The Terrestrial Planets,
Part III
Mars
MARS
The God of War
Physical Data
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Diameter: 6,794 km (0.531 Dearth)
Mass: 6.40x1027 g (0.107 Mearth)
Density: 3.96 g/cm3
Rotation Period: 24.6 hours
o
Tilt of Axis: 25
Surface Temperature: 130-290 K
Physical Data
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Orbital Semi-major Axis: 1.524 AU
Orbital Period: 1.881 years
o
Orbital Inclination: 2
Orbital Eccentricity: 0.093
Surface Gravity: 0.38 Earth Gravity
Physical Data
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Satellites: 2
Magnetic Field: no
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Surface Pressure: 0.01 Earth’s Pressure
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Mars’ Interior
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Relatively small core
size compared to the
mantle
Smallest core
of all the terrestrial
planets compared
to the overall
volume (~9%)
Exact composition of
mantle is unknown
CRUST
( aluminum
silicates )
3393 km
1520 km
CORE
( iron +
iron sulfide )
MANTLE
( iron-magnesium
silicates ? )
Mars’ Atmosphere
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Clouds
Planet-wide Clouds
( from Hubble)
A Cyclonic Event
Mars’ Atmosphere
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95% Carbon Dioxide
2.7% Nitrogen
1.6% Argon
0.6% Carbon Monoxide
0.15% Oxygen
0.03% Water Vapor (variable)
Mars’ Surface
Polar Caps:
 Composed of both
carbon dioxide and
water
South Polar Cap:
 Consists mainly of
frozen carbon dioxide.
 This cap never melts
completely.
 This picture shows it
at its minimum size of
400 km (249 miles).
Mars’ Surface
North Polar Cap:
 Consists of mainly
water-ice.
Seasonal Changes:
 When spring begins in
a hemisphere, the
corresponding cap
shrinks as the carbon
dioxide turns directly
into a gas.
Mars’ Surface
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Polar caps change in size depending on the
Martian seasons.
Mars’ Surface
Olympus Mons:
 Largest mountain
(volcano) in the Solar
System
 24 km (78,000 ft) high
 Base is 500 km in
diameter
 Rimmed by a 6 km
(20,000 ft) high cliff
500 km
Mars’ Surface
Valles Marineris:
 Huge canyon
 Would stretch coast to
coast across the U.S.
 It is 4000 km (2500
miles) long and up to
6 km (4 miles) deep
4000 km
Mars’ Surface
Flight over the Martian Terrain, including
Valles Marineris and Three Volcanos
m
Mars’ Surface
Viking Lander:
 Landed in Chryse
Planitia on July 20,
1976
 Took panoramic
pictures of the surface
 On-board experiments
tested soil for signs of
life. Results were
inconclusive.
Mars’ Surface
Viking Photos:
To the right:
Morning ground
frost
Below: Panorama
and Mars’ pink
sky.
Mars’ Surface
Pathfinder
Photos:
Rover and
“Yogi”
Martian Sunset
Mars’ Surface
Water on Mars?
 There is evidence of
liquid water once
flowing over the
surface of Mars.
Fluvial Features:
 Created by water
flowing around a
crater (right). Probably
caused by a flood.
Mars’ Surface
Dry Riverbeds:
 Created by slow
erosion of running
water.
Mars’ Surface
Dust Storms:
 Mars’ surface winds
churn up surface
material
 Storm sizes range in
size from small local
“dust-devils” to
plumes that sweep
over the entire planet
(right)
Mars’ Moons
PHOBOS:
“Phobos” is Greek for “fear”
Mars’ innermost moon
Size: 27 x 21.6 x 18.8 km
Above: Crater Stickney
Left: Image by Soviet spacecraft
Phobos 2, launched in 1988
Mars’ Moons
DEIMOS:
“Deimos” is Greek
for “panic”
Smallest known moon
in the solar system:
15 x 12.2 x 11 km
Phobos and Deimos are probably captured asteroids
Martian Myths of Yesterday
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Canals of Mars:
“Discovered” by G.V. Schiaparelli in 1877
Percival Lowell (below) built an observatory in
1894 pricipally for the study of the Martian canals
The canals are actually optical illusions
Martian Myths of Today
“The Face”:
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Lies in the Cydonia
region, a region of
weathered, isolated
hills
One hill resembling a
face was photograghed
by Viking 1
Some people believe this is a monument built
by a Martian intelligence, and that other surface
features resemble pyramids, cities, and fortresses