Exploring Mars: Basic Mars Facts

The fourth planet from the Sun.

Distance from the Sun:

Minimum: 206,000,000 kilometers
Average: 228,000,000 kilometers (1.52 times as far as Earth)
Maximum: 249,000,000 kilometers

Eccentricity of Orbit:

0.093 vs. 0.017 for Earth
(0.00 is a perfectly circular orbit)

Distance From Earth:

Minimum: 56,000,000 kilometers
Maximum: 399,000,000 kilometers

Day: 24.6 Earth Hours (1 Mars day is sometimes called 1 sol)

Year: 1.88 Earth years = 687 Earth days = 669 Mars days

Tilt of Rotation Axis: 25.2° vs. 23.5° for Earth

Size:

Diameter: 6792 kilometers vs. 12,756 kilometers for Earth
Surface gravity: 0.38 (about 1/3) times Earth's gravity
Mass: 6.4 x 10²³ kilograms, about 11% of Earth's mass
Density: 3.9 grams/cubic centimeter vs. 5.5 grams/cubic centimeter for Earth

Surface Temperature:

Generally cold
Global extremes: -125°C (-193°F) to 25°C (77°F)
Average at Viking 1 site: high -10°C (14°F); low -90°C (-130°F)

Atmosphere:

Thin and unbreathable
Surface Pressure: about 6 millibars, or about 1/200th of Earth's
Pressure varies with season - during the winter, part of the atmosphere freezes (as dry ice) onto the polar cap
Contains 95% carbon dioxide, 3% nitrogen, 1.5% argon, trace amounts of water, and no oxygen. (Earth has 78% nitrogen, 21% oxygen, 1% argon, and 0.03% carbon dioxide.)

Surface:

Color: Rust red
Ancient landscape dominated by impact craters
Tallest volcano in the Solar System: Olympus Mons, 21 kilometers high and 600 kilometers across, the size of the state of Arizona
Largest canyon system in the Solar System: Valles Marineris, 4000 kilometers long and up to 11 kilometers deep. If placed on Earth, Valles Marineris would stretch from California to Washington D.C.
Ancient channels carved by massive floods
Some rocks are basalt (volcanic lava, as in Hawaii); the composition of other rocks is unknown
Dust is reddish, rusty, like soil formed from volcanic rock

Moons:

Phobos ("Fear"), about 21 kilometers across
Deimos ("Panic"), about 12 kilometers across
Both Phobos and Deimos are very irregular in shape