Download 06 Terrestrial Planets

Chapter 6
The Terrestrial
Planets
Copyright © 2010 Pearson Education, Inc.
Copyright © 2010 Pearson Education, Inc.
Chapter 6
The Terrestrial Planets
Copyright © 2010 Pearson Education, Inc.
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
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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
Which of the following
inner solar system
bodies has the largest
volcanoes?
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.
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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Rotation Rates
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.
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Rotation Rates
Mars
Venus
-243 days
1.03 days
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Rotation Rates
All the planets rotate in a prograde direction,
except Venus, which is retrograde.
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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
Which of the following
inner solar system
bodies has the
densest atmosphere?
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.
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.
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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.
a) nitrogen
b) hydrogen
c) carbon dioxide
d) oxygen
e) sulfuric acid
Venus’ atmosphere is over 96% CO2,
resulting in a surface temperature
exceeding 900 °F.
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.
The Surface of Mercury
Mercury cannot be imaged well from Earth; best
pictures are from Messenger.
Cratering on
Mercury is
similar to that
on the Moon.
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Messenger
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Selected 1999
Launched 2004
Orbit insertion 2011
$446 Billion
5 Billion miles
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Question 5
Mercury is very
hard to observe
from Earth
because
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.
Question 5
Mercury is very
hard to observe
from Earth
because
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.
The Surface of Mercury
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.
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The Surface of Mercury
Caloris Basin,
very large impact
feature; ringed
by concentric
mountain ranges
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Question 6
Mercury has
extreme high and
low temperatures
between night and
day because
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.
Question 6
Mercury has
extreme high and
low temperatures
between night and
day because
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.
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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The Surface of Venus
Venus as a globe,
imaged by
Magellan launched
from STS-30 in
1989.
730 k = HOT!
855 F
90 atm
Sulfuric acid rain
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Question 7
Venus’ surface
shows all of the
following EXCEPT
a) many impact craters of all sizes.
b) shield volcanoes.
c) a continent-sized plateau.
d) huge circular volcanic coronae.
e) lava domes.
Question 7
Venus’ surface
shows all of the
following EXCEPT
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.
The Surface of Venus
Top: Lava domes on
Venus (L), and a computer
reconstruction (R)
Bottom: the volcano Gula
Mons
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The Surface of Venus
Venus corona,
with lava domes
Fly by
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The Surface of Venus
A photograph of the surface, from the Venera
lander. Russia sent more than 16 probes.
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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.
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Fly by
The Surface of Mars
This map shows the main surface features of
Mars. There is no evidence for plate tectonics.
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The Surface of Mars
Mars has largest volcano in Solar System;
Olympus Mons:
• 700 km diameter at base
• 25 km high
• Caldera 80
km in diameter
Three other
Martian
volcanoes are
only slightly
smaller.
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The Surface of Mars
Was there running water on Mars?
Runoff
channels
resemble
those on
Earth.
Left: Mars
Right: Earth
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The Surface of Mars
No evidence of connected river system;
features probably due to flash floods
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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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6.6 The Surface of Mars
Much of northern
hemisphere may have
been ocean.
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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.
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Question 8
What was the most
likely source of the
water that formed the
huge outflow
channels of Mars?
a) 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
Question 8
What was the most
likely source of the
water that formed the
huge outflow
channels of Mars?
a) 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.
The Surface of Mars
Recently, gullies have been seen that seem to
indicate the presence of liquid water;
interpretation is still in doubt.
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The Surface of Mars
Left: Viking photo
Right: Mars rover Sojourner, approaching “Yogi”
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The Surface of Mars
Landscape and close-up
by Opportunity rover
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$ 1 Billion
Opportunity Rover
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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Atmospheric Evolution on Earth,
Venus, and Mars
Earth has a small
greenhouse effect; it is
in equilibrium with a
comfortable (for us)
surface temperature.
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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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