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Astronomy 311
Professor Lee Carkner
Lecture 14
Which best describes the surface of
the Moon?
a) Uniformly covered with craters
b) Rough on the near side and smooth on the
far side
c) Older terrain in the highlands and
younger terrain in the Maria
d) Covered with lava from volcanic eruptions
e) Covered in iron-rich dust
What is one reason that we think the
Moon was formed via impact?
a) We find evidence of the impact crater under
the Yucatan peninsula
b) Moon rocks are similar to earth rocks
c) The Maria must have been formed by a
giant impact
d) Only a giant impact could produce the
Moon’s tidal locking
e) The large amount of oxygen in lunar soil
must be due to an impact
Mars -- The God of War
Shows color more
strongly than other
The Canals of Mars
In 1877 G. Schiaparelli thought that he saw
intersecting straight lines on Mars
This was translated to English as “canals”
implying that somebody built them
Mars was thought to be very dry, so naturally the
inhabitants needed to carefully manage water
Mars Facts
Size: ~1/2 Earth size
Orbit: 1.5 AU
Description: red, dusty, thin atmosphere
Spacecraft to Mars
Viking 1 and 2 (1975) extensively imaged
Mars and also sent landers to the surface
Recent missions:
Mars Odyssey (2001, orbiter)
Mars Reconnaissance Orbiter (2006, orbiter)
Spirit and Opportunity (2003, rover)
Surface Features
Volcanoes -- Mars has many shield volcanoes,
but they are not active today
Canyons -- Mars shows deep canyons, the
result of volcanic activity stressing the crust
Craters --The northern hemisphere is less
heavily cratered than the southern
Dust storms alter the Martian craters
The Surface of Mars
Mars is red due to iron oxide (rust) in the soil
Dust storms sometimes cover large fractions of the
Mars is cold
180 K at night (-135 F)
Mars has seasons due to the tilt of its axis
Your Weight on Mars
Three things effect how much you
Note that weight is a force
We can translate the force on you in
pounds into your mass in kilograms, since
we know the properties of the Earth
Mars’s Atmosphere
Pressure: 0.007 atmospheres
Early Mars may have had a thicker CO2
and H2O atmosphere
Mars has no plate tectonics to return the
CO2 to the atmosphere
Water on Mars
Mars is now a very dry world
A pan of water left out on Mars would boil
It is possible that water exists
Was Mars Wet?
Surface features indicate that water once flowed
freely on the Martian surface
Due to:
Global water (Many oceans, rivers, etc)?
Mars may have been warmer with a thicker
atmosphere in the past
Where is the water now?
Mars may warm up periodically allowing water to form
(Mars may now be in an ice age)
Life on Mars?
Mars shows evidence for liquid water and
higher temperatures in the past
Could that life have survived?
If life was microscopic it might be hard to
Traits of Psuedoscience
Avoidance of Occam’s Razor
Any problems with the theory are someone
else’s fault (e.g. government cover-ups)
Mars’s Interior
Mars has a lower density than the other
terrestrial planets (4000 compared to 5000
No evidence for plate tectonics
There are no seismometers on Mars
Mars may have only a small solid iron core
or no iron core at all
Future Mars Exploration
The Phoenix lander was launched
August 2007
Mars Science Laboratory, a large, longduration rover planned for 2009
Sample return?
Manned mission?
A Possible History of Mars
Mars forms
Mars is cratered
CO2 greenhouse
keeps Mars warm,
liquid water flows
Mars losses internal
heat, crust cools
Atmosphere loses
CO2, atmosphere
Lava flows stop
Next Time
Read Chapter 14.1 and 14.4
No class Friday
Quiz 2 next Monday
Observing Tomorrow (Tuesday) 8-9 pm
Only if you missed the last one
Red, dusty, thin atmosphere
Mars is a medium-sized world
allowing it to retain an atmosphere
(unlike Mercury and the Moon), but not
a thick atmosphere (like Venus and
Mars shows signs of being habitable in
the past, but no good evidence of life
has been found
Summary: Surface
Mars has a red surface composed of
dust, soil and rocks
Mars has large volcanoes and deep
Dust storms often cover the surface
Mars has a low density and may not
have an iron core
Summary: Climate
Mars has a very thin atmosphere and is cold
Low temperature and pressure prevent
liquid water on the surface
Mars may have had a thicker, warmer
atmosphere in the past since there is
substantial evidence for water flows
Early thicker CO2 greenhouse atmosphere
gradually washed out by rainfall
The temperature on Mars may change over time
due to orbital variations