HW 6

A  Earth

B  Venus

C  Mercury

D  Jupiter

A  Mars

B  Saturn

C  Mercury

D  Venus

A  Mercury

B  Saturn

C  Uranus

D  Neptune

A  carbon dioxide

B  carbon monoxide

C  Magnesium

D  Helium

A  Uranus

B  Mercury

C  Venus

D  Mars

A  Mercury

B  Venus

C  Earth

D  Mars

A  Long ago, Mars probably had a thicker atmosphere than it does now, with sufficiently high temperatures and pressure to allow liquid water to exist on its surface.

B  Earth’s atmosphere allows the Sun’s infrared radiation in but doesn’t allow much visible light to escape, resulting in the greenhouse effect.

C  Earth’s atmosphere plays a central role in keeping the planet from freezing cold temperatures.

D  Despite being the closest planet to the Sun, some parts of Mercury have a surface temperatures far below the freezing point of water.

E  Venus is the hottest planet in our Solar System, mainly due to a greatly elevated greenhouse effect.

A  The orbital period of the Moon around the Earth and the rotation period of the Moon around its axis are equal.

B  High tide occurs on the side of the Earth nearest to the Moon, while low tide occurs on the opposite side of the Earth.

C  At any given location on Earth, there are two high tides each day – one caused by the gravitational pull of the Sun, and the other by the gravitational pull of the Moon.

D  The same half of the Moon’s surface is perpetually dark (craters on that side never see sunlight), leading us to call it the “dark side of the Moon.”

E  By observing the Moon long enough from Earth, night after night, we are able to draw a map of its entire surface.

A  older than

B  younger than

C  the same age as

A  the Moon has been around longer than the Earth and has been exposed to more periods of meteor bombardment.

B  the Moon is much more deficient in iron relative to the Earth, causing craters to form more easily.

C  the Moon is more distant than the Earth, causing incoming rocks to hit it first.

D  the Moon experiences almost no erosion compared to the Earth, causing craters to remain much longer.

E  the Moon experiences frequent volcanic eruptions that cause craters.