Today, most of Earth’s surface is covered in water – but scientists believe Earth’s oceans didn’t form until around eight million years after the planet itself. The discovery of ‘ocean-like’ water on a comet by the HiFi instrument on the Herschel Space Observatory hints that Earth’s oceans might have arrived in the form of comet ice.
If so, the impacts (we’d have needed quite a few) would have formed an important stage in the evolution of life on Earth.
‘Life would not exist on Earth without liquid water, and so the questions of how and when the oceans got here is a fundamental one,’ said University of Massachussetts astronomy professor Ted Bergin, ‘It’s a big puzzle and these new findings are an important piece.’
Previous scans of comets led astronomers to believe that the icy bodies could not have brought water to Earth – or at least were only responsible for a very small fraction of it.
HiFi, the Heterodyne Instrument for the Infrared on the Hershel Space Observatory, detected a familiiar, ‘ocean-like’ composition to the water on the comet Hartley 2 – a comet that had been ‘visited’ at a distance of 700km by NASA’s Deep Impact spacecraft.
By ocean-like, of course, the astronomers don’t mean that it is green and swimming with fish.
Hartley-2 is frozen solid in the cold of deep space – the comet is composed of chunks of water ice and frozen carbon dioxide.
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