Drizzle on Titan, clearing later

Space scientists have seen the first clear signs of rain falling on another world in the solar system. Their interplanetary weather check found high cloud producing a widespread and persistent drizzle on Saturn’s biggest moon, Titan.

Northern lakes on TitanThe rain is falling over the foothills of Titan’s largest continent, Xanadu, which is the size of Australia.

Titan is the most Earth-like world in the solar system apart from Mars. Today’s revelation came as it was also announced that Cassini, a spaceprobe orbiting Saturn, has discovered three giant lakes, each bigger than Lake Superior, in Titan’s southern hemisphere.

The vast reservoirs are the first to be found on this half of the planet and follow the finding of a widely-spread lake district in the north. Nasa scientists have also released a new image of this northern region, showing how Cassini is gradually piecing together a jigsaw map of this moon.

Planetary scientists are excited because conditions on Titan seem to be very similar to those on an early Earth and it could become home to primitive life. Apart from lakes, the landscape also features clouds, rivers, coastlines, and mile-high mountains topped with snow. Liquid forming the rain and filling Titan’s rivers and lakes is not water but hydrocarbons such as methane.

The weather findings were made by a team of US astronomers using giant telescopes in Hawaii and Chile to make “heat maps” of Titan by observing in the infrared part of the spectrum.

The discovery team, from the University of California, say the drizzle may turn to mist before it hits the ground, producing a foggy “morning” that lasts around three Earth-days after local sunrise. Titan rotates once every 16 days.

Titan has a thick atmosphere made up mainly of nitrogen which resembles the early atmosphere of Earth. UK scientists led a European team that parachuted an unmanned probe called Huygens onto its surface in January 2005.

Professor John Zarnecki, of the UK’s Open University, who led the lander team, said yesterday: “These results reinforce some of the similarities between conditions on Titan and Earth – cirrus clouds, drizzle, lakes.

“All are indicative of a cycle at work, albeit with methane on Titan. By pooling data gathered from space and ground based observations we can piece together a global picture of this distant world.”

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Paul Sutherland

Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.
Paul Sutherland

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Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.

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