[meteorite-list] In Coming Apart, Comet LINEAR Exposes Its Deepest Secrets

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:46:24 2004
Message-ID: <200105171906.MAA08022_at_zagami.jpl.nasa.gov>

Donald Savage/Dolores Beasley
Headquarters, Washington, DC May 17, 2001
(Phone: 202/358-1547)

Bill Steigerwald
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-5017)

Donna Weaver
Space Telescope Science Institute, Baltimore, MD
(Phone: 410/338-4493)

RELEASE: 01-94

IN COMING APART, COMET LINEAR EXPOSES ITS DEEPEST SECRETS

     Breaking up is hard to do, even for a comet. When such a
cosmic break-up occurred last year, scientists watched it
happen and came away with new insights and new questions.

Teams of scientists, using telescopes ranging from the W. M.
Keck Observatory and NASA's Infrared Telescope Facility, both
on Mauna Kea, HI, to the European Southern Observatory's
(ESO) Very Large Telescope in Chile, the NASA/European Space
Agency (ESA) SOHO satellite and NASA's Hubble Space
Telescope, have been studying Comet LINEAR (C/1999 S4). This
spectacular comet last year broke apart as it circled the
Sun. The researchers' results will appear tomorrow in a
special issue of the journal Science dedicated to studies of
the comet.

One team, led by Dr. Michael Mumma of NASA's Goddard Space
Flight Center, Greenbelt, MD, used the NASA/ESA Solar and
Heliospheric Observatory (SOHO) to examine LINEAR. These
scientists found the first evidence ever seen that supports
the theory that comet impacts may have played a significant
role in the formation of life on Earth by providing most of
the water in Earth's oceans, as well as organic material.
LINEAR is the first comet observed to have a composition that
would allow it to carry the same type of water found in
oceans on Earth.

"The idea that comets seeded life on Earth with water and
essential molecular building blocks is dramatic, and for the
first time, we have seen a comet with the right composition
to do the job," Mumma said.

A separate announcement, also to appear in Science, is a
unique observation that reveals just how much water comets of
this type can carry. LINEAR, with a nucleus estimated at
2,500 to 3,300 feet (about 750 to 1,000 meters) in diameter,
carried about 3.6 million tons (3.3 billion kilograms) of
water within its bulk, according to astronomers who used the
Solar Wind Anisotropies instrument on the SOHO spacecraft to
observe water vapor released as the comet fragmented.

Pictures and more information about these findings can be
found on the Internet at:

http://www.gsfc.nasa.gov/GSFC/SpaceSci/origins/linearwater/linearwater.htm

A second team, led by Dr. Hal Weaver, an astronomer at the
Johns Hopkins University in Baltimore, MD, studied the broken
fragments of LINEAR with the Hubble Space Telescope, the Very
Large Telescope (VLT) and other ground-based telescopes. The
researchers found there is not as much material in the
fragments as there was in LINEAR before it broke apart. The
leftover material just wouldn't add up to a comet as large as
LINEAR.

Information about the Hubble and VLT observations are
available on the Web at:

     http://oposite.stsci.edu/pubinfo/pr/2001/14

There are no new Hubble pictures, but previously released
Hubble Space Telescope images of Comet LINEAR's breakup are
available at:

     http://oposite.stsci.edu/pubinfo/pr/2000/26.html
and
     http://oposite.stsci.edu/pubinfo/pr/2000/27.html

Comet LINEAR completely disintegrated late last July as it
made its closest approach to the Sun, at a cozy 71 million
miles. Hubble tracked the comet, finding at least 16
fragments that resembled "mini-comets" with tails. Now LINEAR
is little more than a trail of debris orbiting the Sun. The
comet is believed to have wandered into the inner solar
system from its home in the Oort Cloud, a reservoir of space
debris on the outskirts of the solar system. It took comet
LINEAR about 60,000 years to travel once around the Sun.

Comet LINEAR was named for the program that first spotted it,
the Lincoln Near Earth Asteroid Research (LINEAR),
headquartered at the Massachusetts Institute of Technology's
Lincoln Labs, Lexington, MA. LINEAR is a highly successful
NASA-funded program to search for near-Earth objects, which
has also become a premier discoverer of comets.

                          - end -
Received on Thu 17 May 2001 03:06:35 PM PDT