[meteorite-list] Clay-Like Minerals Found on Icy Crust of Europa

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 11 Dec 2013 11:15:49 -0800 (PST)
Message-ID: <201312111915.rBBJFnxF004421_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.php?release=2013-362

Clay-Like Minerals Found on Icy Crust of Europa
Jet Propulsion Laboratory
December 11, 2013

A new analysis of data from NASA's Galileo mission has revealed clay-type
minerals at the surface of Jupiter's icy moon Europa that appear to have
been delivered by a spectacular collision with an asteroid or comet. This
is the first time such minerals have been detected on Europa's surface.
The types of space rocks that deliver such minerals typically also often
carry organic materials.

"Organic materials, which are important building blocks for life, are
often found in comets and primitive asteroids," said Jim Shirley, a research
scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. Shirley
is giving a talk on this topic at the American Geophysical Union meeting
in San Francisco on Friday, Dec. 13. "Finding the rocky residues of this
comet crash on Europa's surface may open up a new chapter in the story
of the search for life on Europa," he said.

Many scientists believe Europa is the best location in our solar system
to find existing life. It has a subsurface ocean in contact with rock,
an icy surface that mixes with the ocean below, salts on the surface that
create an energy gradient, and a source of heat (the flexing that occurs
as it gets stretched and squeezed by Jupiter's gravity). Those conditions
were likely in place shortly after Europa first coalesced in our solar
system.

Scientists have also long thought there must be organic materials at Europa,
too, though they have yet to detect them directly. One theory is that
organic material could have arrived by comet or asteroid impacts, and
this new finding supports that idea.

Shirley and colleagues, funded by a NASA Outer Planets Research grant,
were able to see the clay-type minerals called phyllosilicates in near-infrared
images from Galileo taken in 1998. Those images are low resolution by
today's standards, and Shirley's group is applying a new technique for
pulling a stronger signal for these materials out of the noisy picture.
The phyllosilicates appear in a broken ring about 25 miles (40 kilometers)
wide, which is about 75 miles (120 kilometers) away from the center of
a 20-mile-diameter (30 kilometers) central crater site.

The leading explanation for this pattern is the splash back of material
ejected when a comet or asteroid hits the surface at an angle of 45 degrees
or more from the vertical direction. A shallow angle would allow some
of the space rock's original material to fall back to the surface. A more
head-on collision would likely have vaporized it or driven that space
rock's materials below the surface. It is hard to see how phyllosilicates
from Europa's interior could make it to the surface, due to Europa's icy
crust, which scientists think may be up to 60 miles (100 kilometers) thick
in some areas.

Therefore, the best explanation is that the materials came from an asteroid
or comet. If the body was an asteroid, it was likely about 3,600 feet
(1,100 meters) in diameter. If the body was a comet, it was likely about
5,600 feet (1,700 meters) in diameter. It would have been nearly the same
size as the comet ISON before it passed around the sun a few weeks ago.

"Understanding Europa's composition is key to deciphering its history
and its potential habitability," said Bob Pappalardo of JPL, the pre-project
scientist for a proposed mission to Europa. "It will take a future spacecraft
mission to Europa to pin down the specifics of its chemistry and the implications
for this moon hosting life."

For more information about Europa, visit:

http://solarsystem.nasa.gov/europa/home.cfm .

JPL is a division of the California Institute of Technology in Pasadena.

Jia-Rui C. Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook at jpl.nasa.gov

2013-362
Received on Wed 11 Dec 2013 02:15:49 PM PST