The space probe Cassini discovered a significant atmosphere around the Saturnian moon Enceladus during two recent passes close by, the Jet Propulsion Laboratory said on Wednesday. Scientists speculate the atmosphere comes from volcanoes, geysers or some other kind of sub-surface activity, JPL said in a statement. Cassini made passes on Feb. 17 and March 9 and discovered the atmosphere using a magnetometer, which discovered a magnetic field on the moon. Because gravity is weak on Enceladus, a continuous source is needed to maintain the atmosphere, JPL said. The 310-mile-wide (500-km-wide) moon is icy and considered the most reflective object in the solar system, bouncing back about 90 percent of the sunlight that hits it. Titan, another moon of Saturn, also has a substantial atmosphere. The European probe Huygens, which went to Saturn piggy-back on Cassini, landed on Titan in January. Cassini-Huygens is a joint venture of NASA, the European Space Agency and the Italian Space Agency. Scientists at JPL designed, developed and built Cassini.
