[meteorite-list] Ice-teroid

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Thu, 08 Oct 2009 19:19:23 -0500
Message-ID: <ma0tc55dki143fe65fpuot9ve9r7pffc3q_at_4ax.com>

http://www.usnews.com/science/articles/2009/10/08/ice-confirmed-on-an-asteroid.html

Ice Confirmed On an Asteroid
Frozen water leaves its signature over the entire surface of the asteroid 24
Themis

By Ron Cowen, Science News

FAJARDO, Puerto Rico?Space rocks may be dead as doornails but some contain
ingredients that could have given life on Earth a foothold.

Planetary scientists reported October 7 that they have, for the first time,
confirmed that an asteroid contains frozen water on its surface. Evidence of
water-ice, along with organic compounds, on the surface of the asteroid 24
Themis supports the theory that asteroids brought both water and organic
compounds to the early Earth, helping lay the foundation for life on the planet.
Click here to find out more!

Humberto Campins of the University of Central Florida in Orlando and his
colleagues recorded spectra of the asteroid 24 Themis over a seven-hour period,
corresponding to 84 percent of the rotational period of the spinning rock. The
spectra, taken with NASA's Infrared Telescope Facility on Hawaii's Mauna Kea,
revealed the consistent presence of frozen water as different parts of the
asteroid's surface came into view, Campins reported at the annual meeting of the
American Astronomical Society's Division for Planetary Sciences.

The finding corroborates earlier observations (SN Online: 7/18/08

The analyses of the sunlight reflected off the asteroid also show that organic
compounds are widespread on the surface, he added, including polycyclic aromatic
hydrocarbons, CH2 and CH3.

At the asteroid's average distance from the sun ? 3.2 times Earth's distance to
the sun ? frozen water on the surface would readily vaporize, noted Campins.
That means the ice must be continually replenished, possibly by a reservoir of
frozen water within the rock, he speculates.

One possibility is that ice lies buried several meters below the surface of the
roughly 160-kilometer-wide asteroid and makes its way to the top when the
asteroid is pummeled by space debris. Norbert Sch?rghofer of the University of
Hawaii at Manoa proposed last year that ice can persist for billions of years
just below the surface of a dusty space rock if the asteroid's surface
temperature is less than about 145 kelvins. The temperature of 24 Themis lies in
that range.

The presence of frozen water on 24 Themis also suggests that some asteroids
resemble comets, becoming active suddenly and venting material into space when
pockets of ice vaporize, Campins noted.
Received on Thu 08 Oct 2009 08:19:23 PM PDT