Chapter 11 - Plantary Adornments - Moons and Rings - SU 2019 - Copy.pdf

Chapter 11
Planetary Adornments – Moon and Rings

Moons, Part 1
• Dozens of “worlds” of rock and ice exist in our s.s.; some large, some
small. ~200 moons!
• Liquid water under some surfaces.

Moons, Part 2

Moons, Part 3
• The moons are made of rock, ice, or both.
• Some were formed by accretion and differentiation.
• They have many diverse properties, only partially understood.

Regular Moons, Part 1
• Most of the larger moons formed with their planets through the
processes of accretion and differentiation.
• These are called regular moons .
• They revolve around their planets in the same direction as they
rotate.
• Almost all are tidally locked, meaning one hemisphere always faces
the planet the moon is orbiting.

Regular Moons, Part 2
• Other evidence for regular moons? The Galilean moons – the large moons of
Jupiter that are closest to it – decrease in density as you move outward.
• They are called the Galilean moons because these are the ones that Galileo
discovered – the ones that helped proved our s.s. is heliocentric!
The decrease in
density as you move
away from the planet
suggests they were
formed in an orderly
process/accretion
disk, much like our
s.s.

Q: As their distance from Jupiter increases,
the 4 Galilean moons show a consistent

Q: As their distance from Jupiter increases,
the 4 Galilean moons show a consistent

Irregular Moons
• Some moons are objects that formed apart from a planet, but were
later gravitationally captured by one.
• These are called irregular moons .
• They are often on retrograde (“backward”) orbits.
• Largest: Triton (below), moon of Neptune, although most are much
smaller – only a few km across.

Check Your Understanding 11.1
Which of the following is not a characteristic of regular moons?