This view of Titan was taken by the Cassini spacecraft on Jan. 2, 2009.
Credit: NASA/JPL/Space Science Institute
SAN FRANCISCO ? Complex molecules similar to the building blocks of life on Earth may be able to form on Saturn's moon Titan, a new study suggests.
Organic molecules falling out of Titan's atmosphere could react with liquid water on the surface of the moon to form biomolecules like amino acids, according to the study. This liquid water could be delivered by comet strikes or ice-volcano eruptions, and it may stay liquid long enough on the frigid moon for such reactions to take place.
"It's very possible that you could get biomolecules," said study author Catherine Neish of Johns Hopkins University's Applied Physics Laboratory. Neish presented her results here today (Dec. 14) at the 2010 fall meeting of the American Geophysical Union.
Organics in Titan's air
Lots of organic molecules swirl about in Titan's nitrogen-rich atmosphere. That atmosphere doesn't contain much oxygen, though, so the chances of forming biomolecules like amino acids in the air aren't great, Neish said.
But those organics fall to Titan's ground all the time.
"They just continually trickle down out of the air," Neish told SPACE.com.
On the ground, organics might have a chance of mixing with liquid water, which could supply the required oxygen. Water is not a common feature on Titan, which has liquid-hydrocarbon lakes. But it could be delivered by events such as comet strikes or ice-volcano eruptions, Neish said.
Titan's surface is a frosty minus 290 degrees Fahrenheit (minus 179 degrees Celsius), so any such water would eventually freeze. But previous work by other researchers suggests that water supplied by such dramatic events might last surprisingly long ? from 100 to 1,000 years ? because there'd be a lot of it.
Neish was interested in knowing whether complex biomolecules might be able to form in this timeframe. So in the lab, she mixed Titan-like organic molecules with liquid water at low temperatures ? 32 degrees F (0 degrees C) for pure water, and minus 4 F (minus 20 C) for an ammonia-water mix.
In both cases, oxygen-containing molecules were produced very quickly, on the order of several days. Further experiments found that the reactions produced at least four identifiable amino acids: asparagine, aspartic acid, glutamine and glutamic acid.
Titan life still a long shot
These hints of complex chemistry are intriguing, but they don't suggest that the Titan surface is crawling with life, Neish said.
"I'm fairly pessimistic about the prospects of life on Titan," she said. "To sustain life, you need some sort of energy source. And there's just not a lot of energy there."
But she thinks the new study has the potential to yield insights about how life could have arisen on Earth, which may have resembled Titan in many ways long, long ago.
The study suggests, for example, that biomolecules are fairly easy to make, even at low temperatures. So it's not too much of a stretch to think that life may have taken root in cold environments on Earth. An icy surface could protect any nascent biomolecules from damaging ultraviolet radiation, for example, and possibly from impact events, Neish said.
"Darwin talked about life possibly forming in a warm pond," she said. "Well, maybe a freezing pond is a good place for life to begin."
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