Possible sub-glacial eruptions in the Galaxias Quadrangle, Mars

Abstract

We have identified several landforms in the Galaxias Quadrangle of Mars (MTM 35217), 33.0–35.5°N, 216.0–218.0°W which are consistent with this area having been covered by an ancient ice sheet concurrent with volcanic eruptions. Volcanic activity was initiated by the intrusion of several large dikes measuring ∼50–100m wide and protruding up to ∼35m above the present-day surface. These dikes appear to have originated from Elysium Planitia ∼600km to the SE. In one instance, a dike (at an elevation of −3750m) appears to have produced a subglacial mound (referred to here as “Galaxias Mons 2”) that evolved into an extrusive eruption and produced copious volumes of melt water that carved an outflow channel that extends almost 300km to the north. At a lower elevation (−3980m), a second putative dike may have failed to break the surface of the ice sheet and formed Galaxias Mons as a laccolithic intrusion. We numerically model the formation of Galaxias Mons and find that at least 200m of ice may once have existed at this latitude at the time of the dike intrusions. Such a conclusion supports the idea that enigmatic small domes in the area may be pingoes. Collectively, these observations suggest that the previous interpretations for the origin of near-by Hrad Vallis as a sub-aerial eruption may need to be revised.