[meteorite-list] Saturn's Inner Moons - More Rubble Than Ice

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue Feb 14 14:14:38 2006
Message-ID: <200602141912.k1EJCus19132_at_zagami.jpl.nasa.gov>

http://www.newscientistspace.com/article/dn8720--saturns-inner-moons--more-rubble-than-ice.html

Saturn's inner moons - more rubble than ice
Kimm Groshong
New Scientist
14 February 2006

Saturn's small, inner moons may not be huge chunks of ice as once
thought, but rather "rubble piles" of material built up around small
central cores, a team of Cassini scientists suggests.

Before the Cassini mission to Saturn's moons, scientists knew small
moons such as Pan, Atlas, Janus and Epimetheus orbited the ringed
planet. "But we didn't have good pictures of them. We didn't have
measurements of their shape," says Carolyn Porco, Cassini Imaging
Science Team leader from the Space Science Institute in Boulder,
Colorado, US. "It could have been that they were collisional shards,
monolithic pieces of ice."

But now that Cassini has relayed images of those satellites back to
Earth and scientists have examined the moons' shapes, estimated their
masses and calculated their densities, Porco says that does not look to
be the case.

Instead, she says, the "rounded football" shape of Calypso, Telesto
(pictured), Epimetheus, Janus, Pandora, Prometheus, Atlas and Pan is
characteristic of accreted bodies - where material has built up around a
core.

The moons are "almost undoubtedly rubble piles" formed through
accretion, Porco told New Scientist.

Scientists still do not have reliable masses for two of the so-called
Trojan moons of Saturn - Telesto and Calypso - but the team includes
them as satellites likely to have been accreted based on their shape in
Cassini's recent pictures. The very low densities - between about 0.4
and 0.6 grams per cubic centimetre - calculated for the moons with known
masses further support the "rubble pile" theory.

The team is scheduled to present its results at the Lunar and Planetary
Science Conference in Houston, Texas, US, in March 2006.
Received on Tue 14 Feb 2006 02:12:55 PM PST