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Astronomy Chapter 7

STUDY
PLAY
Supposed we use a baseball to represent Earth. On this scale, the other terrestrial worlds (Mercury, Venus, Moon, and Mars) would range in size from approximately form that of _____.
a golf ball to a baseball
From center to surface, which of the following correctly lists interior layers in a terrestrial world?
core, mantle, crust
What do we mean when we say that the terrestrial worlds underwent differentiation?
When their interiors were molten, denser materials sank toward their centers and lighter materials rose towad their surfaces.
A terrestrial world's lithosphere is ___________.
a layer of relatively strong, rigid rock encompassing the crust and part of the mantle.
The two most important processes in heating the interiors of the terrestrial worlds are:
1. Heat deposited by the process of formation.
2. Heat released by radioactive decay.
Which of the following is an example of convection?
warm air expanding and rising while cooler air contracts and falls.
In general, which things below are affect by a magnetic field?
charged particles or magnetized materials such as iron.
What is a magnetosphere?
a region of space around a planet in which the planet's magnetic field can trap charged particles.
The processes responsible for virtually all surface geology are _____.
impact cratering
volcanism
tectonics
erosion
In the context of planetary geology, what do we mean by outgassing?
the release by volcanism of gases that had been trapped in a planetary interior
Which of the following is NOT an example of tectonics?
the gradual disappearance of a crater rim as a result of wind and rain
Which of the following is the most basic definition of a greenhouse gas?
a gas that absorbs infrared light
Suppose we represent Earth with a basketball on this scale, most of the air in Earth's atmosphere would fit in a layer that is __________.
about the thickness of a sheet of paper
Which of the following best describes the lunar maria?
relatively smooth flat plains on the moon
Why does the moon have a layer of "powdery soil" on its surface?
it is the result of countless tiny impacts by small particles striking the moon
What observational evidence supports the idea that Mercury once shrank by 20 km in radius?
the presence of many tall long cliffs
Olympus Mons is __________
a huge volcano on Mars
Which of the following does NOT provide evidence that Mars once had abundant liquid water on its surface?
the presence of Canali, discovered in the later 1800s by Giovanni Schaparelli and mapped by Percival Lowell
Based on its surface features, the most important event on Venus in the past billion years or so was ________.
a global "repaving" that erased essentially all the surface features that had existed earlier.
What do we mean by a runaway greenhouse effect?
a greenhouse effect that keeps getting stronger until all of a planet's greenhouse gases are in its atmosphere
On average, how fast do the plates move on the Earth?
a few centimeters per year
How does the seafloor crust differ from the continental crust?
Seafloor crust is thinner, younger, and higher in density
What is the important of the Carbon Dioxide Cycle?
It regulates the carbon dioxide concentration in our atmosphere, keeping temperatures moderate
In the context of plate tectonics, what is a subduction zone?
a place where a seafoor plate is sliding under a continental plate
Earth has been gradually warming over the past few decades. Based on a great deal of evidence, scientists believe that this warming is caused by ____.
Human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere.
Based on all we know about the terrestrial worlds, what single fact appears to play the most important role in a terrestrial planet's geological destiny?>
its size
The cores of the terrestrial worlds are made mostly of metal because ______.
metals sunk to the centers a long time ago when the interiors were molten throughout
Which internal heat source still generates heat within the terrestrial worlds today?
Heat from radioactive decay
The reason that small planets tend to lose their interior heat faster than larger planets is essentially the same as the reason that __________.
a large baked potato takes longer to cool than a small baked potato
Suppose we had a device that allowed us to see Earth's interior. If we looked at a typical region of the mantle, what would we see happening?
not much- on human time scales, the mantle looks like solid rock
Recent evidence suggests that Mars once had a global magnetic field. Assuming this is true, which of the following could explain why Mars today lacks a global magnetic field like that of Earth's?
Mars's interior has cooled so much its molten core layer no longer undergoes convection.
Which of the following best explains why Venus does NOT have a global magnetic field like that of Earth?
Its rotation is too slow
What are the two geological features that appear to set Earth apart from the other terrestrial worlds?
plate tectonics and widespread erosion
Which of the following general statements about Earth's atmosphere is NOT true?
The nitrogen and oxygen in Earth's atmosphere keep the surface pleasantly warm.
Why is the sky blue on Earth?
Because molecules scatter blue light more effectively than red light
Which of the following best describes how the greenhouse effect works?
A planet's surface absorbs visible sunlight and returns this absorbed energy to space as infrared light. Greenhouse gases slow the escape of this infrared radiation, which thereby heats the lower atmosphere.
Suppose the Earth's atmosphere had no greenhouse gases. Then Earth's average surface temperature would be __________.
well below the freezing point of water
Most of the moon's surface is densely covered with craters, but we find relatively few craters within the lunar maria. What can we conclude?
The maria formed after the heavy bombardment ended
Which of the following best describes the geological histories of the moon and mercury?
Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.
What makes us think that Mars must once have had an atmosphere that was warmer and had higher surface pressure?
The atmosphere is too cold and thin for liquid water today, yet we see evidence that water flowed on the surface in the past.
All of the following statements about Mars is true. Which one might have led to a significant loss of atmospheric gas to space?
Mars lost any global magnetic field that it may have once had.
Why is Mars red?
Chemical reactions between surface rock and atmospheric oxygen literally rusted the surface
All of the following statements below are true. Which one gives the primary reason why the surface of Venus is some 450 degrees C hotter than the surface of Earth?
Venus has a much stronger greenhouse effect than Earth
Many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If this is true, which of the following could explain it?
The high surface temperature that has "baked out" all the liquid water from Venus's crust and mantle.
Which of the following best explain what we think happened to outgassed water vapor on Venus?
Ultraviolet light split the water molecules, and the hydrogen then escaped to space.
All of the following statements about Venus are true. Which one offers evidence of a global repaving about a billion years ago?
Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet.
Which of the following is the underlying reason why Venus has so little wind erosion?
its slow rotation
Why are there fewer large impact craters on the Earth's seafloor than on the continents?
Seafloor crust is younger than continental crust, so it has had less time to suffer impacts
Why is Earth's continental crust lower in density than seafloor crust?
Continental crust is made as the lowest-density seafloor crust melts and erupts to the surface near the subduction zones.
Which two factors are most important to the existence of plate tectonics on Earth?
mantle convection and a thin lithosphere
Why does Earth have so little carbon dioxide cycle in its atmosphere compared to Venus?
Earth has just as much carbon dioxide as Venus, but most of it is locked up in carbonate rocks rather than being free in the atmosphere
What two factors are critical to the existence of the carbon dioxide cycle on Earth?
plate tectonics and liquid water oceans on Earth
Suppose Earth were to cool down a little. How would the carbon dioxide cycle tend to restore temperatures to normal?
Cooler temperatures lead to slower formation of carbonate minerals in the ocean, so carbon dioxide released by volcanism builds up in the atmosphere and strengthens the greenhouse effect.
Which of the following is NOT an expected consequence of global warming?
The entire Earth will warm up by the same amount.
The choices below describe four hypothetical planets. Which one's surface would you expect to be most crowded with impact craters?
Size: same as the moon
Distance from the sun: same as Mars
Rotation rate: once every 10 days
The choices below describe four hypothetical planets. Which one would you expect to have the most features of erosion?
Size: same as venus
Distance from Sun: same as Mars
Rotation rate: once every 25 hours
What's the fundamental reason that Mars, unlike the Earth, has become virtually geologically dead?
its small size compared to Earth
Facts about Mercury:
craters, smooth plains, cliffs
Facts about Venus
volcanoes, few craters
Facts about Earth
Volcanoes, craters, mountains, riverbeds
Facts about Mars
some craters, volcanoes, river beds
Three parts of Earth
1. core: highest density- nickel and iron
2. mantle: moderate density- silicone, oxygen
3. crust: lowest density-granite, basalt
Differentiation:
process of heaviest metals moving to the center. The materials are separated by density.
Stretching rock...
move rock slowly: stretches
move rock quickly: breaks
Heat drives geological activity
convection: hot rock rises, cool rock falls
Heating interior:
1. formation of Earth gave it a lot of heat
2. Radioactive decay is the most important now.
Cooling of Interior
1. Convection: hot material rises, cool material falls
2. Conduction:heat one side of an object to another
3. Radiation: sends energy into space
Small planets cool off faster...
Reason why moon and mercury are geologically dead
Planetary magnetic fields
moving charged particles create magnetic fields

planet's interior can create magnetic fields if its core is electrically conducting, convecting, and rotating
Earth's magnetosphere
protects us from charged particles from the sun.

creates aurorae: Northern lights
What processes shape Earth's surface?
1. impact cratering
2. Volcanism
3. Tectonics
4. Erosion
Effects of atmosphere on Earth
1. Erosion
2. Radiation protection
3. Greenhouse effect
4. makes the sky blue
Moon
volcanic activity 3 billion years ago

lunar maria

now geologically dead
Mercury
long cliffs indicate that Mercury shrank early in history
Mars vs Earth
50% Earth's radius
10% Earth's mass
1.5 AU from Sun
Axis tilt- about the same as Earth
similar rotation period
Thin Carbon Dioxide atmosphere
little greenhouse

MAIN DIFFERENCE: Mars is smaller
Seasons on mars
more extreme in the southern hemisphere because of elliptical orbit. Earth's orbit is almost a circle.
What geological features on Mars tells us there was once water?
Mars is covered with features that indicate presence of H2O.
Olympus Mons
largest volcano in solar system on Mars
Why did Mars change?
Greenhouse effect kept surface warmer

Mars lost most of its atmosphere.. no longer protected from the sun so UV light destroys water

Magnetic field may have preserved early Martian atmosphere.

Solar wind may have stripped atmosphere after field decreased because of interior cooling. It cooled down faster than Earth because it's smaller than Earth.
Why is Venus so hot?
not closest to the sun... the greenhouse effect traps infrared light, and heat rises
Why is greenhouse effect stronger on Earth than it is on Venus?
Venus has a thick atmosphere made of carbon dioxide and a large surface pressure. Earth escapes this because the carbon and water are located in surface water and rocks.
4 features of Earth:
1. surface liquid water, because it is at the right distance from the Sun.
2. Atmosphere oxygen
3. Plate tectonics: important in Carbon Dioxide cycle
4. Climate stability... Carbon Dioxide cycle is a thermostat
Carbon Dioxide Cycle
1. Atmosphere Carbon Dioxide becomes rain
2. Rain erodes minerals that flow into the ocean
3. minerals and carbon make rocks on the ocean floor
4. subduction causes rocks to go down the mantle
5. Rock melts in mantle and outgasses carbon dioxide into atmosphere through volcanoes.