Re: Key "Stardust" spacecraft discovery may have been contamination (Forwarded)


"Andrew Yee" <ayee@xxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:Pine.LNX.4.30.0704151002190.6959-100000@xxxxxxxxxxxxxxxxxxxxxxxxx
American Chemical Society
Washington, D.C.

EMBARGOED FOR 9 A.M., EASTERN TIME, April 9, 2007

Key "Stardust" spacecraft discovery may have been contamination

One of the biggest scientific surprises from last year's "Stardust" space
mission may have resulted from contamination from the spacecraft's rocket
boosters, scientists in Spain are cautioning in a report scheduled for
publication in the May 16 issue of ACS' Energy & Fuels, a bi-monthly
journal.

Stardust was the first U.S. mission to capture samples of a comet (Comet
Wild 2) and return that material, believed to hold clues to the origin of
the solar system, to Earth for scientific analysis. In the report, Jesus
Martinez-Frias and colleagues point out that scientists were surprised to
find that Stardust had collected tiny grains of the mineral osbornite,
which chemically is titanium nitride. Osbornite forms only at ultra-hot
temperatures of about 3,140 Fahrenheit. Scientists thus concluded that the
osbornite could have formed near the sun, and ejected to the outer reaches
of the solar system -- an indication that the infant solar system was a
much more violent and tumultuous place then previous believed.

Martinez-Frias and colleagues stress the plausibility and significance of
such hypothesis, but suggest another possible explanation for osbornite
presence, which they say has not yet been considered. They point out that
Stardust's rocket thrusters used a propellant of ultra-pure hydrazine,
which chemists long have used for the so-called nitration reactions used
to make titanium nitride on Earth.

http://space.newscientist.com/article/mg19425993.400-nasa-says-space-find-isnt-just-rocket-fuel.html
"No chance," says Stardust researcher Michael Zolensky at NASA's Johnson
Space Center in Houston, Texas. "The titanium nitride grains are sitting
inside of other minerals, which are sitting inside other minerals" in a
single particle that penetrated very deep into the fluffy aerogel that
collected the comet dust, Zolensky says.

Also, there is no trace of osbornite elsewhere on the dust collector, nor on
a separate "witness" aerogel that was shielded from comet dust to show up
any contamination from the spacecraft.


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