copyright © 2010 pearson education, inc. chapter 6 the terrestrial planets
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Copyright © 2010 Pearson Education, Inc.Copyright © 2010 Pearson Education, Inc.
Chapter 6The Terrestrial
Planets
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Chapter 6The Terrestrial Planets
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Units of Chapter 6
Orbital and Physical Properties
Rotation Rates
Atmospheres
The Surface of Mercury
The Surface of Venus
The Surface of Mars
Internal Structure and Geological History
Atmospheric Evolution on Earth, Venus, and Mars
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Sputnik 1
Question 1
Which of the following inner solar system bodies has the largest volcanoes?
a) Mercury
b) Venus
c) Earth
d) Mars
e) Moon
Question 1
a) Mercury
b) Venus
c) Earth
d) Mars
e) Moon
Mars’ largest volcano, Olympus Mons, rises more than 25 km
(75,000 ft) above the surrounding plains.
Which of the following inner solar system bodies has the largest volcanoes?
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Orbital and Physical Properties
The orbits of Venus and Mercury show that these planets never appear far from the Sun.
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Orbital and Physical Properties
The terrestrial planets have similar densities and roughly similar sizes, but their rotation periods, surface temperatures, and atmospheric pressures vary widely.
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Rotation Rates
Mercury can be difficult to image from Earth; rotation rates can be measured by radar.
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Mercury was long thought to be tidally locked to the Sun; measurements in 1965 showed this to be false.
Rather, Mercury’s day and year are in a 3:2 resonance; Mercury rotates three times while going around the Sun twice.
Rotation Rates
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Rotation Rates
Venus Mars
-243 days
1.03 days
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Rotation Rates
All the planets rotate in a prograde direction, except Venus, which is retrograde.
Question 2
Which of the following inner solar system bodies has the densest atmosphere?
a) Mercury
b) Venus
c) Earth
d) Moon
e) Mars
Question 2
a) Mercury
b) Venus
c) Earth
d) Moon
e) Mars
Venus’ atmosphere has a pressure about 90 times larger than Earth’s.
Many of its surface features are affected by this immense pressure.
Which of the following inner solar system bodies has the densest atmosphere?
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Atmospheres
Mercury has no detectable atmosphere; it is too hot, too small, and too close to the Sun.
Venus has an extremely dense atmosphere. The outer clouds are similar in temperature to Earth, and it was once thought that Venus was a “jungle” planet. We now know that its surface is hotter than Mercury’s, hot enough to melt lead.
The atmosphere of Mars is similar to Earth in composition, but very thin.
Question 3
The greenhouse effect on Venus is due to ______ in its atmosphere.
a) nitrogen
b) hydrogen
c) carbon dioxide
d) oxygen
e) sulfuric acid
Question 3
The greenhouse effect on Venus is due to ______ in its atmosphere.
Venus’ atmosphere is over 96% CO2, resulting in a surface temperature
exceeding 900 °F.
a) nitrogen
b) hydrogen
c) carbon dioxide
d) oxygen
e) sulfuric acid
Question 4
Mercury’s surface most resembles which of these?
a) the Moon’s far side
b) Venus’ polar regions
c) Earth’s deserts
d) the Moon’s near side
e) Mars’ deserts
Question 4
Mercury’s surface most resembles which of these?
a) the Moon’s far side
b) Venus’ polar regions
c) Earth’s deserts
d) the Moon’s near side
e) Mars’ deserts
Both Mercury and the Moon’s far side are
heavily cratered.
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Mercury cannot be imaged well from Earth; best pictures are from Messenger.
Cratering on Mercury is similar to that on the Moon.
The Surface of Mercury
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Messenger Selected 1999Launched 2004Orbit insertion 2011$446 Billion5 Billion miles
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Mercury is very hard to observe from Earth because
Question 5
a) it always appears only half lit.
b) it is never more than 28° from the Sun.
c) its elliptical orbit causes it to change speed unpredictably.
d) its surface reflects too little sunlight.
e) its surface does not allow radar to bounce back to Earth.
Mercury is very hard to observe from Earth because
Question 5
a) it always appears only half lit.
b) it is never more than 28° from the Sun.
c) its elliptical orbit causes it to change speed unpredictably.
d) its surface reflects too little sunlight.
e) its surface does not allow radar to bounce back to Earth.
Mercury’s inner orbit keeps it close to the Sun, visible only for
an hour or two before sunrise or
after sunset.
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Some distinctive features: Scarp (cliff), several hundred km long and up to 3 km high, thought to be formed as the planet cooled and shrank.
The Surface of Mercury
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Caloris Basin, very large impact feature; ringed by concentric mountain ranges
The Surface of Mercury
Mercury has extreme high and low temperatures between night and day because
Question 6
a) it is so close to the Sun.
b) its surface rocks don’t retain heat.
c) it spins too fast to cool down.
d) Mercury’s axis has no tilt; its equator receives direct sunlight.
e) it has no atmosphere to moderate temperatures over the globe.
Mercury has extreme high and low temperatures between night and day because
Question 6
a) it is so close to the Sun.
b) its surface rocks don’t retain heat.
c) it spins too fast to cool down.
d) Mercury’s axis has no tilt; its equator receives direct sunlight.
e) it has no atmosphere to moderate temperatures over the globe.
Mercury’s very high sunlit surface temperature of 700 K, and low mass, explain why it
has no atmosphere.
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The Surface of Venus
This map of the surface features of Venus is on the same scale as the Earth map below it.
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Venus as a globe, imaged by Magellan launched from STS-30 in 1989.
730 k = HOT!
855 F
90 atm
Sulfuric acid rain
The Surface of Venus
Venus’ surface shows all of the following EXCEPT
Question 7
a) many impact craters of all sizes.
b) shield volcanoes.
c) a continent-sized plateau.
d) huge circular volcanic coronae.
e) lava domes.
Venus’ surface shows all of the following EXCEPT
Question 7
a) many impact craters of all sizes.
b) shield volcanoes.
c) a continent-sized plateau.
d) huge circular volcanic coronae.
e) lava domes.
Venus’ thick atmosphere shields the planet from smaller meteor impacts.
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Top: Lava domes on Venus (L), and a computer reconstruction (R)
Bottom: the volcano Gula Mons
The Surface of Venus
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Venus corona, with lava domes
The Surface of Venus
Fly by
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A photograph of the surface, from the Venera lander. Russia sent more than 16 probes.
The Surface of Venus
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Photography on Venus
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Venera - USSR
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The Surface of Venus
Impact craters. Left: multiple-impact crater Above: Mead, Venus’s largest impact crater
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Mars
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The Surface of Mars
Major feature: Tharsis bulge, size of North America and 10 km above surroundings
Minimal cratering; youngest surface on Mars
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Viking I & II 1976
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Viking 1976
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The Surface of Mars
• Northern hemisphere (left) is rolling volcanic terrain.• Southern hemisphere (right) is heavily cratered
highlands; average altitude 5 km above northern.• Assumption is that northern surface is younger than
southern.• Means that northern hemisphere must have been
lowered in elevation and then flooded with lava.
Fly by
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This map shows the main surface features of Mars. There is no evidence for plate tectonics.
The Surface of Mars
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Mars has largest volcano in Solar System; Olympus Mons:
• 700 km diameter at base• 25 km high
Three other Martian volcanoes are only slightly smaller.
• Caldera 80 km in diameter
The Surface of Mars
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Was there running water on Mars?
Runoff channels resemble those on Earth.
Left: Mars
Right: Earth
The Surface of Mars
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No evidence of connected river system; features probably due to flash floods
The Surface of Mars
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The Surface of Mars
This feature may be an ancient river delta. Or it may be something entirely different.
Okavango
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Much of northern hemisphere may have been ocean.
6.6 The Surface of Mars
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Impact craters less than 5 km across have mostly been eroded away.
Analysis of craters allows estimation of age of surface.
Crater on right was made when surface was liquid.
The Surface of Mars
What was the most likely source of the water that formed the huge outflow channels of Mars?
Question 8a) rainfall
b) catastrophic but rare flooding
c) annual melting of the seasonal ice caps
d) large comets that struck Mars
e) a collision with one of Jupiter’s frozen moons
What was the most likely source of the water that formed the huge outflow channels of Mars?
Question 8a) rainfall
b) catastrophic but rare flooding
c) annual melting of the seasonal ice caps
d) large comets that struck Mars
e) a collision with one of Jupiter’s frozen moons
Flooding on Mars appears to have occurred about 3
billion years ago.
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Recently, gullies have been seen that seem to indicate the presence of liquid water; interpretation is still in doubt.
The Surface of Mars
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Left: Viking photo
Right: Mars rover Sojourner, approaching “Yogi”
The Surface of Mars
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The Surface of Mars
Landscape and close-up by Opportunity rover
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Opportunity Rover$ 1 Billion
Manned mission estimate of more than $10 Billion
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RAT & Möessbauer
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Internal Structure and Geological History
Internal structure of Mercury, Mars, and the Moon, compared to Earth
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Atmospheric Evolution on Earth, Venus, and Mars
At formation, planets had primary atmosphere – hydrogen, helium, methane, ammonia, water vapor – which was quickly lost.
Secondary atmosphere – water vapor, carbon dioxide, sulfur dioxide, nitrogen – comes from volcanic activity.
Earth now has a tertiary atmosphere, 20 percent oxygen, due to the presence of life.
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Earth has a small greenhouse effect; it is in equilibrium with a comfortable (for us) surface temperature.
Atmospheric Evolution on Earth, Venus, and Mars
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Atmospheric Evolution on Earth, Venus, and Mars
Venus’s atmosphere is much denser and thicker; a runaway greenhouse effect has resulted in its present surface temperature of 730 K.
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