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The Terrestrial Planets,Part III
Mars
MARSThe God of War
Physical Data
Diameter: 6,794 km (0.531 Dearth)
Mass: 6.40x1027 g (0.107 Mearth) Density: 3.96 g/cm3
Rotation Period: 24.6 hours Tilt of Axis: 25o
Surface Temperature: 130-290 K
Physical Data
Orbital Semi-major Axis: 1.524 AU Orbital Period: 1.881 years Orbital Inclination: 2o
Orbital Eccentricity: 0.093 Surface Gravity: 0.38 Earth Gravity
Physical Data
Satellites: 2 Magnetic Field: no
Surface Pressure: 0.01 Earth’s Pressure
Mars’ Interior
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
3393 km
1520 km
CORE( iron +
iron sulfide )
MANTLE( iron-magnesium
silicates ? )
CRUST( aluminum silicates )
Mars’ Atmosphere
Clouds
Planet-wide Clouds( from Hubble)
A Cyclonic Event
Mars’ Atmosphere
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’ SurfaceNorth 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
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, includingValles 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: Panoramaand 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’ SurfaceDust 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 moonSize: 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 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”: 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 builtby a Martian intelligence, and that other surfacefeatures resemble pyramids, cities, and fortresses