News and commentary about the Great Frontiers

ISS007-E-10807 (21 July 2003) --- This view of Earth's horizon as the sunsets over the Pacific Ocean was taken by an Expedition 7 crewmember onboard the International Space Station (ISS). Anvil tops of thunderclouds are also visible. Credit: Earth Science and Remote Sensing Unit, NASA Johnson Space Center

Image Credit: ISS007-E-10807 (21 July 2003) – Earth Science and Remote Sensing Unit, NASA Johnson Space Center

Cassini Spots Icy Plumes on Enceladus



Cassini has returned spectacular images of huge plumes of water ice particles emanating from Enceladus, confirming that this tiny moon of Saturn is an active and watery world. Several plumes of various sizes can be seen clearly along the limb of the moon backlit by the Sun. Spraying out into space, these plumes may provide the source material for Saturn’s E ring.

The plumes coincide nicely with the fractured “tiger stripe” region surrounding Enceladus’ south pole. Earlier this year the tiger stripes were found to be warmer than surrounding terrain and the most recently resurfaced area on the moon. In addition to being the probably source for Saturn’s E ring, the activity here also generates a localized thin atmosphere.

The exact mechanism for this activity is still not known. One theory posits that the plumes result from geysers of liquid water created by internal heating that violently escapes to the moon’s surface. Another theory suggests that the plumes are caused by the vaporization of surface ice over internal warm spots. A gravitational tug of war on Encealdus between Titan and Saturn may provide the needed energy to keep Enceladus’s interior warm.

This latest discovery caps an already incredible year of results from the Cassini-Huygens mission to the Saturnian System, including the first known spiral arm of ice and dust particles around a planet, a thin oxygen-rich atmosphere around the rings, and liquid-cut channels and possible lakes of liquid methane on Titan. NASA and the European Space Agency (ESA) plan to present on Wednesday, November 30, 2005 “the latest Huygens probe and Mars Express orbiter results during back-to-back briefings from the agency’s Paris headquarters.” The briefings will be aired live on NASA TV.

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