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