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The Earth's surface is 70% waterNASA/NOAA

It's been one of those questions that has plagued scientists for years – how did water come to be on our planet? Was it here from the beginning or was it brought to us from outer space on meteorites and comets? Researchers from the University of Hawaii believe that they may have found the answer. After analysing rocks found on Baffin Island, Canada, they discovered that the rocks have tiny particles of water within them that had been present, and untouched, for millions of years.

The water had two types of hydrogen − hydrogen and deuterium (known as heavy hydrogen) – which they believe prove that water has been present since the formation of the Earth. Dr Lydia Hallis, previously of the University of Hawaii but now of the University of Glasgow and lead author of the study published in Nature, explains: "The Baffin Island rocks were collected back in 1985, and scientists have had a lot of time to analyse them in the intervening years. As a result of their efforts, we know that they contain a component from Earth's deep mantle.

"On their way to the surface, these rocks were never affected by sedimentary input from crustal rocks, and previous research shows their source region has remained untouched since Earth's formation. Essentially, they are some of the most primitive rocks we've ever found on Earth's surface, and so the water they contain gives us an invaluable insight into Earth's early history and where its water came from.

"We found that the water had very little deuterium, which strongly suggests that it was not carried to Earth after it had formed and cooled. Instead, water molecules were likely carried on the dust that existed in a disk around our Sun before the planets formed. Over time this water-rich dust was slowly drawn together to form our planet.

"Even though a good deal of water would have been lost at the surface through evaporation in the heat of the formation process, enough survived to form the world's water. It's an exciting discovery, and one which we simply didn't have the technology to make just a few years ago. We're looking forward to further research in this area in the future."