The Terrestrial Planets, Part III Mars

MARS The God of War

Physical Data l Diameter: 6,794 km (0.531 D earth ) l Mass: 6.40x10 27 g (0.107 M earth ) l Density: 3.96 g/cm 3 l Rotation Period: 24.6 hours l Tilt of Axis: 25 o l Surface Temperature: K

Physical Data l Orbital Semi-major Axis: AU l Orbital Period: years l Orbital Inclination: 2 o l Orbital Eccentricity: l Surface Gravity: 0.38 Earth Gravity

Physical Data l Satellites: 2 l Magnetic Field: no l Surface Pressure: 0.01 Earth’s Pressure

Mars’ Interior l Relatively small core size compared to the mantle l Smallest core of all the terrestrial planets compared to the overall volume (~9%) l Exact composition of mantle is unknown 3393 km 1520 km CORE ( iron + iron sulfide ) MANTLE ( iron-magnesium silicates ? ) CRUST ( aluminum silicates )

Mars’ Atmosphere l Clouds Planet-wide Clouds ( from Hubble) A Cyclonic Event

Mars’ Atmosphere l 95% Carbon Dioxide l 2.7% Nitrogen l 1.6% Argon l 0.6% Carbon Monoxide l 0.15% Oxygen l 0.03% Water Vapor (variable)

Mars’ Surface Polar Caps: l Composed of both carbon dioxide and water South Polar Cap: l Consists mainly of frozen carbon dioxide. l This cap never melts completely. l This picture shows it at its minimum size of 400 km (249 miles).

Mars’ Surface North Polar Cap: l Consists of mainly water-ice. Seasonal Changes: l When spring begins in a hemisphere, the corresponding cap shrinks as the carbon dioxide turns directly into a gas.

Mars’ Surface l Polar caps change in size depending on the Martian seasons.

Mars’ Surface Olympus Mons: l Largest mountain (volcano) in the Solar System l 24 km (78,000 ft) high l Base is 500 km in diameter l Rimmed by a 6 km (20,000 ft) high cliff 500 km

Mars’ Surface Valles Marineris: l Huge canyon l Would stretch coast to coast across the U.S. l 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: l Landed in Chryse Planitia on July 20, 1976 l Took panoramic pictures of the surface l 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? l There is evidence of liquid water once flowing over the surface of Mars. Fluvial Features: l Created by water flowing around a crater (right). Probably caused by a flood.

Mars’ Surface Dry Riverbeds: l Created by slow erosion of running water.

Mars’ Surface Dust Storms: l Mars’ surface winds churn up surface material l 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 Canals of Mars: l “Discovered” by G.V. Schiaparelli in 1877 l Percival Lowell (below) built an observatory in 1894 pricipally for the study of the Martian canals l The canals are actually optical illusions

Martian Myths of Today “The Face”: l Lies in the Cydonia region, a region of weathered, isolated hills l 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