Analysis of NASA's DART Planetary Defense Mission and Its Implications

Planetary defense researchers have indicated that NASA’s DART asteroid redirection mission may have introduced new challenges for future asteroid deflection missions after its test resulted in boulders moving through space on unanticipated paths.

In September 2022, the DART mission successfully changed the orbit of the asteroid moon Dimorphos. The smaller rocks dislodged by the kinetic impactor achieved three times the momentum of the spacecraft itself.

Moving an Asteroid from Its Orbit

"We succeeded in deflecting an asteroid, moving it from its orbit," said lead author Tony Farnham, a research scientist at the University of Maryland’s Department of Astronomy. "Our research shows that while the direct impact of the DART spacecraft caused this change, the boulders ejected gave an additional kick that was almost as significant."

"That additional factor changes the physics we need to consider when planning these types of missions," Farnham said.

The researchers used data from the Italian cubesat LICIACube, which followed the DART mission. Earth-based observations were not sufficient for precise measurements of the aftermath. In the LICIACube images, the team identified 104 boulders moving at speeds up to 116 miles per hour and tracked their three-dimensional trajectories. These rocks range in diameter from 0.2 to 3.6 meters.

Analyzing the Impact

"We saw that the boulders weren’t scattered randomly in space," Farnham said. "Instead, they were clustered in two distinct groups, with an absence of material elsewhere, which suggests that an unknown factor is influencing the distribution."

Based on the impact, the team believes that DART’s solar panels broke up larger boulders on Dimorphos’ surface before the main body of the spacecraft struck. This initial impact likely created the largest debris cluster, containing about 70% of the identified objects. This group moved away from the asteroid at high velocity.

"DART’s solar panels likely hit two large boulders, called Atabaque and Bodhran, on the asteroid," said second author Jessica Sunshine, a professor of astronomy and geology at the University of Maryland. "Evidence suggests that the southern cluster of ejected material is probably composed of fragments from Atabaque, a 3.3-meter-radius boulder."

Outlook on Planetary Defense

Sunshine, who was also deputy principal investigator on the Deep Impact mission, noted differences between the two missions. Deep Impact involved a NASA probe impacting the Tempel 1 comet to study its interior, but the two space objects had different surface conditions, resulting in different outcomes.

"Deep Impact hit a surface that consisted of very small, uniform particles, so its ejecta was relatively smooth and continuous," Sunshine explained. "In contrast, DART impacted a rocky surface with large boulders, resulting in more complex and filamentary ejecta patterns."

"Comparing these two missions provides insight into how different celestial bodies respond to impacts, which is important for planning planetary defense missions," Sunshine said.

The findings are relevant for the European Space Agency’s upcoming Hera missions, which will enter the Didymos-Dimorphos system in 2026.

"Data gathered from LICIACube provides additional perspectives on impact events, especially as DART was originally designed to rely on Earth-based observations," Farnham said. "Hera will similarly provide a direct view of the impact’s aftermath, using predictions based on DART data."

Collecting comprehensive data from early planetary defense missions is considered important for understanding the physics and outcomes of deflecting space objects.

"If an asteroid was approaching Earth and needed to be moved a specific amount to avoid impact, then these details become very important," Sunshine added.

"You can think of it as a cosmic pool game," she said. "We might not achieve the intended result if all variables are not considered."

The paper "Massive Boulders Ejected During DART Mission Complicate Future Asteroid Deflection Efforts" was published on July 4, 2025, in The Planetary Science Journal.