Deimos moon reshaped by single asteroid impact, study finds

A new study published in Nature Astronomy suggests that the Martian moon Deimos was dramatically reshaped by a single, violent asteroid impact. Researchers propose that a 300-to-360-meter asteroid struck the moon at an oblique angle, creating the massive 10-kilometer-wide depression at its south pole while simultaneously spreading debris across the entire surface.

This impact likely explains Deimos’s uniquely smooth and “youthful” appearance compared to its counterpart, Phobos. The debris from the collision may have acted as a layer of fine dust, burying older craters and scars. High-resolution simulations using the Bern Smoothed Particle Hydrodynamics (SPH) code indicate that Deimos is not a solid boulder but rather a porous rubble pile, similar to asteroids like Bennu and Ryugu.

The findings are supported by data from the European Space Agency’s Hera mission, which performed a flyby of Mars in March 2025. The study, led by Sabina Raducan from the University of Bern, the International Space Science Institute, and VUB, utilized high-performance computing to reconstruct the catastrophic event.