[meteorite-list] Research Finds Asteroid Itokawa Is An Ancient Rock

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 14 Mar 2011 12:01:24 -0700 (PDT)
Message-ID: <201103141901.p2EJ1OwL011803_at_zagami.jpl.nasa.gov>

http://www.spaceflightnow.com/news/n1103/13hayabusa/

Research finds asteroid Itokawa is an ancient rock
BY STEPHEN CLARK
SPACEFLIGHT NOW
March 13, 2011

A preliminary analysis of asteroid samples returned last year by Japan's
Hayabusa probe show evidence the dust grains have a similar composition
to stony meteorites that commonly fall to Earth.
 
Hayabusa returned to Earth last June with a fiery plunge into the
Australia outback. The seven-year robotic mission surveyed asteroid
Itokawa, a potato-shaped rock about the size of a city block.

The initial research also shows the samples inspected so far contain no
organic molecules. Scientists also say the analysis confirms the rocks
at Itokawa were formed 4.6 billion years ago at the dawn of the solar
system.

Researchers believe Itokawa itself was formed when several existing
smaller bodies accreted into a larger asteroid. Scientists describe such
asteroids as "rubble pile" objects.

The early results were presented last week at the Lunar and Planetary
Science conference in Houston.

Hayabusa was intended to approach the surface of Itokawa, fire a pellet
into the regolith and collect bits of rock in a funnel leading to the
spacecraft's sample chamber.

But in two sampling attempts in late 2005, the projectile didn't fire
and scientists feared the mission was a failure.

A crippling fuel leak, ion engine failures, reaction wheel glitches,
battery issues and a two-month communications loss challenged mission
controllers during Hayabusa's flight. Officials had to delay the
mission's return to Earth from 2007 until 2010 to deal with the issues.
 
An analysis of telemetry later showed Hayabusa landed on Itokawa for up
to a half-hour during one of the sampling attempts, giving scientists
renewed hope the probe may have gathered some small dust grains in its
time on the asteroid.

Researchers confirmed their hopes last year when they opened Hayabusa's
sample return capsule in a clean room in Sagamihara, Japan.

They found at least 1,500 individual grains, most of which were
confirmed to be from asteroid Itokawa.

Most of the particles were less than 10 microns in diameter, but a few
samples were 100 microns or larger, comparable to the width of a strand
of human hair, according to papers presented by Japanese scientists.

Teams started their preliminary analyses of the samples in January and
expect to finish their first round of examinations by June at the
curation facility in Sagamihara. The material will then be distributed
to other research sites for further study.

NASA will get about 10 percent of the material in return for U.S.
contributions to the mission's operations and sample recovery efforts.

Hayabusa was the first mission to retrieve samples from the surface of
an asteroid and bring them back to Earth.
Received on Mon 14 Mar 2011 03:01:24 PM PDT