In September 2022, NASA’s DART spacecraft intentionally collided with the asteroid Dimorphos, traveling at approximately 14,500 miles per hour. The mission was designed to test a potential method for diverting asteroids that might pose a threat to Earth, and new analysis suggests the technique could indeed be effective.
Dimorphos is part of a binary asteroid system, meaning it orbits a larger asteroid called Didymos. While the system doesn’t currently present a danger to our planet, it served as an ideal natural laboratory for NASA to test its kinetic impactor technique for planetary defense. Following the impact, researchers determined the mission had altered Dimorphos’ orbit around Didymos, demonstrating humanity’s ability to deliberately change the trajectory of a celestial body. This marked a significant step in planetary protection capabilities.
However, from a planetary defense perspective, the key question is whether humans can alter the orbit of an asteroid around the Sun. This new study confirms that DART did exactly that. Remarkably, the impact not only changed Dimorphos’ orbit around Didymos, but too slightly altered the trajectory of both asteroids as they orbit the Sun. The findings were published on Friday in Science Advances and represent the strongest evidence yet supporting the kinetic impactor technique.
“With this study, we’ve demonstrated for the first time that human interaction can change the orbit of an asteroid,” Steven Chesley, a research scientist at NASA’s Jet Propulsion Laboratory, told Gizmodo. “So we realize it works, and we know how to do it in the real world.”
A Small Change, A Giant Leap
To understand how the DART spacecraft affected the solar orbit of Dimorphos, Chesley and his colleagues analyzed measurements from 5,955 ground-based radars tracking the asteroid’s position, along with 22 measurements from stellar occultation events. These events occur when a celestial body passes in front of a star, allowing astronomers to precisely calculate the object’s trajectory by measuring the duration of the star’s obscured light. The ability to subtly alter an asteroid’s path opens new avenues for proactive planetary defense strategies.
Many “amateur” astronomers located around the globe conduct these occultation measurements, though Chesley emphasizes their dedication and expertise warrant a different descriptor. “The precision of these observations is really astounding,” he said. The team was able to determine a minimal change in the speed of Dimorphos’ solar orbit following the DART impact, finding it was slower by approximately 11.7 micrometers per second, or 1.7 inches per hour.
Although the change is minimal, it did alter the solar orbit of the entire binary system over time. The size of the system’s orbit shrank by roughly 360 meters, meaning its 2.1-year journey around the Sun is now shortened by about 0.15 seconds.
“It’s a tiny change, because the system is much larger than the satellite itself,” Chesley explained. In a real planetary defense scenario, it likely wouldn’t be significant. However, the study does represent an important step forward in our planetary defense capabilities, demonstrating that the kinetic impactor technique can alter the solar orbit of a celestial object.
Questions Remain
Much remains unknown about the impact of the DART mission, and answering these questions is essential to validate the kinetic impactor technique. Previous research by Chesley suggests the DART mission significantly changed the shape of Dimorphos, but a detailed study is needed to determine the asteroid’s current appearance.
That’s where the European Space Agency’s Hera mission comes in. The spacecraft is currently en route to the Dimorphos-Didymos system and, upon arrival in November, will map the entire surface of Dimorphos and much of Didymos in high resolution. Combined with a precise measurement of Dimorphos’ mass, researchers like Chesley could calculate the change in the system’s orbit and reduce uncertainty in their team’s calculations.
Until then, the group of astronomers who contributed the occultation data to this study will continue their operate, according to Chesley. More measurements will also improve the accuracy of the orbital change calculations.
while much work remains before NASA can confidently say the kinetic impactor technique is viable for planetary defense, scientists are closer than ever. With Hera on its way to conduct a revolutionary study, researchers are preparing to turn this concept into a proven strategy for asteroid deflection.
This article has been translated from Gizmodo US by Romina Fabbretti. Here you can find the original version.
