One asteroid strike may explain two mysteries of Mars’ moon Deimos

An international team of researchers from the University of Bern and other institutions has proposed that a single asteroid impact may have shaped Deimos, Mars' smaller and more distant moon. By combining computer simulations with data from the recent ESA Hera spacecraft flyby, the scientists concluded that one powerful but not destructive asteroid collision could account for both Deimos' large southern depression and its smooth, dusty surface.

This finding, published in Nature Astronomy, could guide future missions like Japan's Martian Moons eXploration (MMX) mission. Deimos has a unique appearance compared to Mars' other moon, Phobos, which is heavily cratered. Deimos' surface is smoother due to a layer of loose dust and rocky debris called regolith. The research team used a sophisticated computer model called the Bern Smoothed Particle Hydrodynamics code to simulate the impact scenario.

They found that an asteroid approximately 320 meters in diameter striking Deimos at a 45-degree angle could have produced the observed depression and scattered regolith across the moon. The impact was powerful enough to redistribute material globally, but not strong enough to destroy Deimos. The simulations also suggest that Deimos has a porous interior, which helped absorb some of the collision's energy and prevent its destruction.

While other explanations for Deimos' features are still possible, this impact scenario provides a single mechanism that explains both the southern depression and the smooth, dusty surface.