Why would a NASA spacecraft crash into an asteroid?

Why would a NASA spacecraft crash into an asteroid?

CAPE CANAVERAL, Fla. (AP) — In a first-of-its-kind, world-saving experiment, NASA is set to scan a small, harmless asteroid millions of miles away.

A spacecraft named Dart will zero in on the asteroid on Monday, aiming to hit it head-on at 14,000 mph (22,500 km/h). The impact should be enough to nudge the asteroid into a slightly tighter orbit around its space rock companion—proving that if a killer asteroid were ever headed our way, we’d have a fighting chance of deflecting it.

Cameras and telescopes will monitor the crash, but it will take months to know if it actually changed orbit.

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


The bull’s-eye asteroid is Dimorphos, about 7 million miles (9.6 million kilometers) from Earth. It is actually the sly sidekick of a 2,500-foot-long (780-meter) asteroid called Gemini, Greek for twin. Discovered in 1996, Gemini spins so fast that scientists believe it threw off material that eventually formed a moon. Dimorphos – about 525 feet (160 meters) wide – orbits its parent body at a distance of less than a mile (1.2 kilometers).

“This is really about asteroid deflection, not disruption,” said Nancy Chabot, a planetary scientist and mission team leader at Johns Hopkins University, which is managing the effort. “That’s not going to blow up the asteroid. It’s not going to put it into a lot of pieces.” Instead, the impact will dig a crater tens of yards (meters) in size and hurl about 2 million pounds (1 million kilograms) of rock and dirt into space. .

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


Johns Hopkins took a minimalist approach to developing Dart — short for Double Asteroid Redirection Test — since it’s essentially a battering ram and faces certain destruction. It has a single instrument: a camera used for navigation, aiming and recording the final action. Believed to be essentially a pile of rubble, Dimorphos will emerge as a point of light an hour before impact, appearing ever larger in camera images beamed back to Earth. Managers are confident the Dart won’t crash the larger Gemini by accident. The spacecraft’s navigation is designed to distinguish between the two asteroids and, in the last 50 minutes, target the smaller one.

The size of a small vending machine at 1,260 pounds (570 kilograms), the spacecraft will hit about 11 billion pounds (5 billion kilograms) of asteroids. “Sometimes we describe it as running a golf cart up a Great Pyramid,” Chabot said.

Unless Dart misses — NASA puts the odds of that happening at less than 10 percent — it will be the end of the road for Dart. If he comes screaming through both space rocks, he’ll meet them again in a few years for Take 2.


Little Dimorphos completes one lap around the big Gemini every 11 hours and 55 minutes. The impact from the Dart should shave about 10 minutes off that. Although the bump itself should be immediately apparent, it will take months to verify the moon’s adjusted orbit. Cameras on the Dart and a tagalong mini-satellite will record the collision up close. Telescopes on all seven continents, along with the Hubble and Webb space telescopes and NASA’s asteroid-hunting Lucy spacecraft, may see a bright flash as Dart slams into Dimorphos and sends streams of rock and dirt into space. The observatories will track the pair of asteroids as they circle the sun, to see if Dart has changed Dimorphos’ orbit. In 2024, a European spacecraft named Hera will retrace Dart’s journey to measure the effects of the impact.

Although the intended push should change the moon’s position slightly, it will add up to a significant change over time, according to Chabot. “So if you were going to do this for the defense of the planet, you would do it five, 10, 15, 20 years ahead of time for this technique to work,” he said. Even if Dart misses, the experiment will provide valuable insight, said NASA program manager Andrea Riley. “That’s why we’re testing. We want to do it now and not when there’s a real need,” he said.


Planet Earth is chasing asteroids. NASA has nearly a pound (450 grams) of debris collected from the Earth-bound asteroid Bennu. Stock should arrive next September. Japan was the first to retrieve asteroid samples, accomplishing the feat twice. China hopes to follow suit with a mission to launch in 2025. NASA’s Lucy spacecraft, meanwhile, is headed for asteroids near Jupiter after launching last year. Another spacecraft, the Near-Earth Asteroid Scout, is being loaded onto NASA’s New Moon rocket in anticipation of liftoff. will use a solar sail to fly past a space rock that is less than 18 meters next year. In 2026, NASA will launch a census telescope to locate elusive asteroids that could pose hazards. An asteroid mission is grounded while an independent review board weighs its future. NASA’s Psyche spacecraft was supposed to 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.


Hollywood has produced dozens of killer-space-rock movies over the decades, including 1998’s “Armageddon,” which brought Bruce Willis to Cape Canaveral for filming, and last year’s “Don’t Look Up,” starring Leonardo DiCaprio stars in all- star cast. NASA planetary defense officer Lindley Johnson thinks he’s seen them all since 1979’s “Meteor,” his personal favorite “since Sean Connery played me.” While some of the sci-fi movies are more accurate than others, he noted, entertainment always wins. The good news is that the coast looks clear for the next century, with no known threats. Otherwise, “it would be like the movies, right?” said NASA science mission chief Thomas Zurbuchen. But what is worrying are the unknown threats. Fewer than half of the 460-foot (140-meter) objects have been confirmed, with millions of smaller but still dangerous objects zooming by. “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 solution—or pleading with government leaders to take action like DiCaprio’s character did in vain. If time permits, the best tactic might be to push the threatening asteroid out of our way, like Dart.


The Associated Press Health and Science Section is supported by the Howard Hughes Medical Institute Science Education Division. AP is solely responsible for all content.

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