Mission accomplished: NASA's DART proves humanity can be saved from an asteroid collision

In a historic demonstration of cosmic ingenuity, NASA’s Double Asteroid Redirection Test (DART) mission made history on September 26, 2022, by intentionally colliding with the asteroid Dimorphos.

This event marked a pivotal moment in planetary defense, showcasing the potential of kinetic impactors to divert hazardous asteroids from a collision course with Earth.

Explaining the impact of DART’s collision

Recent findings, as revealed in a study published in the Planetary Science Journal, illuminate the extensive impact of this collision, altering not only the asteroid’s trajectory but its very form.

Dimorphos, a 560-foot-wide asteroid, is part of a binary asteroid system, orbiting the larger near-Earth asteroid Didymos. Prior to DART’s intervention, Dimorphos possessed a symmetrical, oblate spheroid shape, reminiscent of a squashed ball, with a well-defined, circular orbit.

However, the aftermath of the impact has transformed Dimorphos into a triaxial ellipsoid, akin to an oblong watermelon, while also shortening its orbital period by 33 minutes and 15 seconds, as noted by Shantanu Naidu, the study’s lead and a navigation engineer at NASA’s Jet Propulsion Laboratory.

How scientists deciphered DART’s cosmic impact

The comprehensive study employed three primary data sources to assess the consequences of the impact.

First, the DART spacecraft itself provided close-up imagery of Dimorphos before collision, transmitted to Earth through NASA’s Deep Space Network (DSN).

Secondly, the DSN’s Goldstone Solar System Radar played a crucial role in measuring the post-impact position and velocity of Dimorphos relative to Didymos, confirming the mission’s success beyond initial expectations.

Lastly, ground-based telescopes worldwide tracked the light curve changes of both asteroids, offering insights into Dimorphos’ altered motion and the binary system’s dynamics.

Far-reaching effects of the DART mission

Steve Chesley, a senior research scientist at JPL and study co-author, highlighted the precision of their models, which revealed the now slightly eccentric orbit of Dimorphos.

“We used the timing of this precise series of light-curve dips to deduce the shape of the orbit, and because our models were so sensitive, we could also figure out the shape of the asteroid,” said Chesley.

“Before impact,” Chesley continued, “the times of the events occurred regularly, showing a circular orbit. After impact, there were very slight timing differences, showing something was askew. We never expected to get this kind of accuracy.”

The meticulous analysis also detected a slight rocking motion of Dimorphos as it orbits Didymos, showcasing the level of detail achieved in understanding the asteroid’s behavior post-impact.

Post-Impact orbit of Dimorphos and Didymos

The DART mission not only shortened the orbital period of Dimorphos but also brought it approximately 120 feet closer to Didymos. This level of precision in the mission’s outcomes underscores the potential for kinetic impactors as a viable method for asteroid deflection.

Tom Statler, NASA’s lead scientist for solar system small bodies, emphasized the significance of independent research groups arriving at consistent conclusions, underscoring the robustness of these scientific findings.

“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,” Statler explained.

Furthermore, the discovery that Dimorphos resembles a loosely packed “rubble pile” asteroid, akin to Bennu, opens new avenues for understanding asteroid composition and behavior.

Implications and future missions

Looking ahead, the European Space Agency’s Hera mission, set to launch in October 2024, aims to further investigate the DART-impacted asteroid system. This mission promises to enrich our understanding of Dimorphos’ new shape and the broader implications of kinetic impact for asteroid redirection.

In summary, NASA’s DART mission, a landmark achievement in planetary defense, has successfully demonstrated the viability of kinetic impactors for asteroid deflection, marking a significant stride towards safeguarding Earth from potential cosmic threats.

By transforming the motion and shape of the asteroid Dimorphos, this pioneering mission showcases human ingenuity in modifying the course of celestial bodies and deepens our understanding of the nature and behavior of asteroids.

As we look forward to the insights from the forthcoming Hera mission, DART stands as a testament to the potential of science and technology to protect our planet, inspiring future generations of researchers and engineers to continue exploring innovative solutions for planetary security.

The full study was published in the Planetary Science Journal.

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