Ch 6 HW

What is the minimum number of moons that must be orbiting a planet for the moons to have an orbital resonance?

2

What is the orbital resonance among Io, Europa, and Ganymede?

Io completes exactly 4 orbits for every 2 orbits of Europa and every 1 orbit of Ganymede. Feedback: This means that these moons periodically line up in ways that contribute the same gravitational tugs as they move in their orbits.

The tidal force that acts on Io is due primarily to the gravity of __________.

Jupiter

Based on the leading scientific theory of solar system formation, which of the following statements best explains why Uranus and Neptune have a significantly different composition than Jupiter and Saturn?

Jupiter and Saturn captured more gas from the solar nebula than Uranus and Neptune.

Listed following are several objects in the solar system. Rank these objects from left to right based on their orbital period around the Sun from shortest to longest.

Shortest to Longest a typical asteroid in the asteroid belt a typical Kuiper belt object a typical Oort cloud object

Saturn's rings are composed of __________.

lots of individual particles of ice and rock Feedback: Although Saturn's rings appear solid when viewed from Earth, they are actually made of countless icy particles ranging in size from dust grains to small boulders.

What atmospheric constituent is responsible for the blue color of Uranus and Neptune?

methane

Meteors can be viewed only __________.

on worlds with atmospheres

Saturn's many moons affect its rings through

orbital resonances.

The Kuiper belt and Oort cloud can be described as __________.

regions from which comets enter the inner solar system

Suppose that large jovian planets had never formed in our solar system. Which of the following would most likely be true?

Neither the asteroid belt nor Oort cloud would exist.

Which of the following best describes the internal layering of Jupiter, from the center outward?

core of rock, metal, and hydrogen compounds; thick layer of metallic hydrogen; layer of liquid hydrogen; layer of gaseous hydrogen; cloud layer

The comets of the Oort cloud are thought to have formed __________.

in the same region as the jovian planets

Refer to the following choices to answer the questions below. Choose the answer that best describes the chemical composition of Earth's atmosphere. A. nickel and iron B. 80 percent nitrogen, 20 percent oxygen C. 95 percent carbon dioxide D. mostly hydrogen and helium E. frozen methane, ammonia, water, and other gases and dust

B. 80 percent nitrogen, 20 percent oxygen

Listed following are several objects in the solar system. Rank these objects from left to right based on their distance from the Sun, from closest to farthest.

Closest to Farthest a typical asteroid in the asteroid belt a typical Kuiper belt object a typical Oort cloud object

Listed following are some distinguishing characteristics of comets, meteors, and asteroids. Match these to the appropriate category of objects.

Comets -form a coma when near the Sun -most are located either in Kuiper belt or Oort cloud -visible in the sky as a fuzzy patch of light that rises and sets with the stars Meteors -visible in the sky as a bright streak of light for only a few seconds -dust particles entering Earth's atmosphere at high speed Asteroids -compositions similar to that of the terrestrial planets -typically orbit the Sun at approximately 3 AU

T/F: If Jupiter were 10 times more massive, it would generate nuclear fusion in its core and be a star instead of a planet.

False

As you saw in Part A, Io's elliptical orbit is necessary to its tidal heating. This elliptical orbit, in turn, is a result of the orbital resonance among Io, Europa, and Ganymede. This orbital resonance causes Io to have a more elliptical orbit than it would otherwise, because __________.

Io, Europa and Ganymede periodically return to the same orbital positions, creating the same gravitational tugs Feedback: The repeated passes at the same orbital position mean that Io experiences repeated gravitational tugs at the same place in each orbit, and these tugs make its orbit more elliptical than it would be otherwise.

Listed following are some of the distinguishing geological characteristics of the moons orbiting Jupiter. Match each characteristic to the appropriate moon.

Io: -volcanoes currently erupting -hot, glowing lava visible in some photos -source of ionized gas in the donut-shaped charged particle belt around Jupiter Europa: -surface features provide evidence of a subsurface liquid ocean -ice covered surface with few impact craters Ganymede: -largest moon in the solar system -heavily cratered terrain adjacent to much younger terrain Feedback: Remember that these differences are consequences of the different levels of tidal heating these moons experience. Io is very hot because it is the nearest of the three to Jupiter and has the most tidal heating; Europa is intermediate, and Ganymede has the least tidal heating of the three moons.

Why is Newton's version of Kepler's third law so useful to astronomers?

It can be used to determine the masses of many distant objects.

How does tidal heating on Europa compare to that on Io?

It is weaker.

What is unusual about Triton?

It orbits its planet backward.

Sort each of the planetary properties below based on whether they apply to some, all, or none of the four jovian planets in our solar system.

Jupiter and Saturn only: -interior is mostly liquid or metallic hydrogen -composed mostly of hydrogen and helium Uranus and Neptune only: -blue color because of methane -composed mostly hydrogen compounds all four jovian planets: -approximately 10 Earth-mass core -orbited by rings of ice and rock -magnetic field stronger than Earth's -strong atmospheric winds and storms no jovian planets: -solid surface under a thick atmosphere

Which of the following best explains why Jupiter's density is higher than Saturn's?

Jupiter is more massive than Saturn.

According to the leading model, which of the following best summarizes how the jovian planets formed?

Large planetesimals of ice and rock accreted; the gravity of these planetesimals then drew in surrounding gas from the solar nebula.

Listed following are several objects in the solar system. Rank these objects from left to right based on the distance from the Sun at which they are presumed to have formed, from nearest to farthest.

Nearest to Sun to Farthest from Sun a typical asteroid in the asteroid belt a typical Oort cloud object a typical Kuiper belt object

Did a large terrestrial planet ever form in the region of the asteroid belt?

No, because Jupiter prevented one from accreting.

The impact of a 100-meter object will not cause "widespread" devastation, but it could still kill millions of people if it struck a major city. In Part C, you found that the probability of such an impact in any single year is only 1 in 1000. Suppose we learn that it has already been 1200 years since the last such impact. What would that tell us?

Nothing; we would still presume that the chance of such an impact during the next year is 1 in 1000.

Suppose that two planets have the exactly the same composition but very different masses. Which statement will be true?

The more massive planet will have higher density.

Watch the portion of the video that shows the gravitational force on the near and far sides of Io as it orbits Jupiter. What can you conclude about the tidal force acting on Io?

The tidal force varies. It is strongest when Io is closest to Jupiter and weakest when Io is farthest from Jupiter.

Look at the average densities of the jovian planets given in Figure 1. Can you identify a trend in jovian planet densities with mass or distance from the Sun?

There is no clear trend in the densities with mass or distance.

How do typical wind speeds in Jupiter's atmosphere compare to typical wind speeds on Earth?

They are much faster than hurricane winds on Earth.

Which of the following statements best explains why the densities of Uranus and Neptune are higher than that of Saturn, even though Saturn is much more massive?

They have a higher proportion of hydrogen compounds and rock.

We now know of many Jupiter-size planets around other stars. Suppose that future observations show that one of these planets has two orbiting moons. What additional information, if any, would we need to decide whether these moons experience tidal heating?

We need to know their orbital periods.

According to Kepler's third law, an object that is farther from the Sun (larger semimajor axis) has __________.

a longer orbital period than an object closer to the Sun

A rock found on Earth that crashed down from space is called _________.

a meteorite

The moon that experiences the most tidal heating is _____. a) Io b) Europa c) Ganymede

a) Io

What is the probability that an object 100 meters in diameter will hit Earth during the coming year?

about 1 in 1000

According to this graph, the minimum size of an object that could cause a mass extinction is a little less than _____.

about once every 100 million years

We cannot see tidal forces or tidal heating; rather, we predict that they must occur based on the orbital characteristics of the moons. What observational evidence confirms that tidal heating is important on Io?

active volcanoes on Io Feedback: Io is barely larger than our Moon, and the Moon long ago cooled enough so that it no longer has volcanic activity. Without some ongoing source of internal heating, Io would be similarly inactive. Therefore, the fact that Io is the most volcanically active world in the solar system indicates that it must have an ongoing internal heat source, which we identify as tidal heating.

Which of the following statements correctly describes the motion of the particles in Saturn's rings? a) Particles in all the rings hover motionlessly high above Saturn. b) Particles in the inner rings orbit Saturn at a faster speed than particles in the outer rings. c) Particles in the inner rings orbit Saturn at a slower speed than particles in the outer rings. d) All the particles in the rings orbit Saturn with the same orbital period.

b) Particles in the inner rings orbit Saturn at a faster speed than particles in the outer rings. Feedback: In accord with Kepler's third law, particles closer to Saturn orbit at a faster speed than more distant particles.

The asteroid belt is located __________.

between Mars and Jupiter

Which of the following statements best describes the general pattern of composition among the four jovian planets? a) Jupiter is made mostly of hydrogen and helium, while the other three jovian planets are made mostly of hydrogen compounds. b) All four planets have essentially the same composition. c) Uranus and Neptune contain relatively more rock and hydrogen compounds than Jupiter and Saturn. d) Jupiter is made mostly of hydrogen, Saturn is made mostly of helium, Uranus is made mostly of hydrogen compounds, and Neptune is made mostly of rock.

c) Uranus and Neptune contain relatively more rock and hydrogen compounds than Jupiter and Saturn.

Which statement about Io is true? a) It is thought to have a deep, subsurface ocean of liquid water. b) It is the only moon in the solar system with a thick atmosphere. c) It is the largest moon in the solar system. d) It is the most volcanically active body in our solar system.

d) It is the most volcanically active body in our solar system.

Which of the following is furthest from the Sun? a) Neptune b) a comet in the Kuiper belt c) Pluto d) an asteroid in the asteroid belt e) a comet in the Oort cloud

e) a comet in the Oort cloud

Saturn's rings look bright because __________.

light from the Sun reflects off the material in the rings Feedback: Saturn's rings look bright because icy particles in the rings reflect (scatter) sunlight.

The Kuiper belt is located __________.

from about the orbit of Neptune to about twice Neptune's distance from the Sun

Which direction do a comet's dust and plasma tails point?

generally away from the Sun

If a world is subject to tidal heating, we'd expect it to have a __________.

high internal temperature Feedback: Tidal heating affects the interior of a world, making the interior much hotter than it would be otherwise.

The Oort cloud is located __________.

in a spherical region far beyond the orbit of Pluto

Orbital resonance also gives Europa an elliptical orbit, so it experiences tidal heating, too. However, Europa experiences less tidal heating than Io, because Europa __________ than Io.

is farther from Jupiter Feedback: It is Jupiter's gravity that exerts the primary tidal force on the Galilean moons, and both this force and the difference in this force across a moon (the source of tidal heating) weaken with distance from Jupiter. Io is closest to Jupiter and therefore experiences the most tidal heating; Europa experiences less tidal heating, and Ganymede experiences the least tidal heating. (Callisto is not expected to have any tidal heating since it does not participate in the orbital resonance that makes the other moons' orbits more elliptical.)

Io experiences tidal heating primarily because __________.

its elliptical orbit causes the tidal force to vary as Io orbits Jupiter.

According to Figure 9.24, the odds of a 100-meter asteroid hitting the Earth over the course of one year is approximately __________.

somewhat less than 1 in 1000

When a comet passes near the Sun, part of it takes on the appearance of a large, bright ball from which the tail extends. This part is called _________.

the coma

The red line on this graph is based on impact rate data and the number of comets and asteroids that pass near Earth. We can use this line on the graph to determine __________.

the typical time between impacts for an object of any size