Overview
This lecture discusses Mars' two small moons, Phobos and Deimos, their origins, characteristics, orbits, and relevant safety concerns for human exploration.
Mars' Moons: Phobos and Deimos
- Mars has two moons named Phobos and Deimos.
- Both moons are much smaller than Earth's moon, measuring about 12 km wide.
- Phobos and Deimos look like asteroids and are likely captured asteroids from the asteroid belt.
- Their small size means they would appear as tiny dots from the Martian surface.
Orbital Behavior and Future of the Moons
- Phobos' orbit is slowly shrinking, causing it to move closer to Mars with each orbit.
- In millions of years, Phobos will crash into Mars, creating a massive impact.
- Deimos’ orbit is slowly getting larger and may eventually escape Mars’ gravity and drift into space.
- Over time, Mars may lose both of its moons due to these orbital changes.
Impact Events and Safety
- The impact of Phobos with Mars will release huge energy, dangerous even to distant spacecraft.
- Satellites or rovers near the impact zone would be destroyed by the heat and debris.
Names and Mythological Origins
- Phobos and Deimos are named after Greek gods associated with Mars, the god of war.
- Phobos means "fear" (root of the word "phobia"), and Deimos means "terror."
Surface Conditions and Gravity
- The moons have extremely low gravity due to their small size and mass.
- Walking on Phobos or Deimos is dangerous; even a small stumble could launch a person into space.
- Human missions should avoid attempting surface exploration on these moons without being securely anchored.
Key Terms & Definitions
- Asteroid Belt — region between Mars and Jupiter containing many small rocky bodies (asteroids).
- Captured Asteroid — an asteroid pulled into orbit by a planet’s gravity, becoming a moon.
- Orbit — the path an object follows around a planet or star.
Action Items / Next Steps
- Review notes on Mars' moons and their orbital dynamics.
- Prepare for upcoming topics by reading about other planetary moons in the solar system.