Deck 9: Asteroids, Comets, and Dwarf Planets: Their Nature, Orbits, and Impacts

Question 1

Where are the Trojan asteroids located?

A) surrounding Jupiter
B) along Jupiter's orbit, 60° ahead of and behind Jupiter
C) in the center of the asteroid belt
D) on orbits that cross Earth's orbit
E) on orbits that cross Mars's orbit

Answer 1

B

Question 2

Which of the following statements about comets and asteroids is true?

A) Only asteroids collide with Earth.
B) Comets are balls of ice and dust.
C) Most of the trillions of comets in our solar system have tails.
D) All asteroids lie in the asteroid belt between Mars and Jupiter.
E) There are about 1 million known asteroids in the solar system.

Answer 2

B

Question 3

What characteristic distinguishes a meteorite from a terrestrial rock?

A) A meteorite is usually covered with a dark crust from burning in Earth's atmosphere.
B) A meteorite usually has a high metal content.
C) Meteorites have different isotope ratios of particular elements when compared to terrestrial rocks.
D) Meteorites contain rare elements, such as iridium, that terrestrial rocks do not.
E) All of the above are true.

Answer 3

E

Question 4

How do asteroids differ from comets?

A) Asteroids are made of rocky material. Comets are made of icy material.
B) Asteroids are made of icy material. Comets are made of rocky material.
C) Asteroids and comets are both made of rocky and icy material, but asteroids are larger in size than comets.
D) Asteroids and comets are both made of rocky and icy material, but asteroids are smaller in size than comets.

Question 5

Why does the plasma tail of a comet always point away from the Sun?

A) The solar wind blows the plasma ions directly away from the Sun.
B) Radiation pressure from the Sun's light pushes the ions away.
C) The conservation of the angular momentum of the tail keeps it always pointing away from the Sun.
D) Gases from the comet, heated by the Sun, push the tail away from the Sun.
E) It is allergic to sunlight.

Question 6

Meteorites can come from

A) the cores of asteroids.
B) the crusts and mantles of asteroids
C) the Moon.
D) Mars
E) all of the above

Question 7

Why aren't small asteroids spherical in shape?

A) The strength of gravity on small asteroids is less than the strength of the rock.
B) Small asteroids have odd shapes because they were all chipped off larger objects.
C) Large asteroids were once molten and therefore became spherical, but small asteroids were never molten.
D) Large asteroids became spherical because many small collisions chipped off pieces until only a sphere was left; this did not occur with small asteroids.

Question 8

What part of a comet always points most directly away from the Sun?

A) the nucleus
B) the coma
C) the jets of gas
D) the plasma tail
E) the dust tail

Question 9

Why do we sometimes observe asteroids at the distances of the gaps in the asteroid belt?

A) A gap is located at an average orbital distance, and asteroid orbits often have large eccentricities.
B) Jupiter's gravitational tugs keep them there.
C) They are held in place by resonances with other asteroids.
D) They are kept in place by shepherding asteroids.
E) Actually, we never see asteroids in the gaps.

Question 10

What is a meteorite?

A) a streak of light caused by a star moving across the sky
B) a streak of light caused by a small particle from space burning up in Earth's atmosphere
C) a fragment of an asteroid from the solar system that has fallen to Earth's surface
D) a small moon that orbits one of the giant planets
E) a comet that burns up in Earth's atmosphere

Question 11

Processed meteorites with high metal content probably are

A) leftover chunks of rock from the earliest period in the formation of the solar system.
B) pieces of comets rather than of asteroids.
C) chunks of the core of a larger asteroid that was shattered by a collision.
D) chunks of rock chipped off the planet Mercury.
E) chunks of rock chipped off the planet Mars.

Question 12

A typical shooting star in a meteor shower is caused by a ________ entering Earth's atmosphere.

A) boulder-size particle from an asteroid
B) boulder-size particle from a comet
C) pea-size particle from an asteroid
D) pea-size particle from a comet
E) microscopic particle of interstellar dust

Question 13

Kirkwood gaps in the asteroid belt occur at distances where

A) the density of asteroids is high enough for a large collision to pulverize a number of asteroids.
B) the period of an orbiting asteroid would be a simple fraction (like 1/3 or ¼) of Jupiter's orbital period.
C) the period of an orbiting asteroid would be the same as Jupiter's orbital period.
D) the period of an orbiting asteroid would be the same as Mars's orbital period.
E) the orbit would take the asteroid beyond the "frost line" in the solar system.

Question 14

Why do asteroids and comets differ in composition?

A) Asteroids formed inside the frost line, while comets formed outside.
B) Asteroids and comets formed at different times.
C) Comets formed from the jovian nebula, while asteroids did not.
D) Comets are much larger than asteroids.
E) Asteroids are much larger than comets.

Question 15

What do astronomers mean when they refer to "gaps" in the asteroid belt between Mars and Jupiter?

A) There are very few asteroids with diameters between 1 and 100 kilometers, creating a "gap" in the size distribution.
B) Asteroids typically cluster together and this creates "gaps" on the sky.
C) Asteroids seem to avoid certain orbits around the Sun, creating "gaps" in the orbits that asteroids can have.
D) There is a large population of asteroids too faint to see called the "gap" asteroids.
E) There are either pure metal or pure rock asteroids, but no mixtures. Thus there is a "gap" in the composition of asteroids.

Question 16

A rocky leftover planetesimal orbiting the Sun is

A) a comet.
B) a meteor.
C) an asteroid.
D) a meteorite.
E) possibly any of the above

Question 17

What do asteroids and comets have in common?

A) Most are unchanged since their formation in the solar nebula.
B) They have similar densities.
C) They have similar orbital radii.
D) They have a similar range of orbital inclinations.
E) They have nothing in common with each other.

Question 18

Primitive meteorites can be distinguished from other meteorites and terrestrial rocks because they

A) contain a noticeable fraction of pure metallic flakes.
B) resemble the composition of Earth's core.
C) contain a lot of iron and were used by humans to make iron tools.
D) resemble the composition of Earth's mantle.
E) resemble the composition of rocks from lava flows that occurred on asteroids very shortly after the formation of the solar system.

Question 19

An icy leftover planetesimal orbiting the Sun is

A) a comet.
B) a meteor.
C) an asteroid.
D) a meteorite.
E) possibly any of the above

Question 20

What is the approximate diameter of the largest asteroid?

A) 1 km
B) 10 km
C) 100 km
D) 1,000 km
E) 10,000 km

Question 21

According to the nebular theory, how did the Oort cloud form?

A) It is material left over from the interstellar cloud that never contracted with the rest of the gases to form the solar nebula.
B) It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet.
C) It consists of objects that fragmented from the protosun during a catastrophic collision early in the formation of the solar system.
D) It is made of planetesimals between the orbits of Mars and Jupiter that never formed into a planet.
E) It is made of planetesimals formed in the outer solar system that were flung into distant orbits by encounters with the jovian planets.

Question 22

What is the name of the largest known Kuiper Belt Object?

A) Pluto
B) Charon
C) Sedna
D) Quaoar
E) Eris

Question 23

Comets with extremely elliptical orbits, like Hyakutake and Hale-Bopp,

A) come from the asteroid belt.
B) come from the Kuiper belt.
C) come from the Oort cloud.
D) are Trojan comets.
E) are captured by Jupiter.

Question 24

Why was the Shoemaker-Levy 9 impact so important to astronomers?

A) It dredged up material that gave us our first direct look at Jupiter's interior composition.
B) It wiped out the dinosaurs.
C) It was the first direct proof that impacts really occur.
D) It confirmed our theory of solar system formation.
E) It was the first event in modern history that was brighter than the full moon in the sky.

Question 25

What is the typical size of a comet's nucleus?

A) 1 meter
B) 10 km
C) 100 km
D) 1000 km
E) Sizes are unknown because the nucleus is obscured by the coma.

Question 26

How many moons is Pluto known to have?

A) None
B) One
C) Two
D) Three
E) Four

Question 27

According to the nebular theory, how did the Kuiper belt form?

A) It is material left over from the interstellar cloud that never contracted with the rest of the gases to form the solar nebula.
B) It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet.
C) It consists of objects that fragmented from the protosun during a catastrophic collision early in the formation of the solar system.
D) It is made of planetesimals between the orbits of Mars and Jupiter that never formed into a planet.
E) It is made of planetesimals formed in the outer solar system that were flung into distant orbits by encounters with the jovian planets.

Question 28

On average, how often do impacts large enough to produce mass extinction on the Earth occur?

A) once every century
B) once every thousand years
C) once every million years
D) once every hundred million years
E) once in Earth's history

Question 29

Which of the following is furthest from the Sun?

A) Pluto
B) Neptune
C) an asteroid in the asteroid belt
D) a comet in the Kuiper belt
E) a comet in the Oort cloud

Question 30

Where did comets that are now in the Oort cloud originally form?

A) near the jovian planets
B) outside Neptune's orbit
C) inside Jupiter's orbit
D) within the solar nebula, but far outside the orbit of Pluto
E) all of the above

Question 31

What is Eris?

A) Pluto's largest moon
B) the largest known asteroid
C) the largest known Kuiper Belt object
D) The largest moon of Saturn
E) The largest known extrasolar planet

Question 32

How was Pluto's surface mapped?

A) By imaging with powerful ground based telescopes.
B) By imaging with the Hubble Space Telescope.
C) By mapping with the New Horizons spacecraft.
D) By measuring the change in brightness as Charon eclipsed Pluto.
E) Pluto is too far away for its surface to be mapped.

Question 33

Will Pluto collide eventually collide with Neptune?

A) No because Pluto's orbit is completely outside Neptune's orbit.
B) No because Pluto's orbit is completely inside Neptune's orbit.
C) No because Pluto's orbit never comes anywhere close to Neptune's orbit.
D) No because the two planets have an orbital resonance that prevents them from colliding.
E) Yes.

Question 34

Rather than being a planet, Pluto is really just a large member of

A) the asteroid belt.
B) the Kuiper belt.
C) the Oort cloud.
D) the moon system around Neptune.
E) an extrasolar planetary system.

Question 35

What happened to the "Impactor" of the Deep Impact mission?

A) It landed safely on the surface of the comet and returned material to Earth.
B) It created a small crater on the comet.
C) It blasted straight through the comet leaving a small hole.
D) It blasted the comet apart, thus preventing a potential Earth collision.
E) It missed the comet altogether.

Question 36

Which of the following does not lend support to the idea that Pluto is a Kuiper-belt object?

A) Pluto has a cometlike composition and density.
B) Pluto is smaller than many known comets, such as Halley's comet.
C) Some Kuiper-belt objects have their own moons.
D) Pluto has a more eccentric orbit than other planets.
E) Some known Kuiper-belt objects are hundreds of kilometers across.

Question 37

Pluto is different from the Jovian planets in all of the following ways except which one?

A) It formed outside of the frost line in the solar nebula.
B) It is made mostly of ices.
C) Its orbit is not very close to being circular.
D) It has a solid surface.
E) It doesn't have rings.

Question 38

Where did comets that are now in the Kuiper belt originally form?

A) in the asteroid belt
B) inside Jupiter's orbit
C) between the orbits of Jupiter and Neptune
D) near the radius at which they orbit today
E) in the Oort cloud

Question 39

What is Charon?

A) Pluto's largest moon
B) the largest known asteroid
C) the largest known comet
D) one of the Galilean moons of Jupiter
E) a moon of Neptune

Question 40

Approximately how long ago was Pluto discovered?

A) about 25 years ago
B) about 75 years ago
C) about 200 years ago
D) about 2000 years ago
E) in ancient history

Question 41

A spacecraft traveling through the asteroid belt has a high risk of being destroyed through a collision.

Question 42

All comets orbit the Sun in the same direction as the planets.

Question 43

Pluto's surface features are completely unknown and await the visit by the New Horizon's spacecraft in 2015.

Question 44

A spacecraft has captured and brought material to Earth from a comet.

Question 45

Why is Pluto now considered to be a Kuiper-belt object?

Question 46

The Oort Cloud: The objects in the Oort Cloud are frozen "snowballs", each a few kilometers across, seen at a distance of approximately 100,000 astronomical units. What do you think the potential is to directly observe (via some sort of telescope or directly visit (via a space mission) an object in the Oort cloud? Do you think that the existence of this component of the solar system is less well established than other components, such as the Kuiper Belt? What role does the solar nebular theory for the formation of the solar system play in supporting the existence of the Oort Cloud?

Question 47

Describe at least three ways in which our solar system would be different if orbital resonances had never been important.

Question 48

Can rocks fall from the sky? Many astronomers resisted the idea that rocks could fall from the sky until undeniable eyewitness testimony was available. (The tide turned in 1803 when several thousand stone fragments fell to the ground near L'Aigle, France, in the presence of hundreds of witnesses). Suppose that, for whatever reason, no meteorite falls could ever be witnessed. Would it still be possible to make the scientific case that some rocks on the Earth had to have fallen from interplanetary space? How would you make this case?

Question 49

A comet that has an orbit around the Sun inclined to the ecliptic plane by 65° probably originated in the Kuiper belt.

Question 50

All meteorites collected on Earth come from asteroids or comets.

Question 51

Oort-cloud comets are so far from the Sun that the gravity of neighboring stars can alter their orbits.

Question 52

Viewed from Pluto, the Sun would appear more than a thousand times fainter than on Earth.

Question 53

Pluto has 3 known moons.

Question 54

No spacecraft has ever visited an asteroid or comet.

Question 55

Why is the Kuiper belt flat but the Oort cloud spherical?

Question 56

What is Tunguska?

A) A postulated binary companion to the Sun thought to be responsible for mass extinctions.
B) A long period comet that struck Jupiter in 1994.
C) The site of an asteroid impact that occurred in Siberia in 1908.
D) The Gulf of Mexico basin that is the crater of the asteroid impact that caused the mass extinction of the dinosaurs 65 million years ago.
E) A newly discovered moon of Pluto.

Question 57

Aside from Pluto, no Kuiper belt objects are known to have moons.

Question 58

Describe some ways in which a meteorite can be distinguished from a terrestrial rock.

Question 59

Describe the Deep Impact and Stardust missions and what they were designed to achieve.

Question 60

Classification in Science: Usually, the first task of any science is to classify the available observations. Often, the initial classification scheme reflects the historical order of discovery in addition to nature itself. In this question, we will use our solar system as an example. Make a complete list of all of the solar system components that you have studied in the last three chapters. Then try to place this list in historical order of discovery. For example, start your list with the Sun, Moon, Earth, and 5 "classical" planets, which have been known for all of human history, and end your list with Eris, the largest currently known Kuiper Belt object. Can you see the historical order of discovery reflected in the classification of objects on your list? Have there been occasions when this classification scheme has been revised? Finally, does the classification scheme for the solar system introduce any artificial divisions, making strict categories from objects with a continuous range of properties?

Question 61

What are "dwarf planets"?

Question 62

Assume that the average rate of 1-km sized asteroids hitting the Earth is about 1 every million years. The chance of the Earth being hit by a 1-km sized asteroid in the next 100 years is about:

A) one in a million.
B) inevitable, it has to happen sometime.
C) zero.
D) one in 100 million.
E) one in ten thousand.

Question 63

Briefly describe how an impact could lead to a mass extinction.

Question 64

You find yourself in a maelstrom, whipped by winds gusting at 10,000 km/hr, rising and falling in convective currents. On the rare occasions when you can assess your surroundings, you notice a horizon that seems to go on "forever" (or, at least, much farther than the horizon on Earth), and no solid surface anywhere. You get a glimpse of several large moons. The Sun races through your sky, requiring only about 5 hours to rise nearly due east, cross the meridian at an altitude of about 55° in the north, and then set due west.

Question 65

Mercury's core

Question 66

Jupiter

Question 67

Suppose the planet Jupiter had never formed. How do you think the distribution of asteroids and comets in our solar system would be different? Explain.

Question 68

You've been dropped at the edge of a cliff, looking down for what seems to be miles! There's only one way to go from here: up! But it's going to be quite a climb, requiring all of your mountaineering skills. The atmosphere is very thin even at the mean surface level of this place. No matter, though, as you could not breathe this atmosphere anyway because it is mostly carbon dioxide and contains no oxygen. You climb and climb. This mountain must be three times the height of Mt. Everest and much broader at its base. There are clouds around you, and you can find water ice as well. When you try to melt some ice, however, it does not turn to liquid but sublimes to gas.

Question 69

It is very cold, but otherwise comfortable. You breathe deeply. Although there is no oxygen, the air pressure is quite tolerable and seems almost Earth-like (because it is mostly nitrogen). Your vista includes the breathtaking sights of an ocean of liquid methane and methane-snow-capped mountains (although the atmosphere is very smoggy, and the visibility is limited). Your solar day is about 16 Earth days long. A large, ringed object seems to hang in your sky, never rising or setting; however, it does go through phases from new to full and back to new again with the same 16-day period as the rising and setting of the Sun.

Question 70

The last major dinosaurs were wiped out as a consequence of a major impact with the Earth about 65 million years ago. All but one of the following statements would be regarded as evidence for this claim.

A) At least 150 craters from past impacts have been identified, including one of the right age and size in Mexico.
B) A layer of iridium in 65-million year old sediments in the Earth's crust.
C) The fossil record shows a mass extinction event 65 million years ago, where only 25% of the species survived.
D) Multiple historical accounts describe a planetary-level flood and storm that wiped out most living things.

Question 71

the atmosphere of Mars

Question 72

You find yourself on a silent airless world! The of the lack of an atmosphere means that you must be very careful not to look at the Sun so that you will not be blinded by its ultraviolet and X-ray radiation. However, you are able to determine that the Sun has about the same angular size that you are used to on Earth. Although this world is clearly lifeless, you are surprised to find footprints and car tracks etched in the powdery surface.

Question 73

Briefly describe the evidence suggesting that a 10-km asteroid or comet hit Earth at the time of the dinosaur extinction.

Question 74

It's cold. You are sitting on what appears to be a water ice-covered world. The Sun is low on the horizon and circles the horizon once every 24 hours. Despite the low Sun, you can almost "feel" the Sun's ultraviolet radiation on your exposed face because there is little ozone to protect you. Despite these discomforts, you are pleased to find that the air is quite satisfactory; oxygen seems plentiful and you are able to breathe even without the life-support belt.

Question 75

a Kuiper-belt object

Question 76

You are walking on a solid surface. The surface gravity is comfortable, but it is "hot, hot, hot!" Your body is being squeezed in all directions due to the high pressure; its almost like being deep in the ocean. Your life-support belt is corroding. The Sun, barely visible through the haze, is near your meridian. You hope for nightfall (unaware that it would provide no relief), but you already have been stuck on this planet for nearly 72 hours, and the Sun seems not to have moved through the sky (and, if it moved at all, it moved eastward from the meridian).

Question 77

Comet Hale-Bopp

Question 78

If the chance of the Earth being hit by a life-destroying asteroid over the course of one year is one in a million, what is the chance of being hit of the course of one hundred years?

A) One in 100 million
B) One in a million
C) One in ten thousand

Question 79

Earth's atmosphere

Question 80

the atmosphere of Venus