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Moons of our Solar System

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1.7 Sizing moons

Figure 12 The Moon and Tethys, shown to correct relative scale

To give you a feel for the sizes of some moons, have a go at Activity 2 below. There you will see we have provided images of eight moons, but not shown them to scale. All you have to do is guess the correct diameter for each moon (for markedly non-spherical moons we require the length of their long axis). If you get stuck, try consulting the moons data table from Week 1.

These are the moons we have chosen.

• Enceladus: the sixth-largest moon of Saturn and named after a mythological giant of ancient Greece.
• Deimos: the outer moon of Mars and named for the Greek personification of terror.
• Phoebe: thought to have been captured by Saturn’s gravity. It is named after a Titan of Greek mythology who was grandmother to Apollo.
• Iapetus: the third-largest satellite of Saturn, named after the Titan who fathered Atlas and Prometheus.
• Tethys: a medium-sized satellite of Saturn, named after a Titan and aquatic sea goddess.
• Pandora: a satellite of Saturn named after the Greek mythological figure who inadvertently unleashed all the evils of humanity from a jar.
• Prometheus: a moon of Saturn, named after the Titan who stole fire from the gods. Zeus then condemned him to have his liver eaten daily by an eagle for all time.
• The Moon: which goes by many names in different cultures; our own name derives from a Proto-Germanic word, mǣnōn.

Activity 2 Sizing moons – what do you know?

Timing: Allow approximately 20 minutes.

a.

504 km

b.

1062 km

c.

1470 km

d.

12.4 km

a.

Well done.

a.

3474 km

b.

104 km

c.

12.4 km

d.

213 km

c.

Well done.

a.

213 km

b.

1470 km

c.

271 km

d.

208 km

a.

Well done.

a.

1062 km

b.

3474 km

c.

104 km

d.

1470 km

d.

Well done.

a.

136 km

b.

3474 km

c.

1062 km

d.

504 km

c.

Well done.

a.

12.4 km

b.

104 km

c.

271 km

d.

3474 km

b.

Well done.

a.

136 km

b.

1062 km

c.

3474 km

d.

213 km

a.

Well done.

a.

1470 km

b.

1062 km

c.

3474 km

d.

504 km