Of course, we can also try to spot asteroids in the sky. Astronomers have identified a large majority of near-Earth asteroids[3] larger than 1km across, and many smaller examples. From these surveys, we know that the chance of an Earth-impact for asteroids 1-10km in diameter in an average century is about 1 in 6,000, and about 1 in 1.5 million for asteroids larger than 10km across — that is, roughly the size of the asteroid that caused the Cretaceous–Paleogene mass (dinosaur) extinction event.
Interestingly enough, the importance of asteroid size might be overestimated, compared to impact angle and impact site. The asteroid that killed the dinosaurs wouldn’t have been nearly as deadly, hadn’t it struck at one of the worst possible places at one of the worst possible angles.
This 2017 paper used computer models to see if the rock composition of the impact site could’ve made a difference. The computer calculated the amount of soot and sulfates that would be ejected into the atmosphere as well as what that would mean for our planet, since both soot and sulfates can block the sun’s light. The blocked out sun started a global winter that lasted years and this is what killed the dinosaurs, not the impact of the asteroid directly. The researchers found that the composition of the impact site was especially unlucky. And since the Earth is constantly spinning and moving in space, this means that if the asteroid had just arrived a couple minutes later it wouldn’t have hit such a problematic piece of land or might have even hit the ocean where a lot of its impact would have been lessened (in terms of the amount of rock that got ejected into the atmosphere).
This 2020 paper concluded that the asteroid hit from a pretty steep angle, about 45-60 degrees. This vaporized more rock than a shallow strike and released more climate-changing gases than other angles, with 2-3 times as much carbon dioxide released as a vertical impact and 10 times as much as a shallow impact.
Seeing how unlucky the impact timing was means that asteroids probably aren’t as big of a risk as they are imagined to be. And even if we don’t develop the technology to completely deflect asteroids, changing the angle or delaying it so it hits a different impact site might be enough to change a mass extinction into a mere disaster.
Interestingly enough, the importance of asteroid size might be overestimated, compared to impact angle and impact site. The asteroid that killed the dinosaurs wouldn’t have been nearly as deadly, hadn’t it struck at one of the worst possible places at one of the worst possible angles.
This 2017 paper used computer models to see if the rock composition of the impact site could’ve made a difference. The computer calculated the amount of soot and sulfates that would be ejected into the atmosphere as well as what that would mean for our planet, since both soot and sulfates can block the sun’s light. The blocked out sun started a global winter that lasted years and this is what killed the dinosaurs, not the impact of the asteroid directly. The researchers found that the composition of the impact site was especially unlucky. And since the Earth is constantly spinning and moving in space, this means that if the asteroid had just arrived a couple minutes later it wouldn’t have hit such a problematic piece of land or might have even hit the ocean where a lot of its impact would have been lessened (in terms of the amount of rock that got ejected into the atmosphere).
This 2020 paper concluded that the asteroid hit from a pretty steep angle, about 45-60 degrees. This vaporized more rock than a shallow strike and released more climate-changing gases than other angles, with 2-3 times as much carbon dioxide released as a vertical impact and 10 times as much as a shallow impact.
Seeing how unlucky the impact timing was means that asteroids probably aren’t as big of a risk as they are imagined to be. And even if we don’t develop the technology to completely deflect asteroids, changing the angle or delaying it so it hits a different impact site might be enough to change a mass extinction into a mere disaster.