On Monday, in a scene from a sci-fi movie, NASA will ram a spacecraft into a distant asteroid to see if it can bump into its orbit – all in an effort to test a way to protect Earth from possible future threats to protect .
The good news is that there’s no need to panic: The asteroid, part of a binary – or two-body – system poses no threat to our planet, and at least none are known to be heading in the next 100 years. However, space agencies like the US National Aeronautics and Space Administration want to be prepared should a threat ever arise.
NASA’s Double Asteroid Redirection Test (DART) is testing a way for a spacecraft to de-orbit an asteroid on a collision course with Earth.
At 7:14 p.m. ET Monday, the refrigerator-sized spacecraft will plunge at about 4 miles per second into Dimorphos — a small moon orbiting its larger companion Didymos.
The goal is not to knock Dimorphos out of orbit, but to change its 12-hour orbit around Didymos by 10 minutes. That means scientists will know if they’ve succeeded within about 12 hours.
So why target a binary asteroid system rather than a single asteroid to see if you can change its orbit around the sun?
“A binary system was perfect for this test,” said Mallory DeCoster, a senior scientist at the Applied Physics Laboratory at Johns Hopkins University in Maryland and a member of the DART Impact Modeling Working Group.
For one, the size of Dimorphos – about 164 meters in diameter – is perfect for illustrating whether it would be an effective means of deflecting asteroids that pose a threat to Earth. Didymos has a diameter of 780 meters.
“But the other piece is, if we were to hit a single asteroid to characterize whether we’re changing its orbit, we’d have to wait for it to complete its orbit around the Sun, which could take many, many years.”
The other advantage is that the binary star system is relatively close to us astronomically, at only 11 million kilometers.
NASA’s Center for Near-Earth Object Studies says more than 90 percent of near-Earth objects (NEOs) larger than one kilometer have already been discovered. But that doesn’t mean we’re out of the woods when it comes to potentially hazardous asteroids (PHAs).
In 2013, the Chelyabinsk asteroid, about 20 meters in diameter, exploded over parts of Russia, injuring about 1,000 people and serving as a reminder of how dangerous even a small asteroid can be.
Basically, Earth flies through a shooting gallery in space. There are small pieces of debris that burn up in our atmosphere as meteors; larger ones like Chelyabinsk; and then larger ones that can be catastrophic—all remnants of the formation of our solar system.
Because of this, space agencies like NASA and the European Space Agency have tried to devise ways to deflect or nudge a PHA to change its orbit and not pose a threat to Earth.
Mike Daly, a professor at York University’s Lassonde School of Engineering in Toronto and a co-investigator at DART, said one of the most popular concepts is to deflect asteroids before they become a real threat. But that means we need to be warned in advance that one is coming our way.
“So the simplest method is that of DART, which basically consists of crashing a spacecraft into the asteroid at high speed and using that energy transfer from the spacecraft to the asteroid to keep it moving,” he said.
However, the science behind deflecting asteroids in this way is more than just the combination of the spacecraft’s size and incredibly high speed, known as hypervelocity impact.
“In a hypervelocity impact, you induce this pressure wave into the target, which causes a lot of new physics to happen,” said DeCoster of Johns Hopkins University.
“So what’s going to happen, or what we think will happen, is that the size of the spacecraft might not actually matter that much. It could actually be: how does the asteroid react to this pressure wave induced by the hypervelocity impact? And we think it’s likely to expel a lot of material in the form of ejecta. And this ejecta might actually have an important component in changing the orbit. So much ejecta could be ejected that this piece may be more important than the incoming energy from the spacecraft in changing its orbit.”
The DART team is hoping an onboard camera called DRACO will show the approach and then suddenly go black, indicating an impact.
But there’s one latecomer that’s about three minutes behind DART: the Italian Space Agency’s Light Italian Cubesat for Imaging of Asteroids, or LICIACube. His job is to photograph the impact, study the ejection plume, and help determine the asteroid’s morphology, as they may be made of iron, rock, or just lumps of rock held together by gravity.
As this is the first test of some form of planetary defense, scientists are excited not only about the implications of the event itself, but what they will learn from it, and most importantly, what this means for the future of protecting Earth in the could mean future. Telescopes from around the world will observe the event and collect follow-up data.
“We’re really the first generation that can protect ourselves from these potentially catastrophic impacts,” said Daly of York University. “And, you know, fortunately, the really catastrophic ones don’t happen very often, but they could happen, and never before have we been able to change our fate. So I think it’s really up to us given the potentially huge consequences of not being careful and our ability to do it.”
The event will be broadcast on NASA TV, available online and through its app.