37th DPS Meeting, 4-9 September 2005
Session 32 Mars' Surface
Poster, Tuesday, September 6, 2005, 6:00-7:15pm, Music Recital Room

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[32.19] Elastic Lithosphere Thickness and Heat Flux Estimates from Rift Valley Topography: Coracis Fossae, Mars

M. Grott, E. Hauber (DLR, Berlin), S.C. Werner (FU Berlin), P. Kronberg (TU Clausthal), G. Neukum (FU Berlin)

The Coracis Fossae in the Thaumasia region on Mars are two several hundred kilometer long and ~50 km wide extensional structures. Their complex morphology, fractured graben floors and segmented border faults, which are arranged in en echelon pattern, suggest that they are Martian analogues to terrestrial rift systems. At Coracis Fossae's NE segment rift flank uplift is most pronounced, the rift shoulders having heights of more than 1000 m with respect to the surrounding planes. We model the uplift by fitting a flexed broken plate to the topography data obtained by the Mars Orbiter Laser Altimeter. Thus, the elastic thickness at the time of rifting is constrained to 10.3 - 12.5 km. Assuming a diabase composition of the crust, this corresponds to a thermal gradient of 27 - 33 K km-1.

Investigating the key surface units associated with the rifting, the time of rift formation is determined by measuring their crater size-frequency distribution and comparing the results to an impact cratering chronology model. The time of rifting is thus constrained to 3.5 - 3.9 Gyr b.p.

Given the fault block topography and elastic thickness, the stresses acting on the bounding faults which support the topography may be calculated. We estimate that at the Coracis Fossae the faults need not withstand stresses in excess of 5 MPa, a value comparable to terrestrial faults. We take this weakness as an indication that the faults are or have been in contact with liquid water below the surface.

The author(s) of this abstract have provided an email address for comments about the abstract: matthias.grott@dlr.de

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.