People often speak of meteors and meteorites as if they come from far-flung stars, but the truth is that virtually all of them come from the asteroid belt between Mars and Jupiter—essentially, our celestial backyard.
But out of the millions that have bombarded us over the years, we may now know of a single exception. It’s called the Tagish Lake meteorite, and ever since it slammed into northwestern British Columbia in 2000, it’s baffled scientists on account of its unique appearance and composition.
As a new report in The Astronomical Journal suggests, it’s likely the first known meteorite from the Kuiper Belt, the frigid ring of rocks beyond Neptune.
So how did it get here? As Bill Bottke, one of the authors of the paper and an astronomer with the Southwest Research Institute in Boulder, Colorado told New Scientist, its origins may lie with the early days of the solar system when the gravitational pulls of Jupiter, Saturn, Neptune, and Uranus were all jostling with each other. In the process, some rocks from the swarm of comets surrounding the giants may have been tossed toward us. This is especially likely if there’s any truth to the theory that our solar system once had five gas giants instead of four, as the ejection of the fifth giant would have almost certainly sent Kuiper-area objects hurtling our way.
The timing could hardly be better. The Kuiper Belt is currently an area of intense study, in part because of New Horizons’ phenomenally successful visit to Pluto last year and the extension of its mission to other Kuiper Belt objects like 2014 MU69. Having a known object from the belt here on Earth would facilitate research, providing invaluable insight into how the solar system was formed through data comparisons.
Bottke and his colleagues suggest that the Tagish Lake meteorite is “likely a fragment from a D-type asteroid implanted into the inner main [asteroid] belt.” The D-type is a relatively small classification of asteroids which exhibit compositions that bear little resemblance to most other objects found in the asteroid belt but have much in common with objects found around the gas giants. (It’s also been suggested that Mars’ moon Phobos is a “captured” D-type asteroid.)
Some researchers, such as Pierre Vernazza from France’s Marseille Observatory, seem unconvinced by the paper’s suggestion that Tagish Lake rocks match up with the surface observations of D-type asteroids. He is, however, somewhat willing to entertain the idea that the meteorite came from the heart of one of the D-types.
“For now, we don’t have the observations to establish that it is possible,” he said.
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