Why Does a NASA Spacecraft Crash on an Asteroid?


CAPE CANAVERAL, Fla. (TSWT) – In the first of its kind, save-the-world experiment, NASA is about to strike a small, harmless asteroid millions of miles away.

A spacecraft named Dart will approach the asteroid Monday, with the intention of hitting it head-on at 14,000 mph (22,500 km/h). The impact should be just enough to push the asteroid into a slightly tighter orbit around its companion space rock — showing that if a deadly asteroid is heading our way, we have a good chance of distracting it.

“This is stuff from science fiction books and really corny “StarTrek” episodes from when I was a kid, and now it’s real,” NASA program scientist Tom Statler said Thursday.

Cameras and telescopes will watch the crash, but it will take days or even weeks to find out if the orbit has actually changed.

The $325 million planetary defense test began with Dart’s launch last fall.


The asteroid with the bullseye is Dimorphos, about 7 million miles (9.6 million kilometers) from Earth. It’s actually the puny sidekick of a 2,500-foot (780-meter) asteroid named Didymos, Greek for twin. Didymos, discovered in 1996, spins so fast that scientists believe it flung out material that eventually formed a moon. Dimorphos – about 160 meters wide – orbits its mother body at a distance of less than 1.2 kilometers.

NASA insists there is a zero chance that an asteroid will threaten Earth — now or in the future. That’s why the couple was chosen.

Asteroid Strike Explainer


The Johns Hopkins lab took a minimalist approach to developing Dart – short for Double Asteroid Redirection Test – as it is essentially a battering ram and is headed for some sort of destruction. It has a single instrument: a camera that is used to navigate, aim and capture the final action. Assuming it’s essentially a mess, Dimorphos will emerge as a bright spot an hour before the impact, looming larger and larger in the camera images beamed back to Earth. Managers are confident that Dart will not accidentally slam into the bigger Didymos. The spacecraft’s navigation is designed to differentiate between the two asteroids and target the smaller one in the last 50 minutes.

The size of a small automaton weighing 1,260 pounds (570 kilograms), the spacecraft will land in about 11 billion pounds (5 billion kilograms) asteroid. “Sometimes we describe it as driving a golf cart into a Great Pyramid,” Chabot said.

Unless Dart misses — NASA estimates the odds of that happening to be less than 10% — it will be the end of the road for Dart. If it goes past both space rocks, it will run into them again in a few years for Take 2.


The little Dimorphos circles the big Didymos every 11 hours and 55 minutes. Dart’s impact should be about 10 minutes away from that. While the attack itself should be immediately apparent, it could take several weeks or more to verify the moonlet’s modified orbit. Cameras on Dart and a mini tagalong satellite will capture the collision up close. Telescopes on all seven continents, along with the Hubble and Webb space telescopes and NASA’s asteroid-hunting Lucy spacecraft, can see a bright flash when Dart rams Dimorphos, sending streams of rock and debris into space. The observatories will track the pair of asteroids as they orbit the sun, to see if Dart has changed Dimorphos’ orbit. In 2024, a European spacecraft called Hera will track Dart’s journey to measure impact results.

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While the intended push should only slightly change the moon’s position, Chabot says that will lead to a major shift over time. “So if you were doing this for planetary defense, you’d be doing it five, 10, 15, 20 years in advance for this technique to work,” she said. Even if Dart misses, the experiment will still provide valuable insight, said Andrea Riley, director of the NASA program. “That’s why we test. We want to do it now rather than when there is a real need,” she said.


Planet Earth is on an asteroid chase roll. NASA has collected nearly a pound (450 grams) of debris from asteroid Bennu en route to Earth. Stock should arrive in September. Japan was the first to retrieve asteroid samples, completing the feat twice. China hopes to follow suit with a mission to be launched in 2025. NASA’s Lucy spacecraft, meanwhile, is heading for asteroids near Jupiter, after launching last year. Another spacecraft, Near-Earth Asteroid Scout, is being loaded into NASA’s new moon rocket awaiting launch; it will use a solar sail next year to fly past a space rock that is less than 18 meters. In the coming years, NASA also plans to launch a counting telescope to identify hard-to-find asteroids that may pose risks. One asteroid mission is grounded as an independent review committee weighs the future. NASA’s Psyche spacecraft should have launched this year to a metal-rich asteroid between Mars and Jupiter, but the team was unable to test the flight software in time.

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Hollywood has made dozens of killer space rock movies over the decades, including 1998’s “Armageddon,” which brought Bruce Willis to Cape Canaveral to film, and last year’s “Don’t Look Up” starring Leonardo DiCaprio all-star cast. NASA’s planetary defense officer, Lindley Johnson, thinks he’s seen them all since “Meteor” in 1979, his personal favorite “since Sean Connery played me.” While some sci-fi movies are more accurate than others, he noted, entertainment always wins out. The good news is that the coast looks safe for the next century, with no known threats. Otherwise, “it would be just like the movies, right?” said NASA’s head of the science mission, Thomas Zurbuchen. However, what is worrisome are the unknown threats. Less than half of the 460-foot (140-meter) objects have been confirmed, with millions of smaller but still dangerous objects zooming around. “These threats are real, and what makes this time special is that we can do something about it,” Zurbuchen said. Not by blowing up an asteroid like Willis’ character did—that would be a last-minute, last-minute resort—or begging government leaders to take action as DiCaprio’s character did in vain. Time permitting, the best tactic may be to push the impending asteroid out of our way, such as Dart.

The The Switzerland Times Health and Science Department is supported by the Howard Hughes Medical Institute’s Department of Science Education. The TSWT is solely responsible for all content.



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