Here's a neat Russian paper: http://selena.sai.msu.ru/Symposium/phmp-ls.pdf It details the physical and mechanical properties of lunar soil. Much of the data was gathered via robotic probes & the samples they returned, though in-situ data was obviously estimated. I would think that it's being done all over again for Martian soils, albeit more slowly due to a lack of samples, but much can be infered from wheel & airbag impressions, knowing the masses, forces and surfaces that made them. Couple of lunar soil factoids: The soil is remarkably similar all over the lunar surface, and it averages about 4" deep. C. __________________________________ Do you Yahoo!? Yahoo! SiteBuilder - Free web site building tool. Try it! http://webhosting.yahoo.com/ps/sb/