RRM (3 of 3) (IMAGE) NASA/Johnson Space Center Caption An unusual black mark on the Space Station Remote Manipulator System -- a robotic arm on the International Space Station -- had mystified mission directors. Credit NASA/JSC - Image Science and Analysis Group 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.