Phobos Craters (IMAGE) University of California - Santa Cruz Caption In this spacecraft image of Phobos, red arrows indicate a chain of small craters whose origin researchers were able to trace back to a primary impact at the large crater known as Grildrig. Credit ESA/Mars Express, modified by Nayak & Asphaug Usage Restrictions For use only with news coverage of this research 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.