Chapter 7: Earth in Space

The bluish-green color of Uranus is thought to be
caused by methane in its atmosphere.
Uranus Shown in Figure 20, the seventh planet from the Sun
is Uranus. The atmosphere of Uranus, made up mostly of
hydrogen, also contains helium and methane. The methane
gives the planet a distinctive, bluish-green color. This is because
methane gas reflects blue light and absorbs red light. Uranus
is thought to have at least 27 moons. However, additional satellites
might exist.
Neptune The eighth planet from the Sun is Neptune. It is
thought that Neptune’s atmosphere of hydrogen, helium, and
methane gradually changes into a slushlike layer, comprised partially
of water and other melted ices. Toward the interior, this
slushy material is thought to change into an icy solid. In turn,
this icy layer may surround a central, rocky core that is about the
size of Earth.
As with Uranus, the methane in Neptune’s atmosphere gives
the planet its bluish color, as shown in Figure 20. Winds in the
gaseous portion of Neptune exceed speeds of 2,400 km per
hour—faster than winds on any other planet.
At least eleven natural satellites of Neptune have been discovered
so far and many more probably exist. The largest of
these, Triton, has great geysers that shoot gaseous nitrogen into
space. A lack of craters on Triton’s surface suggests that the surface
of Triton is fairly young.
Like Uranus, the blue color of Neptune is also thought
to be caused by methane. The Great Dark Spot was a
storm system similar in size to the diameter of Earth.
Interpreting Your
Creature Feature
Procedure
1. Select any one of the
planets or moons in our
solar system except Earth.
2. Research its surface
conditions.
3. Imagine a life-form that
might have developed on
your chosen planet or moon.
Be sure to indicate how your
creature would eat, breathe,
and reproduce.
Analysis
1. How is this creature
protected from its
environment?
2. How does your creature
obtain nourishment
for survival?
SECTION 3 Our Solar System 199
NASA/JPL