Telescopes in space and around the world have captured the spectacular aftermath of NASA’s DART spacecraft crashing into the asteroid Dimorphos on September 26th. The explosion was “the first human experiment to deflect a celestial body,” says Thomas Zurbuchen, NASA’s Associate Administrator for Science, and “a tremendous success.”
“We’re all pretty excited here,” says Andy Rivkin, a planetary scientist working on the mission at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland.
A ringside view came from LICIACube, a tiny Italian spacecraft that flew with DART and photographed the impact, which took place 11 million kilometers from Earth. The first images from LICIACube, released by the Italian Space Agency on September 27, show a large, firework-like cloud emanating from Dimorphos after DART flew into it. The cloud of rocks and other debris quickly expanded like a huge plume of smoke.
Studying the evolution of the cloud will shed light on the physical properties of Dimorphos, Elisabetta Dotto, leader of the LICIACube science team at the National Institute of Astrophysics in Rome, told a news conference. By analyzing how the cloud formed and dispersed, the researchers can calculate how much of DART’s kinetic energy went into ejecting debris from Dimorphos, and how much may have gone into changing the asteroid’s orbit — the goal the mission.
The spaceship itself is broken. “A lot of it gets pulverized and some of it gets melted,” says Megan Bruck Syal, a physicist at Lawrence Livermore National Laboratory in California. “Hard to say, but I don’t think there will be big chunks left.”
This spaceship has just crashed into an asteroid to change its orbit
LICIACube, Italy’s first space mission, used an autonomous guidance technique to keep its cameras trained on Dimorphos as it whizzed by just 55 kilometers from the asteroid after the DART crash. It used two cameras, a black and white camera called LEIA and a three color camera called LUKE, to photograph Dimorphos before and after the crash. The images show a dramatic brightening at the time of impact, then the cloud expands and drifts outward over the following minutes. The intricate structures in the debris plume — almost “spiny” in places, says Bruck Syal — will help modelers understand exactly how the impact unfolded.
More than 600 images are still on board LICIACube, waiting to be downloaded to Earth in the coming weeks.
A “great jumble of stones”
The DART, which is the size of a golf cart, hit its Great Pyramid-sized target at 7:14 p.m. Eastern Time. The first images from LICIACube arrived at a control center in Turin, Italy, just over three hours later.
Despite the huge cloud of ejected debris, Dimorphos remains mostly intact. Ground telescopes confirmed this by capturing other views of the impact Show the cloud blowing outward as the rest of the asteroid races forward. Dimorphos is currently visible mostly from the southern hemisphere, hence those early observations came from telescopes in places like South Africa and Réunion Island in the Indian Ocean. Dozens of telescopes continue to monitor it to see if its trajectory has changed.
Record number of asteroids whizzing past Earth in 2020
It will be days to weeks before astronomers can confirm whether DART has achieved its primary goal, which is the time it takes for Dimorphos to shorten its partner asteroid Didymos by perhaps 10 minutes or more. None of the asteroids pose a threat to Earth, but the point of the test is to see if humanity could actually change the trajectory of an asteroid should a dangerous space rock heading towards Earth be discovered in the future.
Dimorphos had never been seen up close prior to the arrival of DART. As the spacecraft zoomed in closer and closer, it discovered that Dimorphos is an egg-shaped asteroid. DART captured a series of images during its descent that show the asteroid is also covered in boulders. “It’s clearly a pile of rubble,” says Rivkin. “Just a big jumble of stones.”