Artist’s rendering of the space collision 466 million years ago that gave rise to many of the meteorites falling today. Image © Don Davis, Southwest Research Institute.

Colliding asteroids to blame for Earth’s meteors

Why do the asteroids that fall to Earth have the composition they do? A giant space collision 466 million years ago may be to blame.

“Men of genius are often dull and inert in society; as the blazing meteor, when it descends to earth, is only a stone.” -Henry W. Longfellow

What falls to Earth is a mystery to science. Not because we don’t know what meteorites are or where they come from — they’re overwhelmingly asteroids — but because as we’ve learned more about what exists in our Solar System, what we see landing on Earth doesn’t match up. The asteroids that pass closest to Earth aren’t the majority of what hits us, and the majority of what hits us has changed dramatically over the past few hundreds of millions of years. A radical new idea, with the supporting evidence from the geologic record to back it up, may just solve this puzzle: asteroids collide with one another in space, create debris, and that dominates what falls to Earth for tens-to-hundreds of millions of years.

Unlike meteor showers, which arise from Earth passing through a comet or asteroid’s debris trail, meteorites are large enough to make it to Earth’s surface, leaving a remnant behind. Image credit: NASA.

If you think about it logically, it would make sense if the asteroids that come…