Download Erosion changes the appearance of Mars.

s8pe-41302-ca
10/28/05
12:38 PM
MAZER
Page 425
Venus is too hot to have liquid water, and
the winds do not seem to move much material. Erosion may be slower
on Venus than on Earth.
Weathering and Erosion
Round craters mark the surface here and there.
Older craters have been erased by the other processes. Also, Venus’s
thick atmosphere protects the surface from small impacts.
Impact Cratering
check your reading
Why is Venus not covered with craters?
Erosion changes the appearance of Mars.
Mars is relatively small, with a diameter about half that of Earth.
The orange color of some of the surface comes from molecules
of iron and oxygen—rust. Mars has two tiny moons. They were
probably once asteroids that were pulled into orbit around Mars.
Mars
The atmosphere of Mars is
thin but causes weathering
and erosion.
Surface of Mars
The same processes that affect the other terrestrial planets
affect Mars.
Valleys and raised areas formed on Mars as the mantle
moved. One huge system of valleys, called Valles Marineris,
is long enough to stretch across the United States.
Tectonics
Most of the northern hemisphere has
smooth plains of cooled lava. Several volcanoes
are higher than any mountain on Earth.
The lava must have built up in the same spot
for a long time, so scientists have inferred
that the crust of Mars has cooled more than
Earth’s crust. On Earth, the tectonic plates
move, so chains of smaller volcanoes form
instead of single larger volcanoes.
Mass 11% of Earth’s mass
Diameter 53% of Earth’s
diameter
Average distance
from Sun 1.5 AU
Orbits in 1.9 Earth years
Rotates in 25 hours
Volcanism
volcanoes
Valles Marineris
Fast winds carry
sand that breaks down rocks. Wind and gravity
move the broken material, forming new features
such as sand dunes. There are also landforms
that look like the results of gigantic flash floods
that happened long ago.
Weathering and Erosion
Round craters cover much of the
southern hemisphere of Mars. Many craters are very old
and eroded. A few impact craters on the volcanoes make scientists
think that the volcanoes have not released lava for a long time.
Impact Cratering
Chapter 13: Our Solar System 425
PDF