NASA’s DART Mission Successfully Redirects Asteroid Moonlet in Space
On September 26, 2022, a momentous event occurred in space: the Double Asteroid Redirection Test (DART) spacecraft, sent by NASA, slammed into the asteroid moonlet Dimorphos at 13,000 miles per hour. This impact, which covered 7 million miles, changed the extraterrestrial rock’s orbit around its larger companion asteroid, Didymos. It was the first proof of concept for kinetic impactors—spacecraft which could be used to redirect any future asteroids on a collision course with Earth.
The 525-foot-wide (160 meters) Dimorphos orbits the 780 meter-wide Didymos roughly once every 11.9 hours. It was anticipated that the DART collision would modify the orbital period by approximately 7 minutes. However, researchers analyzing data from the experiment calculated that material ejected from Dimorphos's surface during the collision changed its momentum by a greater amount than DART's impact, pushing Dimorphos into a new orbit that shortened its period by 33 minutes, give or take 1 minute.
The success of the mission is an incredible boon, as it shows that redirecting asteroids and other cosmic bodies like them is possible. This is exceptionally useful if an earth-threatening asteroid is detected, as we could recreate the DART collision in a way to change its orbit.
The aftermath of the collision was observed by the Hubble Space Telescope, which captured the debris being swept back into a comet-like tail by the pressure of sunlight on the tiny dust particles. 17 hours later, dynamic interactions between Didymos and Dimorphos had distorted the cone shape of the ejecta and formed rotating, pinwheel-shaped features.
Launching in October 2024, the European Space Agency's Hera mission will return to the Didymos-Dimorphos system to assess the outcomes of the DART experiment. Of particular interest is the resulting crater and the object’s rotation state. Hera will investigate these and other outstanding questions.
In conclusion, the DART mission has been an immense success, proving that it is possible to change the motion of a natural object in space. This is an invaluable step in planetary defense, as it gives us the ability to protect Earth from potential asteroid impacts.
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