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DC Agle (818) 393-9011
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Dolores Beasley (202) 358-1753
NASA Headquarters, Washington

Lee Tune (301) 405-4679
University of Maryland, College Park

News Release: 2005-113 July 8, 2005

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 about
10 kilometers per
second (6.3 miles per second or 23,000 miles per hour). 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 comet measuring
5-kilometers-wide by 11-kilometers-
long (about 3-miles-wide by 7-miles-long).

"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 Dr. 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 were 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 5 kilometers per second (3.1 miles per second).
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 (165 to 820 feet) wide.

Expectations for Deep Impact's flyby spacecraft were exceeded during its
close brush with the comet.
The craft is more than 3.5 million kilometers (2.2 million miles) from
Tempel 1 and opening the
distance at approximately 37,000 kilometers per hour (23,000 miles per
hour). 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. JPL is a division of the
California Institute of Technology,
Pasadena, Calif.
For information about Deep Impact on the Internet, visit:

www.nasa.gov/deepimpact