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Astronomy Exam 2 Review

Total questions: 93

Worksheet time: 47mins

Name
Class
Date
1.

Which of the following is an example in which you are traveling at constant speed, but not at constant velocity?

a)

 

Rolling freely down a hill in a cart, traveling in a straight line

b)

 

Driving around in a circle at exactly 100 km/hr

c)

 

Jumping up and down exactly 60 times per minute

d)

 

Driving backward at exactly 50 km/hr

2.

Momentum is defined as

a)

 

mass times speed

b)

 

mass times velocity

c)

 

force times velocity

d)

 

mass times acceleration

3.

If your mass is 60 kilograms on Earth, what would your mass be on the Moon?

a)

 

10 pounds

b)

 

10 kilograms

c)

 

60 kilograms

d)

 

60 pounds

4.

Astronauts are weightless inside the International Space Station because ________.

a)

 

the station and the astronauts are constantly falling toward Earth at the same rate.

b)

 

the station has rockets that fire to counteract Earth's gravity.

c)

 

there is no gravity in space.

d)

 

the station is too far from Earth for gravity to be noticeable.

5.

If a net force is applied to an object, what is guaranteed to change?

a)

 

The object's momentum

b)

 

The object's speed

c)

 

The object's mass

d)

 

The object's weight

6.

A comet has an elliptical orbit around the Sun. Its total orbital energy is ________.

a)

 

greatest when it is farthest from the Sun

b)

 

greatest when it is closest to the Sun

c)

 

the same throughout its orbit

7.

According to the universal law of gravitation, the force due to gravity is ________.

a)

 

directly proportional to the square of the distance between objects

b)

 

inversely proportional to the square of the distance between objects

c)

 

directly proportional to the distance between objects

d)

 

inversely proportional to the distance between objects

8.

Which orbital shapes are possible under the force of gravity?

a)

 

Ellipses only

b)

 

Ellipses and spirals

c)

 

Ellipses, parabolas, and hyperbolas

d)

 

Ellipses, spirals, and parabolas

9.

Which of the following describes a velocity (as opposed to a speed)?

a)

 

20 kilometers per hour, headed north

b)

 

300,000 kilometers per second

c)

 

9.8 meters per second squared.

d)

 

5 light-years

10.

The energy attributed to an object by virtue of its motion is known as ________.

a)

 

kinetic

b)

potential

c)

 

radiative

d)

 

mass-energy

11.

Which of the following best describes the origin of ocean tides on Earth?

a)

 

Tides are caused on the side of the Earth nearest the Moon because the Moon's gravity attracts the water.

b)

 

Tides are caused by the 23.5-degree tilt of the Earth's rotational axis to the ecliptic plane.

c)

 

The Moon's gravity pulls harder on water than on land because water is less dense than rock.

d)

 

Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the Earth.

12.

The source of energy that powers the Sun is ________.

a)

 

chemical potential energy of hydrogen

b)

 

mass energy released by nuclear fusion

c)

 

 

thermal energy of the hydrogen atoms in the Sun

d)

 

kinetic energy of the orbital motion of the Sun

13.

The idea that we live in a universe (literally, "one story"), in which the same law of gravity applies both on Earth and in space, was established through the work of ________.

a)

Newton

b)

Copernicus

c)

Kepler

d)

Galileo

14.

Consider Newton's second law states, often written as force = mass × acceleration. If a known force is applied to an object with a known mass, what does this law predict for the object's acceleration?

a)

 

Acceleration = mass × force

b)

 

Acceleration = mass / force

c)

 

Acceleration = force / mass

d)

 

Newton's second law is irrelevant for solving this problem.

15.

How does a rocket launch upward? Choose the statement that correctly answers the question.

a)

 

By expelling gas downward, the rocket is propelled upward.

b)

.

16.

How does an asteroid's orbital angular momentum vary over its orbit?

a)

 

Its angular momentum is greatest when it is closest to the Sun.

b)

 

Its angular momentum is greatest when it is farthest from the Sun.

c)

 

Its angular momentum is the same throughout its orbit.

17.

If a spinning star gets larger in diameter, what happens to its rotation rate?

a)

 

It will not change.

b)

It decreases.

c)

It increses.

18.

At which lunar phase(s) are tides least pronounced (e.g., the lowest high tides)?

a)

 

New Moon

b)

 

Full Moon

c)

 

First quarter

d)

 

Both first and third quarters

19.

When a spinning ice skater pulls in his arms, he spins faster because ________.

a)

 

his angular momentum must be conserved

b)

 

there is less friction with the air

c)

 

there is less friction with the ice

d)

 

there exists an unbalanced reaction force

20.

Radiative energy is ________.

a)

 

energy carried by light

b)

 

heat energy

c)

 

energy from nuclear power plants

d)

 

energy of motion

21.

Which of the following statements is not one of Newton's Laws of Motion?

a)

 

For any force, there always is an equal and opposite reaction force.

b)

 

In the absence of a net force acting on it, an object moves with constant velocity.

c)

 

The rate of change of momentum of an object is equal to the net force applied to the object.

d)

 

What goes up must come down.

22.

According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them ________.

a)

 

decreases by a factor of 9

b)

 

increases by a factor of 9

c)

 

decreases by a factor of 3

d)

 

increases by a factor of 3

23.

Which statement must be true for a rocket to travel from Earth to another planet?

a)

 

It must attain escape velocity from Earth.

b)

 

It must carry a lot of extra fuel.

c)

 

It must have large engines.

d)

 

It must be launched from space, rather than from the ground.

24.

The gravitational potential energy of a contracting interstellar cloud ________.

a)

 

stays the same at all times

b)

 

gradually transforms into other forms of energy

c)

 

gradually grows larger

25.

The Earth exerts a gravitational force on a person standing on the surface. The person also exerts a gravitational force on the Earth. Based on Newton's third law of motion, how do these two forces compare?

a)

 

The forces exerted by the Earth and the person are equal in magnitude (size)

b)

 

The Earth exerts a much stronger force than the person.

c)

 

The person exerts a much stronger force than the Earth.

d)

 

The Earth exerts a slightly stronger force than the person.

26.

On a hot day, molecules of air ________ than on a cold day.

a)

 

move faster on average

b)

 

move slower on average

c)

 

are more massive

d)

 

are less massive

27.

Which of the following statements correctly describes the law of conservation of energy?

a)

 

 

The fact that you can fuse hydrogen into helium to produce energy means that helium can be turned into hydrogen to produce energy.

b)

 

Energy can change between many different forms, such as potential, kinetic, and thermal, but it is ultimately destroyed.

c)

 

It is not really possible for an object to gain or lose potential energy because energy cannot be destroyed.

d)

 

Energy can change between many different forms, such as potential, kinetic, and thermal, but the total quantity of energy in the universe never changes.

28.

An astronaut in space swings a ball attached to a string in a circular motion. If the string suddenly breaks, how will the ball move?

a)

 

It will move in a straight line in whichever direction it was moving when the string broke.

b)

 

It will continue to move in the same circular path it had been following before the string broke.

c)

 

It will move toward the astronaut.

d)

 

It will move in a large elliptical path around the astronaut.

29.

if a material is transparent, then it ________.

a)

 

reflects light well

b)

 

absorbs light well

c)

 

transmits light well

d)

 

emits light well

30.

the wavelength of a wave is ________.

a)

 

how strong the wave is

b)

 

the distance between a peak of the wave and the next trough

c)

 

the distance between two adjacent peaks of the wave

d)

 

equal to the speed of the wave times the wave's frequency

31.

from lowest energy to highest energy, which of the following correctly orders the different regions of electromagnetic radiation?

a)

 

infrared, visible light, ultraviolet, x-rays, gamma rays, radio

b)

 

radio, infrared, visible light, ultraviolet, x-rays, gamma rays

c)

 

gamma rays, x-rays, visible light, ultraviolet, infrared, radio

d)

 

radio, x-rays, visible light, ultraviolet, infrared, gamma rays

32.

how are wavelength, frequency, and energy related for photons of light?

a)

 

longer wavelength means lower frequency and lower energy.

b)

 

longer wavelength means higher frequency and lower energy.

c)

 

longer wavelength means higher frequency and higher energy.

d)

 

longer wavelength means lower frequency and higher energy.

33.

light behave like ________.

a)

waves

b)

particles

c)

both waves and particles

d)

neither waves nor particles

34.

an iron atom has an atomic number of 26 and an atomic mass number of 56. If it is neutral, how many protons, neutrons, and electrons does it have?

a)

 

26 protons, 30 neutrons, 26 electrons

b)

 

26 protons, 30 neutrons, 30 electrons

c)

 

26 protons, 56 neutrons, 26 electrons

d)

 

13 protons, 56 neutrons, 13 electrons

35.

which statement correctly describes units that can be used to measure energy and power?

a)

 

energy and power are both measured in units of joules.

b)

 

energy and power are both measured in units of watts.

c)

 

energy is measured in watts and power is measured in watts per second.

d)

 

energy is measured in joules and power is measured in watts (joules per second).

36.

when a neutral atom loses an electron, we say that it becomes ________.

a)

 

vaporized

b)

 

an isotope

c)

 

ionized

d)

 

a plasma

37.

what do we see when white light passes through a cool cloud of gas?

a)

 

a continuum (rainbow) of visible light

b)

 

thermal radiation

c)

 

an absorption line spectrum

d)

 

an emission line spectrum

38.

when an electron drops to a lower energy level in an atom, but no other interactions take place ________.

a)

 

the atom must emit a photon of light of a specific wavelength

b)

 

the total energy of the atom remains unchanged

c)

 

the atom must slow its speed moving through space

d)

 

the atom must increase its speed moving through space

39.

thermal radiation is defined as ________.

a)

 

radiation produced by a hot object

b)

 

radiation in the infrared part of the spectrum

c)

 

radiation in the form of emission lines from an object

d)

 

radiation that depends only on the emitting object's temperature

40.

a gas heated to millions of degrees would emit ________.

a)

 

mostly radio waves

b)

 

mostly x-rays

c)

 

mostly ultraviolet light

d)

 

no light because it is too hot

41.

which of the following stars has the hottest surface temperature?

a)

 

the blue star

b)

 

the orange star

c)

 

the yellow star

d)

 

the red star

42.

from laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 121.6 nanometers (nm). the spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 121.8 nm. what can we conclude?

a)

 

the star is moving toward us.

b)

 

the star is moving away from us.

c)

 

the star is getting hotter.

d)

 

the star is getting colder.

43.

one of the absorption lines of hydrogen has a rest wavelength of 656 nm. suppose you observe this line in four different stars, and find this line at the wavelengths show below. which wavelength represents the star that is moving toward Earth the fastest?

a)

630 nm

b)

656 nm

c)

670 nm

d)

640 nm

44.

we can see the Moon because it ________.

a)

 

emits visible light

b)

 

emits thermal radiation

c)

 

reflects infrared light

d)

 

reflects visible light

45.

which of the following could not be determined by an observation that only uses spectroscopy?

a)

 

the chemical composition of a distant star

b)

 

the surface temperature of a distant star

c)

 

the speed at which a distant galaxy is moving away from us

d)

 

the angular size of a distant galaxy

46.

how do the light-collecting area and best possible angular resolution of telescope with a 10-meter diameter mirror compare to that of a telescope with a 5-meter diameter mirror?

a)

 

the 10-meter telescope has double the light collecting area, and its angular resolution is better by a factor of 2.

b)

 

the 10-meter telescope has 4 times the light collecting area, and its angular resolution is better by a factor of 2.

c)

 

the 10-meter telescope has 4 times the light collecting area, and its angular resolution is better by a factor of 4.

d)

 

the 10-meter telescope has 10 times the light collecting area, and its angular resolution is better by a factor of 5.

47.

what causes stars to twinkle? 

a)

 

stars constantly vary in brightness as they expand and contract.

b)

 

interstellar gas along the line of sight to the star absorbs different amounts of radiation.

c)

 

the human eye has difficulty seeing faint objects.

d)

 

moving gases in Earth's atmosphere randomly bend light rays from stars.

48.

why are astronomers interested in building observatories capable of detecting neutrinos, cosmic rays, and gravitational waves?

a)

 

these things are the highest energy forms of light, even more energetic than gamma rays, and therefore can tell us about explosive processes in the universe.

b)

 

these things should in principle be much easier to detect than light, which means we could build these observatories cheaply.

c)

 

these things are emitted from the same objects that emit x-rays, but unlike x-rays they can be detected with observatories on the ground.

d)

 

these things are not forms of light, and therefore can provide different types of information than light about objects that emit them.

49.

the angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see?

a)

 

the photo will seem to show only one star rather than two.

b)

 

the two stars will appear to be touching, looking rather like a small dumbbell.

c)

 

the stars will not show up at all in your photograph.

d)

 

you will see two distinct stars in your photograph.

50.

which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?

a)

 

it is closer to the stars.

b)

 

stars do not twinkle due to an atmosphere when observed from space.

c)

 

it can observe infrared and ultraviolet light, as well as visible light.

d)

 

it never has to close because of cloudy skies.

51.

which of the following properties is used to distinguish between the core, mantle, and crust of a planet?

a)

temperature

b)

 

rock strength

c)

density

d)

color

52.

the lithosphere of a planet is the layer that consists of ________.

a)

 

material between the crust and the mantle

b)

 

the rigid rocky material of the crust and uppermost portion of the mantle

c)

 

material above the crust

d)

 

the softer rocky material of the mantle

53.

which of the following best describes differentiation in planetary geology?

a)

 

gravity separates molten materials according to density.

b)

 

one planet's surface evolves differently from another planet's surface.

c)

 

one part of a planet's surface evolves differently from another part of the same planet's surface.

d)

 

dense materials condense at higher temperatures than less dense materials.

54.

which internal energy source is the most important in continuing to heat the terrestrial planets today?

a)

accretion

b)

differentiation

c)

radioactivity

d)

 

tidal heating

55.

which of the following best describes convection?

a)

 

warm material expands and rises while cool material contracts and falls.

b)

 

warm material gets even warmer and cool material gets even cooler.

c)

 

a liquid separates according to density, such as oil and water separating in a jar.

d)

 

bubbles of gas move upward through a liquid of the same temperature.

56.

what is the main process by which heat flows upward through the lithosphere?

a)

conduction

b)

convection

c)

 

radiation

d)

differentiation

57.

which terrestrial world has the strongest magnetic field?

a)

mars

b)

earth

c)

venus

d)

mercury

58.

what conditions are thought to be necessary for a terrestrial planet to have a strong magnetic field?

a)

 

a molten metallic core only

b)

 

a rocky mantle only

c)

 

both a molten metallic core and reasonably fast rotation

d)

 

both a metal core and a rocky mantle

59.

what can we conclude when we see a region of a planet that is not as heavily cratered as other regions?

a)

 

the planet is rotating very slowly and only one side was hit by impactors.

b)

 

the planet formed after the age of bombardment and missed out on getting hit by leftover planetesimals.

c)

 

the surface in the region is older than the surface in more heavily cratered regions.

d)

 

the surface in the region is younger than the surface in more heavily cratered regions.

60.

which of the following surface features may result from tectonics?

a)

mountains

b)

valleys

c)

volcanos

d)

 

all of the above

61.

how does the greenhouse effect work?

a)

 

greenhouse gases transmit visible light, allowing it to heat the surface, but then absorb infrared light emitted by the surface, trapping the heat near the surface.

b)

 

greenhouse gases are ionized by sunlight, making them heat up their surroundings.

c)

 

greenhouse gases absorb x-rays and ultraviolet light from the Sun, which then heat the atmosphere and the surface.

d)

 

greenhouse gases absorb infrared light from the Sun, which then heats the atmosphere and the surface.

62.

why are sunsets and sunrises red?

a)

 

the Sun emits more red light when it's near the horizon.

b)

 

sunlight must pass through more atmosphere to reach our eyes at those times, so more blue light is scattered away.

c)

 

sunlight must pass through more atmosphere to reach our eyes at those times, which means it passes through a larger volume of red air molecules.

d)

 

the lower temperatures of morning and evening (compared to midday) make the sky redder in color.

63.

the Caloris Basin on Mercury covers a large region of the planet and contains relatively few smaller craters. from this, we conclude that ________.

a)

 

erosion destroyed most of the smaller craters that formed on the basin

b)

 

Mercury's atmosphere prevented smaller objects from hitting the surface

c)

 

only very large impactors hit Mercury's surface in the past

d)

 

the Caloris Basin formed toward the end of the heavy bombardment

64.

which of the following is the best explanation for the tremendous cliffs on Mercury?

a)

 

they were probably formed by tectonic stresses when the entire planet shrank as its core cooled.

b)

 

they probably formed when a series of large impacts hit Mercury one after the other.

c)

 

they are almost certainly volcanic in origin, carved by flowing lava.

d)

 

they represent one of the greatest mysteries in the solar system, as no one has suggested a reasonable hypothesis for their formation.

65.

Valles Marineris is a ________.

a)

 

vast plain on Mars

b)

 

huge series of cliffs on Mercury

c)

 

large canyon on Mars

d)

 

large canyon on Venus

66.

which of the following could explain why Venus does not have a strong magnetic field?

a)

 

it does not have a metallic core.

b)

 

its rotation is too slow.

c)

 

it is too close to the Sun.

d)

 

it has too thick an atmosphere.

67.

the polar caps on Mars are composed of ________.

a)

 

frozen carbon dioxide only

b)

 

both frozen carbon dioxide and water ice

c)

 

frozen hydrogen

d)

 

water ice only

68.

why can't astronomers study the surface of Venus with visible light telescopes?

a)

 

venus' thick atmosphere prevents us from seeing the surface.

b)

 

we do not have telescopes with good enough angular resolution.

c)

 

venus doesn't reflect any visible light.

69.

mars' atmosphere is mostly carbon dioxide. why does it not experience a runaway greenhouse effect like Venus?

a)

 

mars is protected by its magnetic field.

b)

 

mars does not have enough additional water vapor to magnify the warming.

c)

 

mars' atmosphere is too thin.

d)

 

mars has a CO2cycle like Earth that regulates the amount of carbon dioxide.

70.

ridges in the middle of the ocean are places where ________.

a)

 

hot mantle material rises upward, creating volcanic islands

b)

 

hot mantle material rises upward and spreads sideways, pushing the plates apart

c)

 

plates push together, creating ocean mountain chains

d)

 

plates slip sideways relative to one another

71.

which of the following can act like a long-term "thermostat" that helps keep Earth's average temperature fairly stable?

a)

 

radioactive elements trapped in the Earth's mantle

b)

 

heat stored in the Earth's magnetosphere

c)

 

heat stored in the Earth's liquid core

d)

 

the carbon dioxide cycle that moves carbon dioxide between Earth's atmosphere, oceans, and rock

72.

in what ways is Earth different from the other terrestrial planets?

a)

 

its lithosphere is broken into plates that move around.

b)

 

it has a much higher percentage of oxygen in its atmosphere.

c)

 

most of its surface is covered with liquid water.

d)

 

all of the above are true.

73.

how much of the solar system's total mass is contained in the Sun?

a)

 

about 90%

b)

 

about 95%

c)

 

about 99.8%

d)

 

exactly 100%

74.

uranus's large axis tilt causes it to ________.

a)

 

have extreme seasonal variations

b)

 

be very cold

c)

 

have very short days and nights

d)

 

keep one side facing the Sun at all times

75.

the most massive planet in our solar system is ________.

a)

Saturn

b)

Uranus

c)

Jupiter

d)

Neptune

76.

Which statement about Pluto is not true?

a)

 

its surface temperature is very cold.

b)

 

it is made mostly of rock and ice.

c)

 

it is the most massive object in the Kuiper belt.

d)

 

it was visited by the New Horizons spacecraft in 2015.

77.

neptune's largest moon, Triton, orbits in a direction opposite to the direction in which Neptune rotates. which of the following is most likely implied by this fact?

a)

 

Triton experiences very strong tidal forces.

b)

 

Triton probably was captured into orbit by Neptune.

c)

 

Triton probably formed in its current orbit around Neptune.

d)

 

Triton probably has a rocky, asteroid-like composition.

78.

in what region of the solar system is Pluto found?

a)

 

the asteroid belt

b)

 

the Kuiper belt

c)

 

the Oort cloud

d)

 

the terrestrial planet region

79.

other than Earth, which of the following has visible polar caps?

a)

Mercury

b)

Venus

c)

 

the Moon

d)

Mars

80.

which planet has the highest average surface temperature and why?

a)

 

Mercury, because it is closest to the Sun

b)

 

Mercury, because of its dense carbon dioxide atmosphere

c)

 

Venus, because of its dense carbon dioxide atmosphere

d)

 

Mars, because of its red color

81.

which of the following planets has a ring system?

a)

Jupiter

b)

Saturn

c)

Uranus

d)

 

all of the above

82.

which of the following is not a characteristic of all the terrestrial planets?

a)

 

they have solid, rocky surfaces.

b)

 

they are located closer to the Sun than the Jovian planets.

c)

 

they have substantial atmospheres.

d)

 

they have higher densities than the Jovian planets.

83.

which of the following is not a characteristic of the Jovian planets?

a)

 

they have higher average densities than the terrestrial planets.

b)

 

they have thick atmospheres.

c)

 

they are primarily made of hydrogen, helium, and hydrogen compounds.

d)

 

they are located further from the Sun than the terrestrial planets.

84.

which of the following is farthest from the Sun?

a)

Pluto

b)

 

an asteroid in the asteroid belt

c)

 

a comet in the Kuiper belt

d)

 

a comet in the Oort cloud

85.

what is the major difference between asteroids and comets?

a)

 

asteroids are low in density and comets are high in density.

b)

 

asteroids are rocky and comets are icy.

c)

 

asteroids never have tails and comets always have tails.

d)

 

asteroids are smaller than comets.

86.

which of the following is a feature of our solar system that should be predicted by a successful theory of solar system formation?

a)

 

the fact that all the planets in our solar system orbit the Sun in the same direction

b)

 

the fact that there are exactly four terrestrial planets and exactly four Jovian planets

c)

 

the fact that Earth has a 23-1/2° axis tilt

d)

 

the fact that Jupiter has the most known moons in the solar system

87.

what is our best hypothesis for why all the planets in our solar system orbit in the same direction as the Sun rotates?

a)

 

the planets and Sun formed from the same, single, rotating gas cloud.

b)

 

the planets were pulled out of the Sun by a major interaction with another star.

c)

 

almost everything in our Galaxy rotates in the same direction.

d)

 

the Sun did not initially rotate, but the planets gravity caused it to start rotating in the direction in which the planets orbit.

88.

which of the following is most important in causing a cloud of gas to collapse to form a star and planets?

a)

 

pressure from light from nearby stars pushes the gas inward.

b)

 

pressure from other gas clouds pushes the gas inward.

c)

 

some gas is sent outward, causing the rest to move inward to conserve momentum.

d)

 

gravity pulls all the gas inward.

89.

why did the solar nebula heat up as it collapse?

a)

 

nuclear fusion occurring in the core of the forming Sun produced energy that heated the nebula.

b)

 

as it shrank in size, gravitational potential energy was converted to thermal energy.

c)

 

the shock wave from a nearby supernova heated the gas.

d)

 

collisions among planetesimals generated friction and heat.

90.

according to our theory of solar system formation, which law best explains why the solar

a)

 

Kepler's first law of planetary motion

b)

 

the law of conservation of angular momentum

c)

 

the law of universal gravitation

91.

what happened during the accretion phase of the early solar system?

a)

 

atoms of hydrogen and helium gas bonded together and solidified.

b)

 

particles grew by colliding and sticking together.

c)

 

the solar nebula differentiated into metals inside of the frost line and ices beyond.

d)

 

large planetesimals captured atmospheres from the solar nebula.

92.

what is the giant impact hypothesis for the origin of the Moon?

a)

 

the Moon originally was about the same size as Earth, but a giant impact blasted most of it away so that it ended up much smaller than Earth.

b)

 

the Moon formed just like Earth, from accretion in the solar nebula.

c)

 

the Moon formed when two gigantic asteroids collided with one another.

d)

 

the Moon formed from material blasted out of Earth's mantle and crust by the impact of a Mars-size object.

93.

in the context of the formation of planets in the solar nebula, the frost line marks the distance from the Sun beyond which ________.

a)

 

the temperature was low enough for hydrogen compounds to condense into ices

b)

 

the temperature was low enough for solid rock to condense from the gas

c)

 

hydrogen compounds were particularly abundant

d)

 

planets could be cold enough to have snow