Science & Space
Mars
Mars is a cold, rocky planet known for its reddish surface, thin atmosphere, enormous volcanoes, deep canyons, and evidence of ancient water.
Mars is the fourth planet from the Sun and a cold, rocky world with a thin atmosphere. Iron minerals in its surface materials oxidize, giving the planet its familiar reddish appearance. Mars is about half Earth's diameter and has seasons, polar ice caps, extinct volcanoes, canyons, dust storms, and two small moons.
Spacecraft observations show that ancient Mars had rivers, lakes, deltas, and floods when its climate was warmer and wetter. Water remains today mainly as ice, while robotic missions examine the planet's geology, atmosphere, climate history, and past potential to support microbial life.
Quick facts
- Mars is the fourth planet from the Sun and has a radius of about 2,106 miles, or 3,390 kilometers.
- A Martian day lasts about 24.6 hours, while a Martian year lasts 687 Earth days.
- Mars has two small, irregularly shaped moons named Phobos and Deimos.
- Its thin atmosphere consists mostly of carbon dioxide, with smaller amounts of nitrogen and argon.
- Ancient river valleys, deltas, lakebeds, rocks, and minerals provide evidence that liquid water once existed on its surface.
A surprising fact
Olympus Mons, the largest known volcanic structure in the solar system, is more than 600 kilometers across and rises over 27 kilometers above the reference level.
