18-4 A Catalog of Sinuous Rilles on the Tharsis Montes Rift Aprons, Mars

Session: Surface Processes Across the Solar System

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Abstract:

Channels presumably formed by flowing lava have been observed on Venus, the Moon, and Mars, with lengths ranging from 10s to 1000s of kilometers. Exotic lava compositions and high effusion rates have been proposed to explain these landforms, which may represent either erosional or constructional processes. On Mars, the spatial distribution, morphology, and emplacement conditions of these channels are key to understanding its volcanic history, interior and surface evolution. The Tharsis volcanic province covers approximately a third of the planet’s surface and presents the largest volcanic region.  Numerous sinuous rilles are observed in the flanks of the Tharsis Montes, three large shield volcanoes trending NE-SW.  Specifically, each volcano displays a rift apron, a large wedge of effusive deposits postdating the formation of the main shield edifice. The aprons represent an understudied region with relatively young deposits.  We mapped and characterized sinuous rilles on the Tharsis Montes (Arsia, Pavonis, and Ascraeus) rift aprons.

We delineated rift apron subregions using previously published geologic maps and boundaries (e.g. Plescia 2004, Skinner et al., 2006). Using Mars Odyssey Thermal Emission Imaging System (THEMIS) infrared data at 100 m/px and Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) at ~6m/px, we have identified  169 sinuous rilles. On the rift aprons of Arsia Mons, extending from an elevation of ~12 - 13 km, we have identified 74 sinuous rilles. Their lengths range from ~2 - 90 km with a mean length of ~19 km and a median length of ~13 km. Regional slopes range from ~0.3 - 3°. On Pavonis Mons, we have identified 27 sinuous rilles. Channels range in length from ~3 - 72 km with a mean length of ~16 km and a median length of ~9 km. Regional slopes range from ~0.08 - 1.5°. On Ascraeus Mons, extending from an initial elevation of ~6 km in the north and ~8.5 km in the south, we have identified 68 sinuous rilles. Channels range in length from ~2 - 235 km with a mean length of ~27 km and a median length of ~17 km. Regional slopes range from ~0.08 - 2°. To date, we have calculated 76 channel widths with a mean of .209 km. These preliminary observations suggest that long-lived effusive eruptions were part of the later evolution of these large shield volcanoes on Mars.

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