Science Focus by Colin Stuart 6/17/2023
History has shown that even small asteroids can cause a significant amount of damage - and we can't even detect them.
It is the ultimate cosmic catastrophe. A killer space rock is locked on a collision course with Earth. When it hits, the curtain comes down on humanity as we fade into the shadows of history just like the dinosaurs before us.
Despite being the subject of a string of apocalyptic Hollywood blockbusters, there is some good news. A recent study found that we're unlikely to be hit by any of the nearly one thousand known near-Earth asteroids above a kilometre in diameter within the next 1,000 years.
The asteroid that unleashed hell upon T.rex and co 66 million years ago is thought to have been between 10 and 15 kilometres wide. The new work, led by Oscar Fuentes-Muñoz from the University of Colorado Boulder, is a marked improvement on previous work, which could only forecast a century ahead.
Although, according to Prof Phil Bland, an asteroid expert at Curtin University in Australia, the claim comes with some important caveats. Most notably, it only applies to the big asteroids we already know about.
“It doesn’t speak to the five per cent that are still out there waiting to be discovered,” he says. “It doesn’t include comets either, which we’ll never be able to constrain.”
This could be important, as many comets, which can be as big as asteroids, fly in from the outer solar system having never entered the inner solar system before. We have no way of tracking them until they are already very close to us.
Then there are all the asteroids smaller than a kilometre across. “We’re not good at all at tracking smaller stuff,” Bland says.
Such asteroids don't even have to strike the planet's surface to inflict significant harm. “Objects as small as 50 metres can cause an airburst that is really devastating over a local area,” Bland says.
In February 2013 a 13-metre object exploded in the atmosphere above Chelyabinsk in Russia. Almost 1,500 people were injured and more than 7,000 buildings damaged. The total cost of repairs came to around £26 million.
More:
https://www.sciencefocus.com/news/earth-tiny-city-destoying-space-rocks/
