Scientists from NASA and our Department of Physics have used supercomputer simulations to reveal that Mars’ moons may have been formed from destroyed asteroid fragments.
The researchers found that an asteroid passing near Mars could have been pulled apart by the planet's gravity, with the resulting rock fragments strewn into a range of orbits.
The fragments that remain in Mars’ orbit are tugged by the gravity of both Mars and the Sun.
Some of those remaining asteroid pieces are set on paths to collide with one another, with each encounter grinding them down further and spreading more debris.
Many collisions later, the smaller chunks and debris from a former asteroid could have settled into a disc orbiting the planet.
Over time, some of this material would have gradually clumped together, forming Mars’ two small moons, Phobos and Deimos.
To test this theory, the researchers explored hundreds of scenarios of different asteroids having a close encounter with Mars.
The team used a high-performance, open-source computing code called SWIFT to study in detail the initial disruption, followed by simulating the subsequent orbital evolution of the debris.
This was supported by the advanced computing systems of the DiRAC Memory Intensive service hosted at Durham.
The team found that, in many of the scenarios, enough asteroid fragments survive and collide in orbit to serve as raw material for the moons.
Dr Vincent Eke from our Institute for Computational Cosmology says the next step is to build on this proof-of-concept project to simulate and study in greater detail the full timeline of the moons’ formation.
The team also wants to examine the structure of the disc itself to make more detailed predictions for what an upcoming mission to Mars’ moons could find.
The research is published in the journal Icarus.
Testing different ideas for Mars’ moon formations is the primary goal of the upcoming Martian Moons eXploration (MMX) mission led by JAXA (Japan Aerospace Exploration Agency).
The spacecraft will survey both moons to determine their origin and collect samples of Phobos to bring to Earth for study.
A NASA instrument on board will identify the chemical elements that make up Phobos and help select sites for the sample collection.
Understanding what the moons are made of is one detail that could help distinguish between an asteroid origin and a planet-plus-impactor source.
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