IS THERE A LINK BETWEEN METEORITE IMPACTS AND LANDSLIDES IN VALLES MARINERIS?

Valles Marineris provides a unique opportunity to investigate whether there is a relationship between meteorite impacts and landslides on Mars. Quantin et al. (2004) dated landslides on Mars using isochron diagrams (Hartmann and Neukum, 2001). Bigot-Cormier and Montgomery (2007) examined gradients of stable slopes and landslides to show that rocks in Valles Marineris could withstand ground accelerations up to 0.2 g_Mars. Using this value, an equation relating impact energy to seismic magnitude, and the equation given in Wilson and Keefer (1985), we developed an equation relating crater diameter to the maximum distance to landslides. A major uncertainty is in the estimate of seismic efficiency (fraction of impact energy converted to seismic energy). Estimates of seismic efficiency range from 10^-3 to 10^-5 and our preferred value is 10^-4. The expression relating crater diameter to maximum distance to landslide allowed us rule out many craters as causes of landslides. The remaining craters were dated using the polynomial expression of Ivanov (2001) relating age to the area-normalized number of included craters ≥ 1 kilometer. Our estimates came from images from JMARS and GoogleEarth©. We are presently determining isochron ages.

Our preliminary results are as follows: Impacts played no role in the development of landslides younger than 200 MY or between 2-3 GY in age. In Tithonium and Ius Chasms meteorite impacts could explain landslides between 0.9-1.5 GY in age. In Eastern Melas and Corporates Chasms impacts might explain landslides between 1.0-1.8 GY. In Ophir and Hebes Chasms, impacts might explain landslides 200-500 MY in age. In Ganges Chasm impacts were found that might explain 3.0 GY landslides. These results suggest that the majority of landslides are tectonic in origin. However, meteorite impacts may play a role in explaining increasing landslide activity as the present is approached.