Exam 22: The Earths Companions

The sun,its eight planets and their moons,together with smaller objects such as asteroids and comets,form the ____.

The gravity of Jupiter,Saturn,Uranus,and Neptune resulted in their becoming surrounded by envelopes of nitrogen-rich gas.

Biological processes have removed most of the _______ from the Earth's atmosphere.

Our galaxy is called the ____.

Asteroids are generally rocky,solid bodies orbiting the Sun and ranging in diameter from a few meters to hundreds of kilometers.

Perhaps the most obvious of ______ surface features are its polar ice caps.

When 17^th century astronomer _______ first viewed Jupiter with his telescope he saw four satellites orbiting the planet.

The Earth's atmosphere is rich in _____,a product of plant photosynthesis.

Io is the most volcanically active body in the solar system at this time.

The absence of fold mountains and the presence of many _______ imply that Mars has been geologically quiet for billions of years

Of all the planets in the solar system only Earth has an atmosphere.

The Moon's _____ explains why it is different from Earth.

To measure vast distances in the solar system,astronomers use the ____,the Earth's average distance from the Sun.

Small _____ are rocky or iron bodies in our solar system that remain irregular in shape because of their weak gravity.

The existence of huge channels that look like dry riverbeds on Mars is strong evidence that it ____.

The four planets nearest the sun are basically balls of rock and include ____.

The nucleus of a comet is a block of _____.

Jupiter,Saturn,Uranus,and Neptune are surrounded by atmospheres of _______.

The Apollo astronauts brought _____ rocks back to the Earth.

This star provides the energy that drives Earth's external heat engine.