The Inner Planets

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The Inner Planets
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• Watch the Leonid Meteor Shower!
• Predicted Time 330 AM, November 19th (Tuesday
  morning)
• Predicted Rate 3,500 per hour, though there is
  a full moon and you will not see the dimmer
  meteors.
• Lecture at the Planetarium on Saturday evening
  following More than Meets the Eye at 830
• There is also a penumbral lunar eclipse at 646
  PM on November 19th, so its a good day for sky
  watching.

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Sky watch days have been changed to Tuesday and
Wednesday. As usual, meet on the mall near the
cactus garden. Essay Number 2. New Format. You
will receive a grade on your first draft along
with comments. You can then pass in both a
revised draft and the original to improve your
grade. To get a better grade you have to do more
than correct the specific mistakes marked on the
original draft.
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Mars

• Distance from the Sun
• Radius
• Temperature
• Surface Pressure
• Atmospheric Composition

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Mars

• Distance from the Sun
• Radius
• Temperature
• Surface Pressure
• Atmospheric Composition

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Surface of Mars
This is a composite picture made from the Viking
Orbiters. The gash across the center of the
picture is the Valle Varineris. To the left are
3 extinct volcanoes. Numerous craters are seen
and the whole surface is covered with a reddish
dust. Thin clouds veil the surface at various
locations.
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Olympus Mons The Solar Systems Largest Mountain
Olympus Mons is about 26 km (16 miles) high and
covers an area the size of Arizona. It is a
shield volcano, like the volcanoes in Hawaii.
Notice the caldera at the top.
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Valle Marineris
Valle Marineris is about 5000 km long (the size
of the USA) and roughly 8 km wide. Depth ranges
from 2 to 7 km. Unlike the Grand Canyon, it was
not created by erosion, but by faulting.
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Water on Mars?

• Mars can not have liquid water at the current
  temperature and pressure of its atmosphere, yet
  there are numerous forms on the surface that
  appear to have been caused by the flow of water.
  This is one of the main questions facing
  planetary scientists today. Was Mars once warmer
  and wet? If so, what happened to change it?

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Evidence for Water?
What does this look like to you? An ancient
river system perhaps?
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More Images of Possible Ancient River Beds
From Hartmann and Impey
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Islands in the Stream
The teardrop shape is characteristic of water
flowing past an obstacle.
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Ancient Sediments?
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Evidence for Water?
A series of troughs and layered mesas in the
Gorgonum Chaos region of the martian southern
hemisphere appears in the chaotic terrain.
Gullies proposed to have been formed by seeping
ground water emanate from a specific layer near
the tops of trough walls, particularly on
south-facing slopes. Such a layer is called an
aquifer, and this one appears to be present less
than a few hundred meters (few hundred yards)
beneath the surface in this region. This image
was taken by the Mars Global Surveyor camera on
January 22, 2000.
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Dust on Mars
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Dunes on Mars
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Dust Storms on Mars
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The Southern Polar Cap
Mars has both north and south polar caps that
contain CO2 and H2O ice.
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Frost on the Surface
As winter approaches, the atmosphere freezes out
on the surface.
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Atmospheric Temperatures
Fig. from The New Solar System
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Atmospheres of Earth, Venus, and Mars
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Interiors of the Terrestrial Planets
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Venus
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Why are Venus, Earth, and Mars so Different?
Strength of the Greenhouse Effect. The large
greenhouse effect on Venus makes it a very
inhospitable place. Mars lacks a significant
greenhouse effect and is too cold for liquid
water to exist. Earth has a mild greenhouse
effect and, in some locales, is a temperate
planet. But this begs the question, why is the
greenhouse effect so different on these 3
planets? Distance from the Sun. The more
intense sunlight at Venus probably plays a role.
The runaway greenhouse effect, where the
temperature rises until all the water is in the
form of steam, may be the explanation. Why then
does Mars not have a significant greenhouse
effect? Perhaps in its past it did, thus
explaining the evidence for surface water. But
why would Mars cool off?
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Why are Venus, Earth, and Mars so Different?
Plate Tectonics. Probably the largest
difference between the Earth and Mars and Venus
is that our interior is more active. The Earth
is the only planet with plate tectonics. This
constantly resupplies the surface with new
material such as H2O and CO2. Lacking this
resupply mechanism, carbon and oxygen on Mars may
be bound chemically in inert molecules. As a
result the Martian atmosphere and polar caps are
tiny in comparison with Earth.
A volcanic eruption on Earth. Though the molten
rock and noxious fumes get all the attention, the
primary product of a volcanic eruption is water.
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Carbon Cycle on Earth
On Earth, CO2 dissolves in the oceans and is
eventually incorporated in carbonate sediments on
the sea floor. Subduction at plate boundaries
carries these sediments far below the surface
where they are decomposed at high temperature
reforming CO2. The CO2 is released back to the
atmosphere through volcanoes. Fig. from The New
Solar System.