Mars
Mars is the fourth planet from the Sun and the second-smallest planet in our solar system. Named after the Roman god of war for its blood-red appearance, Mars has captivated humanity as a potential second home. It has the tallest mountain and the deepest canyon in the entire solar system.
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- Diameter
- 6,792 km
- Mass
- 0.107 Earths
- Distance from Sun
- 1.524 AU
- Surface gravity
- 3.72 m/s²
- Average temperature
- -65°C
- Known moons
- 2
- Orbital period
- 1.9 Earth years
- Rotation period
- 24.6 hours
- Ring system
- No
Source: NASA Planetary Fact Sheets (nssdc.gsfc.nasa.gov)
Atmosphere
Thin carbon dioxide (95.3%), nitrogen (2.7%), argon (1.6%). Surface pressure less than 1% of Earth's.
In Depth
Mars is a cold, dusty desert world with a thin atmosphere that cannot support liquid water on the surface today. Yet abundant evidence — from dry river valleys to mineral deposits that form only in water — tells us Mars was once warm and wet. Olympus Mons towers 21.9 km above the surrounding plains, nearly 2.5 times the height of Mount Everest. It is a shield volcano so wide (600 km) that an observer on its summit could not see the base. Valles Marineris stretches 4,000 km along the equator, up to 7 km deep and 200 km wide — it would span the entire continental United States. Mars has two small, irregularly shaped moons: Phobos (22 km) and Deimos (12 km), likely captured asteroids. The planet's thin atmosphere (less than 1% of Earth's surface pressure) means liquid water boils away almost instantly, but subsurface ice is abundant. Mars experiences seasons similar to Earth because its axial tilt is nearly identical (25.2° vs 23.4°), though each season lasts roughly twice as long. Global dust storms can envelop the entire planet for months.
Notable Features
- 01
Olympus Mons — the tallest volcano in the solar system at 21.9 km
- 02
Valles Marineris — a canyon system stretching 4,000 km, dwarfing the Grand Canyon
- 03
Polar ice caps made of water ice and dry ice (frozen carbon dioxide)
- 04
Evidence of ancient river channels and lake beds suggesting past liquid water
Exploration & Missions
Mars is the most explored planet beyond Earth. NASA's Mariner 4 made the first flyby in 1965. The Viking 1 lander (1976) was the first to successfully operate on the surface. Since the 1990s, a fleet of orbiters, landers, and rovers have studied Mars: Pathfinder/Sojourner (1997), Spirit and Opportunity (2004), Curiosity (2012), and Perseverance with the Ingenuity helicopter (2021). The ESA's Mars Express has orbited since 2003. Perseverance is currently collecting rock samples for a future sample-return mission. China's Zhurong rover (2021) explored Utopia Planitia. Human missions to Mars are actively planned by NASA and SpaceX for the 2030s.
Fun Facts
A year on Mars lasts 687 Earth days, but a Mars day ('sol') is only 37 minutes longer than an Earth day.
Mars appears red because its surface is rich in iron oxide — essentially rust covering the entire planet.
The Opportunity rover was designed for a 90-day mission but operated for nearly 15 years (2004-2019).
Ingenuity, the Mars helicopter, was designed for 5 flights but completed over 70 before retiring.
Frequently Asked Questions
Could humans live on Mars?▾
Not without extensive technology. Mars has no breathable atmosphere, extreme cold (averaging -65°C), intense radiation (no magnetic field), and very low atmospheric pressure. Settlers would need pressurized habitats, radiation shielding, and either imported or locally manufactured oxygen and water. NASA and SpaceX are developing technologies to address these challenges.
Was there ever water on Mars?▾
Yes, strong evidence shows Mars once had rivers, lakes, and possibly an ocean covering much of the northern hemisphere. Minerals like clays and sulfates (which form in water) are found across the surface. The Curiosity and Perseverance rovers have explored ancient lakebeds. Mars likely lost most of its water 3-4 billion years ago as its magnetic field weakened and the solar wind stripped away the atmosphere.
Why is Mars red?▾
Mars is red because its surface rocks and dust are rich in iron oxide (Fe₂O₃), commonly known as rust. Billions of years ago, iron in Martian rocks reacted with small amounts of oxygen in the atmosphere and water, oxidizing the surface. Fine rust-colored dust gets lofted into the atmosphere, giving even the sky a butterscotch tint.
Learn More
The 8 Planets in Order: An Interactive Guide for Students — an in-depth article covering all 8 planets, with size comparisons and learning activities.
Data source: NASA Planetary Fact Sheets
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