Hubble Captures Rare Triple-Moon Conjunction (IMAGE) NASA/Goddard Space Flight Center Caption NASA's Hubble Space Telescope captured the rare occurrence of three of Jupiter's largest moons racing across the banded face of the gas-giant planet: Europa, Callisto, and Io. Credit Image Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) 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.