NASA Spacecraft Strikes an Asteroid in First Planetary Defense Test
At about 4:30 am this morning, everyone on Earth was rooting for the fall of Dimorphos. Dimorphos is a small satellite of an asteroid approximately the size of a stadium, and NASA on Monday intentionally rammed a spacecraft straight into it, scoring “basically a bullseye” as scientists called it.
These are the victory pursuits of the mission called the Double Asteroid Redirection Test (DART), essentially a program to defend Earth from a doomsday-like scenario, one that occurred some 66 million years ago and ended the age of dinosaurs. The DART mission was the first planetary defense test against a possible threat, shifting the trajectory of the asteroid by a noticeable margin.
It is a “new era of humankind,” said Lori Glaze, NASA’s planetary science division director. An era where humankind can dream of protecting itself against a threat that wiped out a species far more formidable than us.
“[It’s] an era in which we potentially have the capability to protect ourselves from something like a dangerous hazardous asteroid impact. What an amazing thing. We’ve never had that capability before.”Lori Glaze, planetary science division director at NASA
To be fair, Dimorphos doesn’t represent an immediate peril. But what the test demonstrates is should an asteroid find Earth in the court of its orbit, the strategy could be used to deflect impact.
The curious thing about milestones is they never quite play out in the way they are envisioned. In theory, the best way to deflect the force of a celestial body seems to be to obliterate it. Movies like Don’t Look Up, Armageddon, and Deep Impact reflect similar anxieties around extinction by way of an asteroid strike. But in real life, the defense involved more of what Morgan Freeman did in Deep Impact: to collide a spacecraft at the speed of 15,000 miles per hour with the asteroid just enough to change its 12-hour orbit.
“We’re not blowing up the Death Star,” said Andy Rivkin, part of the DART’s investigation team at the John Hopkins University Applied Physics Laboratory. “We’re using the momentum from the spacecraft to change the orbit of the asteroid.”
“Conventional wisdom for planetary defense is that you don’t want to disrupt an object and blow it into a million pieces, but you want to keep it intact and just move it all as one piece,” he further explained. “Because if you move it all in one piece then you can keep track of it a lot easier. If you blow it into a million pieces, then some of them might still [collide with] Earth, and you don’t want to miss a thing.“
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This premise is also what made Dimorphos, and the asteroid Didymos, fitting test subjects. Didymos was just small enough that it could be moved with a strike — “but not so small that we wrecked the moon (Dimorphos),” Rivkin pointed out.
Planetary defense is a growing concern. In 2019, NASA spent almost $150 million on projects and research around managing this perilous future. The first brush with the tangibility of an Armageddon-esque scenario happened back in 1994, when fragments of a comet rammed straight into our neighbor Jupiter. It created “powder burns” in the atmosphere that could be seen from our telescopes too, a “sobering” reminder that celestial bodies do present a threat to life. There have been dangerous liaisons with asteroids and comets since; in 2020, we had a brush with an asteroid named 2020 QG, which passed 2,950 km above the Southern Indian Ocean making it the closest recorded non-impacting asteroid.
Our defense involves the identification of possible threats, of all near–Earth objects (NEOs) that may cause unprecedented catastrophe. Then comes observation, where scientists spend years determining how far these objects are, their size, shape, speed, what they are made of — anything that can help determine their orbit. Investment in powerful telescopes is key here; namely the NASA’s tracking station at Goldstone, California and the 305-meter-wide dish at Arecibo Observatory in Puerto Rico. Arecibo was the most powerful radar system in the world, but was decommissioned in 2020. Its 57-year-long run had to come to an end.
Perhaps, what’s marvelous about the current attempt is that we’ve managed to piece together some semblance of an answer for a what-if scenario.
This is very antithetical to human nature; we aren’t programmed to measure long-term threats and we typically ignore a crisis until it stares us in the face. The investment in planetary defense is the result of anxieties around a threat that has come to pass before, embers of dust from comets and asteroids lie in our museums to remind us of our fallibility. There is a disconnect in how we respond to other catastrophes like climate change, given that asteroids and climate change share some features in representing existentilal threats, as writer Robin Llyod pointed out.
In 2010, a a paper noted:“The asteroid-threat community has been much more successful than the climate change community in characterizing the dominant worst-case scenarios and communicating them to policymakers, the media, and the public—even though the climate change threat is more than a thousand times greater.” An external, outer-planet threat involves fewer stakeholders and corporate lobbies who would be negatively impacted by addressing it, but climate efforts are constantly blocked by industries. Moreover, an asteroid impact is an outworldly threat, not quite catalyzed by deliberate greed, misinformation, and denialism. How we conceive of and respond to existential threats is a matter of money, resources, political will, and the ability to articulate a crisis that is the product of
For now, we’ve managed to make progress with at least one of these competing catastrophes. The scientists will observe the test over the next few weeks to confirm if the asteroid’s path was indeed changed with the force of impact. How do you measure a collision’s impact on an asteroid? Tom Statler, DART’s program scientist, explained in 2020: “The orbit of Dimorphos around Didymos is just like a ticking clock. Every 12 hours, it goes around and around, always the same. What we’re doing with DART is whacking the clock.” Now, scientists will measure how fast the clock ticks, and if all goes well, the orbital period should change by 10 minutes.
“It was basically a bullseye. I think, as far as we can tell, the first planetary defense test was a success, and we can clap to that,” deputy program manager Elena Adams said. Humanity’s prospects against a giant asteroid slamming into Earth are indeed looking good.