NASA’s Asteroid-Deflection Mission focuses on planetary defense efforts

Can the National Aeronautics and Space Administration shift an asteroid’s orbit by smashing into it with a fast-moving spacecraft? The agency may find out on Monday, when a bus-sized craft traveling at a speed of more than 14,000 miles per hour tries to hit a 525-foot-wide space rock.

The expected collision between the unmanned spacecraft and the asteroid, named Dimorphos, marks the climactic moment for NASA’s $325 million Double Asteroid Redirection Test mission. DART is the world’s first mission to test a technology that could one day protect Earth from a catastrophic asteroid impact.

Double Asteroid Redirection Test

NASA plans to smash a spacecraft into Dimorphos, a small asteroid orbiting a larger one called Didymos, to change Dimorphos’ orbit.

Dimorphos pose no threat to our planet. It will be millions of miles away at the moment of impact – expected Monday at 7:14 p.m. ET. But an asteroid that size could cause a “natural disaster on a scale we’ve never seen before” if it hits a populated area, causing tens of billions of dollars in damage and human casualties, NASA’s planetary defense officer said. Lindley Johnson.

More than a million asteroids, varying in size, shape and composition, are known to move in different orbits around the sun. None are known to be on a collision course with Earth in the next century, according to NASA. But planetary defense remains a focus of the agency.

Andrew Cheng, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., and a research team leader for DART, said the mission reflects a change in thinking about the threat posed by asteroids.

“Ten years ago, certainly 20 years ago, there was a big laugh factor” about the idea that we could defend the planet from asteroids, said Dr. Cheng. “But we’ve moved beyond that.” People understand not only that the danger is real, he added, but that “the opportunity to do something about it is also real, and that’s DART.”

Concern about the threat posed by asteroids is fueled in part by past asteroid strikes, including some that have had dramatic consequences. An impact from a 6-mile-wide space rock played a role in the extinction of the dinosaurs tens of thousands of years ago. In 2013, a roughly 60-foot fireball hit Russia, damaging thousands of buildings and injuring about 1,500 people. Scientists believe an asteroid up to 10 times larger flattened 800 square kilometers of remote Siberian forest in 1908.

A SpaceX Falcon 9 rocket exploded with the DART spacecraft on board last November.


Bill Ingalls/NASA

“These objects hurtling through space have, of course, scarred the face of the moon, and over time, on Earth as well, had major consequences and influenced our history,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate, at a recent press briefing . There will be more such impacts “if you wait long enough,” added Dr. Zurbuchen.

Congress mandated in 2005 that NASA find and track 90% of all asteroids and comets larger than 140 meters in size whose orbits can bring them within 30 million miles of Earth’s orbit. Less than half of these so-called near-Earth objects are believed to have been discovered, in part because many of them are difficult to see with ground-based telescopes because they reflect so little light.

Photos: NASA’s DART mission to redirect a distant asteroid

“We have a huge blind spot for asteroids that are in the intermediate size range,” said Megan Bruck Syal, the director of the Planetary Defense Project at Lawrence Livermore National Laboratory in California and a co-investigator on the DART mission.

Mission scientists monitoring the DART spacecraft expect its collision with Dimorphos to transfer enough momentum to change the asteroid’s orbit by about 1%.

“You’re just trying to change it by a very, very small amount,” said DART coordination manager Nancy Chabot, a planetary scientist at Johns Hopkins APL who built and oversees the operation of the DART spacecraft at the direction of NASA’s Planetary Defense Coordination Office .

In order for this so-called kinetic-impactor technology to work, added Dr. Chabot, space agencies need to be able to spot a dangerous asteroid early enough to take a mission. “This is not something you go up and do at the last minute,” she said. “You want to do this five, 10, 15, 20 years in advance” of an expected collision.

NASA’s DART spacecraft will deliberately collide with an asteroid on Monday in an attempt to alter the space rock’s trajectory. The mission aims to test technology that can defend Earth against potential asteroid threats. Photo illustration: NASA and Laura Kammermann

That’s where another one of NASA’s planetary defense efforts comes in: the Near-Earth Object Surveyor space telescope, whose infrared imaging capabilities should make it possible to spot asteroids more easily and determine their sizes and orbits more quickly, according to NASA’s Mr. Johnson. The agency is on track to launch it by 2028 at the latest, he said, despite budget cuts that played a role in delaying the space telescope’s launch date by two years.

“I hope that DART is a catalyst for this – to get the telescope approved and flying soon,” said Dr. Bruck Syal. “NASA obviously has to balance a lot of competing priorities, but planetary defense is something that everyone can connect with on a visceral level.”

Planetary defense was included in the National Academies of Sciences, Engineering, and Medicine’s Planetary Decadal Survey released in April. This study, prepared at NASA’s request every 10 years, recommends science and funding priorities for the coming decade. The agency’s annual planetary defense budget was 40 times larger in 2019 compared to 2009, according to the Planetary Society, a California-based nonprofit that promotes space exploration.

Johnson said the agency is considering other ideas for deflecting or destroying dangerous asteroids, adding that the kinetic-impactor technique to be tested by the DART mission “should be just one tool in the toolbox.”


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Other possible approaches include shooting asteroids with ion beams or altering their orbits using a so-called gravity tractor — a spacecraft that looms near an asteroid and exerts a gravitational pull on the space rock for an extended period of time. Sending a spacecraft to detonate a nuclear device near an incoming asteroid to break it up on short notice also remains an option under consideration, according to Dr. Bruck Syal.

NASA will live stream the climax of its DART mission on Monday, beginning about an hour and 15 minutes before the expected collision.

Write to Aylin Woodward at

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