Facts about Mars

Diameter: 6794 km (about half the diameter of Earth)

Surface area: 145 million sq km (about the same as Earth’s land area)

Gravity: 3.711 m/s² (about one third of Earth’s gravity)

Density: 3.93 g/cm³ (Earth: 5.51 g/cm³)

Average distance from the Sun: 227 940 000 km (1.52 times that of Earth)

Martian day (a ‘sol’): 24 hours 37 minutes

Martian year: 669 sols or 687 Earth days

Average temperature: –55ºC (from –133ºC at the winter pole to +27ºC during summer)

Atmosphere: 95.32% carbon dioxide, 2.7% nitrogen, 1.6% argon, 0.13% oxygen

Atmospheric pressure at the surface: 6.35 mbar (less than one hundredth of Earth’s atmospheric pressure)

Moons:         
Phobos: 27 x 22 x 18 km; ~6000 km above Mars; Deimos: 15 x 12 x 11 km; ~20 000 km above Mars

Geological time:
Pre-Noachian: (4.5–4.1 billion years ago)
Noachian (4.1–3.7 billion years ago)
Hesperian (3.7–2.9 billion years ago)
Amazonian (2.9 billion years ago to present)