If a moon revolves opposite to the planet's rotation, it probably a. was captured after the planet formed. b. had its orbit altered by a collision. c. has a different composition than other moons have. d. formed very recently in the Solar System's history.

A captured moon is one that was not originally formed alongside its parent planet. Instead, it was gravitationally captured by the planet after both had already formed.
Captured moons often have irregular orbits that can be very different from the orbits of moons that formed with their planet.
These irregular orbits are usually elliptical or highly inclined. Sometimes, captured moons can even revolve opposite to the rotation of their parent planet.
This opposite direction orbit is called a retrograde orbit. One famous example of a captured moon is Neptune's moon, Triton.
Retrograde orbits are strong indicators that the moon was likely captured by the planet's gravity.
This is because typical moon formation follows the direction of the planet's spin, making retrograde motion unusual unless external forces like capture are involved.

Orbital mechanics is the study of the motions of celestial bodies under the influence of gravitational forces.
This concept helps us understand why moons and planets move the way they do in space.
The path of a moon or satellite around a planet is determined by the gravitational attraction between them. If a moon has a retrograde orbit, meaning it moves in the opposite direction of the planet's rotation, this can be explained by orbital mechanics.

• If an object is captured by a planet's gravity, it can enter into various types of orbits, depending on its velocity and the angle of capture.
• Orbital mechanics laws, such as Kepler's laws of planetary motion, help to predict the orbits of these celestial bodies.
• Understanding these mechanics is crucial for space missions, satellite launches, and predicting the movement of natural celestial bodies in our Solar System.

Overall, orbital mechanics provides the foundation for why certain moons might behave differently.

Planetary formation is the process by which a planet forms from a disk of gas and dust surrounding a new star.
During this time, moons can also form from the same material orbiting the young planet. This typical moon formation results in moons that orbit in the same direction as the planet's rotation.
However, sometimes a moon does not follow this norm. If a moon has a retrograde orbit, it often means that it was captured after the planet was fully formed.
Contrastingly, moons like the ones that formed with the planet usually have prograde orbits, meaning they move in the same direction as the planet's rotation.

• The presence of a retrograde moon suggests a more dynamic history, including potential gravitational interactions with other celestial bodies.
• This has implications for understanding the history and evolution of the planet as well as the overall architecture of the Solar System.

Thus, studying planetary formation gives us insights into the various stages and processes that result in the diverse set of moons we observe today.