In a landmark achievement, NASA has demonstrably altered the orbit of an asteroid around the sun. The mission, known as the Double Asteroid Redirection Test (DART), successfully impacted the asteroid Dimorphos in September 2022, and new data confirms that the collision not only shifted the asteroid’s orbit around its companion, Didymos, but also subtly changed the entire binary system’s path around our star. This is the first time humanity has intentionally and measurably altered the orbit of a natural object around the sun.
The DART Mission and Its Implications
The DART mission deliberately crashed a spacecraft into Dimorphos, a smaller asteroid orbiting the larger Didymos. The goal wasn’t immediate planetary defense – neither asteroid poses a threat to Earth – but rather to test humanity’s ability to deflect potentially hazardous asteroids. The impact slowed Dimorphos’s orbit by roughly 30 minutes, proving that kinetic impact could be an effective redirection method.
However, the latest research, published in Science Advances, reveals an even more profound effect: the collision slowed the binary system’s solar orbit by approximately 12 microns per second, equivalent to about 370 meters per year. This means we now have evidence that altering a celestial body’s orbit is achievable, even if the changes are small.
How the Change Was Measured
Researchers led by Rahil Makadia from the University of Illinois Urbana-Champaign used a combination of radar measurements and observations of the binary system transiting in front of the sun to precisely compare its pre- and post-impact orbits. The subtle shift was detectable, confirming scientists’ theoretical predictions. The impact also created a measurable “momentum enhancement factor,” where ejected debris from the collision contributed to an increased orbital change, effectively doubling the force of the spacecraft alone.
“If [an asteroid] is ever on its way to hitting the Earth, we can more confidently now say that we have the ability to push them around and away from the Earth,” says Makadia.
Beyond Planetary Defense: New Insights into Asteroid Formation
The findings have implications beyond planetary defense. By independently calculating the mass of both Dimorphos and Didymos, scientists gained a deeper understanding of their structure and composition. This new data could reveal key insights into how binary asteroid systems form and evolve.
According to Jay McMahon of the University of Colorado Boulder, “Like any experiment, you can make a prediction about what will happen, but then you have to take the measurements to prove it… And so, this proves it.”
Future Missions and Ongoing Research
The European Space Agency’s Hera mission, scheduled to arrive later this year, will conduct a more detailed assessment of the DART impact crater and refine the orbital measurements. This independent verification will further validate the findings and potentially provide even more accurate data.
This experiment underscores the capability of altering the trajectory of asteroids, providing humanity with a new tool in the ongoing effort to protect Earth from potential cosmic threats. The success of DART and the subsequent analysis pave the way for more targeted planetary defense strategies in the future.
