A rock fragment about the size of a biscuit recently mined in a Swedish limestone quarry is believed to be part of a 470-million-year-old meteorite that is completely different and, well, alien from any other rock from outer space ever found on Earth.
Reporting in the journal Nature Communications, geology professor Birger Schmitz, of Sweden's Lund University, suggests this highly unusual object may offer scientists more detailed information on the early history of our solar system:
"This may be the first documented example of an 'extinct' meteorite, that is, a meteorite type that does not fall on Earth today because its parent body has been consumed by collisions. The meteorites found on Earth today apparently do not give a full representation of the kind of bodies in the asteroid belt [between Mars and Jupiter].
"The asteroid belt has been evolving through collisions over the history of the solar system, and many of the original asteroids have undoubtedly been destroyed. The record of fossil meteorites on Earth (or on other planetary bodies) provides the only evidence for their former existence and the only way to investigate the collisional evolution of the solar system.
"We know that remnants of Earth building blocks are not present in our meteorite collections. Such meteorites are extinct now but clearly built the Earth in the distant past."
The small meteorite is thought to be a piece of a much larger rock, 12-19 miles wide, that hundreds of millions of years ago collided with another huge body, resulting in young Earth getting showered with meteorite debris.
This meteorite is classified as a chondrite, which most likely originated in the asteroid belt. Along with about 100 chondrite pieces so far discovered, this new alien fragment originally sank to the bottom of an ocean. That ocean covered what today is the limestone quarry (pictured below) in Sweden where the rock was discovered.
"The single meteorite that we now found ... is of a type that we do not know of from today's world," Schmitz told AFP. "The object contains very high concentrations (compared to Earth materials) of elements, such as iridium, which is very rare on Earth. The meteorite also contains high concentrations of rare isotopes of the element neon."
"Apparently, there is potential to reconstruct important aspects of solar-system history by looking down on Earth sediments, in addition to looking up at the skies," the study authors conclude.