During this horrible pandemic year, humans around the world have had ample opportunity to reflect on the threats we face here on Earth. But if you’d like to take a break from the existential dread provoked by deadly contagions and shift your focus to a possible apocalypse-from-space, you might be interested in a new NASA mission that aims to defend our planet from future asteroid impacts.
The Double Asteroid Redirection Test (DART), due for launch this summer, is NASA’s first flight demonstration for planetary defense—in other words, it’s a spaceship that will directly punch an asteroid.
The mission’s target is an asteroid system called Didymos, which contains two space rocks that orbit each other. In late 2022, DART will forcefully impact the smaller asteroid in this system, a tiny moon called Dimorphos, so that scientists can assess the feasibility of knocking any space rocks that threaten Earth off course in the future.
“Up until now, we haven’t had too many options for what we might do if we found something that was incoming,” said Andy Rivkin, a planetary astronomer at the Johns Hopkins University Applied Physics Laboratory and the investigation team lead for DART, in an interview with VICE News.
“DART is the first test of how we might be able to deflect something without having to resort to a nuclear package, or sitting in our basements, waiting it out, and crossing our fingers,” he added.
In blockbuster movies like Armageddon and Deep Impact, an asteroid that threatens Earth simply must be blasted apart by a nuclear weapon to ensure the maximum explosive entertainment value for audiences chomping on popcorn. In real life, this is not an ideal option, because it could create smaller space rocks that rain down on Earth, causing damage to multiple locations.
DART will pioneer a subtler form of planetary defense, in which the trajectory of an asteroid is changed by a very small amount that becomes significant over time. Late next year, the mission will crash into Dimorphos at about seven kilometers per second. Shortly before the collision, the spacecraft will deploy a small satellite provided by the Italian Space Agency that is tasked with watching “the mess we make,” Rivkin said.
Observations from the Italian satellite, as well as from powerful telescopes on Earth, will reveal just how much Dimorphos was affected by the crash. Rivkin and his colleagues expect the change in orbital speed to be small—about one millimeter per second—which would add up to a shortening of the orbital period by about 10 minutes. But even this very slight shift would be enough to redirect the trajectory of a hazardous asteroid that threatened Earth, provided scientists have a lead-time of a decade or two before the projected impact.
In the worst case scenario, we might discover an asteroid that’s on track to collide with Earth in a matter of months or years, which could potentially trigger a nuclear option. But Rivkin said that the aim of an emergency nuclear response would still be to deflect an intact asteroid in one direction, not explode it into pieces as seen in movies.
He also emphasized that this terrifying possibility is incredibly unlikely, and that asteroid scientists like him are much more interested in the scientific wonders of these abundant space rocks than the risk they pose to humankind.
“If asteroids are to keep you awake at night, let it be with excitement about how cool they are, and not concern,” Rivkin said.