Enceladus is a "Cosmic Graffiti Artist," Astronomers Discover (Forwarded)

Media Relations
University of Virginia
Charlottesville, Virginia

Contact:
Fariss Samarrai, Senior News Officer
(434) 924-3778

Anne Verbiscer
(434) 243-8940

Feb. 8, 2007

Enceladus, A Moon of Saturn, is a "Cosmic Graffiti Artist," Astronomers
Discover

Astronomers from the University of Virginia and other institutions have
found that Enceladus, the sixth-largest moon of Saturn, is a "cosmic
graffiti artist," pelting the surfaces of at least 11 other moons of Saturn
with ice particles sprayed from its spewing surface geysers. This ice
sandblasts the other moons, creating a reflective surface that makes them
among the brightest bodies in the solar system (Enceladus, itself a ball of
mostly ice, is the single most reflective body in our solar system).

"Enceladus' art is a work-in-progress, constantly altering the surfaces of
other moons orbiting within this moon's beautiful swirl of ice particles,"
said Anne Verbiscer, a research scientist in the astronomy department at the
University of Virginia and the study's lead investigator. "We've dubbed
Enceladus a graffiti artist because of its ability to alter the appearance
of the other moons."

A paper about her and her colleagues' findings appears in the Feb. 9 issue
of the journal Science.

The ring of ice particles Enceladus forms around Saturn is known as the
E-ring. At least 11 other moons orbit within the E-ring and are constantly
subjected to high velocity collisions with Enceladus's icy wake.

A series of geysers at Enceladus's south pole continually erupt, ejecting
ice particles, spewing a swirling wispy trail in the moon's wake and
ultimately forming a cloudy ring of ice particles. The ring is added to over
and over as Enceladus repeats its orbit. The particles may persist for
thousands of years, until they collide with one of the embedded moons,
including Enceladus as it flows through its own emissions.

"We asked ourselves why those other moons in the E-ring are so bright,
though they are not geologically active like Enceladus? The answer, we now
know, is that the other moons are being 'sand-blasted', so to speak, by the
ice particles ejected from Enceladus," Verbiscer said. "These are physical
characteristics not previously known."

Verbiscer added that Enceladus is of great interest to astrobiologists who
believe primitive microorganisms could, in theory, exist beneath the surface
of that moon because of the existence of liquid water below the surface.

Planetary astronomers are particularly interested in Enceladus because of
its geological activity. At 314 miles in diameter, Enceladus is nearly seven
times smaller than the Earth's moon. But unlike our moon, Enceladus is
continually changing as its geysers spew ice and liquid water, the likely
result of heat and pressure deep within.

The surface of Enceladus is quite young, possibly less than 100 million
years. It is the sixth largest moon of the more than thirty known moons that
orbit Saturn. Because of its icy surface, Enceladus has the highest albedo,
or surface reflectivity of any body in the solar system. Astronomer William
Herschel discovered the moon in 1789.

The satellite's surface of ice includes smooth areas of plains, ice vents,
ridges and long lines of cracks at its south pole. The cracks are the source
of the ice plumes released from the body that escape into its orbit,
trailing and accumulating in its path, creating a highly visible cloudy ring
around Saturn.

Enceladus is named for a Roman and Greek mythological giant who was
considered responsible for volcanic fires on Mt. Etna in Sicily. "That
analogy certainly holds true with the realization that Enceladus is
geologically active and spraying ice particles out of its south pole,"
Verbiscer said. "But we've extended the gigantic influence that it has,
because of its ability to alter the appearance of its neighboring moons."

Verbiscer's co-investigators are Richard French of Wellesley College, Mark
Showalter of the SETI Institute and Paul Helfenstein of Cornell University.

Audio:

Anne Verbiscer discusses findings on the "cosmic graffiti artist",
http://www.virginia.edu/uvapodcast/n...it=true&id=367

Additional Resources:

* Astronomy Department
http://www.astro.virginia.edu/

IMAGE CAPTION:
[http://www.virginia.edu/uvatoday/pho...seq=1&id=1461]
Wispy fingers of bright, icy material reach tens of thousands of kilometers
outward from Saturn's moon Enceladus into the E-ring, while the moon's
active south polar jets continue to fire away. Photo courtesy NASA/JPL/Space
Science Institute