Class 3 : Craters in the solar system.

Recap last class… Patterns in the solar system. Theory for solar system formation. How do we test this theory?

Variety of surfaces in the solar system Classifying surfaces. The processes at work.

I : Classification of surfaces

Can classify surfaces in the Solar System into the following groups: Heavily cratered. Mildly cratered. Blotchy/linear features. Shrouded by an atmosphere.

Processes that are relevant: Impacts by asteroids, comets etc. Volcanic activity. Atmospheric erosion.

Let’s look at this in some more detail.

II : Heavily cratered bodies

Far side of The Moon

Two kinds of terrain: highlands and maria

The Moon & Mercury

Very little or no atmosphere… All incoming meteors hit the surface

(different from Earth where small objects burn or break up).

Once made, craters stay (any erosion processes happen very very slowly).

Located in the inner solar system More rocky (outer moons are icy), so craters

survive longer. More debris to cause craters.

Lunar Terrain

Highlands Several kilometers higher. Heavily cratered. 4 – 4.4 billion years old. Aluminum rich rock (light colored).

Maria (“seas”) Younger (3.2 – 3.9 billion years old). Iron rich rock (dark color). Old Lava flows (like Hawaii on Earth today).

Another sign of lava flows… lunar rilles are believed to be remains of old lava flows.

III : Volcanism in the solar system

Io – the most active volcanic region in the Solar System

Examples…

Io Very smooth surface – no craters or rilles. Thought to be a very young surface – lava

has filled all craters and valleys. Strong stretching/pulling by Jupiter heats

interior and causes volcanic activity. Mars

Possesses some giant dead volcanoes (e.g. Olympus Mons… 27km high, 600km wide).

Example of a crater not caused by impacts.

IV : The outer moons – ice geology at work.

Europa

Surface ice sheet occasionally seems to break and float around on an underlying liquid water ocean