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Dynamics of a fluid flow on Mars: lava or mud?

Research output: Contribution to journalJournal article

Published

Journal publication date1/05/2014
JournalIcarus
Volume233
Number of pages13
Pages268-280
Original languageEnglish

Abstract

A distinctive flow deposit southwest of Cerberus Fossae on Mars is analyzed. The flow source is a similar to 20 m deep, similar to 12 x 1.5 km wide depression within a yardang associated with the Medusae Fossae Formation. The flow traveled for similar to 40 km following topographic lows to leave a deposit on average 3-4 km wide. The surface morphology of the deposit suggests that it was produced by the emplacement of a fluid flowing in a laminar fashion and possessing a finite yield strength. We use topographic data from a digital elevation model (DEM) to model the dynamics of the motion and infer that the fluid had a Bingham rheology with a plastic viscosity of similar to 1 Pa s and a yield strength of similar to 185 Pa. Although the low viscosity is consistent with the properties of komatiite-like lava, the combination of values of viscosity and yield strength, as well as the surface morphology of the flow, suggests that this was a mud flow. Comparison with published experimental data implies a solids content close to 60% by volume and a grain size dominated by silt-size particles. Comparison of the similar to 1.5 km(3) deposit volume with the similar to 0.03 km(3) volume of the source depression implies that similar to 98% of the flow material was derived from depth in the crust. There are similarities between the deposit studied here, which we infer to be mud, and other flow deposits on Mars currently widely held to be lavas. This suggests that a re-appraisal of many of these deposits is now in order.