Brown geologists Takahiro Hiroi and Carle Pieters and
a colleague from NASA have identified the location from which an unusually
well-preserved meteorite fell — the mid-to-far end of the asteroid belt
between Mars and Jupiter. Their results confirm that the Tagish Lake
meteorite is made of probably the oldest materials in the solar system.
To the amazement of observers, the fireball fell in northern British
Columbia in January 2000. The event was photographed, recorded by satellites,
and resulted in hundreds of fragments being collected from a frozen lake.
The meteorite was probably the size of van, but broke into fragments that
were preserved in ice from the lake.
Hiroi, Pieters and Michael Zolensky of NASA’s Johnson Space Center in Houston
are the first to identify the carbon-rich meteorite as having broken off from
a D-type asteroid, the kind that most scientists acknowledge contains the
oldest raw materials among asteroids. Their results were published by the
journal Science, within the "Science Express" Web site, on Aug. 23, 2001
[http://www.sciencemag.org/cgi/content/abstract/1063734v1].
Their method, reflectance spectroscopy, provides an optical fingerprint
showing a meteorite’s composition. Data is obtained by measuring the amount
of reflected light as wavelength is changed from visible to near-infrared.
Their study provides clues in determining the formation of the solar system
4.6 billion years ago. The research was funded by grants from NASA.
A second article on the "Science Express" Web site details the organic
content of the Tagish Lake meteorite. Brown assistant professor Yongsong
Huang is a co-author with lead investigator Sandra Pizzarello of the Arizona
State University Chemistry Department.
At Brown, the researchers used state-of-the art technology to measure the
isotopic composition of individual compounds. The findings provide insight
to an outcome of early solar chemical evolution that differs from any seen
in meteorites so far.
