Every so often, the fossil record shows, ecological disasters wipe large numbers of species off the face of Earth. These mass extinctions occur roughly every 26 million to 30 million years—about the same interval at which our solar system passes through the plane of the Milky Way. Putting two and two together, some researchers have proposed that clouds of dust and gas in the galactic plane might disrupt the orbits of far-flung comets and trigger planet-smacking collisions. A new study suggests an additional culprit may lie behind those times of woe: dark matter.
Some of Earth’s past mass extinctions have been caused by the impacts of extraterrestrial objects, such as the asteroid that struck near Mexico’s Yucatán Peninsula and wiped out the dinosaurs about 66 million years ago. Others have occurred during extended periods of geological disruption that include region-smothering volcanic eruptions. Both kinds of catastrophes seem to occur on a cycle of about 30 million years, notes Michael Rampino, a geoscientist at New York University in New York City. “It’s always been a mystery as to how extraterrestrial impacts could cause these long-lived geological effects,” he says. But invisible dark matter, he proposes, could trigger both extraterrestrial impacts and geological upheavals in one fell swoop.
Scientists still don’t know what dark matter is, but its gravitational pull on other objects in space shows that there’s a lot of it out there. Researchers estimate that in the plane of the galaxy, each square light-year contains about one solar mass of dark matter. Like the clouds of dust and gas that astronomers can see, clouds of dark matter may be perturbing the orbits of distant comets, causing them to fall into the inner solar system where they can strike Earth. Via Did dark matter kill the dinosaurs?