Floating Pile of Rubble a Pristine Record of Solar System's History (Itokawa)

http://www.umich.edu/news/?Releases/2006/Jun06/r060106c

Floating pile of rubble a pristine record of solar system's history
University of Michigan News Release
June 1, 2006

ANN ARBOR, Mich. - A small, near-Earth asteroid named Itokawa is just a
pile of floating rubble, probably created from the breakup of an
ancient
planet, according to a University of Michigan researcher was part of
the
Japanese space mission Hayabusa.

The finding suggests that asteroids created from rubble would be
pristine records of early planet formation.

A global view of the Asteroid Itokawa, with white box showing region
where the Hayabusa spacecraft landed to collect samples. Photo courtesy
Japan Aerospace Exploration Agency, Institute of Space and Aeronautical
Science

Daniel Scheeres, U-M associate professor of aerospace engineering, was
part of the team that determined the asteroid's mass, surface
environment, and gravitational pull and helped interpret the images
that
were taken of the asteroid from the spacecraft. Some of the findings
will be discussed in a special issue of the journal Science on June 2.
The mission is led by the Japan Aerospace Exploration Agency.

The Hayabusa space probe arrived at asteroid Itokawa last fall and
orbited for three months. During that time it descended twice to the
surface of the asteroid, which is named for the father of Japanese
rocketry, to collect samples. In 2010 the probe will return to Earth
and
eject a sample canister that will reenter the atmosphere and land in
central Australia. Researchers hope this will be the first asteroid
sample brought back to Earth.

Scheeres said that the confirmation of Itokawa's makeup as rubble
rather
than a single rock has large implications for theories of how asteroids
evolved, and will lead to a better understanding of the early solar
system. Asteroids are thought to be the remnants of material that
formed
the inner planets, which include Earth, and could bear the record of
events in the early stages of planet formation. It is a significant
finding that Itokawa is a pile of rocks ranging in size from tiny sand
grains all the way up to boulders 50 meters wide, because it verifies a
number of theories about the makeup and history of asteroids.

The existence of very large boulders and pillars suggests that an
earlier "parent" asteroid was shattered by a collision and then
re-formed into a rubble pile, the researchers conclude in the paper.

It's likely that most asteroids have a similar past, Scheeres said.
"Analysis of the asteroid samples will give us a snapshot of the early
solar system, and provide valuable clues on how the planets were
formed."

Also, knowing if an asteroid is a single, big rock or a pile of rubble
will have a major influence on how to nudge it off course, Scheeres
said, should its orbit be aimed at Earth. An asteroid collision with
Earth, while unlikely, could have disastrous consequences. It's widely
thought that an asteroid collision caused the mass extinction of
dinosaurs 65 million years ago, so some have discussed ways to demolish
or steer an approaching asteroid, should we see one coming.

Another striking finding, Scheeres said, is that regions of Itokawa's
surface are smooth, "almost like a sea of desert sand" and others are
very rugged. This indicates that the surfaces of asteroids are, in some
sense, active, with material being moved from one region to another.
Gravity holds the mass of rubble together.

"These are the first such detailed observations of an asteroid from
this
close," Scheeres said.

The University of Michigan College of Engineering is ranked among the
top engineering schools in the country. Michigan Engineering boasts one
of the largest engineering research budgets of any public university,
at
more than $130 million. Michigan Engineering has 11 departments and two
NSF Engineering Research Centers. Within those departments and centers,
there is a special emphasis on research in three emerging areas:
nanotechnology and integrated microsystems; cellular and molecular
biotechnology; and information technology. Michigan Engineering is
seeking to raise $110 million for capital building projects and program
support in these areas to further research discovery. Michigan
Engineering's goal is to advance academic scholarship and market
cutting-edge research to improve public health and well-being. For more
information, see the Michigan Engineering home page:
http://www.engin.umich.edu

Hayabusa mission http://www.isas.jaxa.jp/e/index.shtml

Daniel Scheeres
http://aerospace.engin.umich.edu/people/faculty/scheeres/

U-M Aerospace Engineering http://aerospace.engin.umich.edu/



Contact: Laura Bailey
Phone: (734) 647-7087 or (734) 647-1851