One leading theory suggests the moons of Mars, Phobos and Deimos, were formed from a huge collision with a protoplanet one third the mass of Mars that formed a ring around Mars.
The Collision Theory
Current scientific understanding, supported by the provided reference, points to a dramatic origin for the Martian moons. Unlike Earth's Moon, which is widely believed to have formed from a single giant impact, the formation of Phobos and Deimos is thought to have involved a subsequent process after the initial ring formation.
Here's a breakdown of the process:
- Giant Impact: The process began with a significant impact. A large object, specifically described as a protoplanet approximately one third the mass of Mars, collided with the red planet.
- Ring Formation: This immense collision generated a vast amount of debris. This debris didn't immediately form moons but instead settled into a ring around Mars.
- Inner Moon Formation: The material closer to Mars within this ring coalesced. The reference states that the inner part of the ring formed a large moon. This initial moon was likely much larger than present-day Phobos and Deimos.
- Outer Moons (Phobos and Deimos) Formation: The final stage involved gravitational interactions. Gravitational interactions between this large inner moon and the outer ring formed Phobos and Deimos. These interactions likely caused the larger moon to eventually fall back to Mars or disperse, leaving the smaller, outer moons we see today.
This theory explains several characteristics of Phobos and Deimos, such as their small size, irregular shapes, and orbits that are close to Mars and relatively low in inclination.
Understanding the Martian Moons
Mars has two small, irregularly shaped moons:
- Phobos: The larger and inner moon. It orbits Mars much faster than the planet rotates.
- Deimos: The smaller and outer moon. It orbits Mars just slightly faster than the planet rotates.
| Feature | Phobos | Deimos |
|---|---|---|
| Average Diameter | approx. 22 km (14 miles) | approx. 12 km (7.5 miles) |
| Orbit | Inner, faster than Mars rotation | Outer, slightly faster than Mars rotation |
| Shape | Irregular | Irregular |
| Composition | Similar to carbonaceous asteroids | Similar to carbonaceous asteroids |
While the collision theory described above is a leading model, other hypotheses, such as the capture of asteroids, have also been considered but face challenges explaining the moons' specific orbital characteristics. However, the reference provided specifically details the collision scenario.
This formation mechanism involving a large initial moon and subsequent interactions within a debris ring provides a compelling explanation for the unique pair of moons orbiting Mars.
