While NASA’s planetary defence test this week got off to a great start, new findings from the moon suggest the agency’s got its work cut out.

The Double Asteroid Redirection Test (DART) saw a probe slam into a far-away asteroid at more than 10km a second. The hope is that deflecting an incoming asteroid could prevent it from slamming into Earth and sending us the way of the dinosaurs.

It’s not clear yet if the orbit of the target, Dimorphos, was altered in any way. 

While hitting it dead-on is no doubt an achievement, new research suggests in the event the Earth comes under threat from a killer asteroid, it won’t be alone. 

An international team of scientists led by Australia’s Curtin University has found asteroid impacts on the moon dating back millions of years coincided with rains of rocks here on Earth – including that which helped kill off the dinosaurs

They examined microscopic glass beads in lunar rocks brought back from the moon by China’s Chang’e-5 mission, some up to 2 billion years old. 

“We found that some of the age groups of the lunar glass beads coincide precisely with the ages of some of the largest terrestrial impact crater events, including the Chicxulub impact crater responsible for the dinosaur extinction event,” said Alexander Nemchin from Curtin University.

“The study also found that large impact events on Earth such as the Chicxulub crater 66 million years ago could have been accompanied by a number of smaller impacts. 

“If this is correct, it suggests that the age-frequency distributions of impacts on the moon might provide valuable information about the impacts on the Earth or inner solar system.”

Chicxulub was about 10 to 15km across, but something much smaller – about 140m across – could be enough to wipe out an entire city

The good news is that to completely wipe out life on Earth, it’s estimated an impactor would have to be nearly 100km wide – not only would we see that coming a long way off, there aren’t any that we know of. Yet. 

The research was published this week in Science Advances.