Accidental Boulder Swarm Unleashed by NASA’s Planetary Defense Mission
During NASA’s first planetary defense mission, a boulder swarm comparable to the devastation caused by the Hiroshima atomic bomb was accidentally unleashed. Scientists at the University of California, Los Angeles (UCLA), identified 37 boulders up to 22 feet wide that scattered from the surface of the moonlet Dimorphos after a spacecraft crashed into it.
The mission, known as the Double Asteroid Redirection Test (DART), aimed to divert the moonlet from its orbit in the event of an asteroid heading towards Earth. While the test was successful in pushing the moonlet, it resulted in unintended consequences. The team at UCLA warned, “Smaller rocks flying off into space could create their own problems.”
Even a 15-foot boulder hitting Earth would release the same amount of energy as the atomic bomb dropped on Hiroshima during World War II. The team likened the swarm of space rocks to a “cloud of shrapnel expanding from a hand grenade,” traveling at a speed of 13,000 miles per hour.
Although none of the debris poses a direct threat to Earth, scientists are concerned that future asteroid deflection attempts could result in a boulder storm with the potential to impact our planet at the same speed as the asteroid, causing significant damage.
NASA launched DART in 2022 to move Dimorphos off its orbit around its parent asteroid, Didymos. On September 26, the world witnessed as DART approached Dimorphos, reaching speeds of 15,000 miles per hour. The impact changed Dimorphos’ orbit from 11 hours and 55 minutes to 11 hours and 23 minutes.
Considered a success, DART is now touted as a means of protecting Earth from catastrophic asteroid impacts. However, a new study led by UCLA astronomer David Jewitt warned that the large boulders, due to sharing the speed of the targeted asteroid, have the potential to cause significant damage on their own.
Dimorphos, located six million miles from Earth, was selected as the test target because it was never a threat to our planet. Images taken by NASA’s Hubble Space Telescope in December 2022 revealed that 37 boulders had been released from Dimorphos’ surface, likely due to the shock of the impact. A photograph taken by DART just moments before the collision shows a similar number of boulders on the asteroid’s surface.
These boulders, among the faintest objects observed in the solar system, were meticulously examined using the powerful Hubble telescope. Jewitt expressed hope that further observations would pinpoint the precise trajectories of these boulders and shed light on their origin.
The UCLA team believes that the boulders were either expelled from the impact site or launched from the surface due to seismic shaking. While NASA’s DART mission was successful in its goal of planetary defense, the unintended release of these boulders highlights the need for careful planning and consideration of potential consequences in future asteroid deflection attempts.