for National Geographic News
Jets of water vapor blasting out of Saturn's moon Enceladus at supersonic speeds are coming from vents each about the size of a professional sports stadium, a new study says.
Research later determined that the water geysers are gushing out at about 1,000 miles (1,609 kilometers) an hour from a series of 100-mile-long (161-kilometer-long) fissures dubbed tiger stripes.
The new finding indicates that the gas and dust are escaping from relatively small vents along those fissures.
"We are making the distinction between the whole plume and individual jets in it, like streamers or searchlight beams," said team member Larry Esposito, of the University of Colorado in Boulder.
The researchers think the jets are formed when liquid water from pools not far beneath the icy moon's surface accelerates as vapor passes through a maze of nozzle-like channels before erupting into space.
"It's one more little piece of evidence that the source of the plume is liquid water," said lead study author Candice Hansen, a planetary scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.
Swimming Pools and Ping Pong
The Cassini spacecraft observed the way the plume dimmed starlight shining from behind as the probe zipped past Enceladus in 2005 and 2007.
The data allowed scientists to determine the vapor jets' speed and density as low as 9 miles (15 kilometers) above the surface.
That, in turn, allowed them to calculate the likely size of the vents from which the vapor is emerging.
"It's certain the jets are not coming from the whole fissure," Esposito said.
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