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38 Cards in this Set

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How is Einstein's famous equation, E=mc 2, important in understanding the Sun?
It explains the fact that the Sun generates energy to shine by losing some 4 million tons of mass each day.

*The "lost" 4 million tons is converted to an amount of energy equal to this mass times the speed of light squared. Note that although 4 million tons per day sounds like a lot, it is quite small compared to the Sun's total mass.
In what way is Venus most similar to Earth?
Both planets are nearly the same size.

*This similarity in size means the two planets are probably quite similar in their interior structures and fundamental properties, though they have obvious and important differences on their surfaces.
Which of the following statements about the recently-discovered object Eris is not true?
It orbits the Sun in the same direction as the other planets.
It lies well beyond Pluto and Neptune.
It is slightly larger than Pluto.
It is thought to be the first example of a new class of object.

*Actually, it's very similar to Pluto, so it's not a new kind of object.
Mars has two moons that are most similar in character to:
small asteroids
Which planet listed below has the most extreme seasons?
Mars
Jupiter
Earth
Uranus

*Remember that seasons are caused primarily by axis tilt. Uranus essentially rotates on its side compared to its orbit, giving it very extreme seasons.
Which of the following is not a major pattern of motion in the solar system?
Nearly all comets orbit the Sun in same direction and roughly the same plane.
The Sun and most of the planets rotate in the same direction in which the planets orbit the Sun.
Most of the solar system's large moons orbit in their planet's equatorial plane.
All of the planets orbit the Sun in the same direction - counterclockwise as viewed from above Earth's north pole.

Correct

This statement is untrue because comets of the Oort cloud, which are the most numerous of all comets, have randomly oriented orbits going in all directions around the Sun.
According to our theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size?
To conserve angular momentum, the cloud particles had to move faster around the cloud center as their distance from the center decreased.
According to our theory of solar system formation, which law best explains why the central regions of the solar nebula got hotter as the nebula shrank in size?
The law of conservation of energy

*As it shrank in size, gas particles lost gravitational potential energy. Since energy must be conserved, this energy became thermal energy.
According to our present theory of solar system formation, which of the following best explains why the solar nebula ended up with a disk shape as it collapsed?
It flattened as a natural consequence of collisions between particles in the nebula.

*These collisions tend to change random motions into more orderly ones.
What is the primary basis upon which we divide the ingredients of the solar nebula into four categories (hydrogen/helium; hydrogen compound; rock; metal)?
The temperatures at which various materials will condense from gaseous form to solid form.
What is the primary basis upon which we divide the ingredients of the solar nebula into four categories (hydrogen/helium; hydrogen compound; rock; metal)?
The locations of various materials in the solar nebula.
The temperatures at which various materials will condense from gaseous form to solid form.
The atomic mass numbers of various materials.
The amounts of energy required to ionize various materials.

Condensation determined the materials available in solid form in different regions of the nebula.
According to our present theory of solar system formation, which of the following statements about the growth of terrestrial and jovian planets is not true?
Swirling disks of gas, like the solar nebula in miniature, formed around the growing jovian planets but not around the growing terrestrial planets.
Both types of planet begun with planetesimals growing through the process of accretion, but only the jovian planets were able to capture hydrogen and helium gas from the solar nebula.
The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal.
The terrestrial planets formed inside the frost line of the solar nebula and the jovian planets formed beyond it.

*The planetesimals in the outer solar system were not made only of ice: they also contained rock and metal. Remember, if it's cold enough for ices to condense from hydrogen compounds, it's certainly cold enough for rock and metal to condense as well.
According to our present theory of solar system formation, how did Earth end up with enough water to make oceans?
The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars.

Water ice could condense from the solar nebula gas only beyond the frost line, which lay beyond the orbit of Mars.
According to our present theory of solar system formation, why were solid planetesimals able to grow larger in the outer solar system than in the inner solar system?
Hydrogen compounds were much more abundant than rock and metal, so their condensation into ice meant much more solid material was available to accrete into planetesimals.
According to our basic scenario of solar system formation, why do the jovian planets have numerous large moons?
As the growing jovian planets captured gas from the solar nebula, the gas formed swirling disks around them, and moons formed from condensation accretion within these disks.

*That is, the formation of large moons around jovian planets was much like a smaller version of the formation of planets around the Sun.
Which of the following is NOT evidence supporting the idea that our Moon formed as a result of a giant impact?
The Pacific Ocean appears to be a large crater - probably the one made by the giant impact.
Suppose you find a rock that contains 10 micrograms of radioactive potassium-40, which has a half-life of 1.25 billion years. By measuring the amount of its decay product (argon-40) present in the rock, you conclude that there must have been 80 micrograms of potassium-40 when the rock solidified. How old is the rock?
3.75 billion years

The current 10 micrograms of potassium-40 is 1/8 of the original 80 grams, which means the amount of potassium-40 has declined by a factor of 8. Therefore, three half-lives have passed (since 23 = 8) and the rock is 3(1.25 = 3.75 billion years old.
Which of the following statements is not true about the planets so far discovered around other stars?
Photographs reveal that most of them have atmospheres much like that of Jupiter.

*With rare (and very low-resolution) exceptions, we cannot yet obtain images of extrasolar planets.
Which new idea has been added into our theory of solar system formation as a result of the discoveries of extrasolar planets?
Jovian planets can migrate from the orbits in which they are born.

*Migration is necessary to explain how some very massive extrasolar planets came to be in orbits very close to their stars.
You observe a star very similar to our own Sun in size and mass. This star moves very slightly back and forth in the sky once every 4 months, and you attribute this motion to the effect of an orbiting planet. What can you conclude about the orbiting planet?
A distant planet would have a long orbital period, not a short one.

According to Kepler's third law, a planet with a shorter orbital period must be closer to the star, assuming the star has the same mass as the Sun.
The region of our solar system between Mercury and Mars has very few asteroids, while the region between Mars and Jupiter has many asteroids. Based on what you have learned, what is the most likely explanation for the lack of asteroids between Mercury and Mars?
There were very few planetary leftovers in this region, because most of the solid material was accreted by the terrestrial planets as the planets formed.

*In other words, the objects that might have become asteroids were all swept up in this region.
Based on everything you have learned about the formation of our solar system, which of the following statements is probably not true?
Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.

*Spinning disks are a natural consequence of how we think stars form, which is one reason we expect planets to be quite common; the fact that we have now discovered hundreds of extrasolar planets lends further support to the idea that disks and planets should both be common.
Which internal heat source still generates heat within the terrestrial worlds today?
Convection is not a source of heat, but rather occurs if there is strong heating from below.

Radioactive decay generated even more heat in the past, since there are fewer radioactive materials left as time goes by.
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?
Mantle convection involves solid (not molten) rock going both up and down.

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?
Mars's interior has cooled so much its molten core layer no longer undergoes convection.

*Convection of the molten core is required for a global magnetic field.
What are the two geological features that appear to set Earth apart from all the other terrestrial worlds?
All the terrestrial planets have dense cores.
Volcanism and tectonics have affected Venus and Mars as well.


plate tectonics and widespread erosion
Why is the sky blue (on Earth)?
Because molecules scatter blue light more effectively than red light.

*Therefore blue light from the Sun is scattered all over the sky. At sunset or sunrise, when we see the Sun through more atmosphere (because it is on the horizon), so much blue light is scattered away that we are left with a red sunset (or sunrise).
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 that Earth's atmosphere had no greenhouse gases. Then Earth's average surface temperature would be ________.
well below the freezing point of water

*Without the greenhouse effect, Earth's average temperature would be about -16°C, which is well below freezing (0°C). Thanks to the greenhouse effect, the actual global average temperature is about 15°C.
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.

*That pretty much summarizes the geological histories of the Moon and Mercury.
The atmosphere is too cold and thin for liquid water today, yet we see evidence that water flowed on the surface in the past.
What makes us think that Mars must once have had an atmosphere that was warmer and had higher surface pressure?
All the following statements about Mars are true. Which one might have led to a significant loss of atmospheric gas to space?
Mars lost any global magnetic field that it may once have had. This allowed the solar wind to strip atmospheric gas into space.
All of the statements below are true. Which one gives the primary reason why the surface of Venus today is some 450°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?
Without water, the rock would be stronger and the lithosphere could become thicker.

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.

*This did not occur on Earth, because the temperatures allowed the water vapor to condense into liquid water and rain down to the surface.
Which of the following is the underlying reason why Venus has so little wind erosion?
its slow rotation

Without rotation, it lacks significant wind and therefore lacks wind erosion.
All 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.

This suggests that older impact craters were covered over everywhere on the planet.
Why are there fewer large impact craters on the Earth's seafloor than on the continents?
The oceans are only a few kilometers deep and therefore do not appreciably affect the speed of impactors of this size or larger

Seafloor crust is continually recycled, so that the seafloor is nearly everywhere younger than about 200 million years. Therefore evidence of any earlier impacts has been erased as the seafloor crust was recycled.