Transcript The Nine Planets, KEY QUESTIONS

MERCURY
Q: Why
are there so many craters?
Mercury
We see so many craters because:
• No atmosphere means no
weather.
• No weather means no
weathering and erosion.
We see so many craters because:
No plate
tectonics
to “recycle”
the crust.
Why Mercury so hot?
Mercury is hot because:
• It is so close to the sun!
Energy reaching a planet from
the sun
decreases rapidly
with distance
INVERSE SQUARE LAW
(any property) varies inversely as the square
of the distance from an object
1
d2
So….
With distance, same energy must be
spread over larger and larger area
Mercury
Why are the
day/night temps so
different?
Temperatures are so extreme
because there is no atmosphere :
• to block radiation from
reaching the surface
• To prevent heat from leaving.
Venus
• Q:
Why is it so hot when it is
farther from sun than Mercury?
VENUS
Venus is so hot because:
• Its atmosphere traps heat and
won’t let it out.
The Greenhouse Effect
Why DOES Venus have an
atmosphere?
• OUTGASSING—
gases are
released by
volcanic activity.
• And…
And…
gravity to
• It has enough
hang on to the gas.
Why does the earth’s atmosphere
have so much oxygen?
Photosynthesis
Cyanobacteria began to
oxygenate the earth
about 2.4 BYA
Where do we find the only life
forms in the universe?
Is there life on MARS?
Uh, no.
Is there WATER on MARS?
YES
Penetrating radar shows there is
lots of water frozen under the
poles.
Was there ever surface water
on MARS?
(maybe)
There are erosional features
that look as though made by
liquid.
On the other hand…
the atmospheric pressure
is so low (0.01atm) that
liquid water would boil
away.
Why is Jupiter “banded?”
1. Convection within atmosphere.
In a fluid, hot stuff rises, cool stuff sinks.
On our planet, warmer rises from
the equator, sinks at the poles.
• If the earth did
not rotate, all
winds would
blow north and
south.
2. Rapid rotational speed (10
hours)
Compared to its
axis, a planet
is rotating
faster at the
equator than
at the poles.
So, as air moves away from the
poles…
It moves over a
faster moving
surface, and
appears to curve
to the right.
When air moves to the north
from the equator,
• It curves to the
right
The earth’s global wind belts,
showing the Coriolis effect.
3. The Coriolis Effect.
Why does Jupiter have so many
‘moons” ?
MORE MASS,
MORE GRAVITY.
What are the rings of Saturn?
Mostly ice crystals
and carbon dust.
Size = few cm
to few m
Only few hundred
m thick.
How did Saturn’s rings form?
• Collisions among satellites
due to complex gravitational
“tides”
Why does Uranus “lie on its
side?”
MASSIVE collision.
Why is Neptune blue?
• Methane in upper atmosphere absorbs red
wavelengths, letting blue though.
Neptune’s moon Triton is
unique because…
• It orbits backwards (retrograde)
• It is volcanically active.