11 Chapter 11 – Why are the Terrestrial Planets different?
OpenStax Astronomy Chapter 8 (Earth), Chapter 9 (Moon & Mercury) & Chapter 10 (Venus & Mars)
Impact Craters
I. create
A. Caused by material on a surface
B. terrestrial planets experienced impacts in Solar System
C. Form impact
D. from impact form
E. forms peak in of crater (Rebound Peak)
F. Large impacts release huge amounts of
1. Enough to rock
2. Form new
G. On Earth, impacts disrupt and cause mass
1. Example:
II.
A. All planets had of impacts (almost 4 billion years ago), but planets look now
B. Current of craters indicates the of features and rocks
C. craters means an surface and geologic activity
1. Example: are covered with millions of craters
D. surface with craters is , by geologic activity
1. Tectonism, volcanism, and erosion can craters
E. have relatively craters
1. Geologically
2. Partially protected by that burn up meteors before impact
G. has a of craters and smooth surfaces
1. Evidence of and geologic activity
If you could see the Moon 1 billion years ago, what would the surface look like?
Origin of the Moon
III. of the
A. Moon likely formed in a between Earth and a smaller
1. However, there are theories
B. A collision would have blasted off some of Earth’s
1. Smaller planet was
C. Debris formed a , then a around Earth, then formed the Moon
1. to how planets form around Sun
D. Best for this theory: Moon’s is the as Earth’s crust and mantle
Tectonism
Earth: Section 8.2, Mercury: Section 9.5, Venus: Section 10.2 & Mars: Section 10.4
IV.
A. of planet surface driven by from the surface
1. Heat mostly from of elements
2. Heat from hot to
3. Causes , plate movement, and stretching of the surface
V. Tectonism on the
A. Only has its crust broken into
1. Plates due to heat flow in mantle, called
2. Surface features and where plates
B. terrestrial planets have had some under the surface
C. interior cooled and , causing crust to crack and buckle
1. Left long , called
2. Evidence that it is shrinking
D. has had extensive tectonism, probably due to
1. Causing large like the (Mariner Valley)
E. has
1. Hot material forming volcanoes
2. Or, spots where the crust , melts and with mantle material below forming crust
How many of the 4 terrestrial planets have a crust broken into tectonic plates?
Volcanism
Earth: Section 8.2, Moon: Section 9.2, Venus: Section 10.2 & Mars: Section 10.4
VI.
A. rises from planet
B. Rock near surface into , volcanoes bring to surface
VII. Volcanism on the
A. Volcanoes on all terrestrial planets
1. Only Earth’s are known to be (still erupt)
B. : volcanoes, but has had from cracks that surface erasing craters
1. Old lava flows are called , Latin for “seas”
2. Maria have craters, formed most in early Solar System
C. : some smooth surfaces from , and a volcanoes
D. : More than is covered with rocks
1. Very volcanoes, some even have on slopes
2. volcano in the Solar System, is the biggest
3. Active million yrs ago
E. : of the planets
1. All kinds of volcanoes and lava flows over whole surface
2. be active today or recently
Erosion and Water
VIII. Weathering and
A. – Wind, water, and solar radiation rocks
1. weathering on Moon and Mercury slowly affects minerals
B. – Wind, water, and ice weathered material
1. high places and the low places
2. Forms
3. old features like craters
IX.
A. Venus, Earth, and Mars have with
1. Smooths surface and builds
B. Planets atmospheres and inactive geology still have , like Moon and Mercury
X.
A. : erosion created and reformed formed most surface features
1. Example:
B. : too hot to have water or for erosion
1. Some water in atmosphere of Venus
C. : some under surface, but erosion
What would you expect to see on a small rocky planet or moon with no atmosphere?
A. Lots of craters
D. : surface changed by water in
1. Water features that look like from when Mars was warmer and had thicker atmosphere
2. , and maybe lakes, surface
Tutorial Activity – Terrestrial Planet Surfaces
1. Consider the surfaces of the terrestrial planets (and Earth’s moon).
(a) Which ones are heavily cratered?
(b) Which ones seem to have lots of geologic activity (volcanoes, erosion)?
(c) Based on this, what characteristic of planets seems to contribute most to geological activity?
(d) Why is that characteristic so important?
2. List the 4 main geological processes that can occur on a planet and give an example of each and the planet where it occurs.
a.
b.
c.
d.
3. Why are the moon and Mercury effectively ‘dead’ geologically speaking?
4. Decide whether each of the following potential discoveries would be expected or surprising.
(a) We find a planet that is the same size as the Earth but as heavily cratered as the Moon.
(b) New data reveal that Venus has an erupting volcano.
(c) New spacecraft images of Mercury reveal evidence of past liquid water on its surface.
and at the same distance from its star, which is similar to our sun. Describe the type of geology you
would expect this planet to have.
