Rolling Boulder Simulations (IMAGE) Brown University Caption Researchers used computer models to trace the possible path of boulders ejected from Stickney crater on Mars' moon Phobos. The simulations showed that boulders could have carved the iconic grooves seen on Phobos' surface. Credit Ken Ramsley / Brown University 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.