Homework

1. Is there a good scientific question?2. Is there a good explanation for why the

topic/question is worthy of research? 3. Is there a good hypothesis (if / then)?4. Are there at least 10 quality sources?5. Will the project need special approval?6. What questions or comments do you

have for the person?

The Earth’s Moon

09.10.07 / 09.11.07

Concept: The Moon

►EQ: What hypotheses have been developed to explain the evolution of the Moon?

Earth's Moon

General characteristics • Size

• unusually large relative to the Earth• Most satellites are much smaller than

their parent planets.

• Density • Comparable to Earth's crust• Too low to contain a significant iron core

Earth's Moon

General characteristics • No atmosphere• Tectonics no longer active• Surface is bombarded by small

meteorites which slowly smoothes the landscape

• Oldest rocks are about 4.5 by, in contrast to Earth’s oldest rock, which 3.8 by

Lunar topography

Lunar Surface

Two types of terrain•Maria (singular, mare), Latin for

"sea“•Highlands, English for land that

is high

Lunar surface

Maria• Dark region• Fairly smooth lowlands• Originated from asteroid impacts and

lava flooding the surface • Form most of the near side of Moon• Were once thought to be seas because

of their dark color

Formation of Maria

Lunar surface Lunar highlands

• Bright, densely cratered regions• Bright, densely cratered regions• Make up most of the Moon• Make up nearly all of the far side of

the Moon• Older than maria

Craters

►Produced by an impact from a meteoroid which produces Ejecta Rays (associated with younger craters)

►Craters within craters are common►Crater layering can be used for

relative dating

A 20-kilometer-wide crater on the Moon

The Copernicus crater is 93 km wide.

Graphic: from Lunar and Planetary Institute

Earth’s Moon

►Central PeaksThe physics of large impacts are mind-boggling…. The rocks are subjected to stresses hundreds of times their failure strengths. This means that the rocks effectively behave as if they were water…. They flow plastically as if they were fluids.

Source: http://www.uwgb.edu/dutchs/planets/cratform.htm

Source: http://www.uwgb.edu/dutchs/planets/cratform.htm

Check up

►How are central peaks formed?►What are maria?►Why are highlands more cratered than

maria?►What is a major visual difference

between the near side and far side of the Moon?

Lunar Regolith

Regolith means “blanket”• Covers all lunar terrains• Gray, unconsolidated debris • Soil-like layer produced by meteoric

bombardment• Varies in depth from about 2 – 20

metersRegolith on earth produced by

weathering

Lunar Regolith

Where did it come from?► Hypothesis 1: fission (daughter)

Moon was ejected from Earth Mathematical models show it is impossible

► Hypothesis 2: coaccretion (sister) Earth and Moon formed together from same

material Cannot explain Moon’s lack of core

► Hypothesis 3: capture (spouse) Moon was another planet caught by Earth’s gravity Cannot explain why Moon and Earth are so

chemically similar This is very unlikely to ever happen

Giant Impact Hypothesis

►A Mars-sized object hit the Earth in our planet’s early history Material was ejected into orbit and formed

Moon Has been supported by mathematical

model Explains why the Moon:

►is very similar in age to Earth►has identical materials to Earth’s crust►does not have an iron core

Check up

►Describe the three models of Lunar evolution that were replaced by the giant impact hypothesis.

►Describe evidence for the giant impact hypothesis

►Why are regolith on highlands thicker than on maria?

►How can scientists determine relative ages of Lunar craters?