NASA on Monday accomplished a feat humanity never before attempted: deliberately smacking a spacecraft into an asteroid to slightly deflect its orbit, in a key test of our ability to stop cosmic objects from devastating life on Earth.
The Double Asteroid Redirection Test (DART) spaceship launched from California last November and hit its target, which posed no threat to Earth, at roughly 14,000 miles (22,500 kilometers) per hour.
The galactic slam occurred 7 million miles (11.3 million kilometers) away. Scientists expected the impact to carve out a crater, hurl streams of rocks and dirt into space and, most importantly, alter the asteroid’s orbit.
“We have impact!” Mission Control’s Elena Adams announced, jumping up and down and thrusting her arms skyward.
Telescopes around the world and in space aimed at the same point in the sky to capture the spectacle. Though the impact was immediately obvious — DART’s radio signal abruptly ceased — it will take as long as a couple of months to determine how much the asteroid’s path was changed.
The $325 million mission was the first attempt to shift the position of an asteroid or any other natural object in space.
“As far as we can tell, our first planetary defense test was a success,” Adams later told a news conference, the room filling with applause. “I think Earthlings should sleep better. Definitely, I will.”
IMPACT SUCCESS! Watch from #DARTMIssion’s DRACO Camera, as the vending machine-sized spacecraft successfully collides with asteroid Dimorphos, which is the size of a football stadium and poses no threat to Earth. pic.twitter.com/7bXipPkjWD
— NASA (@NASA) September 26, 2022
NASA Administrator Bill Nelson reminded people earlier in the day via Twitter that, “No, this is not a movie plot.” He added in a prerecorded video: ”We’ve all seen it on movies like ‘Armageddon,’ but the real-life stakes are high.”
Monday’s target: a 525-foot (160-meter) asteroid named Dimorphos. It’s a moonlet of Didymos, Greek for twin, a fast-spinning asteroid five times bigger that flung off the material that formed the junior partner. DART was around the size of a vending machine.
To be sure, neither Dimorphos nor the big brother it orbits pose any threat as the pair loop the Sun, passing about 7 million miles from Earth at nearest approach.
But NASA has deemed the experiment important to carry out before an actual need arises.
By striking Dimorphos head-on, NASA hopes to push it into a smaller orbit, shaving ten minutes off the time it takes to encircle Didymos, which is currently 11 hours and 55 minutes — a change that will be detected by ground telescopes in the days or weeks to come.
DART’s on-board camera, a key part of this smart navigation system, caught sight of Dimorphos barely an hour before impact. “Woo hoo!” exclaimed Adams, a mission systems engineer at Johns Hopkins.
With an image beaming back to Earth every second, Adams and other ground controllers in Laurel, Maryland, watched with growing excitement as Dimorphos loomed larger and larger in the field of view alongside its bigger companion. Within minutes, Dimorphos was alone in the pictures; it looked like a giant gray lemon, but with boulders and rubble strewn on the surface. The last image froze on the screen as the radio transmission ended.
Flight controllers cheered, hugged one another and exchanged high fives. Their mission complete, the DART team went straight into celebration mode. There was little sorrow over the spacecraft’s demise.
“Normally, losing signal from a spacecraft is a very bad thing. But in this case, it was the ideal outcome,” said NASA program scientist Tom Statler.
Johns Hopkins scientist Carolyn Ernst said the spacecraft was definitely “kaput,” with remnants possibly in the fresh crater or cascading into space with the asteroid’s ejected material.
A toaster-sized satellite called LICIACube, which already separated from DART a few weeks ago, will make a close pass of the site to capture images of the collision and the ejecta — the pulverized rock thrown off by impact.
LICIACube’s pictures will be sent back in the next weeks and months.
A full picture of what the asteroid system looks like will be revealed when a European Space Agency mission four years down the line called Hera arrives to survey Dimorphos’ surface and measure its mass, which scientists can currently only guess at.
How much momentum DART imparted on Dimorphos will depend on whether the asteroid is solid rock, or more like a “rubbish pile” of boulders bound by mutual gravity — a situation that’s not yet known.
Scientists said DART would not shatter Dimorphos. The spacecraft packed a scant 1,260 pounds (570 kilograms), compared with the asteroid’s 11 billion pounds (5 billion kilograms). But that should be plenty to shrink its 11-hour, 55-minute orbit around Didymos.
The anticipated orbital shift of 1% might not sound like much, scientists noted. But they stressed it would amount to a significant change over years.
“Now is when the science starts,” said NASA’s Lori Glaze, planetary science division director. “Now we’re going to see for real how effective we were.”
The mission marked the first step toward a world capable of defending itself from a future existential threat.
Planetary defense experts prefer nudging a threatening asteroid or comet out of the way, given enough lead time, rather than blowing it up and creating multiple pieces that could rain down on Earth. Multiple impactors might be needed for big space rocks or a combination of impactors and so-called gravity tractors, not-yet-invented devices that would use their own gravity to pull an asteroid into a safer orbit.
“The dinosaurs didn’t have a space program to help them know what was coming, but we do,” NASA’s senior climate adviser Katherine Calvin said, referring to the mass extinction 66 million years ago believed to have been caused by a major asteroid impact, volcanic eruptions or both.
An asteroid the size of Dimorphos would only cause a regional impact, such as devastating a city, albeit with greater force than any nuclear bomb in history.
The non-profit B612 Foundation, dedicated to protecting Earth from asteroid strikes, has been pushing for impact tests like DART since its founding by astronauts and physicists 20 years ago. Monday’s feat aside, the world must do a better job of identifying the countless space rocks lurking out there, warned the foundation’s executive director, Ed Lu, a former astronaut.
Significantly less than half of the estimated 25,000 near-Earth objects in the deadly 460-foot (140-meter) range have been discovered, according to NASA. And fewer than 1% of the millions of smaller asteroids, capable of widespread injuries, are known.
The Vera Rubin Observatory, nearing completion in Chile by the National Science Foundation and U.S. Energy Department, promises to revolutionize the field of asteroid discovery, Lu noted.
Finding and tracking asteroids, “That’s still the name of the game here. That’s the thing that has to happen in order to protect the Earth,” he said.