question

According to our present theory of solar system formation, which of the following objects now reside quite far from the place where they formed originally?

answer

Oort cloud comets

question

According to our present theory of solar system formation, how did Earth end up with enough water to make oceans?

answer

The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars.

question

According to our theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size?

answer

The law of conservation of angular momentum

question

Many meteorites appear to have formed very early in the solar system's history. How do these meteorites support our theory about how the terrestrial planets formed?

answer

The meteorites appearance and composition is just what we'd expect if metal and rock condensed and accreted as our theory suggests.

question

About 2% of our solar nebula consisted of elements besides hydrogen and helium. However, the very first generation of star systems in the universe probably consisted only of hydrogen and helium. Which of the following statements is most likely to have been true about these first-generation star systems?

answer

There were no comets or asteroids in these first-generation star systems.

question

Why are terrestrial planets denser than jovian planets?

answer

Only dense materials could condense in the inner solar nebula.

question

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?

answer

The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal.

question

Which of the following is not a line of evidence supporting the hypothesis that our Moon formed as a result of a giant impact?

answer

The Pacific Ocean appears to be a large crater - probably the one made by the giant impact.

question

How do scientists determine the age of the solar system?

answer

Radiometric dating of meteorites

question

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?

answer

It flattened as a natural consequence of collisions between particles in the nebula.

question

Which of the following best describes the geological histories of the Moon and Mercury?

answer

Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.

question

What are the two geological features that appear to set Earth apart from all the other terrestrial worlds?

answer

plate tectonics and widespread erosion

question

What's the fundamental reason that Mars, unlike the Earth, has become virtually geologically dead?

answer

its small size compared to Earth

question

Which internal heat source still generates heat within the terrestrial worlds today?

answer

Heat from radioactive decay.

question

Many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If this is true, which of the following could explain it?

answer

The high surface temperature that has "baked out" all the liquid water from Venus's crust and mantle.

question

Which of the following is the underlying reason why Venus has so little wind erosion?

answer

its slow rotation

question

The choices below describe four hypothetical planets. Which one would you expect to have the hottest interior? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)

answer

Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.

question

The choices below describe four hypothetical planets. Which one would you expect to have the most features of erosion? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)

answer

Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.

question

The cores of the terrestrial worlds are made mostly of metal because ______.

answer

metals sunk to the centers a long time ago when the interiors were molten throughout

question

Which two factors are most important to the existence of plate tectonics on Earth?

answer

mantle convection and a thin lithosphere

question

All the following statements about Mars are true. Which one might have led to a significant loss of atmospheric gas to space?

answer

Mars lost any global magnetic field that it may once have had.

question

How is it possible that the Moon might have some water ice today?

answer

Ice brought by comet impacts may be frozen in craters near the Moon's poles.

question

Suppose Earth were to cool down a little. How would the carbon dioxide cycle tend to restore temperatures to normal?

answer

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.

question

All of the following have occurred over long periods of time on Earth. Which one is not thought to have played a major role in long-term changes in Earth's climate?

answer

A gradual rise in the atmospheric content of oxygen.

question

Which two factors are critical to the existence of the carbon dioxide (CO2) cycle on Earth?

answer

plate tectonics and liquid water oceans

question

Which of the following general statements about Earth's atmosphere is not true?

answer

The sea level temperature depends primarily on the total amount of gas in our atmosphere.

question

Which characteristic of Earth explains why we have an ultraviolet-absorbing stratosphere?

answer

the existence of photosynthetic life

question

Deuterium is much more abundant on Venus than Earth. What do we think this fact tells us about Venus?

answer

That it has lost a tremendous amount of water as a result of molecules being split by ultraviolet light and the hydrogen escaping to space.

question

Which of the following best explain what we think happened to outgassed water vapor on Venus?

answer

Ultraviolet light split the water molecules, and the hydrogen then escaped to space.

question

Why is the Coriolis effect so weak on Venus?

answer

Because Venus rotates so slowly.

question

Which of the following best explains why many jovian moons have been more geologically active than the Moon or Mercury?

answer

Jovian moons are made mostly of ice that can melt or deform at lower temperatures than can the rock and metal that make up the Moon and Mercury.

question

Which of the following most likely explains why Jupiter's interior releases so much heat?

answer

Jupiter is contracting very gradually.

question

What would happen to Jupiter if we could somehow double its mass?

answer

Its density would increase but its diameter would barely change.

question

Which of the following gases is not a significant ingredient of the jovian planet atmospheres?

answer

carbon dioxide

question

Which statement about Saturn's rings is not true?

answer

The rings must look much the same today as they did shortly after Saturn formed.

question

Which of the following best why we see horizontal "stripes" in photographs of Jupiter and Saturn?

answer

The light stripes are regions of high clouds, and the dark stripes are regions where we can see down to deeper, darker clouds.

question

Why does Jupiter have three distinct layers of clouds?

answer

The three layers represent clouds made of gases that condense at different temperatures.

question

Which of the following is most unlikely to be found on Titan?

answer

lakes of liquid water in the warmer equatorial regions

question

Which of the following is not a piece of evidence supporting the idea that Europa may have a subsurface ocean?

answer

Astronomers have detected small lakes of liquid water on Europa's surface.

question

Why is the radiation so intense in the region that traces Io's orbit around Jupiter (the Io torus)?

answer

The region is full of gases that become ionized after they are released from volcanoes on Io.

question

When we see a meteor shower, it means that _________.

answer

Earth is crossing the orbit of a comet

question

Which of the following statements best describes the size of the largest asteroid, Ceres?

answer

It is a little less than half the diameter of our Moon.

question

Suppose there were no solar wind. How would the appearance of a comet in our inner solar system be different?

answer

It would have only one tail instead of two.

question

Suppose you find a meteorite made almost entirely of metal. According to current science, which of the following statements must be true?

answer

Your meteorite is a fragment from the core of a large asteroid that shattered in a collision.

question

In science fiction movies, spaceships are often shown dodging through large numbers of closely spaced, boulder-size objects. Which of the following real things in our solar system would look most like such science fiction dangers?

answer

the rings of Saturn

question

If we could put all the asteroids together, their total mass would be ______.

answer

much less than the mass of any terrestrial planet

question

Which of the following is not a piece of evidence supporting the idea that Pluto is a large comet of the Kuiper belt?

answer

Pluto grows a coma and a long tail when it is at the point in its orbit closest to the Sun.

question

What is Pluto's moon Charon thought to have in common with our own Moon?

answer

It probably formed as a result of a giant impact.

question

Suppose we discover a new comet on an orbit that brings it closer to the Sun than Mercury every 125 years. What can we conclude?

answer

It has been on its current orbit for only a very short time compared to the age of our solar system.

question

Why won't Pluto collide with Neptune?

answer

Pluto orbits the Sun exactly 2 times for every 3 Neptune orbits, which ensures they never come close together.

question

Why is it so difficult to take pictures of extrasolar planets?

answer

Their light is overwhelmed by the light from their star.

question

Assuming that our ideas about how "hot Jupiters" ended up on their current orbits are correct, why didn't our own solar system end up with any hot Jupiters?

answer

Our solar nebula must have been blown into space shortly after the formation of the jovian planets.

question

Current evidence suggests that many massive jovian planets orbit at very close orbital distances to their stars. How do we think these planets ended up on these close orbits?

answer

These planets migrated inward after being born on orbits much farther from their stars.

question

Suppose a planet is discovered by the Doppler technique and is then discovered to have transits. In that case, we can determine all the following about the planet except ______________.

answer

its rotation period

question

The astrometric technique looks for planets with careful measurements of a star's _________.

answer

position in the sky

question

Which of the following is not expected for a "hot Jupiter" that orbits 0.05 AU from its star

answer

intense volcanism

question

All the following statements about known extrasolar planets are true. Which one came as a surprise to scientists who expected other solar systems to be like ours?

answer

Some of the planets orbit their star more closely than Mercury orbits the Sun.

question

When is the soonest we are likely to have images and spectra of Earthlike planets around other stars?

answer

In a decade or two, through space missions now in the early planning stages.

question

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?

answer

The planet must be closer to the star than Earth is to the Sun.

question

In general, which type of planet would you expect to cause the largest Doppler shift in the spectrum of its star?

answer

a massive planet that is close to its star

question

Why do sunspots appear dark in pictures of the Sun?

answer

They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.

question

The star Alpha Centauri A is the same type of star as the Sun, but its luminosity is about 1.6 times that of the Sun. What can we conclude?

answer

Alpha Centauri A fuses hydrogen into helium in its core at a higher rate than our Sun.

question

In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot due to gravitational contraction. What was the major drawback to this idea?

answer

It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.

question

What do we mean when we say that the Sun is in gravitational equilibrium?

answer

There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.

question

How can we best observe the Sun's chromosphere and corona?

answer

The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes.

question

Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?

answer

Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.

question

If the Sun's core suddenly shrank a little bit, what would happen in the Sun?

answer

The core would heat up, fusion rates would increase, the core would re-expand.

question

The intricate patterns visible in an X-ray image of the Sun generally show _________.

answer

extremely hot plasma flowing along magnetic field lines

question

When is/was gravitational contraction an important energy generation mechanism for the Sun?

answer

It was important when the Sun was forming from a shrinking interstellar cloud of gas.

question

Which of the following choices is not a way by which we can study the inside of the Sun?

answer

We can send a space probe into the Sun's photosphere.

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