Phobos

Definition

Phobos is one of the two moons of Mars, characterized by its irregular shape and rapid orbital period. It orbits Mars at an exceptionally close distance, completing a full orbit in just about 7 hours and 39 minutes, which is shorter than the Martian day. This unique relationship highlights the interactions between small celestial bodies like Phobos and their parent planet, Mars.

5 Must Know Facts For Your Next Test

1. Phobos is gradually spiraling inward towards Mars and is expected to either crash into the planet or break apart due to tidal forces in about 50 million years.
2. The surface of Phobos is heavily cratered and features large grooves and trenches, indicating a history of impact events and geological activity.
3. Phobos has a very low density, suggesting it may be composed of carbon-rich material or be a captured asteroid from the asteroid belt.
4. The largest crater on Phobos is called Stickney, measuring about 9 kilometers (5.6 miles) in diameter, dominating its surface landscape.
5. Phobos has been studied by several spacecraft, including NASA's Mars Reconnaissance Orbiter, which has provided valuable data about its surface composition and structure.

Review Questions

• How does the unique orbital characteristics of Phobos affect its relationship with Mars?
  • Phobos' extremely close orbit around Mars allows it to complete a full revolution in just about 7 hours and 39 minutes. This rapid orbital period means that Phobos rises in the west and sets in the east on Mars, which is opposite to most celestial bodies. Additionally, because it is slowly spiraling inward due to tidal forces, this will eventually lead to either its collision with Mars or its disintegration as it gets pulled apart by gravitational forces.
• Discuss the geological features of Phobos and what they reveal about its history.
  • Phobos exhibits a heavily cratered surface marked by large grooves and trenches. The presence of these features indicates a history of significant impact events that have shaped its landscape over time. The largest crater, Stickney, not only serves as a prominent landmark but also suggests that Phobos has undergone geological changes due to both external impacts and internal processes. Analyzing these features helps scientists understand the moon's evolution and its interactions with Mars.
• Evaluate the implications of Phobos' eventual fate on our understanding of small celestial bodies in planetary systems.
  • The gradual inward spiral of Phobos towards Mars highlights important aspects of planetary dynamics and tidal interactions within a system. Its predicted fate—either colliding with Mars or breaking apart—offers insights into how small celestial bodies can evolve over time due to gravitational influences. Studying this process enhances our understanding of the life cycle of moons and small asteroids, informing us about their potential role in planetary formation and evolution across the solar system.

Related terms

Deimos: Deimos is the smaller and more distant moon of Mars, discovered alongside Phobos, and it has a more circular orbit compared to its larger counterpart.

Tidal Forces: Tidal forces are gravitational interactions that can cause deformation in celestial bodies, influencing their shape and orbital dynamics.

Impact Cratering: Impact cratering refers to the process by which a celestial body is struck by another object, resulting in craters that can be observed on surfaces like those of Phobos and Deimos.