Jay Melosh, Purdue University (IMAGE) Purdue University Caption Jay Melosh, a Purdue distinguished professor of Earth, atmospheric and planetary sciences, stands in front of a map showing the moon's gravity field. As a member of the science team of NASA's Gravity Recovery and Interior Laboratory, or GRAIL, mission, Melosh led a study of large concentrations of mass beneath the lunar surface. The team confirmed that the mass concentrations, or "mascons," were caused by massive asteroid impacts billions of year ago and determined how these impacts changed the density of material on the moon's surface and, in turn, its gravity field. Credit Purdue University photo/Mark Simons; image of lunar gravity field courtesy of NASA Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.