[meteorite-list] NASA Says Stardust Samples Not Contaminated by Rocket Fuel

[Ron Baalke]

http://space.newscientist.com/article/mg19425993.400-nasa-says-space-find-isnt-just-rocket-fuel.html

NASA says space find isn't just rocket fuel
New Scientist
13 April 2007

Stardust looped thrice around the sun, flew past comet Wild 2 and 
brought back the first ever sample of comet dust. So the last thing 
NASA wants to hear is that the sample may be contaminated by the 
spacecraft's own fuel.

Stardust's capsule of comet dust parachuted down to the Utah desert 
in January 2006. NASA scientists found an unusual titanium nitride 
mineral inside a single particle of dust collected by the probe. 
This mineral, called osbornite, forms only at high temperatures, 
and researchers put it down to material that came from the inner 
solar system.

However, Jesu's Martinez-Frias of the NASA Astrobiology Institute 
in Madrid, Spain, and colleagues point out that Stardust was 
propelled by hydrazine, which reacts with titanium to produce 
titanium nitride particles (Energy Fuels, DOI: 10.1021/ef070014r). 
So could the hydrazine have reacted with titanium compounds from 
the spacecraft or the comet to form osbornite?

"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.

>From issue 2599 of New Scientist magazine, 13 April 2007, page 6