Opal, a stunningly colorful precious stone formed from silica, has been discovered within an Antarctic meteorite.
The find, which comes on the heels of a similar discovery last summer involving a Martian meteorite, further lends support to the theory that Earth's water came from extraterrestrial sources.
The opal shards were discovered in a meteorite named EET 83309, a conglomerate made up of thousands of broken pieces of rock and minerals. It likely came from a much-larger parent asteroid that was regularly bombarded by radiation, other asteroids, and possibly even comets.
"The pieces of opal we have found are either broken fragments or they are replacing other minerals," team leader Professor Hilary Downes of Birkbeck College London said in a statement. "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."
Earth-formed opals are valued for their stunning beauty, which comes after millions of years of silica hardens in water. (Photo: Dpulitzer/Wikimedia Commons)
What makes the opal discovery so intriguing is the fact that the mineraloid requires water to form. On Earth, this involves water picking up sand and silica as it runs along the surface. It then becomes trapped in cracks and, over millions of years, turns into colorful opal as water evaporates and the silica hardens. In fact, opals dug out of the Earth today may contain anywhere from 3 percent to 21 percent water by volume.
"This is more evidence that meteorites and asteroids can carry large amounts of water ice," Downes added. "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."