Opal embedded in Antarctic meteorite gives clues on the origin of Earth's water.
For years, scientists have debated how the Earth got its water. Some suggest it was already present when the Earth was forming while others believe that water was brought here by asteroids. Now, new evidence also supports the view that water on Earth came from asteroids hitching a ride on meteorites and supplied the Earth with the ingredients necessary for the evolution of life.
Planetary scientists have discovered pieces of opal embedded in an Antarctic meteorite. Opal is a gem made up of silica - a compound which contains 30% of water. The precious stone has not been identified in the surface of any asteroid and it is just the second instance when tiny crystals of opal have been found buried in a meteorite sample.
When researchers studied the meteorite, named EET 83309, they found it is a blend of thousands of broken pieces of rocks and minerals, suggesting that meteorite originally came from the bedrock of an extraterrestrial object and was constantly exposed to the radiation of the sun while still being a part of the object.
The meteorite also contains fragments from other kinds of meteorites which indicates that its parent body might have been collided with other objects several times before some of its surface broken up and entered the atmosphere of the Earth in the form of meteorite. One of those impacts likely carried water ice to the asteroid’s surface and helped it form the precious stone called opal.
“The pieces of opal we have found are either broken fragments or they are replacing other minerals,” said lead researcher Hilary Downes, professor from Birkbeck College London.
“Our evidence shows that the opal formed before the meteorite was blasted off from the surface of the parent asteroid and sent into space, eventually to land on Earth in Antarctica.”
Researchers used various sophisticated techniques to find the compositional properties of the opal and tried to determine where it came from. The gem could have been formed while the meteorite was sitting in the Antarctic using some of the components available in the water but researchers ruled out that possibility and confirmed its alien origin.
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“This is more evidence that meteorites and asteroids can carry large amounts of water ice,” said Downes. “Although we rightly worry about the consequences of the impact of large asteroid, billions of years ago they may have brought the water to the Earth and helped it become the world teeming with life that we live in today.”