Some planets have atmospheres.
An atmosphere is composed of material that is in its gaseous
state and is held to a body by gravity. There are differences
of opinion about the composition of the earth's early atmosphere,
but it is thought that
it was composed of
hydrogen, helium,
nitrogen, and carbon
dioxide,
with little or no free
oxygen.
Planetary atmospheres
vary in density and
composition. A
small planet has less
gravity than a large
one, which makes it
easier for gases to
escape into
space. Planets
close to their suns
are bombarded by the
solar wind, and
atmospheric particles
are stripped away.
Some planets have
dense
atmospheres.
Venus has an
atmosphere that has 90
times the pressure of
the earth's
atmosphere.
On a day to day level
we talk about weather,
and weather happens in
the atmosphere.
Different atmospheric
layers have different
temperatures, and
temperature changes
lead to winds.
Winds pick up dust and
moisture and move heat
about from place to
place. Water
evaporates, rain
falls. The
rotation of the planet
affects wind and ocean
movements.
We call long term
weather trends
climate. For
example, on earth the
climate in the arctic
is different from the
climate in
Hawaii. Although
weather changes from
day to day, the
fluctuations stay
within predictable
ranges. Life
forms adapt to the
climates that they
live in. The climates
that you have on your
world will influence
the kinds of life
forms that you can
have there.
Information
Assignment:
Your group will work to
- decide on the weather of your planet
- Sketch out major air and ocean currents
- draw maps to show the climate zones, using your relief maps
- write a description of your planet's climate and weather.
Homework: Bring to class next session:
- The written description of your planet's climate and weather.
.
- A diagram of major climatic ocean and air currents.
- Your computer drawn maps of the climatic zones, now modified
to show temperature and rainfall zones.
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