Since life started on Earth, there have been five mass extinction events that have led to the obliteration of 99.9 percent of all the species that have ever lived. There are a lot of theories about the causes of those events, but the most compelling and —perhaps not coincidentally — widely accepted has long been that asteroids and other objects from space slammed into the planet, triggering a massive die-off. This is, most children are taught, how the dinosaurs died 65 million years ago.
Scientists aren’t all satisfied by that explanation. Since asteroids tend to hit the planet in strange 35 million year cycles, a more massive object must be causing some sort of clockwork effect. Maybe it’s the mysterious elusive Planet X? Maybe a set of other strange-acting comets in unstable orbits? Or maybe it’s dark matter. Last year, astrophysicists Lisa Randall and Matthew Reece at Harvard University started pushing a credible if not popular theory that a dense cloud of dark matter sitting along the central plane of the Milky Way could be causing comets, asteroids, and other space objects to head our way on the regular.
Scientists think about 85 percent of the total matter in the universe is dark, which is pretty mind-boggling consider we’ve never detected the stuff. Still, there is reason to conclude that it exists because something has to account for the strange gravitational effects we witness in the movements and speeds of the Milky Way and other galaxies. Specifically, Randall and Reece believe a disk of dark matter stretching out a staggering 35 light-years thick is disturbing the trajectory of large asteroids and other objects and flinging them to the Earth. Their analysis of large impact craters on the surface of the planet — more than 12 miles wide, created in past 250 million years — indicates the likelihood these crashes were in some way influenced by the dark matter cycle is three times greater than the odds they are just random events.
By itself, three-to-one odds aren’t statistically impressive. And, of course, while we kind of know dark matter is a thing, we don’t really know anything about dark matter. But the research itself is a sign that we are beginning to integrate more of what we know about astrophysical phenomena into the deep-time history of life (and death) on Earth. This is maybe the first time someone has linked the mystery of the dinosaurs extinction to the mystery of dark matter.
One scientist, New York University geologist Michael R. Rampino, takes this one step further and suggests that our own solar system actually moves through this cloud of dark matter periodically. Perhaps this movement doesn’t just knock asteroids into us, but it may heat up the planet and cause violent volcanic activity. For this to be true, a lot of other things have to happen. Among them, the dark matter disk has to be more dense than the galaxy’s highest concentration of stars. Also, the dark matter particles need to interact with Earth in such a way as to affect thermo-volcanic activity, but not completely melt the Earth’s core. It’s improbable but far from impossible.
And that’s not even the weirdest theory that combines extinction and dark matter. Dayong Cao is a Beijing-based researcher who leads the Avoid Earth Extinction Association, an organization dedicated to highlighting and studying potential extraterrestrial threats to our planet (i.e. asteroids). He’s written several papers detailing his ideas on dark matter and asteroids.
In short, Cao thinks asteroids moving through the dark matter clouds in the Milky Way are then infused with dark matter itself. These “dark asteroids or “dark comets” — which we can’t directly observe — slam into Earth, and bring dark matter to the planet itself. It’s only by studying the gravitational effects of these objects that we can predict if and when they will hit us. Cao’s theory kind of mashes the previously aforementioned ones into one, super-crazy annihilating idea.
At this point, the only way to prove any of these theories is to find dark matter. There are detectors running all around the world, though the prevailing thought is that we need to prove dark matter indirectly by better studying its gravitational effect on other celestial objects. Whatever the methods, the day we can finally say we’ve discovered dark matter could be the day we kill two science birds with one dark-matter soaked stone.
That is, if dark matter doesn’t manage to kill us off first.