[meteorite-list] NASA's Deep Impact Tells a Tale of the Comet

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Jul 8 19:28:11 2005
Message-ID: <200507082327.j68NROO02611_at_zagami.jpl.nasa.gov>

Dolores Beasley
Headquarters, Washington July 8, 2005
(Phone: 202/358-1753)

DC Agle
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone: 818/393-9011)

Lee Tune
University of Maryland, College Park, Md.
(Phone: 301/405-4679)

RELEASE: 05-177

NASA'S DEEP IMPACT TELLS A TALE OF THE COMET

Data from Deep Impact's instruments indicate an immense
cloud of fine powdery material was released when the probe
slammed into the nucleus of comet Tempel 1 at 6.3 miles per
second.

The cloud indicated the comet is covered in the powdery stuff.
The Deep Impact science team continues to wade through
gigabytes of data collected during the July 4 encounter with
the 3-mile-wide by 7-mile-long comet.

"The major surprise was the opacity of the plume the impactor
created and the light it gave off," said Deep Impact Principal
Investigator Dr. Michael A'Hearn of the University of Maryland,
College Park. "That suggests the dust excavated from the
comet's surface was extremely fine, more like talcum powder
than beach sand. And the surface is definitely not what most
people think of when they think of comets -- an ice cube."

How can a comet hurtling through our solar system be made of a
substance with less strength than snow or even talcum powder?
"You have to think of it in the context of its environment,"
said Pete Schultz, Deep Impact scientist from Brown University,
Providence, R.I. "This city-sized object is floating around in
a vacuum. The only time it gets bothered is when the sun cooks
it a little or someone slams an 820-pound wakeup call at it at
23,000 miles per hour."

The data review process is not overlooking a single frame of
approximately 4,500 images from the spacecraft's three imaging
cameras taken during the encounter. "We are looking at
everything from the last moments of the impactor to the final
look-back images taken hours later, and everything in between,"
added A'Hearn. "Watching the last moments of the impactor's
life is remarkable. We can pick up such fine surface detail
that objects that are only four meters in diameter can be made
out. That is nearly a factor of 10 better than any previous
comet mission."

The final moments of the impactor's life are important,
because they set the stage for all subsequent scientific
findings. Knowing the location and angle the impactor
slammed into the comet's surface is the best place to start.
Engineers have established the impactor took two not unexpected
coma particle hits prior to impact. The impacts slewed the
spacecraft's camera for a few moments before the attitude
control system could get it back on track. The penetrator hit
at an approximately 25 degree oblique angle relative to the
comet's surface. That's when the fireworks began.

The fireball of vaporized impactor and comet material shot
skyward. It expanded rapidly above the impact site at
approximately 3.1 miles per second, and the crater was just
beginning to form. Scientists are still analyzing the data
to determine the exact size of the crater. Scientists say
the crater was at the large end of original expectations,
which was from 50 to 250 meters.

Expectations for Deep Impact's flyby spacecraft were exceeded
during its close brush with the comet. The craft is more
than 2.2 million miles from Tempel 1 and opening the distance
at approximately 23,000 mph. The flyby spacecraft is
undergoing a thorough checkout, and all systems appear to
be in excellent operating condition.

The Deep Impact mission was implemented to provide a glimpse
beneath the surface of a comet, where material from the solar
system's formation remains relatively unchanged. Mission
scientists hoped the project would answer basic questions
about the formation of the solar system by providing an
in-depth picture of the nature and composition of comets.

The University of Maryland is responsible for overall Deep
Impact mission science, and project management is handled by
JPL. The spacecraft was built for NASA by Ball Aerospace &
Technologies Corporation, Boulder, Colo. For information
about Deep Impact on the Internet, visit:

http://www.nasa.gov/deepimpact

For information about NASA and agency programs on the Web,
visit:

http://www.nasa.gov/home/index.html

-end-
Received on Fri 08 Jul 2005 07:27:24 PM PDT