Tiny Enceladus May Hold Ingredients of Life

TINY ENCELADUS MAY HOLD INGREDIENTS OF LIFE
From Lori Stiles, UA Office of University Communications, 520-621-1877
September 5, 2005

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Contact information listed at end of release
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Saturn's tiny moon Enceladus is "absolutely" a highlight of the
Cassini
mission and should be targeted in future searches for life, Robert H.
Brown
of The University of Arizona, leader of the Cassini visual and infrared
mapping spectrometer team, said last week.

Brown and other Cassini scientists attended a meeting in London last
week
and are at the 37th annual Division of Planetary Sciences meeting at
Cambridge University this week.

"Enceladus is without a doubt one of the most spectacular things
Cassini
has seen," Brown said in a phone interview Thursday. "It's one of the
biggest puzzles. It'll be a long time before anyone comes up with a
good
explanation of how Enceladus does what it does, and for a scientist,
that's
pure, unmitigated fun. Solving the biggest puzzles is the thrilling
part of
doing science."

Scientists got their first glimpse of Enceladus's geology when Voyager
2
flew by the icy bright satellite in August 1981. They were completely
baffled. Voyager photographed areas of young, smooth terrain that told
them
that the moon must have been geologically active as late as 100 million
years ago.

But nothing explained how tiny Enceladus -- only 314 miles across --
could
get hot enough to melt. It seemingly doesn't have enough interior rocks
for
radioactive heating, an eccentric enough orbit for tidal heating, or
enough
ammonia to lower its melting temperature. After Voyager, researchers
shelved
Enceladus as an unsolvable problem for a while.

This year, Cassini turned its more powerful cameras and instruments on
Enceladus during Feb. 17, March 9 and July 14 flybys. Results have
stunned
and delighted.

The diminutive moon turns out to have a primarily water vapor
atmosphere
tinged with nitrogen, carbon dioxide and other simple carbon-based
molecules
(organics) concentrated at its south pole. Its south pole is a hotspot,
hovering at a relatively balmy minus -183 degrees Celsius compared to
the
expected temperature of -203 degrees Celsius.

Enceladus's south pole is a hotbed of geological action. The south
pole
region is cut by parallel cracks roughly 81 miles long and 25 miles
apart.
The cracks, dubbed "tiger stripes," vent vapor and fine ice water
particles
that have crystallized on Enceladus's surface as recently as 1,000
years to
10 years ago. The fine ice material is probably the major source of
particles that replenish Saturn's outermost ring, its E ring.

"The kind of geophysical activity we see is quite likely being driven
by
liquid water below the surface," Brown said. Cassini hasn't seen ice
geysers
or ice volcanoes, but the lack of ammonia, and the sheer volume of
water
vapor escaping suggests there's pure-water volcanism on Enceladus, he
added.

"We detected simple organics in the tiger stripes," Brown said. The
simple
organics include carbon dioxide and hydrogen-and-carbon-containing
molecules
like methane, ethane and ethylene. "Methane (basically natural gas) has
probably been locked up inside Enceladus since the solar system formed
and
is now bubbling up through the vents."

The visual and infrared mapping spectrometer can't detect nitrogen,
but
Cassini's ion neutral mass spectrometer may have found nitrogen in
Enceladus's atmosphere. All other results from these two very different
instruments are entirely consistent, which gives Cassini mission
scientists
confidence in their results, Brown said.

"So you've got subsurface liquid water, simple organics and water
vapor
welling up from below. Over time -- and Enceladus has been around 4.5
billion years, just like Earth and the rest of the solar system --
heating a
cocktail of simple organics, water and nitrogen could form some of the
most
basic building blocks of life," Brown said. "Whether that's happened at
Enceladus is not clear, but Enceladus, much like Jupiter's moon Europa
and
the planet Mars, now has to be a place where we eventually search for
life."

The $3.2 billion Cassini-Huygens mission is a joint venture between
the
NASA, the European Space Agency and the Italian Space Agency. The Jet
Propulsion Laboratory, a division of the California Institute of
Technology
in Pasadena, manages the mission for NASA's Science Mission
Directorate,
Washington.

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Contact Information
Robert H. Brown, UA Lunar and Planetary Lab
520-907-2688 (cell) 520-626-9045 (office)


Related Web sites

NASA Cassini
http://www.nasa.gov/mission_pages/ca...ain/index.html

JPL Cassini
http://saturn.jpl.nasa.gov/home/index.cfm

VIMS
http://wwwvims.lpl.arizona.edu/