Mars' Moon Deimos Shaped by Ancient Impact, Study Finds

• ESA’s Hera spacecraft observations and advanced simulations reveal that Mars' moon Deimos was shaped by a massive ancient impact.
• Though its surface appears smooth, Deimos hides a heavily cratered landscape under a thick layer of fine regolith caused by the same impact event.
• New research suggests Deimos is a 'rubble-pile' body, similar to many asteroids, rather than a solid, cohesive rock.

Research and Simulation

• Researchers at the University of Bern used the Bern Smoothed Particle Hydrodynamics (SPH) code to run approximately 100 impact simulations.
• The results indicate that a 320-meter-wide asteroid struck Deimos at a 45-degree angle, creating a 10-km-wide southern polar depression.
• This impact ejected material that fell back onto the surface, creating a global regolith blanket up to 200 meters deep, which obscures older craters and gives the moon its smooth appearance.

Internal Structure

• The study reveals that Deimos has low surface cohesion and high porosity, confirming it is a fragile rubble pile similar to asteroids like Bennu or Ryugu.
• Its porous interior dampened impact shockwaves, which allowed earlier, smaller craters to remain preserved beneath the regolith layer.
• Brian May, Queen guitarist and astrophysicist, contributed to the research team by providing spectroscopic depictions of Hera mission images.

Future Exploration

• The upcoming JAXA Martian Moons eXploration (MMX) mission provides an opportunity to test these findings.
• While MMX’s primary goal is a sample return from Phobos, its high-resolution imaging, LIDAR, and gamma-ray spectrometer measurements will help refine models of Deimos' mass, density, and regolith composition.