On September 11, 2022, a flight control center in Turin, Italy, sent a radio signal into deep space. This signal was directed at NASA’s DART spacecraft, which was on its way to an asteroid over 5 million miles away. This command triggered the spacecraft to release a small satellite called LICIACube, contributed by the Italian Space Agency (ASI).
Fifteen days later, DART intentionally collided with asteroid Dimorphos. LICIACube zoomed past it to capture the only images of this groundbreaking moment. Scientists from NASA and ASI recently published their findings from LICIACube’s photos in the Planetary Science Journal. They estimated that the collision released around 35.3 million pounds (16 million kilograms) of dust and rocks, which revised earlier estimates based on distant observations.
Although this debris was less than 0.5% of Dimorphos’ total mass, it was still a staggering 30,000 times heavier than DART. The debris altered Dimorphos’ path significantly; the force from the debris was actually several times stronger than the impact from DART itself. “The plume of material released from the asteroid was like a short burst from a rocket engine,” said Ramin Lolachi, a research scientist at NASA.
This mission showed that a small spacecraft can change the course of an asteroid, particularly “rubble-pile” asteroids like Dimorphos, which are loosely held together by gravity. Dave Glenar, a planetary scientist, noted that understanding the effects of the debris plume is essential for future asteroid defense missions.
NASA selected Dimorphos, a harmless target, because it orbits Didymos, a larger asteroid. This close relationship allowed scientists to measure the time taken for Dimorphos to orbit Didymos. After the collision, they found that DART had shortened the moonlet’s orbit by 33 minutes, but earlier observations were too far away to analyze the debris in detail. That was LICIACube’s job.
LIICIACube had only 60 seconds to take its critical images as it sped past Dimorphos at 15,000 miles per hour. It captured pictures of the debris about every three seconds, with the closest shot taken just 53 miles from the asteroid’s surface. This close approach allowed for detailed imaging of the debris cloud.
Initial images showed a bright plume, indicating it was mostly composed of larger particles. As the camera moved, sunlight illuminated the debris, revealing its structure. The scientists estimated that nearly 45% of the material in the plume was hidden due to its thickness, using models and data from other rubble-pile asteroids for reference.
While DART proved that a collision can adjust an asteroid’s trajectory, not all asteroids will react the same way. Timothy Stubbs, a planetary scientist, reminded us that different types of asteroids, especially those denser and more rigid, may respond differently. “Every time we interact with an asteroid, we find something that surprises us,” he said. “But DART is a significant step in planetary defense.”
The DART mission was managed by the Johns Hopkins Applied Physics Laboratory for NASA’s Planetary Defense Coordination Office.
For more about planetary defense efforts, you can check out the NASA Planetary Defense Coordination Office.
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Asteroids, DART (Double Asteroid Redirection Test), Didymos & Dimorphos, Goddard Space Flight Center, Planetary Defense, Planetary Science, The Solar System
