Mars
Terrestrial Planet
Distance from Sun
227.9M km
About
Mars is the fourth planet from the Sun and the second-smallest planet in the solar system, after Mercury. Known as the "Red Planet" due to the iron oxide (rust) that covers its surface, Mars has captivated human imagination for centuries and remains the primary target for future human exploration beyond the Moon.
Mars has a thin atmosphere composed of 95.3% carbon dioxide, with surface pressure less than 1% of Earth's. Despite this, the planet experiences weather, including wind, dust storms that can engulf the entire globe, and thin clouds of water ice. Evidence from multiple missions strongly suggests that liquid water once flowed on Mars's surface billions of years ago, carving vast canyon systems and river channels.
The planet features some of the most dramatic geological landmarks in the solar system: Olympus Mons, the tallest volcano and largest shield volcano known, rises 21.9 km above the surrounding plains. Valles Marineris, a system of canyons stretching over 4,000 km, dwarfs the Grand Canyon. Mars also has distinct polar ice caps composed of water ice and dry ice (frozen CO&sub2;) that grow and shrink with the seasons.
Key Facts
- Olympus Mons on Mars is the tallest known volcano in the solar system at 21.9 km — nearly 2.5 times the height of Mount Everest.
- Mars has two small, irregularly shaped moons — Phobos and Deimos — likely captured asteroids.
- A day on Mars (called a "sol") is only 37 minutes longer than an Earth day, making it the most Earth-like day in the solar system.
- Mars's thin atmosphere means the sky appears butterscotch-colored during the day and sunsets appear blue.
- Global dust storms on Mars can last for months and completely obscure the surface from orbit.
- In 2015, NASA confirmed that liquid briny water flows intermittently on Mars's surface today as recurring slope lineae.
- Phobos is slowly spiraling inward toward Mars and is expected to break apart into a ring or crash into the surface in about 50 million years.
Exploration History
1971
Mariner 9
First spacecraft to orbit another planet; mapped 85% of Mars's surface and discovered Olympus Mons and Valles Marineris.
1976
Viking 1 & 2
First successful Mars landers; conducted biological experiments searching for life and returned the first surface photographs.
1997
Mars Pathfinder / Sojourner
First successful Mars rover; demonstrated low-cost landing technology and explored nearby rocks.
2004–18
Opportunity Rover
Designed for a 90-sol mission, it operated for over 14 years, traveling 45.16 km across the Martian surface.
2012–
Curiosity Rover
Car-sized rover exploring Gale Crater; confirmed Mars once had conditions suitable for microbial life.
2021–
Perseverance & Ingenuity
Rover collecting samples for future return to Earth; Ingenuity achieved the first powered flight on another planet.
Fun Fact
If you weigh 100 kg on Earth, you would weigh only about 38 kg on Mars. And if you could shout on Mars, nobody would hear you very well — the thin atmosphere carries sound waves, but at much lower volume. NASA's Perseverance rover recorded the first-ever audio from Mars's surface, revealing an eerily quiet world with occasional gentle wind sounds.