Space Forum / Space Science / September 2005

http://www.umich.edu/news/?Releases/2005/Aug05/r081605c

Look out: Asteroid's near-miss may be home run for scientists
University of Michigan
August 16, 2005

ANN ARBOR, Mich. - A University of Michigan-led research team has
discovered that for the first time in history, scientists will be able
to observe how the Earth's gravity will disrupt a massive asteroid's
spin.

Scientists predict a near-miss when Asteroid 99942 Apophis passes Earth
in 2029. An asteroid flies this close to the planet only once every
1,300 years. The chance to study it will help scientists deal with the
object should it threaten collision with Earth.

Only about three Earth diameters will separate Apophis and Earth when
the 400-meter asteroid hurtles by Earth's gravity, which will twist the
object into a complex wobbling rotation. Such an occurrence has never
been witnessed but could yield important clues to the interior of the
sphere, according to a paper entitled, "Abrupt alteration of the spin
state of asteroid 99942 Apophis (2004 MN4) during its 2029 Earth
flyby,"
accepted for publication in the journal Icarus.

The team of scientists is led by U-M's Daniel Scheeres, associate
professor of aerospace engineering, and includes U-M's Peter
Washabaugh,
associate professor of aerospace engineering.

Apophis is one of more than 600 known potentially hazardous asteroids
and one of several that scientists hope to study more closely. In
Apophis' case, additional measurements are necessary because the 2029
flyby could be followed by frequent close approaches thereafter, or
even
a collision.

Scheeres said not only is it the closest asteroid flyby ever predicted
in advance, but it could provide a birds-eye view of the asteroid's
"belly."

"In some sense it's like a space science mission 'for free' in that
something scientifically interesting will happen, it will be observable
from Earth, and it can be predicted far in advance," Scheeres said.

If NASA places measuring equipment on the asteroid's surface,
scientists
could for the first time study an asteroid's interior, similar to how
geologists study earthquakes to gain understanding of the Earth's core,
Scheeres said. Because the torque caused by the Earth's gravitational
pull will cause surface and interior disruption to Apophis, scientists
have a unique opportunity to observe its otherwise inaccessible
mechanical properties, Scheeres said. Throwing the asteroid off balance
could also affect its orbit and how close it comes to Earth in future
years.

"Monitoring of this event telescopically and with devices placed on the
asteroid's surface could reveal the nature of its interior, and provide
us insight into how to deal with it should it ever threaten collision,"
Scheeres said.

The asteroid will be visible in the night sky of Europe, Africa and
Western Asia.

The asteroid was discovered late last year and initially scientists
gave
it a 1-in-300 chance of hitting the Earth on April 13, 2029. Subsequent
analysis of new and archived pre-discovery images showed that Apophis
won't collide with Earth that day, but that later in 2035, 2036, and
2037 there remains a 1-in-6,250 chance that the asteroid could hit
Earth, Scheeres said. Conversely, that's a 99.98 percent chance that
the
asteroid will miss Earth.

The asteroid is relatively small, about the length of three football
fields. If it hit it wouldn't create wide-scale damage to the Earth,
but
would cause major damage at the impact site, Scheeres said.

The team of scientists also includes Lance Benner and Steve Ostro of
NASA's Jet Propulsion Laboratory, Alessandro Rossi of ISTI-CNR, Italy,
and Francesco Marzari of the University of Padova, Italy.

The University of Michigan College of Engineering is ranked among the
top engineering schools in the country. It boasts one of the largest
engineering research budgets of any public university, at $135 million
for 2004. 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. Its 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 .

Contact: Laura Bailey <baileylm@umich.edu>
Phone: (734) 647-7087 or (734) 647-1848