Figure 25.18: Mars has two small moons, Phobos (left) and Deimos (right). ( 8 )- Mercury is the smallest planet and the closest to the Sun. It has an extremely thin
atmosphere, with surface temperatures ranging from very hot to very cold. Like the
Moon, it is covered with craters. - Venus is the second planet from the Sun and the closest planet to Earth, in distance
and in size. It has a very thick, corrosive atmosphere, and the surface temperature is
extremely high. - Radar maps of Venus show that it has mountainous areas, as well as volcanoes sur-
rounded by plains of lava. - Venus rotates slowly in a direction opposite to the direction of its orbit.
- Earth is the third planet from the Sun. It is the only planet with large amounts of
liquid water, and the only planet known to support life. Earth has a large moon, the
only large moon around a terrestrial planet. - Mars is the fourth planet from the Sun. It has two small moons. Mars is reddish in
color because of oxidized iron (rust) in its soil. Mars has the largest mountain and the
largest canyon in the solar system. - There is a lot of water ice in the polar ice caps and under the surface of Mars.
Review Questions
- Name the inner planets in order from the Sun outward. Then name them from smallest
to largest. - Why do the temperatures on Mercury vary widely?
- VenusisfartherfromtheSunthanMercury. WhydoesVenushavehighertemperatures
than Mercury? - How are maps of Venus made?
- Name two major ways in which Earth is unlike any other planets.