What's Inside a Comet? Brown Geologist Helps NASA Find Out

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Distributed June 23, 2005
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NASA's 'Deep Impact'

What's Inside a Comet? Brown Geologist Helps NASA Find Out

On July 4, scientists at NASA's Jet Propulsion Laboratory will witness
fantastic fireworks when comet Tempel 1 slams into a space probe at
23,000 miles per hour. Brown University professor and NASA mission
member Peter Schultz will help analyze collision data to determine
what's inside this primordial ball of ice.

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PROVIDENCE, R.I. - When comet Tempel 1 collides with a NASA space probe
in the early morning hours of July 4, 2005, scientists at the Jet
Propulsion Laboratory expect some holiday sizzle - a brilliant flash
and
a dramatic spray of debris.

This cosmic collision will create a crater exposing Tempel 1's
interior.
Like all comets, Tempel 1 consists of the frozen remains of material
that formed the solar system. But what, precisely, is this stuff? How
is
it put together? Peter Schultz, crater expert, will help find out.

Schultz is a professor of geological sciences at Brown University and a
leading expert in impact cratering, the science of what happens when a
massive, fast-moving cosmic train slams into something. His work helps
explain when and how comets, asteroids and other space travelers shaped
the face of planets such as Earth and Mars, as well as the Moon and
other satellites.

Pete Schultz
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Peter Schultz
Professor of Geological Sciences

Schultz, a leading expert in impact cratering, is a partner in the Deep
Impact mission.

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Schultz's expertise landed him a spot in the inner scientific circle
for
"Deep Impact," the joint space mission coordinated by the Jet
Propulsion
Lab and the University of Maryland. Schultz is one of 13
co-investigators overseeing the mission, which will provide a
first-ever
look inside a comet when scientists release an impactor into Tempel 1's
path for a planned collision.

"This is heady stuff," Schultz said. "The ice inside comets has been in
the deep freeze since the creation of the solar system. Now we are
finally going to see what this stuff looks like and what it is made of.
This is important information. Comets may have been the messengers that
carried the ingredients of life to Earth."

To prepare for the mission, Schultz ran dozens of experiments at NASA's
Ames Vertical Gun Range in California. Using a machine three stories
tall, Schultz fired marble-size beads into surfaces of dust, ice and
snow. The beads - which travel more than 10 times faster than a
speeding
bullet - made craters of all shapes and sizes. Working with different
combinations of ice, snow and dust in various thicknesses, Schultz
recorded the trajectory of flying debris as well as crater size and
speed of formation.

These observations will be important for Deep Impact. Cameras and an
infrared spectrometer aboard an orbiter will record the Tempel 1
collision, relaying images and data during creation of the crater which
can be used to determine the comet's composition.

"We know comets are like dirty snowballs," Schultz said. "But is the
crust thick or thin? Is the interior light or dense? By running these
scenarios, we can make better predictions when the real impact happens.

"Comets were made 4.5 billion years ago, yet remain such mysteries," he
said. "Now we're going to get our closest look at one. That's why this
project is cool."

######

Peter Schultz should refrain from making absolute statments like:
"We know comets are like dirty snowballs,"
"Comets were made 4.5 billion years ago."
The crater made by "Deep Impact" will be very shallow because the short
period comets are solid rock bodies, as could be seen from images of
comet Borrelly. Those photos caused scientists to retreat to a
position that comets have been covered with dark dust over billions of
years, but are still ice inside. They hope to penetrate the dark crust
and see lots of ice ejected from the interior, but it ain't going to
happen.
Solid rock bodies cannot form in the weightlessness of space because
there is no gravitational force to compact them to rock-like densities,
therefore they are not primordial. Normal density rock can only form
on a planet-sized body.
Its true that the 'comets' or rather the rock comprising them were made
4.5 billion years ago, when Mars formed. But I maintain that the short
period comets were all ejected from Mars within the last 6,000 years,
along with the Near Earth Asteroids (NEAs). The 'comets' are just
bodies from near the surface, i.e. containing aquifers, and it is the
small amount of water from these that produce the cometary halo, while
the asteroids, which were ejected hot from greater depths within the
planet, contain little or no water.
It will be interesting to read the new explanations from the planetary
science community when 'Deep Impact' produces a big 'thud.'