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Project Progress

Dietrich Group

Our original premise was that the channels on Mars identified as formed by seepage would be excellent sites to explore for signs of life because of the combined effects of sustained water (to cause erosion) and the subsurface nature of the flow (away from harmful UV radiation). Our research now strongly suggests that seepage channels will not form in resistant bedrock, like basalt, and that the morphology of channels that have been used to suggest seepage origin (amphitheater headed canyons) is not a reliable indicator of seepage processes. Based on our field work, literature review, and examination of images of Mars, we have written a paper that argues these two main points and questions the importance of seepage erosion on Mars (Lamb, et al., in press). We have also submitted a paper proposing that the spectacular canyons in Kohala, Hawaii (long argued to be of seepage origin) were created by waterfall erosion and head-scarp retreat following a massive landslide (Lamb et al., in review) (Figures 1 and 2). New dating techniques have now firmly established that Box Canyon (our field site in Idaho) was formed between 100,000 and 50,000 years ago (Aciego, et al., submitted) and field data show signs of flow scour of bedrock (Figure 3), strongly suggesting that the erosion occurred by huge floods rather than seepage. We are now focused on alternative mechanisms of headwall retreat in stratified basalt. Initial experimental and theoretical work suggests that block toppling may play a primary role. This produces large boulders, and theoretical work has begun (with experiments to follow) on flows needed to transport boulders. Work of this kind has helped guide collaborative work on the origin of the channels on Titan (Perron et al., in press). Finally, the rover observations on Mars, revealing surprisingly similar landscapes to that found on Earth, led us to write a review paper for Nature entitled: The Search for a Topographic Signature of Life (Dietrich and Perron, 2006).

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Manga Group:

Liquid water influences the mobilty and hence runout distances of landslides. In order to search for the evidence of abundant near-surface liquid water during the Amazonian we reinterpreted the runout distances of the numerous Amazonian landslides in Valles Marineris. We find that the distance they travelled is best explained by models for dry landslides implying the availability of limited amounts of liquid water (Soukhovitskaya and Manga 2006).

The shaking caused by impacts can potentially release large amounts of liquid water on the surface on a planet. Our empirical summary of earth-based responses to shaking caused by earthquakes suggests this effect would have been widespread and could have occurred often (Wang et al., 2005). Our empirical observations also suggest that the energy deposition need to liquefy loose material during impact may be less than commonly assumed (Wang et al., 2006).