Homework
description
Transcript of Homework
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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?
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The Earth’s Moon
09.10.07 / 09.11.07
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Concept: The Moon
►EQ: What hypotheses have been developed to explain the evolution of the Moon?
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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
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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General characteristics • No atmosphere• Tectonics no longer active• Surface is bombarded by small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
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Lunar topography
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Lunar Surface
Two types of terrain•Maria (singular, mare), Latin for
"sea“•Highlands, English for land that
is high
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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
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Formation of Maria
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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
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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
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A 20-kilometer-wide crater on the Moon
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The Copernicus crater is 93 km wide.
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Graphic: from Lunar and Planetary Institute
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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
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Source: http://www.uwgb.edu/dutchs/planets/cratform.htm
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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?
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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
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Lunar Regolith
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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
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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
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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?