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鈥檚 own fuel.
Stardust鈥檚 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, Jes煤s Mart铆nez-Fr铆as 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?
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鈥淣o chance,鈥� says Stardust researcher Michael Zolensky at NASA鈥檚 Johnson Space Center in Houston, Texas. 鈥淭he titanium nitride grains are sitting inside of other minerals, which are sitting inside other minerals鈥� 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 鈥渨itness鈥� aerogel that was shielded from comet dust to show up any contamination from the spacecraft.
