Mars

Mars, the Red Planet, is one of the most studied worlds beyond Earth. Its soil contains iron oxide (rust), giving it its distinctive red color. Mars has a thin atmosphere composed mostly of carbon dioxide, providing little insulation or protection from radiation. Surface temperatures often fall below –60°C (–80°F).

Despite being dry today, Mars once had a warm, wet climate billions of years ago. Rivers, lakes, and possibly vast northern oceans once flowed there. Evidence includes dried-up riverbeds, layered sediments, and minerals that can only form in water.

Mars is home to the largest volcano in the Solar System, Olympus Mons, standing 22 km tall, and the gigantic canyon system Valles Marineris, which stretches over 4,000 km long—nearly the width of the United States.

Dust storms are common and can engulf the entire planet for months. Mars also has two small, oddly shaped moons—Phobos and Deimos—which may be captured asteroids. Because of its water-rich past, Mars remains one of the best places in the Solar System to search for ancient microbial life.