A New Investigation into Planetary Defense

Two years after NASA's DART mission successfully collided with the asteroid Dimorphos in a groundbreaking planetary defense experiment, a new European mission is arriving to examine the results of the strike. The European Space Agency’s (ESA) Hera probe, which launched in October 2024, is currently maneuvering to begin its detailed inspection of the crash site.


The original mission, conducted on September 26, 2022, aimed to test whether humans could alter the trajectory of a threatening asteroid. By slamming the DART spacecraft into the small asteroid Dimorphos, scientists successfully shortened its orbit around the larger asteroid, Didymos, by roughly 33 minutes. While the mission was a clear success, the exact structural consequences of the impact remain a mystery.


«Hera wants to be the detective, like Inspector Colombo, going back to the crash scene,» explained Patrick Michel, a planetary scientist at the French National Centre for Scientific Research (CNRS) and principal investigator of the Hera mission.


Unraveling the Mysteries of the Impact

Despite years of monitoring via ground-based and space telescopes, many questions remain regarding the physical state of the asteroids. Scientists are eager to determine the size of the crater created by DART and understand whether the asteroid’s surface boulders were significantly redistributed.


«We know that there was a lot of material kicked up,» noted Angela Stickle, a planetary scientist at Johns Hopkins University's Applied Physics Laboratory. «We know that we probably left a pretty significant mark on Dimorphos.»


Adding to the intrigue is the discovery that the post-impact behavior of the system is more complex than initially anticipated. Cristina Thomas, a planetary astronomer at Northern Arizona University, noted that the orbital changes continued to fluctuate for months after the collision in ways that researchers still do not fully understand.


The Arrival and Upcoming Objectives

Hera is scheduled to perform its initial arrival maneuver on October 15. The spacecraft will execute a series of braking maneuvers to slow its approach. By early November, it is expected to be within 30 kilometers of the asteroids, with even closer observation passes planned for December.


The mission objectives are diverse:

  • Mapping the surface to identify the crater dimensions.
  • Searching for remnants of the DART spacecraft, though experts believe the probe likely disintegrated upon impact.
  • Conducting an in-depth analysis of the binary asteroid system.

Future Exploration with CubeSats

In January, Hera will deploy two smaller companion spacecraft, Milani and Juventas. Milani is tasked with identifying the composition of materials surrounding the asteroid, while Juventas will utilize radar to examine the internal structure of Dimorphos. This will mark the first time researchers have gained direct insight into the interior of such a space rock. Both secondary probes may eventually attempt to land on the asteroid, marking a dramatic conclusion to their investigative work.


The mission is expected to continue operations through at least September 2027, offering scientists an unprecedented view of this unique binary system.