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How did the DART mission change Dimorphos’s orbit?

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Illustration showing a massive asteroid above a city map with a dinosaur silhouette for scale, highlighting the asteroid's size compared to major urban areas. — Asteroid This rock would take out more than just a *T. rex*.

The Double Asteroid Redirection Test (DART) mission successfully demonstrated the ability to alter an asteroid's trajectory as a method of planetary defense.

Prior to the impact on September 26, 2022, Dimorphos orbited the larger asteroid Didymos with an orbital period of 11 hours and 55 minutes. Mission scientists defined a successful test as an orbital period change of at least 73 seconds. Following the collision, the orbital period was reduced to 11 hours and 23 minutes, representing a change significantly greater than the initial goal.12

This substantial shift in the orbital period was not caused solely by the kinetic impact of the spacecraft. The momentum transfer was significantly enhanced by the ejection of tons of material from the asteroid upon impact. Furthermore, the collision resulted in the redistribution of approximately eight percent of Dimorphos’s mass, which significantly altered the asteroid's physical shape.12