No-stick science. The Curiosity's rock drill will contaminate samples with Teflon, posing a problem for researchers.

NASA Rover Will Contaminate Its Samples of Mars

Dick writes about Earth and planetary science for Science magazine.

The Curiosity rover will definitely find evidence of an advanced civilization if it lands safely on Mars. That's because any rock samples the rover drills will be contaminated with bits of Teflon from the rover's machinery, NASA announced during a press teleconference today.

That problematic bit of information was buried among news that the rover is otherwise in great shape for its arrival at Mars on 6 August.

Curiosity's $2.5-billion mission includes searching for the carbon-containing molecular remains of any life that inhabited ancient Mars. The rover's Sample Analysis at Mars (SAM) instrumentation, for instance, will study samples drilled or scooped from the martian surface. The drill assembly repeatedly bangs a drill bit into the rock to extract a sample, a procedure thoroughly tested mechanically before the drill was accepted for flight on the rover. But, it later turned out, that action also rubs bits of Teflon—the familiar polymer of nonstick fry pans made of carbon and fluorine atoms—off of two seals in the drill assembly. The bits of Teflon can then mix with the sample, which will be vaporized for analysis. The problem for the scientists is that Teflon is two-thirds carbon—the same element they are looking for on Mars.

Lab testing of a backup version of the drill uncovered the contamination problem shortly before launch of the rover and its drill last November, according to Paul Mahaffy of NASA's Goddard Space Flight Center in Greenbelt, Maryland. But Curiosity team members are guardedly upbeat that they can overcome it, although laboratory analysis of the problem will not be complete until the rover arrives on Mars. Mahaffy says the Teflon appears at concentrations of, at most, parts per million, roughly the same level that organic matter appears in the rocks of Earth. But lab work is showing that those levels do not endanger the operation of the drill or the rest of the sampling and analysis system. And team members can likely minimize the amount of Teflon getting into the analytical system by altering operation of the drill.

Once in SAM, Teflon causes limited problems, says Mahaffy. When the heating that drives gaseous compounds into the analytical instrumentation reaches about 600°C on its way to 1000°C, most of the Teflon decomposes. It produces mostly small, easily identified compounds of carbon and fluorine, he says. And they contaminate only a small fraction of the range of compounds expected from biologically produced carbon compounds, at least the sort remaining from earthly life. But as project manager Peter Theisinger of NASA's Jet Propulsion Laboratory in Pasadena, California, remarked in the teleconference about the whole business of going to Mars, "There are still the unknown unknowns that could get us in the end."

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