Asteroid Dimorphos changes its orbit as well as shape due to DART impact

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A new study led by NASA’s JPL (Jet Propulsion Laboratory) has shown that the asteroid Dimorphos has changed not only its orbit but also its shape due to the DART (Double Asteroid Redirection Test) impact mission.

Dimorphos is a satellite asteroid (moonlet asteroid) of diameter 560 feet (170 meters) that orbits a larger near-Earth asteroid Didymos.

NASA's DART spacecraft captured the asteroid Dimorphos just two seconds before its impact on September 26, 2022 — NASA’s DART spacecraft captured the asteroid Dimorphos just two seconds before its impact on the surface of Dimorphos on September 26, 2022. (Image credit: NASA/Johns Hopkins APL)

On September 26, 2022, NASA intentionally slammed the DART spacecraft into asteroid Dimorphos, and as a result, the asteroid changed its orbit.

The DART mission was the first planetary defense test mission of NASA, which demonstrated how the orbit of a near-Earth object can be shifted through kinetic impact (momentum transfer).

The DART mission technique will help us to protect our planet from a collision with an asteroid if we ever discover an asteroid headed our way. Please remember that DART’s target asteroid, Dimorphos, was not a threat to Earth. This mission was a test of technology.

Evolution of shape

The shape of the asteroid Dimorphos before and after the DART impact (artist’s illustration). (Image credit: NASA/JPL-Caltech)

Before the DART impact, the asteroid Dimorphos had a roughly symmetrical “oblate spheroid” shape – like a squashed ball that is wider than it is tall.

After the DART impact, “the entire shape of the asteroid has changed, from a relatively symmetrical object to a ‘triaxial ellipsoid’ – something more like an oblong watermelon.” according to the statement of Shantanu Naidu, a navigation engineer at NASA’s Jet Propulsion Laboratory in Southern California, who led the study.

Evolution of orbit

The orbit of the asteroid Dimorphos before and after the DART impact (artist’s illustration). (Image credit: NASA/Johns Hopkins APL)

Before the DART impact, Dimorphos had a circular orbit at a distance of about 3,900 feet (1,189 meters) from Didymos and it took 11 hours and 55 minutes to orbit around Didymos.

After the DART impact, the orbit of Dimorphos has shrunk and become eccentric. Now Dimorphos has a mean orbital distance of about 3,780 feet (1,152 meters) from Didymos – about 120 feet (37 meters) closer than before impact and its orbital period has shortened to 11 hours, 22 minutes, and 3 seconds – about 33 minutes and 15 seconds shorter than before impact.

The new study was published in the Planetary Science Journal on March 19, 2024, which shows that the DART impact has changed not only the orbit of Dimorphos but also its shape.

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