonis Planitia basin with water, which widens and deepens towards the northern plains. This phenomenon was triggered by deformation of the Martian crust by tectonics and hydrothermalism during the development of the Tharsis volcanic shield. According to the analysis of the HRSC images, it was found that the Isara Vallis delta comes from a valley created by ground water sapping, from aquifers that come from Tharsis. The high-resolution images and digital terrain models, reveal that the studied delta is a Gilbert-type, stepped, shallow-water delta with a dug main fan channel, which witnesses different mean water levels from the receiving basin. This allowed to reconstruct the fluvial and marine dynamics of Mars during the formation of this delta. </p><p>The satellite images allowed the production of very detailed cartography, enabling a better reading of the delta's shapes and characteristics, through which it will be possible to understand the hydrological cycle of Mars, at a regional and global levels.</p>