Chapter 10
1. What is the greenhouse effect? How does it affect the average temperature on
Earth? Certain gases (like CO2 and H2O) in the atmosphere are able to trap
infrared radiation. The Sun shines on the Earth and the Earth gives off Infrared
radiation. The greenhouse gases trap that radiation and cause the atmosphere to
warm up a little before the radiation can leak out. The warms the temperature of
the Earth about 74 degrees from -17 to 57 degrees on average.
2. How does our planet’s magnetic field protect life on Earth? The magnetic field
protects life by deflection high energy particles in the solar wind. Without the
magnetosphere some of these particles would do harm to life on the surface of the
Earth.
3. Why is the Earth the only planet with an oxygen-rich atmosphere? Because the
Earth is the only planet with a biosphere. The oxygen in the atmosphere comes
primarily from photosynthesis in plants.
4. What is global warming? Why should they concern us? Global warming is the
fact that global temperatures have been rising over the last century (about). Long
term warming of the surface of the Earth could cause melting of the polar ice caps
which would raise water levels everywhere.
5. Describe various ways in which the Earth is unique among planets in the solar
system. The Earth has continental plates which are in motion. It has liquid water
over most of its surface and that water is in constant motion. The Earth’s
atmosphere has oxygen, and the Earth has a biosphere.
6. Describe how energy is transferred from the Earth’s surface to the atmosphere by
both convection and radiation. The Earth’s surface is warmed by light from the
Sun. The warmed surface emits Infrared radiation which is absorbed by and heats
the atmosphere. The warm air near the surface then expands and rises and warms
the air higher in the atmosphere. Un the upper atmosphere the layers are heated
by absorbing ultraviolet light or x-rays from the Sun.
7. In what ways does Venus’ atmosphere differ radically from our own? Venus
atmosphere is 96% carbon dioxide (Earth’s is less than a percent CO2). The
atmospheric pressure at Venus’ surface is 90 times what it is on Earth. The air
circulation on Venus is much simpler, and the winds all blow from east to west at
all latitudes (unlike on Earth).
8. Why do astronomers suspect that there are active volcanoes on Venus? First,
astronomers see lots of volcanoes. The sulfur content of the atmosphere indicates
that there has been recent geologic activity (suggesting volcanoes), particularly
since astronomers have seen rapid rising and falling of the levels of sulfur in the
atmosphere in the last 50 years. Also the reflectivity of the ground around the
volcanoes is very high, indicating recent eruptions.
9. Why is there almost no water on Venus today? The water evaporated from the
surface because of the runaway greenhouse effect, once the water was in the
atmosphere, it was decomposed by ultraviolet light from the Sun.
10. Why do astronomers think that water was once very common on Venus?
Astronomers believe that Venus and Earth were similar in their early years.
Venus would have water in its atmosphere just as Earth did. Since the Sun was
cooler then, the water would have condensed into oceans. As the Sun warmed up
the runaway greenhouse effect was started by the water in the atmosphere.
11. What role does the greenhouse effect play in the atmospheres of Venus and
Earth? The greenhouse effect keeps Venus’ atmosphere at about 860 degrees F
even on the nighttime side of the planet and near the poles (this is 750 degrees
higher than the average temperature the planet would have if it had no
atmosphere). On Earth the greenhouse effect raises the temperature about 74
degrees from what it would otherwise be.
12. Why is it hotter on Venus than on Mercury? Because of the runaway greenhouse
effect on Venus. (Mercury has no atmosphere.)
13. How does the Circulation of Venus’ atmosphere differ from Earth’s? Circulation
on Venus is simple because Venus doesn’t rotate (much). There is upper
atmospheric circulation from the equator to the poles and back again along the
surface. Venus has wind direction from east to west at all latitudes. Because it
rotates, Earth’s circulation is much more complicated. Venus’ circulation looks
like figure 10.13 on page 300. Earth’s looks like figure 10.16 on p 302.