Single Asteroid Hit May Explain Deimos' Deep South Depression and Dusty Surface
Researchers propose that a roughly 320-meter asteroid struck Mars' moon Deimos, creating its large southern basin and spreading a thick dust layer across the entire body.
An international collaboration, headed by Sabina Raducan of the University of Bern, combined detailed numerical modeling with fresh observations from ESA's Hera spacecraft to investigate Deimos' puzzling geology. Simulations using the Bern SPH code indicate that an asteroid about 320 meters across, impacting at a 45-degree angle, could have formed the moon's prominent southern depression without shattering it. The same collision would have lofted vast amounts of material, redistributing it globally and creating the smooth, dust-covered surface seen today, with regolith thickness exceeding 200 meters in some regions.
The study also reveals that Deimos' outer layers are extremely weak and its interior highly porous, traits more akin to rubble-pile asteroids than to typical moons. These insights provide testable predictions for JAXA's Martian Moons eXploration mission, slated for launch in 2026, regarding regolith depth and mechanical properties. The research appears in Nature Astronomy and marks the first use of Hera flyby data in a scientific analysis of Deimos.
Why it matters
Understanding Deimos' formation helps scientists assess asteroid impact risks and prepares future missions to Mars' moons.
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