A billion miles away

The chances of a better economic outlook, perhaps ?

Well no – this considers the question as to the best place in the solar system to look for extraterrestrial life. The answer being Enceladus which – as a satellite of distant Saturn – really is a billion miles away.

Enceladus – named after a child of Earth goddess Gaia – is one of Saturn’s 62 moons, and is just 310 miles in diameter. It has a unique combination of liquid water, organic material, and internal heat. There are suggestions of a subterranean liquid ocean, and geothermal energy similar to Earth.  Crucially Enceladus has water geysers that erupt into space, and which contain organic compounds (propane, ethane, acetylene). The droplets then freeze and feed Saturn’s rings.

These discoveries are due to the Cassini probe. It was launched in 1997, aimed generally at Saturn rather than Enceladus, and took seven years to get there. In 2005, based on a hunch, a decision was taken to direct Cassini towards Enceladus. It descended to 173 km and for the first time confirmed the presence of an atmosphere (water vapour / carbon dioxide / methane / nitrogen), organic compounds, and liquid water – found nowhere else in the solar system.

None of this necessarily means life. But Enceladus does offer the best hope of discovering life within our solar system. If there are lifeforms they should be easy to pick up, because they are being vented into space. This contrasts with better-known Mars or (the icy moons of) Jupiter. In both cases, if there is water it will be buried, perhaps by metres or by kilometres, making it very difficult to access.

So what next ?

Although these materials have been detected the key to real progress is to bring physical samples back to Earth. A 14-year roundtrip, plus a decade for planning, calls for long term commitment. However such a mission could be done at (relatively) low cost: under $500 million.

The above is a summary of a piece I read in the Observer a few months back. My thanks are due to science and technology editor Robin Mckie for bringing this wonderful story to my attention.


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