H. Jay Melosh
Election Year: 2003
Primary Section: 16, Geophysics
Secondary Section: 15, Geology
Membership Type: Member
I am principally interested in the physical processes shaping the surfaces of the terrestrial planets (including the Earth), and in the origin and evolution of the planetary system. One of my major concerns is the process of impact cratering. I also maintain an active research program focused on terrestrial and planetary tectonics and the physics of very large landslides. I am very much attracted by apparent paradoxes, situations where observation and theory seem to be in conflict. Thus, the discovery that the SNC meteorites had been launched from the surface of Mars, in apparent conflict with the best impact cratering theories at the time, was an obvious area needing clarification. In another apparent paradox, very large landslides and collapsing impact craters exhibit a surprisingly high mobility that cannot be explained by current ideas on rock friction. I proposed a mechanism, acoustic fluidization, which successfully explains the long runout of "Sturzstrom" landslides and the form of collapsed impact craters on the Earth and other planets. This mechanism may also explain the now-incontrovertible evidence for very low coefficients of friction along such faults as the San Andreas in California. Continuing work on this process includes both laboratory experiments and theoretical modeling.