Exam 22: The Earths Companions

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

____ is the largest planet in both radius and mass.

A planet's mass and radius have no effect on its interior temperature and thus the level of its tectonic activity.

From the small number of impact craters on ____,planetary geologists suspect that virtually all its original surface has been covered over by younger volcanic activity.

Astronomers estimate that our galaxy contains ______ stars.

Like most stars the sun is made mainly of hydrogen.

______ is the planet that is most like the Earth in diameter and mass.

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

Large,smooth,dark areas visible on the Moon with the unaided eye are called _____.

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

The multitude of craters that formed on the Earth has been obliterated by erosion and plate tectonics.

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

______ dominate the topography of lunar highlands.

The Moon and Mercury lack ______.

Martian winds have created ____.

The Moon's low average density tells us that the interior contains relatively little _______.

The atmosphere of Venus is dominated by _________.

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

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

The nebular hypothesis proposes that our solar system was born about 1 billion years ago.