Nasa: asteroid strike accidentally unleashes boulder storm which could be 'as deadly as Hiroshima'

Nasa accidentally unleashed a storm of boulders "as deadly as Hiroshima" when attempting to change the trajectory of an asteroid.

Scientists have found that last September, Nasa crashed a spacecraft into the asteroid Dimorphos. This action was the first in a first planetary defence experiment aimed at finding ways to protect humanity from an extinction-level event.

However, although the impact knocked the asteroid off course, it also dislodged 37 boulders - which are currently hurtling through space at 13,000mph.

It is estimated that around 1,000 1,000 tonnes of debris were blasted away.

The loose boulders were spotted via the Hubble Telescope, and range from three feet to 22ft across - and are drifting away from the asteroid at little more than a half-mile per hour.

These boulders were already scattered on the surface and were knocked off by the shock of the impact from the Dart (Double Asteroid Redirection Test).

The research was published in the journal Astrophysical Journal Letters.

While none of the rubble is on a collision course with Earth, scientists are concerned a boulder storm from a future asteroid deflection could impact our planet at the same speed the asteroid was travelling — fast enough to cause tremendous damage.

Even a 15-foot boulder hitting Earth would deliver as much energy as the atomic bomb dropped on the Japanese city during World World II.

David Jewitt, who led the study and a professor of Earth and planetary sciences at UCLA, said: “The boulder swarm is like a cloud of shrapnel expanding from a hand grenade. Because those big boulders basically share the speed of the targeted asteroid, they’re capable of doing their own damage.”

Jewitt said that given the high speed of a typical impact, a 15-foot boulder hitting Earth would deliver as much energy as the atomic bomb that was dropped on Hiroshima.

Nasa launched its Dart in 2022 to move Dimorphos off its orbit, circling its parent asteroid Didymos. Dimorphos was never a threat to Earth so was chosen by Nasa as the test target because it is six million miles from our planet.

"If we follow the boulders in future Hubble observations, we may have enough data to pin down the boulders' precise trajectories," Jewitt said.

"And then we'll see in which directions they were launched from the surface and figure out exactly how they were ejected."

A close-up photograph taken by Dart just two seconds before the collision showed a similar number of boulders sitting on the asteroid’s surface – and of similar sizes and shapes.

The European Space Agency is planning an in-depth study of the aftermath of the impact of its Hera mission, due to launch in 2024 and scheduled to reach Dimorphos by Christmas 2026.