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Mars
Astronomy 311
Professor Lee Carkner
Lecture 14
Mars -- The God of War
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The Canals of Mars
In 1877 G. Schiaparelli thought that he saw
intersecting straight lines on Mars
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
Percival Lowell built an observatory near
Flagstaff, AZ and published elaborate maps
of a network of canals and oasis on Mars
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Mars Facts
Size: ~1/2 Earth size
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Orbit: 1.5 AU
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Description:
Celestial Motions of Mars
Mars rotates on its axis with a period of
24 1/2 hours

Mars has an orbital period of 23 months
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Mars is tilted on its axis
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Spacecraft to Mars
Mariner 4 was the first spacecraft to visit
Mars in 1964
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Recent missions:
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Mars Express (2003, orbiter)
Mars Reconnaissance Orbiter (2006, orbiter)
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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
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Craters --The northern hemisphere is less
heavily cratered than the southern


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Dust storms alter the Martian craters
Tharsis Rise
Olympus Mons
Valles Marineris
Cratering on Mars
Mars Topological Map
The Surface of Mars
Mars is red due to iron oxide (rust) in the soil


Surface is covered with reddish soil and is rocky
and broken
Mars is cold


Mars has seasons due to the tilt of its axis
Standing on Mars
Mars’s Atmosphere
Composition: 95% CO2, 3% N2, trace
amounts of water vapor and oxygen
Pressure: 0.007 atmospheres

Early Mars may have had a thicker CO2
and H2O atmosphere


Water on Mars
Mars is now a very dry world


Water ice may be present in the polar
ice caps (along with frozen CO2)

It is possible that water exists
underground
Frost on Mars
Polar Ice Cap
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)
Dried-up River Bed
Past Water Erosion on Mars
Life on Mars?
 Mars shows evidence for liquid water and higher
temperatures in the past


 Viking tested soil samples but the results were inconclusive
 We do have a few meteors that were blasted off the surface
of Mars

 AH84001 shows some features that look a little like the remains of
life-forms, but evidence is not very strong
Viking’s Soil Scoop
Fossil Life in Martian
Meteorite?
Cydonia “Face” on Mars
Traits of Psuedoscience
Certainty

Avoidance of Occam’s Razor

Paranoia

Mars’s Interior
Mars has a lower density than the other terrestrial
planets (4000 compared to 5000 kg/m3)

No evidence for plate tectonics
We have very little other data on Mars’s interior


Continuing Mars Exploration
Phoenix, a small “scout” lander
mission, to be launched 2007

Sample return?

Manned mission?

A Possible History of Mars
Mars forms

Volcanism creates
volcanoes and lava
flows
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Mars losses internal
heat, crust cools

Atmosphere loses
CO2, atmosphere
cools

Water freezes
Summary
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
Earth)
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
chasms
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 must 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