NASA DART impact shortens asteroid Dimorphos' orbit by 33 minutes
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NASA's DART spacecraft collided with asteroid Dimorphos on September 26, 2022, in a test of planetary defense. The impact shortened the asteroid's orbit around Didymos by 33 minutes, researchers report in Nature, far surpassing the mission's minimum success threshold of 73 seconds.
The Impact
The 580-kilogram DART spacecraft struck the 150-meter rubble-pile asteroid Dimorphos at 6 kilometers per second. NASA set a success benchmark of a 73-second change in the asteroid's orbit around Didymos. Initial analysis showed a 32-minute shortening; subsequent research led by Cristina Thomas in Nature refined the figure to 33 minutes.
Momentum Enhancement
A direct momentum transfer from the spacecraft would have shortened the orbit by roughly 7 minutes. The additional 26 minutes came from recoil produced by the impact-ejected debris. Andrew Cheng and colleagues calculated a momentum enhancement factor of about 3.6, meaning the ejecta plume pushed harder than the spacecraft itself.
Reshaping and Ejected Debris
Shantanu Naidu's follow-up study found the impact reshaped Dimorphos from a squashed sphere into a lumpier body on a non-circular orbit. Hubble observations identified 37 boulders up to 7 meters across drifting away at just over 1 kilometer per hour. Modeling by Marco Fenucci and A. Carbognani suggests the debris swarm could cross Mars' orbit repeatedly over 20,000 years, with a chance of eventual impact.
What's Next
NASA and its partners continue to analyze DART data to refine deflection strategies for potential future threats. It remains unclear how a similar kinetic impactor would perform on a more solid asteroid, and no imminent asteroid threat has been identified.
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NASA DART impact shortens asteroid Dimorphos' orbit by 33 minutes
