spacetoday.net: Cassini finds atmosphere around Enceladus

Posted: Fri, Mar 18, 2005, 6:00 AM ET (1100 GMT)
Enceladus seen by Cassini (NASA/JPL)

NASA's Cassini spacecraft has detected a tenuous atmosphere surrounding the Saturnian moon Enceladus, scientists said this week. The discovery was based on observations of Saturn's magnetic field made by the spacecraft during two flybys of the small moon in the last month. During each flyby Cassini observed deflection of magnetospheric plasma and oscillations in the magnetic field in the vicinity of the moon, which scientists said would be caused if the moon was surrounded by a thin atmosphere, most likely of water vapor. Because Enceladus is a small moon, only 500 kilometers across, it is not massive enough to hold an atmosphere for any length of time, and thus would need to have the atmosphere replenished continuously, perhaps through geysers or volcanic eruptions. Scientists have long speculated that the icy moon is geologically active and is the source of Saturn's E ring.