The comet dust brought to Earth by the Stardust spacecraft may be contaminated. Photo: NASA
Reading The cometary dust brought down to earth by the Stardust spacecraft last year is contaminated with residues from the fuel of the rocket engine that brought the spacecraft into space. This is suspected by Spanish scientists and thus dampen the enthusiasm of astronomers for finds of the mineral Osbornit in the sample. Since this compound is formed only at very high temperatures, researchers had assumed that they had formed near the sun and thrown from there into outer regions of the solar system. However, the Osbornit could also have originated from the nitrogen contained in the fuel and the titanium used in the probe, the researchers said. The NASA Space Stardust spacecraft launched into space in 1999 to collect dust samples in space and while flying past the comet "Wild 2". To do this, it was equipped with a special dust collector, which uses a highly porous material to collect tiny particles. In January 2006, a hermetically sealed capsule returned the collector to Earth, where the collected dust particles have since been examined.

To date, scientists have been particularly surprised by the discovery of the mineral osbornite, a compound of the metal titanium with nitrogen. Osbornite is produced only at temperatures of over 1, 700 degrees Celsius, as they prevail in the solar system only near the sun. Scientists concluded that the youth of our solar system was very turbulent and therefore there had to be a lively exchange of material between the outer and inner solar systems.

However, the researchers around Jesús Martínez-Frías urge caution regarding this interpretation of the results of the Stardust mission. They point to the rocket fuel hydrazine, which can also form osbornite with titanium. The Titan could come either from the comet or even from the spacecraft itself, whose tank is made of high strength and light metal. The scientists therefore recommend that the true origin of the osbornite in the Stardust samples be determined in further analyzes. This could be made possible by investigations of the crystal structure or by the variants of titanium atoms contained in the sample.

Jesús Martínez-Frías (Center for Astrobiology, Madrid) et al .: Energy & Fuels, online pre-publication, DOI: 10.1021 / ef070014r ddp / Ulrich Dewald ad


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