copyright © 2010 pearson education, inc. chapter 6 the terrestrial planets

Chapter 6The Terrestrial

Planets

Chapter 6The Terrestrial Planets

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

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?

The orbits of Venus and Mercury show that these planets never appear far from the Sun.

The terrestrial planets have similar densities and roughly similar sizes, but their rotation periods, surface temperatures, and atmospheric pressures vary widely.

Rotation Rates

Mercury can be difficult to image from Earth; rotation rates can be measured by radar.

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

Venus Mars

-243 days

1.03 days

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?

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.

Mercury cannot be imaged well from Earth; best pictures are from Messenger.

Cratering on Mercury is similar to that on the Moon.

Messenger Selected 1999Launched 2004Orbit insertion 2011$446 Billion5 Billion miles

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.

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.

Caloris Basin, very large impact feature; ringed by concentric mountain ranges

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.

This map of the surface features of Venus is on the same scale as the Earth map below it.

Venus as a globe, imaged by Magellan launched from STS-30 in 1989.

730 k = HOT!

90 atm

Sulfuric acid rain

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.

Top: Lava domes on Venus (L), and a computer reconstruction (R)

Bottom: the volcano Gula Mons

Venus corona, with lava domes

Fly by

A photograph of the surface, from the Venera lander. Russia sent more than 16 probes.

Photography on Venus

Venera - USSR

Impact craters. Left: multiple-impact crater Above: Mead, Venus’s largest impact crater

The Surface of Mars

Major feature: Tharsis bulge, size of North America and 10 km above surroundings

Minimal cratering; youngest surface on Mars

Viking I & II 1976

Viking 1976

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

This map shows the main surface features of Mars. There is no evidence for plate tectonics.

The Surface of Mars

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

Was there running water on Mars?

Runoff channels resemble those on Earth.

Left: Mars

Right: Earth

The Surface of Mars

No evidence of connected river system; features probably due to flash floods

The Surface of Mars

This feature may be an ancient river delta. Or it may be something entirely different.

Okavango

Much of northern hemisphere may have been ocean.

6.6 The Surface of Mars

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.

Recently, gullies have been seen that seem to indicate the presence of liquid water; interpretation is still in doubt.

The Surface of Mars

Left: Viking photo

Right: Mars rover Sojourner, approaching “Yogi”

The Surface of Mars

Landscape and close-up by Opportunity rover

Opportunity Rover$ 1 Billion

Manned mission estimate of more than $10 Billion

RAT & Möessbauer

Internal Structure and Geological History

Internal structure of Mercury, Mars, and the Moon, compared to Earth

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.

Earth has a small greenhouse effect; it is in equilibrium with a comfortable (for us) surface temperature.

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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