Olympus Mons, Mars: Constraints on Lava Flow Silica Composition

Olympus Mons, Mars, the largest known volcano in our solar system, contains numerous enigmatic lava flow features. Lava tubes have received attention as their final morphologies may offer habitable zones for both native life and human exploration. Such tubes were formed through mechanisms involving several volatile species with significant silica content. Olympus Mons, a shield volcano, might be expected to have flows with silica content similar to that of terrestrial basaltic flows. However, past investigations have estimated a slightly more andesitic composition. Data pertaining to lava tubes such as flow width and slope are collected from the Mars Reconnaissance Orbiter's Context Camera, Mars Odyssey's THEMIS instrument, and Mars Express' HRSC instrument. Compiling this data in GIS software allows for extensive mapping and analysis of Olympus Mons' seemingly inactive flow features. A rheological analysis performed on 62 mapped lava tubes utilizes geometric parameters inferred from mapping. Lava was modeled as a Bingham fluid on an inclined plane, allowing for the derivation of lava yield stress. Percent silica content was calculated for each of the 62 mapped flows using a relationship derived from observations of terrestrial lava yield strengths and corresponding silica composition. Results indicate that lava tube flows across Olympus Mons were on average basaltic in nature, occasionally reaching into the andesitic classification: percent silica content is 51% on average and ranges between roughly 40% and 57%.