Asteroids are a top qualifier when it comes to possible phenomena that wiped out the dinosaurs 66 million years ago—but can we actually predict if we’re also doomed?
Some studies have unearthed evidence of massive extinction events like the dinosaur apocalypse going déjà vu every 26-30 million years, which has led scientists to ask if deadly asteroid showers occur at regular intervals. The answer could possibly keep our species from going extinct, especially now that NASA is planning an asteroid redirect mission. What we need to prove to avoid a potential doomsday prophecy is whether there even is a definitive answer.
Earth is pockmarked with at least 190 impact craters from comets and asteroids that could be anywhere from a few meters to over 50 miles across, a few years to a few billions of years old, in places as diverse as layers of sediment and even the bottom of the ocean. Most of these are impossible to recognize unless you’ve devoted your life to obsessing over them. Whether they were formed by regular asteroid collisions that could possibly be forecasted or just pieces of space rock pelting our planet’s surface at random is the mystery.
There have been almost as many theories about this as there are asteroids in the Kuiper Belt. One revolves around the sun having a hypothetical evil twin named, appropriately enough, Nemesis. This faint red or brown dwarf star supposedly orbits the sun from 1.5 light-years away and is thought to creep up on our solar system every so often (“so often” being in terms of tens of millions of years), provoking massive comet showers. Nemesis wouldn’t be considered bizarre, since there is more than one star in most star systems. Except that astronomers now doubt it exists, because none have ever actually observed it. Another possibility involves keeping a telescopic eye on the sun itself as it orbits the Milky Way, because its crossing the galactic disc every 30 million years is thought to unleash a barrage of comets. That also has yet to be proven.
Evidence for periodicity has been elusive. The study that almost shook the astronomy world with supposed evidence of periodicity was not so Earth-shattering once the data was put under a microscope. Most of the crater ages were either incorrect, outdated or inconclusive after analysis, and the methods used to determine age were outdated. Then there is the issue of clustered ages. Determining that two different asteroids struck in the exact same place at the exact same time could be solid proof of an asteroid shower, but double impact craters can give the illusion of multiple asteroid impacts. The few clustered craters that have been found are explained by asteroid showers that were completely random.
This doesn’t necessarily mean that regular asteroid impacts are relegated to prehistory and science fiction. Stats tend to get complex when you involve variables like ages of rocks that are a headache to figure out, craters fading with the aeons, some being identified more easily than others depending on the period they were formed, and some of those at the bottom of the ocean remaining undiscovered. A study recently published in Monthly Notices of the Royal Astronomical Society states that while periodicity may not be impossible, it is questionable. Proof of asteroid shower patterns telling of regular events that could obliterate thousands of species has yet to be found.
So there is no way to really predict an asteroid-pocalypse if that’s how we’re going to go, but I might avoid looking at my horoscope from now on.