Research interests focus on impact cratering processes revealed by hypervelocity laboratory impact experiments, the planetary surface record, and terrestrial ground truth.  For the last twenty-five years, he has served as the Science Coordinator for the NASA Ames Vertical Gun Range (AVGR) and actively uses the facility as well with his students.  AVGR studies (with his students) have included atmospheric effects on crater formation and ejecta emplacement, survival of the impactor, high-speed spectroscopy of impact vapor/plasma, magnetic field generation by hypervelocity impacts, impact angle effects on vaporization, impact angle effects on shock propagation and target damage, and general crater scaling relations. 

Insights from such experiments led to his participation as a Co-Investigator in NASA’s Discovery mission called “Deep Impact.”  This mission sent a 360 kg mass into a comet at 10.2 km/sec.  These experiments are always placed in the context of understanding craters and the cratering process in contrasting planetary settings.  For example, studies suggest that the atmosphere, instead of water, is the controlling variable for the fluidized ejecta around Martian craters.  As a Magellan Guest Investigator, experiments allowed interpreting the nature of the ejecta deposits and crater morphology on Venus.  In addition, his experiments have provided insights for the survival of bodies following enormous collisions. 

He is currently participating as a science team member on the LCROSS (Lunar Crater Observing and Sensing Satellite), NExT (the mission to return to Comet Tempel), and DIXI (the continuation of the DI spacecraft to look at Comet Boethin).

Most recently, impacts into particulate targets enabled recognizing widespread impact melt deposits scattered within certain stratigraphic levels in late Cenozoic Argentine sediments.  To date, at least seven separate events (from 6 ka to almost 10 Ma) have been discovered.  He and his colleagues are using these dated glasses to redefine the stratigraphy of the Argentine sediments across the Pampas. 

He also continues to participate in a wide range of public and education outreach activities and is the Director of both the Rhode Island Space Grant Program and the Northeast Planetary Data Center at Brown University.  In the several years, he appeared in three different television programs highlighting:  Fireballs from Space (Discovery Channel), 96 Worlds and Counting (Discovery Channel), and Projectiles (The Learning Channel, BBC).  He received the 2004 Barringer Medal, an award for his contributions to the study of the impact cratering process from the Meteoritical Society.


He is presently Professor of Geological Sciences at Brown University.  He received his PhD from the University of Texas at Austin and BA from Carleton College, Northfield, MN.