REVISITING PHREATOMAGMATIC VOLCANOES IN MARGARITIFER TERRA, MARS

Since mapping projects that used Viking Orbiter data, it has been known that the Margaritifer Terra region of Mars experienced a complex history of fluvial transport, collection, and discharge in addition to impact cratering and aeolian processes. More recent geologic mapping using MOC and THEMIS images and MOLA topographic data revealed more detailed information about fluvial activity in the Samara and Parana-Loire Valles systems and in the Uzboi-Ladon-Margaritifer mesoscale outflow system. Additionally, a feature near the confluence of the Samara and Loire Valles systems that could not be identified in Viking-era mapping due to image resolution has been interpreted as a volcanic landform that likely resulted from a phreatomagmatic eruption. Further analysis also identified two other volcanic landforms in the same vicinity as the largest feature.

Since the initial interpretation of the volcanic features, more orbital images have been collected by THEMIS, HRSC, and the HiRISE and CTX instruments on Mars Reconnaissance Orbiter. Although limited in number, these additional images help to further identify volcanic features associated with the volcanoes, which aids in determining whether or not these are indeed phreatomagmatic landforms. The images have also been used to identify a probable lava flow, and they are being used to determine whether any fluvial activity was present in the valles systems when the eruptions took place. Because of the water and heat interactions during a phreatomagmatic eruption, this location remains interesting as an area where conditions could have existed for past life on Mars.