Chapter 7 Earth and the Terrestrial Worlds. Mercury craters smooth plains cliffs.
MERCURY Q: Why are there so many craters?. Mercury.
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Transcript of MERCURY Q: Why are there so many craters?. Mercury.
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MERCURY
Q: Why are there so many craters?
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Mercury
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We see so many craters because:
• No atmosphere means no weather.
• No weather means no weathering and erosion.
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We see so many craters because:
No plate tectonics to “recycle” the crust.
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Why Mercury so hot?
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Mercury is hot because:
• It is so close to the sun!
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Energy reaching a planet from the sun
decreases rapidly with distance
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INVERSE SQUARE LAW
(any property) varies inversely as the square of the distance from an object
1
d2
So….
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With distance, same energy must be spread over larger and larger area
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Mercury
Why are the day/night temps so different?
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Temperatures are so extreme because there is no atmosphere :
• to block radiation from reaching the surface
• To prevent heat from leaving.
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Venus• Q: Why is it so hot when it is
farther from sun than Mercury?
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VENUS
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Venus is so hot because:
• Its atmosphere traps heat and won’t let it out.
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The Greenhouse Effect
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Why DOES Venus have an atmosphere?
• OUTGASSING—gases are released by volcanic activity.
• And…
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And…
• It has enough gravity to hang on to the gas.
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Why does the earth’s atmosphere have so much oxygen?
Photosynthesis
Cyanobacteria began to oxygenate the earth
about 2.4 BYA
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Where do we find the only life forms in the universe?
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Is there life on MARS?
Uh, no.
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Is there WATER on MARS?
YESPenetrating radar shows there is
lots of water frozen under the poles.
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Was there ever surface water on MARS?
(maybe)There are erosional features that look as though made by
liquid.
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On the other hand…
the atmospheric pressure is so low (0.01atm) that liquid water would boil
away.
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Why is Jupiter “banded?”
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1. Convection within atmosphere.
In a fluid, hot stuff rises, cool stuff sinks.
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On our planet, warmer rises from the equator, sinks at the poles.
• If the earth did not rotate, all winds would blow north and south.
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2. Rapid rotational speed (10 hours)
Compared to its axis, a planet is rotating faster at the equator than at the poles.
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So, as air moves away from the poles…
It moves over a faster moving surface, and appears to curve to the right.
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When air moves to the north from the equator,
• It curves to the right
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The earth’s global wind belts, showing the Coriolis effect.
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3. The Coriolis Effect.
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Why does Jupiter have so many ‘moons” ?
MORE MASS, MORE GRAVITY.
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What are the rings of Saturn?
Mostly ice crystals and carbon dust.
Size = few cm to few m
Only few hundred m thick.
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How did Saturn’s rings form?
• Collisions among satellites due to complex gravitational “tides”
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Why does Uranus “lie on its side?”
MASSIVE collision.
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Why is Neptune blue?
• Methane in upper atmosphere absorbs red wavelengths, letting blue though.
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Neptune’s moon Triton is unique because…
• It orbits backwards (retrograde)
• It is volcanically active.