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Welcome to a new Eden – two billion miles from Earth

May 10

Full Article: Welcome to a new Eden – two billion miles from Earth

No other body in the solar system more closely resembles Earth than Saturn’s moon, Titan. It has methane lakes and seas and scientists now believe that an underground ocean could even harbour life, says Robin McKie

“There are lakes and seas that make Titan the only other place, other than the Earth, in the solar system with large, stable bodies of liquid on its surface,” says Zarnecki. “There are also river channels; great stretches of dunes; weather and meteorology; complex hydrocarbons; and – most excitingly – powerful signs that Titan has a subsurface ocean that could provide a home for primitive life. Titan turns out to be an incredible place. It’s a moon that would be a planet.”

In fact, Titan looks like Earth in many ways – with one critical exception. It is extraordinarily cold, with atmospheric temperatures 200 degrees below that of our planet. Ten times further from the Sun than Earth, Titan consequently receives a hundredth of the solar heat that bathes our world. There may be complex organic material littering the place, but conditions are simply too cold on Titan for life to evolve from this material on the surface.

It turns out that those rivers, lakes and seas on the surface are not watery affairs but are made of methane which plays the same meteorological role on Titan as water does on Earth. It evaporates from great seas of liquid methane, like the giant Kraken Mare. Then it condenses and falls as methane rain, sometimes setting off flash floods that carve out riverbeds like the ones picked out by the cameras on Huygens.

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In any case, this moon may yet have its day as a home of complex lifeforms. “In a couple of billion years, our Sun will expand to become a type of star called a red giant and will envelop Earth in superhot plasma,” says Zarnecki. “Our oceans will boil off and the Earth will become a very unpleasant place to live. By contrast, temperatures will go up nicely by a couple of hundred degrees on Titan. This will be the new Eden.”

As for the make-up of that liquid layer, evidence points to water as the prime candidate. And that, in turn, has exciting consequences, say scientists. Titan probably has a hot core which is keeping that layer of water in a warm liquid state. Thus, we have the prospect of a rich soup of hydrocarbons filtering through Titan’s crust to a subterranean ocean.

“These discoveries make Titan very interesting biologically. We have got loads of organics on the surface and liquid water down below. Can the two mix? Have they been mixing for billions of years? In other words, are there thriving colonies of bugs down there, crawling about and living very happily below Titan’s surface?”

Not surprisingly, such a prospect is fuelling scientists’ appetites for a return mission to Titan. Several probes are being planned including a joint European-American mission that would carry airships and balloons. These would take advantage of the moon’s thick atmosphere, which is denser than Earth’s, and its low gravity, which is a seventh of ours.

“Flying on Titan should be easy and by following its winds, we should be able to sail round it in a couple of weeks, looking for promising places to land and investigate,” says Zarnecki. “We could also sail robot ships on its methane seas and become the first extraterrestrial mariners. Most important, however, we could try and find signs of simple biology on Titan. That would be pure gold.”

Full Article: Welcome to a new Eden – two billion miles from Earth

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