Small size (the diameter is one-half as large as Earth's)

Beyond our orbit, surface temperatures -20F to 70F

Evidence of surface evolution

• High volcanoes (Olympus Mons: 16 miles high) and a history of volcanic eruptions
• Deep canyons (Valles Marineris: 4 miles deep, 120 miles wide, 2500 miles long)
• Floods (× 10,000 more water than the Mississippi River)
• Craters with "splash" features suggesting water landings
• Erosion features

Thin, cool atmosphere (carbon dioxide)

Little or no water vapor or liquid water (ice caps?) now, but probable in the past ...

Meteorites show water damage, traces of biological life!

Two moons (Phobos and Deimos, each 20 kilometers in size, distorted in shape)

Great Dust Plains	Canyon and Volcanoes	Valles Marineris
Daily Global Image	Cerberus (dark patch)	Ius Chasma
Images of our sister planet Mars, with its two moons and tremendous volcanoes. [NASA]