The James Webb Space Telescope has given astronomers a new forensic tool to study how planets are destroyed. A team led by Kate Su of the Space Science Institute analysed 21 young star systems caught in the aftermath of giant planetary collisions.

The study, published in The Astrophysical Journal, combined Webb’s mid-infrared spectra with archival data from the retired Spitzer telescope. The systems, called extreme debris disks, hold unusually large amounts of warm dust.

The dust fell into two classes. Silica-rich disks came from head-on, hypervelocity collisions between Mars-sized planets that vaporised rock into glass. Silica-poor disks came from gentler grazing impacts between Moon-sized bodies.

Silica-rich disks appear only around stars younger than about 300 million years. Such disks are rare, seen around roughly 1 per cent of young stars.

The silica-rich fingerprint matches what the Moon-forming impact between Earth and Theia would have left behind. Researchers say the work reveals how common or unusual the violent birth of our own world may have been.