NASA's Asteroid-Hitting DART Mission Shrinks Dimorphos Orbit, Changing its Shape

NASA's DART mission, aimed at redirecting asteroids, has resulted in significant alterations to the shape and orbit of asteroid Dimorphos, as revealed by a study led by JPL.

DART Impact Changes the Shape and Motion of Dimorphos

Following the historic collision between NASA's DART (Double Asteroid Redirection Test) spacecraft and a 560-foot-wide asteroid on September 26, 2022, the mission demonstrated the efficacy of kinetic impactors in deflecting hazardous asteroids.

A recent study indicates that the impact not only influenced the asteroid's motion but also transformed its shape.

Dimorphos orbits a larger near-Earth asteroid named Didymos. Prior to the impact, Dimorphos boasted a symmetrical "oblate spheroid" shape, akin to a squashed ball with a wider diameter than height.

Positioned approximately 3,900 feet away from Didymos, Dimorphos completed a single orbit around its host every 11 hours and 55 minutes.

Shantanu Naidu, a navigation engineer at NASA's Jet Propulsion Laboratory (JPL) and the study's lead researcher, remarked on the profound changes observed after impact.

Dimorphos' orbit no longer maintains its circularity, with its orbital period now shortened by 33 minutes and 15 seconds. Additionally, the asteroid's shape has evolved from a symmetrical object to a "triaxial ellipsoid," resembling an oblong watermelon.

Dimorphos' Post-Impact State

The study used three primary data sources to construct computer models elucidating the asteroid's post-impact state. Firstly, DART itself captured images of Dimorphos as it approached, providing invaluable insights into the dimensions and proximity of both asteroids.

Secondly, the Goldstone Solar System Radar facilitated precise measurements of Dimorphos' position and velocity relative to Didymos after the impact.

Finally, ground-based telescopes worldwide monitored the asteroids' light curves, enabling researchers to discern alterations in Dimorphos' motion.

By analyzing the timing of light curve dips during mutual events, where one asteroid eclipses the other from Earth's perspective, researchers inferred changes in Dimorphos' orbit and shape.

Steve Chesley, a senior research scientist and study co-author at JPL, highlighted the unprecedented precision achieved in modeling Dimorphos' orbit, revealing subtle timing discrepancies indicative of orbital eccentricity.

Furthermore, the study detailed the evolution of Dimorphos' orbital period post-impact, showcasing a gradual reduction attributable to material loss and orbit compression.

These findings underscore the dynamic interplay between asteroids and offer novel insights into their behavior and composition.

"The results of this study agree with others that are being published," said Tom Statler, lead scientist for solar system small bodies at NASA Headquarters in Washington.

"Seeing separate groups analyze the data and independently come to the same conclusions is a hallmark of a solid scientific result. DART is not only showing us the pathway to an asteroid-deflection technology, it's revealing new fundamental understanding of what asteroids are and how they behave."

As researchers continue to unravel the mysteries of Dimorphos, future missions like ESA's (European Space Agency) Hera mission, slated for launch in October 2024, will further elucidate the asteroid's reshaping and provide invaluable insights into asteroid-deflection technologies.

The findings of the study were published in the Planetary Science Journal.