Explosive Volcanoes on Mercury (image) Brown University Caption Data from NASA's MESSENGER spacecraft has shown that pyroclastic deposits are widespread on Mercury. The deposits are the telltale sign of explosive volcanism, which scientists long thought Mercury did not have. Credit NASA/ MESSENGER/ Head Lab/Brown University Usage Restrictions None 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.