NASA’s historic experiment to change the trajectory of an asteroid using the DART spacecraft proved more difficult than expected. Scientists discovered that after the impact, the asteroid Dimorphos began to behave unpredictably due to its loose structure, reminiscent of “gravitationally bound rocks.”
When NASA’s DART probe crashed into the asteroid Dimorphos, orbiting the larger Didymos, in 2022, it marked humanity’s first attempt to change the orbit of a celestial body. The experiment exceeded expectations: Dimorphos’s orbital period was shortened by 33 minutes—more than 20 times more than scientists had predicted.
However, the joy was short-lived. Subsequent observations revealed that the asteroid system was behaving erratically. A giant plume of dust and debris formed around Dimorphos, and its orbit continued to change even after the impact.
Now NASA has provided an explanation. Studies have shown that Dimorpho is not a solid rock, but a so-called “rubble pile,” composed of numerous fragments held together by weak gravity. After the impact, some of the material was ejected into space, and the remaining fragments began to shift within the asteroid, changing its mass and generating additional momentum.
These processes continue to influence Dimorpho’s motion even two years after the impact. Scientists note that the DART mission, designed as a simple kinetic impact test, unexpectedly revealed complex physical mechanisms underlying the behavior of small bodies in the Solar System.
Despite the unpredictability of the outcome, NASA considers the mission a success. The data obtained will help improve planetary defense methods and develop more accurate models for future missions.
The next step will be the European Space Agency’s Hera project, which will travel to the asteroid to study the impact’s aftermath in detail and better understand how celestial bodies respond to human intervention.
