Recent observations confirm that the 2022 DART impact not only expedited the orbital cadence of Dimorphos around its progenitor asteroid, Didymos, but also subtly perturbed the trajectory of the entire co-orbital asteroid pair as it circulates the Sun.
This artist’s illustration depicts the expulsion of a particulate cloud subsequent to the collision of NASA’s DART spacecraft with the asteroid Dimorphos. Image credit: ESO / M. Kornmesser.
Upon the DART spacecraft’s impact with Dimorphos, a substantial conflagration of lithic detritus was expelled into the cosmos, thereby modifying the geometry of the asteroid, which has a transverse dimension of 170 meters (560 feet).
The outward propulsion of this ejected material carried its own momentum away from the asteroid, imparting a propulsive force to Dimorphos, a phenomenon scientists refer to as the momentum enhancement factor.
The momentum enhancement factor attributed to the DART impact was approximately two, signifying that the dissipation of debris effectively doubled the propulsive effect generated by the spacecraft alone.
Prior investigations had established that the moonlet’s diurnal orbital cycle around Didymos, which measures 805 meters (nearly 0.5 miles) in diameter, experienced a reduction of 33 minutes.
The current investigation reveals that the impact ejected such a considerable quantity of material from the binary system that it also influenced the binary’s annual orbital period around the Sun by 0.15 seconds.
Dr. Rahil Makadia, a researcher affiliated with the University of Illinois Urbana-Champaign, stated, “The alteration in the binary system’s orbital velocity was approximately 11.7 microns per second, equivalent to 1.7 inches per hour.”
He further elaborated, “Over an extended temporal span, such a minute deviation in an asteroid’s trajectory can be the determinative factor in whether a perilous celestial body impacts or narrowly misses our planet.”
To substantiate DART’s discernible influence on the binary system, the research team required exceedingly precise measurements of its solar orbit.
Consequently, in conjunction with radar sweeps and other terrestrial-based astronomical observations, they meticulously monitored stellar occultations – events occurring when an asteroid precisely intercepts the path of a star, causing its pinpoint luminescence to momentarily extinguish.
This observational methodology yields exceptionally accurate data pertaining to the asteroid’s velocity, configuration, and spatial orientation.
The study’s authors depended significantly on the contributions of amateur astronomers situated globally, who meticulously documented 22 stellar occultation events between October 2022 and March 2025.
Dr. Steve Chesley, a research scientist at NASA’s Jet Propulsion Laboratory, remarked, “When assimilated with extensive prior terrestrial observations spanning numerous years, these stellar occultation records proved instrumental in our computation of DART’s impact on Didymos’ orbital parameters.”
He also noted the inherent challenges, stating, “This endeavor is critically contingent upon prevailing meteorological conditions and frequently necessitates expeditions to remote locales, with no assured outcome.”
“The successful attainment of this outcome would have been unattainable without the unwavering commitment of scores of volunteer observers of occultations across the globe.”
An examination of the fluctuations in Didymos’ orbital dynamics also facilitated the researchers’ determination of the densities of both celestial bodies.
Dimorphos exhibits a slightly lower density than previously surmised, lending credence to the hypothesis that it originated from the rocky fragments expelled by a rapidly rotating Didymos.
This loosely aggregated material eventually coalesced to form Dimorphos, an asteroid characterized as a ‘rubble pile’.
Our findings substantiate the viability of targeting the secondary component of binary asteroid systems as a potential strategy for kinetic impact deflection, thereby augmenting humanity’s capacity for planetary defense.
Dr. Preeti Cowan, a researcher from the University of Auckland, commented, “The DART mission had already been recognized as a triumph. An asteroid system posing no immediate threat to Earth was deliberately chosen, and NASA deliberately propelled a spacecraft into the smaller moon, thereby accelerating its revolution around its parent asteroid.”
“This subsequent analysis uncovers an even more extraordinary – and still benign – consequence.”
“The cumulative propulsive force, resulting from both the impact of the spacecraft and the expulsion of material from the diminutive asteroid moon, was sufficient to elicit a measurable alteration in the binary system’s solar trajectory.”
“While this deviation may appear negligible, in the realm of orbital mechanics, even a minuscule perturbation, if applied sufficiently early, can yield significant ramifications.”
Professor Roberto Armellin, a researcher at the University of Auckland, declared, “This represents a significant advancement for planetary defense.”
“In a genuine hazardous scenario, even a minor adjustment implemented early in the asteroid’s trajectory could result in a potentially calamitous object bypassing Earth.”
“The subsequent phase of this research will be undertaken by ESA’s Hera mission, slated for launch in 2024. This mission is scheduled to rendezvous with the Didymos system later this year to meticulously document the impact crater, ascertain the asteroid’s mass and internal structure, and evaluate the efficiency of the impact event.”
“These forthcoming measurements will be pivotal in transforming this groundbreaking experimental endeavor into a dependable planetary defense methodology.”
The findings have been published in the esteemed journal Science Advances.
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Rahil Makadia et al. 2026. Direct detection of an asteroid’s heliocentric deflection: The Didymos system after DART. Science Advances 12 (10): 10.1126/sciadv.aea4259
