Posted on behalf of Richard A. Lovett

A thousand kilometers above the surface, Saturn’s giant moon Titan may be producing the building blocks of life, a team of U.S. and European scientists have discovered.

Working in a French laboratory, the scientists put together a Titan-style atmosphere combining nitrogen, methane, and a trace of carbon monoxide, which is present on Titan at 50 ppm levels. They then ionized the gases with microwaves to simulate the effect of solar ultraviolet light.

What they found was a mix of surprisingly complex organic chemicals, says Sarah Horst, a graduate student in planetary sciences at the University of Arizona, Tucson, who reported at a meeting of the American Astronomical Society’s Division of Planetary Sciences, 7 October in Pasadena, California.

So far, chemical formulas have been assigned to more than 5,000 of these chemicals, although only a few have been fully identified. But they include the five bases [corrected] used in DNA and RNA, and two are amino acids. Eleven more amino acids may also be in the mix, she said, although these chemicals have not yet been fully analyzed.

The study was prompted by samples of Titan’s upper atmosphere taken on close approaches by the Cassini spacecraft, Horst said – samples that included compounds with very high molecular weights, equivalent to nearly 1,000 carbon atoms. “This was completely unexpected,” she said. “We had no idea that the chemistry could proceed this far in the upper atmosphere of any planet.”

Also exciting was the fact that the experiment conducted by Horst’s group produced a haze of aerosol particles similar to particles that appear to exist in Titan’s upper atmosphere.

Does this mean there is life on Titan? Probably not, Horst says. Titan’s surface conditions are so different from Earth’s – cold and waterless – that life there probably couldn’t use the same chemicals we use. But it may say a lot about the origin of life on Earth and potentially elsewhere. Traditional hypotheses suggest that the building blocks of life here were created by lightning strikes in Earth’s primordial atmosphere, or were delivered by objects from outer space. Now there’s a third possibility, Horst says: the formation of these chemicals high in the infant planet’s atmosphere.

In other words, Horst’s team suggests, Earth’s primordial soup might have begun as a primordial haze.