Download Small objects are made of ice and rock.

KEY CONCEPT
Small objects are made
of ice and rock.
STANDARDS
8–4.1 Summarize the
characteristics and
movements of objects
in the solar system
(including planets,
moons, asteroids,
comets, and meteors).
VOCABULARY
asteroid p. 679
comet p. 680
meteor p. 681
meteorite p. 681
BEFORE, you learned
NOW, you will learn
• Smaller bodies formed with the
Sun and planets
• Planets in the inner solar system consist of rock and metal
• The outer solar system is cold
• About Pluto and the moons
of the giant planets
• How asteroids and comets
are similar and different
• What happens when tiny
objects hit Earth’s atmosphere
THINK ABOUT
Do small space bodies
experience erosion?
Image not available for electronic use.
Very small bodies in space often Please refer to the text in the textbook.
have potato-like shapes. Some
are covered with dust, boulders,
and craters. Solar radiation can
break down material directly or
by heating and cooling a surface. Broken material can slide downhill,
even on a small asteroid. What other processes do you think might
act on small and medium-sized bodies in space?
Most objects in the outer solar system are
made of ice and rock.
The name of Earth’s satellite
is the Moon, but the word
moon is also used to refer
to other satellites.
The materials in a space body depend on where it formed. The disk
of material that became the solar system was cold around the outside
and hottest in the center, where the Sun was forming. Far from the
center, chemicals such as carbon dioxide, ammonia, and water were
frozen solid. These ices became part of the material that formed bodies
in the outer solar system. Bodies that formed near the center of the
solar system are made mostly of rock and metal. Bodies that formed
far from the center are mostly ice with some rock and a little metal.
Some of the bodies had enough mass to become rounded. Some
even melted and formed cores, mantles, and crusts. Many of these
bodies have mountains and valleys, volcanoes, and even winds and
clouds. The processes at work on Earth also affect other space bodies.
What do the proportions of ice, rock, and metal show about a
space object?
676 Unit 5: Space Science