Formation Constraints on Martian North Polar Volcanic Edifices

Terrestrial Subglacial Volcanism: Many terrestrial subglacial volcanic features have been identified in Iceland [1-3], British Columbia, Canada [4], the Tuva Republic, Russia [5], Alaska [6], and Antarctica [7]. These features are though to follow a typical sequence of events although interpretations and details may differ by author and/or location: a single volcanic vent or short fissure opens under an ice sheet [8] releasing hot, magmatic gas which begins to melt the overlying ice, creating a subsurface lake of meltwater [8,9]. If the hydrostatic pressure is sufficiently higher than the gas pressure, pillow lavas form beneath the ice [10,11]; if the hydrostatic pressure is low relative to the magmatic gas pressure, then the erupting magma fragments into hyaloclastite due to the rapid heat transfer between the magma and ice [12]. Hyaloclastite layers build on top of the pillow lavas causing the edifice to near the surface of the ice, which drastically reduces the hydrostatic pressure from the overburden of lake water and ice; the gas in the magma expands, meltwater seeps into the vent causing steam explosions , and the eruption enters into an explosive phase producing greater amounts of hyaloclastites [8,11 and forming moberg subglacial cones or ridges [3]. When the edifice emerges from the lake and ice, further effu-sive activity produces flat, cap-rock lavas and effectively forms a tuya (stapi in Icelandic) [3,8,11]. Martian Subglacial Volcanism: Identification of subglacial volcanism on Mars is more difficult than on earth due to resolution of satellite data as well as the lack of a stratigraphic column necessary for unequivol-cal confirmation. However, despite the obvious obstacles , many possible subglacial features have been noted in various regions of Mars including Acidalia Motivation and Data: This study focuses on possible volcanic features in the north polar region of Mars in an effort to constrain their formation mechanisms and to estimate the thickness of a former possible ice-sheet. NASA works on the assumption that both water and energy sources, such as heat, are necessary for life [19], and this study considers both as the interaction between volcanoes and ice. Using MOLA, THEMIS, and HiRISE data, we conduct topographic characheristic analyses of 109 putatitve volcanic edifices in the Borealis Volcanic Field (Fig. 1) within 69º-81ºN and 197º-330ºE. As it is rarely possible to identify rock types on Mars such as palagonite or hyalo-clastite, we are limited to the use of topography data and images alone in …