[M-IS12] Planetary Volcanology

[MIS12-P04] The extent of shallow underground water-ice in the Amazonian period on Mars inferred from the distribution of rootless cones

*Rina Noguchi¹ (1.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency)

Keywords:Mars, rootless cone, ground water-ice

On Mars, volcanism in the Amazonian period is characterized by the emplacement of flood lava, contrasting to that of Noachian and Hesperian that built large shield volcanoes (e.g., Keszthelyi et al., 2006). Previous studies have found conical mounds on Amazonian lava flows which have been considered to be possible rootless cones (e.g., Greeley and Fagents, 2001; Fagents and Thordarson, 2007; Keszthelyi et al., 2010). Rootless cones are formed by intermittent explosions that occurred by the interaction of lava and water (ice)-logged sediments (Thorarinsson, 1953). Thus, the existence of rootless cones suggests not only volcanic activity but also the presence of water-ice in the shallow subsurface. Possible rootless cone fields have been described in several places. According to Fagents and Thordarson, 2007, candidates of rootless cone fields are mapped in Amazonis Planitia, Olympus Mons aureole, Acidalia Planitia, S. Utopia Planitia, Isidis Planitia, Hephaestus Fossae, Elysium Planitia, Cerberus, Marte Valles, and Arrhenius. Most of the fields are located in low-mid latitudes of the northern lowland plains. Since this mapping was based on studies before 2000 with low-resolution images, those rootless cone fields are uncertain and should be revised with higher resolution images. In the presentation, I update and summarize possible rootless cone fields on Mars, and discuss the extent of groundwater-ice in Amazonian.