The Huygens probe that roared through Titan's atmosphere has provided the strongest evidence yet to suggest Saturn's giant moon is geologically active beneath its icy surface.
The ratio of carbon isotopes 12C and 13C in Titan's atmosphere, measured by the probe's Gas Chromatograph and Mass Spectrometer (GCMS) instrument, indicates that methane is being replenished on the freezing world. Continuing geological activity beneath the surface is thought to be the most likely source.
The Cassini-Huygens mission has already produced remarkable insight into the enigmatic and inhospitable moon, which is unique among the planetary satellites in our solar system in having its own atmosphere.
Previous evidence suggested that lighter isotopes of oxygen and nitrogen have escaped from Titan's atmosphere into space at a greater rate than the heavier isotopes. This changes the isotopic ratio of the elements - a process called fractionation. But the atmospheric carbon isotopes do not show the same trait, implying the gas is being replenished.
Astronomer Tobias Owen, of the University of Hawaii and one of the original planners of the mission, says this suggests methane is being added to Titan's atmosphere by geological processes rumbling beneath the surface. It is the best evidence so far that the icy moon is a geologically active body, he says.
Owen adds that how Titan produces its methane will be the subject of much speculation. "There are going to be a lot of models made about Titan," he told New Scientist.
Spectrographic analysis using Earth-based telescopes has also previously suggested that the carbon in Titan's atmosphere is not fractionated. And the Ion Neutral Mass Spectrometer aboard Cassini also picked up evidence for this as it passed through the moon's upper atmosphere in January.
Huygens was dispatched to the surface of Titan on 15 January 2005. It gathered a wealth of valuable data during the descent and for an hour after landing on the frozen surface, as planned. It also sent back spectacular images of the moon's frigid landscape, revealing evidence of methane streams and craggy ice hills.
All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
If you are having a technical problem posting a comment, please contact technical support.
10:45 10 October 2008
19:00 09 October 2008
