Exam 23: The Earths Companions

____ is the most volcanically active object in our solar system at the present time.

The Earth is but one of eight planets that orbit the sun.

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

A compass would be useful to an astronaut lost on the moon.

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

As planetismals struck the growing Earth, their impact energy in combination with ______ melted the planet.

Venus and Earth have ________ surfaces and atmospheres.

The inner planets are sometimes called the terrestrial planets because of their resemblance to ____.

The giant meteor impact at the end of the Cretaceous Period (65 million years ago) did not influence the evolution of life on Earth.

______ is the smallest of the inner four planets and closely resembles our moon.

The surface of Venus is hidden by clouds so astronomers use ____ to map the planet's surface.

Martian winds have created ____.

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

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

The nucleus of a comet is a block of _____.

Astronomers think that most comets come from the Oort cloud.

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

Our galaxy is called the ____.

All the planets are exactly the same size.

To the best of our knowledge, the Earth, Sun, and Moon are all the same age, about _______ years old.