Theory: Saturn Moon's Heat From Decay
Pastor Dale Morgan
Theory: Saturn Moon's Heat From Decay*
Tuesday March 13, 2007 2:46 AM
By ALICIA CHANG
AP Science Writer
LOS ANGELES (AP) - Scientists believe heat from radioactive decay inside
a tiny, icy Saturn moon shortly after it formed billions of years ago
may explain why geysers are erupting from the surface today. The Cassini
spacecraft last year beamed back dazzling images of Yellowstone-like
geysers spewing from a warm section on Enceladus, raising the
possibility that the moon, which has an overall surface temperature of
about minus-330 degrees, may have an internal environment suitable for
primitive life.
However, scientists have been stumped by the origin of Enceladus'
interior heat. Now a new model suggests ancient radioactive decay played
a key role in shaping the moon's warm south pole region, where plumes of
water vapor and ice crystals periodically vent.
According to the theory, Enceladus formed some 4.5 billion years ago by
the mixing of ice and rock containing radioactive isotopes of aluminum
and iron. Over a period of several million years, the rapid decay of the
isotopes produced a burst of heat that resulted in a rocky core enclosed
by an ice sheet. Over time, the remaining decomposition in the core
further warmed and melted the moon's interior.
If confirmed, the model suggests Enceladus possesses the necessary
ingredients to support life - a stable heat source, organic materials
and liquid water.
``It tells us that conditions inside Enceladus either were or still are
conducive to biochemical reactions,'' project scientist Dennis Matson
said in a telephone interview.
Results were presented Monday at the annual Lunar and Planetary Science
Conference in Texas and will be published in the April issue of the
astronomical journal Icarus.
The Cassini team previously theorized that the geysers likely came from
underground reservoirs of water close to the surface, indicating a
lasting heat source inside. Matson said the latest model helps explain
where the interior heat might have come from.
Last year, another research team published a study that cast doubt on
the existence of water near Enceladus' surface. That study suggested
that buried ice clathrates - not liquid water - were responsible for
releasing the plumes through a tectonic shift in the crust. Clathrates
are lattice-like molecular structures that trap other types of molecules.
Cassini scientists plan to measure the composition of the gas rising
from the plume during an Enceladus flyby in 2008.
The Cassini mission is a project of NASA, the European Space Agency and
the Italian Space Agency. Launched in 1997, the spacecraft entered orbit
around Saturn in 2004, exploring its rings and moons.
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On the Net:
Cassini mission: http://saturn.jpl.nasa.gov/home/index.cfm