In 2022, NASA’s Double Asteroid Redirection Test (DART) spacecraft made history when it collided with Dimorphos, a moon orbiting the asteroid Didymos. This groundbreaking mission was intended to demonstrate Earth’s ability to defend itself from potential asteroid threats, but it achieved much more than anyone had predicted. According to a new study, the collision with Dimorphos caused a dramatic reshaping of the moon, creating a large crater and permanently altering its trajectory through space. These unforeseen consequences could have lasting implications for our understanding of how small celestial bodies form, evolve, and respond to external impacts.
Dimorphos: The Unexpected Fallout of a Cosmic Collision
Led by Derek Richardson, an astronomy professor at the University of Maryland, the study published in the Planetary Science Journal on August 23, 2024, revealed the surprising aftermath of the DART mission. Before the impact, Dimorphos was believed to be oblate, shaped like a hamburger, and aligned with its parent body, Didymos. However, post-impact observations showed that the moon had stretched into a prolate shape, more like a football, derailing it from its evolutionary course.
This shift in shape wasn’t just a cosmetic change. The impact disrupted the gravitational balance between Dimorphos and Didymos, potentially setting Dimorphos into chaotic tumbling as it struggles to regain its gravitational equilibrium. “We had expected the impact to alter the moon’s orbit, but the extent of the shape change and its effects on the system took us by surprise,” Richardson explained. This discovery opens up new lines of inquiry into how asteroid moons interact with their parent bodies and evolve over time.
Gravity’s Tug-of-War: How DART Knocked Dimorphos Out of Balance
Although the DART spacecraft struck only Dimorphos, the collision affected the entire system. The force of the impact, combined with the scattering of debris, shortened Dimorphos’ orbit around Didymos, further unbalancing the duo. Intriguingly, while Dimorphos experienced dramatic changes, Didymos remained largely unaffected. Its sturdy, rigid structure stayed intact, shedding light on the different ways celestial bodies respond to collisions and mass loss.
Richardson noted that Dimorphos had likely been in a state of equilibrium before the impact, with one side always facing Didymos, much like how Earth’s moon always shows the same face to us. But now, the moon is knocked out of alignment, possibly tumbling unpredictably through space. “We may have caused it to rotate chaotically, which raises questions about how long it will take to stabilize,” Richardson said. The team now waits to see when the debris from the collision will settle and whether Dimorphos will regain its former steady rotation.
Shaping the Future of Asteroid Defense and Exploration
This mission is far from over. The European Space Agency’s upcoming Hera mission, scheduled to arrive at the Didymos system in 2026, will conduct a more in-depth investigation of the impact’s effects. Hera will provide detailed analyses of Dimorphos’ internal properties and assess how the collision may have altered the moon’s structure permanently. Understanding these changes could be crucial for future asteroid deflection missions.
Dimorphos’ chaotic state presents unique challenges for future exploration. One critical question is whether the moon will be stable enough for spacecraft to land on it and deploy research equipment. “It could take decades for Dimorphos to fully stabilize, but what we’re learning now could one day be key to saving Earth from a hazardous asteroid,” Richardson said.
The knowledge gained from the DART mission and Hera’s forthcoming analysis will inform our strategies for planetary defense. While the threat of an asteroid collision with Earth remains uncertain, the DART mission has added an essential tool to our arsenal against potential space-based dangers. “There’s a nonzero chance that an asteroid could endanger Earth in the future,” Richardson emphasized. “This mission helps us prepare for such threats and strengthens our ability to protect the planet.”
As we await the next chapter of this cosmic saga, one thing is clear: DART’s mission to nudge an asteroid was more than a successful experiment—it was a leap forward in our quest to safeguard Earth. The story of Dimorphos and Didymos reminds us that space is unpredictable, but with cutting-edge science and international collaboration, we may have what it takes to stand up to the universe’s greatest threats.
