Dr. Harry (Hap) McSween,  Chancellor’s Professor Emeritus of the UTK Department of Earth and Planetary Sciences and NASA researcher will discuss Asteroid Exploration by the Dawn Spacecraft

Meeting Time: Monday March 20, 2023, at 7:00 p.m. Eastern Time

Dr. Harry (Hap) McSween, Chancellor’s Professor Emeritus of the UTK Department of Earth and Planetary Sciences, will discuss Asteroid Exploration by the Dawn Spacecraft in the City Room (A-111) of the Coffey-McNally Building on the Oak Ridge campus of Roane State Community College on Monday, March 20, 2023, at 7:00 p.m. This Richard D. Smyser Community Lecture is co-sponsored by ORION and the Friends of ORNL (FORNL). Hors d'oeuvres and non-alcoholic beverages will be served starting at 6:15 p.m. Enter parking lot B at 701 Briarcliff Ave. and enter the Coffey-McNally Building.  The City Room (A-111) is just off the lobby.


Asteroids are leftover planetary raw materials, and their compositions and structures provide basic constraints on planet formation.  Two of the largest bodies in the asteroid belt, Vesta and Ceres (both recognized by astronomers more than two centuries ago), have been explored recently by the Dawn spacecraft mission.  Vesta is the parent body of more than a thousand meteorites, and comparison of these samples with visible/near-infrared and gamma-ray/neutron spectra obtained by Dawn as it orbited Vesta allowed mapping of lavas on the surface and the deeper mantle exposed within large impact basins.  Dawn also revealed some surprises, such as the presence of water on Vesta delivered by foreign objects.  Precise tracking of Dawn’s orbit allowed a model of Vesta’s interior, which is dominated by a massive iron core.  Unlike Vesta, Ceres contains large amounts of ice, as well as alteration minerals formed by interaction of minerals with liquid water.  Although no meteorites are recognized to have come from Ceres, its composition is much like carbonaceous chondrites, but more pervasively altered.  Surprisingly, Ceres hosts cryovolcanoes that erupt brines, probably in the present day, and organic compounds have been found as well.  Models of Ceres’ interior indicate a soft, muddy mantle and a rigid crust of ice, silicates, and salts.  The Dawn mission, combined with analyses of extraterrestrial samples, is transforming these bodies from astronomical points of light into worlds shaped by more-or-less familiar geologic processes.

Hap McSween







Biographical Sketch: Hap McSween

 Chancellor’s Professor Emeritus Harry (Hap) McSween was a member of the University of Tennessee faculty for four decades before recently retiring.  He holds chemistry and geology degrees from The Citadel, the University of Georgia, and Harvard University.  He served as Head of the Department of Earth and Planetary Sciences (twice) and Interim Dean of the College of Arts and Sciences (twice).  He is a member of the U. S. National Academy of Sciences and a fellow of the American Academy of Arts and Sciences.  He is the only planetary geoscientist to have been elected president of the Geological Society of America.

Unlike most geochemists, Hap's attention is drawn to rocks falling from the heavens rather than to those already underfoot.  For four decades NASA funded his research on meteorites, and he has published hundreds of scientific papers dealing with meteorites and their implications for understanding the formation and evolution of the solar system.  He has also been involved in spacecraft missions – most recently as co-investigator for the Mars Exploration rovers, the Mars Odyssey orbiter, and the Dawn asteroid orbiter.  He is particularly interested in communicating the excitement of science to the public, and he is the author of three popular books on meteorites and planetary science, as well as widely used textbooks in geochemistry, cosmochemistry, and planetary geoscience.