Saturday, June 18, 2005
Volcano on Saturn's moon, Titan.
TITAN appears to have a volcano that spews methane into the atmosphere, a finding that helps to explain an enduring riddle surrounding the Saturnian moon, according to a study published last week.Infra-red images of Titan were taken by the US probe Cassini in a flyby on October 26 last year.
Analysis of them by a US-French team, published in the British weekly science journal Nature, points to a "cryovolcano" some 30km across with winged outflows.
Unlike terrestrial volcanic mounds, which are formed by the upwelling of lava, this feature is probably formed by plumes of frozen methane, forced from underground, which then slowly evaporate into methane gas.
Titan is the only moon in the Solar System to have a substantial atmosphere, a thick mix of nitrogen and methane.
It is suspected to be undergoing chemical reactions similar to those that unfolded on Earth billions of years ago. That process eventually provided the conditions for life on our planet.
Scientists have long pondered the source of Titan's methane, given that this chemical should have been degraded by the weak light from the Sun within a hundred million years or so.
The answer, says the study, is that the methane supply is continually replenished by volcanic eruptions, which could be driven by heat from a tidal movement of liquids that whirl around beneath Titan's surface as the moon swings in an elliptical orbit around Saturn.
Contrary to widespread speculation, "the images show that a widespread methane ocean does not exist," it says.
Scientists had wondered whether Titan's relatively uncratered surface meant that it was awash with liquid methane, but it appears likely that this youthful appearance is simply methane ice, continually refreshed by the eruptions.
Cassini went into orbit around Saturn on July 1 2004 on a mission devoted to observing the giant's rings, atmosphere and satellite.
It dispatched a European probe, Huygens, on a one-day suicide mission to Titan that relayed home reams of data and more than 300 pictures.