Mars
Mars, the fourth planet from the Sun, is one of the most fascinating worlds in the Solar System. Known as the Red Planet, it gets its reddish color from iron oxide, or rust, that covers much of its surface.
Among the planets, Mars is one of the most Earth-like in its seasons, polar ice caps, and day length. These similarities make it a leading place to search for evidence of ancient life beyond Earth.
A Rocky World with Extreme Landscapes
Mars is a rocky planet about half the size of Earth. Its surface includes giant volcanoes, vast canyons, ancient river valleys, polar ice caps, and dust-covered deserts. The planet's thin atmosphere is mostly carbon dioxide and provides little protection from cold temperatures or harmful radiation.
Olympus Mons and Valles Marineris
Mars is home to Olympus Mons, the largest volcano in the Solar System. It rises about 13.6 miles (22 kilometers) above the surrounding plains, more than twice the height of Mount Everest.
Nearby lies Valles Marineris, an enormous canyon system stretching more than 2,500 miles (4,000 kilometers) across Mars. It is far longer and deeper than Earth's Grand Canyon.
Dust Storms and Climate
Strong winds regularly lift fine dust into the Martian atmosphere. Some dust storms grow large enough to cover much of the planet and can last for weeks or even months.
Mars is cold and dry today, but evidence from its surface shows that it was once wetter billions of years ago. Its earlier climate may have supported rivers, lakes, and long-lasting bodies of water in some regions.
Key Facts About Mars
Diameter: About 4,212 miles (6,779 kilometers)
Mass: About 0.107 times Earth's mass
Average Distance from the Sun: About 142 million miles (1.52 AU)
Day Length: 24 hours and 37 minutes
Year Length: 687 Earth days
Average Surface Temperature: About -81°F (-63°C)
Evidence of Ancient Water
Scientists have found dried river channels, ancient lake beds, water-formed minerals, and delta-shaped deposits on Mars. These features show that liquid water once flowed across parts of the planet's surface.
Today, much of Mars's water exists as ice in the polar caps and beneath the surface. Some salty liquid water may occur briefly under very limited conditions, but stable liquid water is not known to exist on the surface today.
Mars Exploration
Mars is one of the most explored worlds in the Solar System. Active missions include NASA's Perseverance and Curiosity rovers, along with several spacecraft orbiting the planet.
Ingenuity, the small helicopter that traveled with Perseverance, became the first aircraft to achieve powered, controlled flight on another planet in 2021. Its mission ended in 2024 after 72 flights.
Perseverance is studying Jezero Crater and collecting rock and soil samples that could be returned to Earth by future missions for detailed analysis.
Moons of Mars
Mars has two small moons, Phobos and Deimos. Their origins are still debated, although they may be captured objects or remnants from material that formed around Mars after an ancient impact.
Phobos orbits so close to Mars that it is slowly moving inward. In tens of millions of years, it may break apart into a ring or collide with the planet.
The Next Frontier for Humans
Mars is widely considered a leading destination for future human missions beyond the Moon. Its relative accessibility, water ice, and Earth-like day length make it an important target for long-term exploration.
From giant volcanoes and frozen deserts to ancient river valleys and ongoing robotic missions, Mars remains one of the most compelling worlds in the Solar System.