Solar System

Mars

Terrestrial planet · The rusted frontier · Known since antiquity

A cold desert world half the size of Earth, Mars carries dry riverbeds and the largest volcano in the Solar System — evidence of a more active past.

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Texture: Solar System Scope (CC BY 4.0)

Key facts

Distance from Sun 1.52AU 228.0 million km
Radius 3,390km 0.53× Earth
Mean temperature −65°C −140 to 30 °C

Time & motion

A day (one spin) 24.6 hours A Martian day is remarkably close to Earth's.
A year (one orbit) 687 Earth days (1.88 years) One Martian year is nearly two Earth years.
Surface gravity vs Earth
3.7 m/s² 0.38 g
0Earth = 1 g2.5×

Mass & physical characteristics

Mass 6.42 × 10²³kg 0.107× Earth
Density 3.93g/cm³ Water = 1.0 g/cm³
Escape velocity 5.0km/s Speed to break free
Orbital velocity 24.1km/s Speed around the Sun
Axial tilt 25.2° Close to Earth's tilt, so Mars has similar seasons.

Atmosphere & magnetosphere

Atmosphere

95% carbon dioxide, 2.7% nitrogen, 1.6% argon. Far too thin to hold liquid water on the surface today.

Surface pressure ≈ 0.6% of Earth's Relative to Earth's 1 bar

Magnetic field

No global field today — only patchy magnetism frozen into the crust.

Moons & rings

Known moons 2 Two small moons: Phobos and Deimos.
Notable moons
PhobosDeimos

Make-up

Composition

Thin CO₂ atmosphere; iron-oxide dust gives the surface its red colour.

Notable features

  • Olympus Mons — the tallest volcano in the Solar System, about 22 km high.
  • Valles Marineris — a canyon system more than 4,000 km long.

Fun facts

  • Olympus Mons on Mars is about three times the height of Mount Everest.
  • Valles Marineris is so long it would stretch across the United States.
  • Mars has seasons like Earth because its axis is tilted about 25°.
  • Its two tiny moons, Phobos and Deimos, were discovered only in 1877.
  • Phobos orbits so close that it will break apart or crash into Mars within ~50 million years.

Exploration

Viking 1 & 2 1976 First spacecraft to land and operate on Mars.
Curiosity 2012– Nuclear-powered rover studying Gale Crater.
Perseverance 2021– Caching samples; flew the Ingenuity helicopter.