SCIENCE LAB SCALING : POISON GAS LIFE

Signs Of Fertility : On Enceladus - a small ocean moon of Saturn, a poison gas points to life.

Scientists have detected hydrogen cyanide  among the molecules emanating from Enceladus, a small icy moon of Saturn. The colorless gas is deadly to many Earth creatures, but it could have played a key role in setting the stage for the advent of life.

'' It's sort of the Swiss Army Knife of prebiotic chemistry,'' said Jonah Peter, a biophysics graduate student at Harvard.

Mr. Peter was excited when he found hydrogen cyanide on Enceladus, which has a subsurface ocean that makes it among the most promising places to look for other life in the solar system.

In a paper published in the Journal Nature Astronomy, Mr. Peter, with Tom Nordheim and Kevin Hand of NASA's Jet Propulsion Laboratory in California, reported their findings.

Mr. Peter and his collaborators delved into data from NASA's Cassini spacecraft. They started with a list of 50 compounds that they thought might be present at Enceladus.

Then they constructed models of 10 to 15 of those compounds, and they tested which models best fit what Cassini observed.

Experiments have shown that hydrogen cyanide could be a precursor to the molecules that had to be present for life to arise.

'' It can be combined in different ways to produce amino acids, which are precursors for proteins as well as nuclear bases and sugars which are needed to make RNA and DNA,'' Mr. Peter said.

Earlier this year, another team of scientists reported that icy particles in the Enceladus plumes contained phosphate, which are also thought to be essential for life.

'' Indeed, the prospects for development of life are getting better and better on Enceladus,'' said Frank Postberg, a professor of Planetary Science at the Free University of Berlin who led the phosphates study.

These discoveries do ''not reveal'', the source of complex organic matter in the ocean,''  said Alfonso Davila, a researcher at NASA's Ames Research in California.

'' But it will bring us an inch closer to the answer.'' [ Kenneth Chang ]