Explosive Source (IMAGE) Brown University Caption New research shows that a strange Martian mineral deposit, imaged here from orbit, was likely made by ashfall from ancient volcanic explosions. Credit NASA/Christopher Kremer/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.