How to spot oceans on alien worlds

Space scientists have made a breakthrough that will help them to spot planets just like Earth orbiting other stars. They have discovered a technique for discovering oceans of water – a key clue to life as we know it – on worlds otherwise too distant to see close-up.

Deep Impact/Epoxi spacecraftThe US scientists found the new method by turning detectors on a faraway spacecraft onto the Earth itself.

In effect, they were acting as aliens might to view the distant blue speck of our own planet to check it out for possible life.

The scientists used instruments aboard Deep Impact, a spacecraft that hit the headlines in July, 2005, when it blasted a missile into a comet called Tempel 1. They studied the light from Earth over two 24-hour periods in different parts of the spectrum.

This revealed small deviations in colour caused when clouds or oceans rotated into view. The results mean they should now be able to recognise similar features on alien planets using giant telescopes in space.

Chief discoverer Nicolas Cowan, of the University of Washington, said: “You could tell that there were liquid oceans on the planet. Liquid water on the surface of a planet is the gold standard that people are looking for.”

The observations were made last year when the Deep Impact spacecraft was between 17 million and 33 million miles from Earth. They will be reported in the Astrophysical Journal.

Deep Impact is itself now hunting for new worlds on a mission called Epoxi. Chief investigator Drake Deming of NASA’s Goddard Space Flight Centre, Maryland, said: “We’re on the hunt for planets down to the size of Earth, orbiting some of our closest neighbouring stars.”

Read a press release about the breakthrough here.

Picture: An artist’s impression of the Deep Impact probe – now on a mission renamed Epoxi – as it fired its missile at the comet. (NASA)

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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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