Didymos Asteroid Slows Down After Impact Test

By Space.Fan Editorial DeskOctober 4, 2026 at 5:02 AM UTC

Scientists found that the main asteroid Didymos changed its rotation speed after the DART mission impacted its smaller moon.

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The Drop

In 2022, NASA’s DART mission crashed into Dimorphos, a small orbiting a larger called Didymos. The goal was to test if we could change an ’s path. While the impact was aimed at the smaller , new data shows the main , Didymos, also felt the effects. Scientists noticed that Didymos ted spinning a tiny bit slower than it did before the mission. To figure out why, researchers used a math model to study the ’s movement. They think the crash caused a lot of dust and rocks, called ejecta, to fly off the surface. As this loose material moved around and reshaped the , it caused the larger body to change how it spins. The team calculated that if enough material shifted on the surface, it could account for the change in rotation speed that we saw through telescopes. This is a complex puzzle because the is not a solid rock but a collection of loose material that can move when hit.

Why It Matters

Understanding how Didymos reacts to an impact helps us learn more about what s are made of. Since we know s are often loose piles of rubble, seeing how they reshape themselves helps scientists predict how they might behave in the future. This confirms that even distant impacts can have ripples that affect the whole system, not just the target that was hit directly.

The Catch

While the model explains the spin-down, it struggles to explain everything. The system experienced an extra change in its orbital path later on that the current model cannot fully account for. This means there might be other forces at work that scientists do not yet understand, and the current calculations for how much surface material actually moved remain estimates rather than direct measurements.

Put That in Perspective

This study is a precursor to the upcoming visit from the European Space Agency's Hera mission. Hera is currently traveling toward the Didymos system and will eventually arrive to take a close look. Its cameras and sensors will provide the first direct evidence to verify if these mathematical models accurately predicted how the asteroid changed its shape.

Source October 4, 2026

PSJ

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