麻豆传媒

The Huygens probe that roared through Titan鈥檚 atmosphere has provided the strongest evidence yet to suggest Saturn鈥檚 giant moon is geologically active beneath its icy surface.

The ratio of carbon isotopes ¹²C and ¹³C in Titan鈥檚 atmosphere, measured by the probe鈥檚 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鈥檚 atmosphere into space at a greater rate than the heavier isotopes. This changes the isotopic ratio of the elements 鈥� a process called fractionation. But the atmospheric carbon isotopes do not show the same trait, implying the gas is being replenished.

Rumbling on

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鈥檚 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. 鈥淭here are going to be a lot of models made about Titan,鈥� he told 麻豆传媒.

Spectrographic analysis using Earth-based telescopes has also previously suggested that the carbon in Titan鈥檚 atmosphere is not fractionated. And the Ion Neutral Mass Spectrometer aboard Cassini also picked up evidence for this as it passed through the moon鈥檚 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鈥檚 frigid landscape, revealing evidence of methane streams and craggy ice hills.