Can we protect the Earth from an asteroid hurtling towards us
The best-known asteroid to collide with Earth is the Chicxulub crater, which struck the Yucatán Peninsula 65 million years ago. It is known for having wiped out the dinosaurs, as well as three quarters of life on the planet. Other huge craters like the Vredefort Crater in South Africa and the Sudbury Basin in Ontario, Canada were even larger and likely headed our way a few billion years ago.
In recent years, meteoroids have hit us, the smaller cousin of the asteroid. Tunguska hit Siberia in 1908 and lit up the skies as far away as London; and Chelyabinsk, another Russian hit, was filmed in 2013.
A big one hasn’t hit us in a while, but the next one is somewhat inevitable, according to Nancy Chabot, a planetary scientist at Johns Hopkins University. “Although there are currently no known asteroids that are about to hit us in the foreseeable future, asteroids have been hitting Earth for billions of years and it is truly a cosmic inevitability,” Chabot says.
But what will happen when a huge object rushes towards us? Will we know in advance and will we be able to defend ourselves?
According to Chabot, scientists already track about 90% of the largest asteroids (about a kilometer or more), using ground-based telescopes that take multiple photos over multiple nights. They then trace their orbit. Once we track asteroids, we can know where they are for decades or even a century. None of these currently pose a threat.
However, planetary defense experts are much more concerned with smaller objects, a few hundred meters or even longer. These asteroids could do a lot of damage to the planet and we only track less than half of them, says Chabot. They are smaller and therefore harder to find. Although the objects we know of are not currently a threat, there is a world of undiscovered asteroids or comets that could hit the planet without warning.
“If something this smaller in size hit Earth, it wouldn’t necessarily be an extinction-level event, but it would be regional devastation,” Chabot says.
NASA’s next big thing in planetary defense is putting a telescope in space that’s “good for finding asteroids,” she says. It would be an infrared telescope, or infrared telescope, that could detect infrared radiation and find those smaller, darker objects hidden deep in the night sky.
“Most of the telescopes we put up in space are designed to observe very distant objects, but these objects are very close to the Earth in our solar system, so they move very quickly. This telescope should be good for observing the things nearby,” explains Chabot.
Once we know where the asteroids are, we will have enough time to warn us if they are heading our way. That’s where NASA’s latest planetary defense project, Double Asteroid Redirection Test (DART), comes in. DART is an autonomous rocket that can nudge or deflect asteroids to slightly alter their trajectory so they don’t hit not the planet. DART uses “kinetic impact technology,” which Chabot says is like crashing a spacecraft into an object to slightly redirect its orbit. DART lifted off last November and will reach the Didymos asteroid system around September. It will test its deflection technology on a 160-meter-wide asteroid.
But the only way DART works is if you have enough warning time to send your rocket into space and start pushing it. What happens when we miss the window and it’s ready to crash into the planet?
Phillip Lubin majors in planetary defense at the University of California, Santa Barbara. His recent research describes a technique called Pulverize It (PI) that would use “penetrating rods” to smash the asteroid into fragments small enough to burn before hitting Earth. If it was a “planet killer” sized asteroid, nuclear-capable interceptors would have to break up the object and scatter the pieces. All the while, they were far enough away not to touch the planet.
Ultimately, we need to know where the objects are, and then we need to know the possibility of intercepting them to push or break them. But Lubin says, we’re not there yet. We potentially have the technology that could stop most threats, but we are still in a “detailed analysis and simulation phase”.
“Humanity does not currently have a robust planetary defense program – period. We largely track threats and hope they don’t hit us,” Lubin says.