In a groundbreaking mission, NASA’s Double Asteroid Redirection Test (DART) successfully altered the shape of an asteroid through an orbital collision. The mission, which took place in September 2022, tested a deflection method that could be crucial in protecting Earth from potential asteroid impacts. However, instead of leaving behind an impact crater, the collision transformed the target asteroid, Dimorphos, revealing its unique composition.
Dimorphos is a 558-foot-wide (170-meter) space rock that orbits its larger companion, Didymos, which measures 2,625 feet wide (800 meters). Through simulations conducted by a team of researchers and published in Nature Astronomy, the impact of the DART mission on Dimorphos was revealed. The simulations showed that the collision led to significant reshaping and resurfacing of the asteroid.
Sabina Raducan, a planetary scientist at the University of Bern and lead author of the study, explained that the simulations indicated Dimorphos is likely a rubble-pile asteroid. Before the DART mission, scientists were uncertain about what to expect from the system due to its distance from Earth. The impact caused approximately 1% of Dimorphos’ mass to be ejected into space, while around 8% of its mass shifted around its body.
The simulations not only shed light on the aftermath of the collision but also provided insights into Dimorphos’ composition. The study suggests that the asteroid is held together by weak gravity rather than cohesive strength, making it a rubble pile. As a result, the impact created a wide cone-shaped ejecta or plume of material that expanded up to 160 degrees and continued to expand due to the asteroid’s weak gravity and low material cohesion.
Furthermore, the study findings indicate that Dimorphos likely formed from material shed by Didymos, which was then re-accumulated and gravitationally bound to orbit the larger asteroid like a tiny moon. Raducan emphasized that these findings contribute to a broader understanding of the formation and evolution of similar binary systems in our solar system.
The European Space Agency (ESA) has plans for a follow-up mission to the binary asteroid system. The Hera mission, scheduled for launch in 2024, will provide a closer look at the changes made to Dimorphos following its encounter with DART. These follow-up observations will offer valuable insights into asteroid formation and help refine asteroid deflection methods, ensuring preparedness for potential Earth collisions.
Raducan highlighted the implications for planetary defense, stating that small, rubble-pile asteroids like Dimorphos are highly efficient to deflect using the kinetic impactor technique. However, accurate assessment of an asteroid’s properties through a reconnaissance mission would be necessary before attempting deflection.
The success of the DART mission opens up new possibilities for protecting Earth from potential asteroid impacts. By understanding the composition and behavior of asteroids, scientists can develop effective deflection methods and safeguard our planet. The ongoing exploration of our solar system continues to provide valuable insights into its formation and evolution, contributing to our broader understanding of the universe.
