A NASA-funded project is studying exactly that scenario. It sounds like something out of Deep Impact, Armageddon, or Don’t Look Up. But it’s possible that a small but dangerously sized asteroid could evade detection until it’s mere weeks away, rather than years or decades, says Philip Lubin, a University of California, Santa Barbara astrophysicist who leads the project. NASA and other organizations track as many near-Earth objects as possible to get a long warning time. But while they have spotted almost all the potential planet-killers in the solar system, they’ve found less than half of the ones 140 meters across or larger. Those are big enough to destroy a city, causing widespread devastation.
In fact, just this summer, an asteroid called 2023 NT1 came from the direction of the sun, and no one spotted it until July 15, two days after it flew within 60,000 miles of the Earth. According to a new study Lubin and his team are completing, it’s probably around 30 to 60 meters across, a bit larger than the meteors that hit Tunguska in 1908 and Chelyabinsk in 2013, both sparsely populated parts of Russia. It would’ve been big enough to inflict large-scale damage if it had hit the Earth.
Lubin and his colleagues are using computer simulations to explore the idea of throwing one or more large bullet-shaped interceptors, rather than a boxy DART-like spacecraft, into an asteroid. The vending-machine-sized DART ultimately achieved a minor deflection of the 160-meter Dimorphos, shortening its 11-hour, 55-minute orbit around the larger asteroid Didymos by 32 minutes. Lubin’s team suggests that instead of merely putting a ding into an asteroid and nudging its trajectory, they could instead penetrate its heart so that the ensuing shockwave pulverizes it, like a jackhammer breaking up concrete into manageable chunks. “We found that we could, in theory, take apart Dimorphos completely—which probably people would be bummed about—with a modest interceptor. Instead of making a dent in it, we could destroy it,” Lubin says.
Lubin’s team’s work suggests a short warning time might not mean the end of the world. Their simulations show that a SpaceX Falcon 9, like the one that propelled DART into space last year, or a larger rocket could launch such an interceptor and blow a 160-meter asteroid apart. They think that any resulting rocks would be small enough to not be dangerous if they continued on their Earthward trajectory.
In the meantime, scientists are working on getting a closer look at what DART wreaked. As Dimorphos and Didymos continue on their path around the sun, by the spring of 2024 they’ll be close enough that they’ll be easier for Hubble and ground-based telescopes to spot. The European Space Agency is also sending a follow-up mission, called HERA, to inspect the aftermath of the impact. HERA is planned to launch in October 2024 and reach Dimorphos in late 2026.
Then, in mid-2028, NASA plans to launch NEO Surveyor, which is designed to find at least two-thirds of near-Earth objects 140 meters or larger—potentially hazardous Dimorphos-sized asteroids. It will use infrared sensors, which must be deployed in space since Earth’s atmosphere blocks most infrared light.
Chabot hopes to see more planetary defense-related missions after that. Last year, in a once-in-a-decade report, planetary scientists endorsed investing in a variety of asteroid defense techniques, not just kinetic impactors like DART. These include using ion beams to deflect them, or using the “gravity tractor” technique to pull one onto a slightly different course by flying a spacecraft beside it for years. It’s important to have more than one tool available, Chabot says. “We’re proud of DART, and it brought a lot of attention to planetary defense,” she says. “But there’s a lot more to do and test out to be in a place where we could protect our planet in the future.”
English (US)