Transcript Powers of ten notation

Terrestrial Planets
Planetary size and heat loss
Large planets retain internal heat longer
Small planets cool off quickly
Geologic processes
1) Impact cratering
2) Volcanism
3) Tectonics
4) Erosion
Discussion
The Moon has lots of impact craters, while the
Earth has very few. Why do you think there is
a difference?
Surface age
The more impact craters on a surface, the
older that surface is.
The age of a surface refers to when that
surface solidified.
Discussion
Which area on the Moon is older, the light
region to the left or the dark region in the
center of the picture?
Discussion
Why do you think a more heavily cratered
planetary surface is older than a smooth
one?
Why?
All the terrestrial planets probably receive
about the same number and size distribution
of impacts. All the other geologic processes
(volcanism, tectonics, and erosion) tend to
erase impact craters on the surface.
Discussion
Rank the terrestrial planets (include the
Moon) in terms of the age of their surfaces
from youngest to oldest to try and predict
which planets will have the most craters.
1.
2.
3.
4.
5.
Earth
Venus
Mars
Mercury
Moon
Smaller planets retain less heat and
therefore have less geologic activity.
Discussion
Almost all impact creators are round.
Why do you think there are not many
elliptically shaped craters?
Almost all impact craters are
round
In general, impactors will hit with a velocity
greater than the escape velocity. The high
speed collision results in the almost
complete vaporization of the impactor. This
explosion of super-heated, vaporized rock is
what creates the crater.
Moltke Crater (7 km)
Bessel crater (16 km)
Euler Crater (25 km)
King Crater (77 km)
Copernicus Crater (95 km)
Schrodinger (320 km)
Mare Orientale (930 km)
Mare Imbrium (1100 km)
Meteor Crater (1.2 km)
Arizona from the Shuttle
Wolf Creek (0.85 km)
New Quebec Crater (3.4 km)
Clearwater Lakes (26 km)
Chichxulub Crater (250 km)
Manicouagan Crater (100 km)
Discussion
Why is the Manicouagan crater inverted, with
a lower rim and higher center?
Hint: It is at high northern latitude and is
rather old.
Radar images of Venus
Bright areas in radar images indicate rough
terrain, while dark areas are smooth. Typically,
rough terrain is younger than smooth terrain.
Discussion
Why are rough areas younger?
Adivar Venus (29 km)
Meitner basin Venus (150 km)
Discussion
What does the fact that there are so few
eroded craters tell you about Venus?
Plate Tectonics
No plate tectonics on Venus
Venus may not have an asthenosphere, due to
the lack of water in Venus’s mantle.
Alternatively, the crust of Venus may be too
plastic to form large-scale faults.
Colaris basin Mercury (1340 km)
Hellas basin Mars (2000 km)
Discussion
Notice anything unusual about this crater
on Mars? What can you conclude about
the surface of Mars where this crater
formed?
Why are craters important
• Numbers of craters provide relative ages
• Transition size between simple and
complex craters as well as ejecta blanket
size and distribution provide clues to the
strength of the surface.
Liquid Water
All life on Earth depends on liquid water.
Earth is the only body in the solar system
with liquid water on its surface.
Atmospheres
All the terrestrial planets and the Moon
have some atmosphere.
The Moon and Mercury have very thin
atmospheres while Venus has the thickest.
Venus at inferior conjunction
Effects of atmospheres
Atmospheric pressure keeps liquids from
boiling
Protects the surface from solar wind and
cosmic rays and, depending on composition,
ultraviolet and x-ray radiation
Moderates surface temperatures
Discussion
How do you think an atmosphere can
moderate a planet’s surface temperature?
As the Sun shines on the planets surface, it
heats the soil and rocks. Without an
atmosphere that heat is radiated away
mostly in the low-energy infrared region of
the spectrum.
If the planet has an atmosphere, the heat
can be transferred to the gas molecules and
stored, acting as a blanket.
Discussion
Rank the terrestrial planets (including the
Moon) in terms of their daily temperature
swings from most extreme to the least
extreme?
Surface temperatures
Mercury – day: 425 C
Moon – day: 125 C
Mars
– day: -3 C
Earth
– day: 15 C
Venus – day: 470 C
night: -175 C
night: -175 C
night: -96 C
night:
3C
night: 470 C
Discussion
Although Venus is closer to the Sun than Earth,
its cloud cover reflects nearly 60% of the light
that falls on it. The surface therefore receives
less energy from the Sun that the Earth’s surface
does.
So why is Venus so much hotter than Earth?
The greenhouse effect
Carbon dioxide (as well as water vapor and
methane) absorb infrared radiation. Sunlight can
pass to the surface of Venus and heat it. But the
infrared radiation it emits can not escape back
into space.
Exam next Tuesday
Covers chapters 1-4 in the text + Seasons
(p265) and all lecture notes including this
week
4 essay questions in which you will be asked
to explain concepts
Allowed one sheet of notes with writing on
one side only