Scientists Discover Opal in a Meteorite

H. Downes
H. Downes / H. Downes

Asteroids and meteors might lead to our doom, but they might also be the reason we are here in the first place, according to findings reported yesterday, June 26, at the Royal Astronomical Society's National Astronomy Meeting being held at the University of Nottingham. After studying a meteorite found in Antarctica, a team of scientists led by geochemist Hilary Downes, of Birkbeck, University of London, discovered pieces of opal within. The discovery has implications way beyond the fashioning of galactic jewelry. In fact, it may provide clues about the origins of some of the water on Earth.

The meteorite, called EET 83309, hails from the regolith—the loose outer surface—of an unknown asteroid. For eons, this mystery asteroid was bombarded by rocks from across the solar system. (Scientists know this because the meteorite studied contains fragments from all sorts of other meteorites.) At some point, one of the cosmic asteroid impacts led to the formation of the opal. That opal-bearing chunk of asteroid was later knocked free and landed in Antarctica, where it was discovered in 1983.  

The formation of opal on the asteroid—and not later in Antarctica—is hugely important, because opal is made of 30 percent water. In other words, one of the rocks that collided with the asteroid contained said water, likely in the form of ice. The upshot is that we now have further evidence that asteroids and meteorites are indeed the bearers of massive amounts of water, and that billions of years ago, they undoubtedly brought an awful lot of that water to Earth.

"Although we rightly worry about the consequences of the impact of large asteroid," Downes said in a press statement, "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."

How do we know the opal was formed on the asteroid and not in Antarctica? Because while there have been interactions between the meteorite and Antarctic ice, and the results of those interactions do not match the minerals found on the original meteorite, which have their own distinct, extraterrestrial characteristics.

This is not the first time that opal has been found on a meteorite. Last year, it was discovered to be present in a rock found in Egypt in the early 20th century that originated from Mars, suggesting Martian hot springs that are both mineral-rich and conducive to microbial life. Meteorites allow scientists to study celestial evolution. Because some are tens of millions of years older than the Earth itself, they provide an intimate glimpse of the building blocks of the solar system.