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READ MORE: Scientists baffled after discovering a unique asteroid-comet hybrid
With an abundant supply of liquid water, Earth is one of the few places in the universe where life can develop and flourish.
But scientists have long wondered where exactly all of our life-giving water came from in the first place.
Finally, scientists from the
University of Oxford
have the answer – and say that, contrary to popular belief, Earth’s water
did not come from asteroids after all.
Instead, the researchers believe that the ingredients for the water in our oceans and rivers were actually part of Earth from the very beginning.
In their study, the team analysed a rare asteroid made of a material very similar to the rocky debris which came together to make Earth.
Using a powerful beam of X-rays, the scientists found that these materials were ‘incredibly rich’ in hydrogen, which forms water when combined with oxygen.
Co-author Tom Barrett, a PhD student at the University of Oxford, told MailOnline: ‘The big conclusion of this study is that hydrogen, and by extension the ingredients for water, were incorporated into Earth by its primary building blocks, making it an inevitable consequence of our planet’s formation.
‘This may mean that water on the surface of planets is not as unlikely as previously thought.’
To explain how life was able to develop on Earth, and whether it could exist on other planets, scientists first need to figure out how liquid water came to exist.
We know that the water on Earth was formed by the combination of hydrogen and oxygen, so
the debate has often centred on how these elements came to Earth.
Many believed that the rocks which came together to make the Earth 4.55 billion years ago were too poor in hydrogen to explain all the water we see on the planet today.
It was therefore suggested that
water might come from space rocks rich in hydrogen or covered with ice from elsewhere in the universe
which hit the Earth 100 million years ago.
Since we can’t see what the early Earth was like directly, the best way to test this theory is to look for meteorites that have been drifting through space since the planet formed.
In their new study, published in the journal Icarus, researchers studied a meteorite dubbed LAR 12252 which had been found in Antarctica.
LAR 12252 is a rare type of meteorite called an ‘enstatite chondrite’ which has a composition similar to that of the early Earth.
A French research team had previously shown that this rock contained hydrogen hidden inside tiny spherical structures called chondrules.
But the way in which their study was conducted meant it wasn’t clear whether this hydrogen was an original ‘intrinsic’ part of the rock or whether it was contamination from Earth.
To learn more Dr Barrett and his co-authors used a technique called X-Ray Absorption Near Edge Structure spectroscopy.
This works by shining a very powerful X-ray beam onto the material and looking at each atom absorbs energy to work out what element it is and what kind of chemical it is part of.
When the researchers shone the X-ray on the edges of the chondrules, where water had been found before, they found that these areas were extremely rich in a chemical called hydrogen sulphide.
Since this rock is so similar to the composition of the Earth when it formed, this suggests that the planet may have already had enough hydrogen for liquid water to form.
Dr Bryson says: ‘Our work suggests that water did not need to be delivered from asteroids.
‘The material that created Earth likely contained enough hydrogen, in the form of hydrogen sulphide, to explain the entire water budget of Earth.’
Additionally, the location of the hydrogen-rich chemicals in the meteorite is a strong sign that their findings are accurate.
While the material around the spherical chondrules was rich in hydrogen sulphide, parts of the meteorite which had signs of contamination such as cracks or rust had none.
This tells the researchers that the hydrogen in the meteorite must have been part of its structure before it arrived on Earth.
Co-author Dr James Bryson, associate professor of mineralogy at the University of Oxford, told MailOnline: ‘We are pretty confident that the meteorites we have measured are a good repression of Earth’s building blocks.
This is because the meteorite contains the same ratio of stable isotopes, types of elements, as found near the interior of Earth.
This doesn’t mean that none of Earth’s water came from asteroid impacts, since we have good evidence that some water on the planet’s surface was delivered in this way.
However, this shows that some of the water on the surface and most of the water in the interior, which is the majority on the planet, was there from the beginning.
Dr Bryson says: ‘Our findings just show that there was enough hydrogen in Earth from its inception to form abundant water – we don’t know when or how that happened, but we hope our research will inspire those questions to be examined.’
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