Space · Planets
Mars
The rust-red fourth planet, the most-visited body beyond the Earth–Moon system, with polar ice caps that grow and shrink with its seasons.
Quick facts
Type
Terrestrial
Distance from Sun
1.524 AU
227.9 million km
Diameter
6,792 km
Mass
0.107 Earth masses
6.42 × 10²³ kg
Surface gravity
3.71 m/s²
Day length
24.62 Earth hours
Year length
687 Earth days
1.881 Earth years
Mean surface temperature
−153 to 20 (−63 mean) °C
Atmosphere
95% CO₂, 2.8% N₂, 2% Ar (0.006 bar)
Confirmed moons
2
Naming origin
Roman god of war
What's there
Mars is a cold desert with active geology. The reddish color comes from iron oxide in the surface dust — literal rust, blown around by global dust storms that occasionally cover the whole planet. The atmosphere is thin (about 0.6% of Earth's pressure at the surface), so water cannot exist as a liquid on the open surface today, but the polar caps are made of water ice covered seasonally by frozen CO₂, and subsurface liquid water has been detected by radar beneath the southern polar layered deposits.
Mars carries the largest volcano in the solar system (Olympus Mons, 22 km tall) and the largest canyon (Valles Marineris, 4,000 km long). NASA rovers (Sojourner, Spirit, Opportunity, Curiosity, Perseverance) and landers (Viking 1 & 2, Pathfinder, Phoenix, InSight) have mapped the surface chemistry, listened to marsquakes, and confirmed that liquid water flowed extensively in the planet's early history. Whether Mars ever hosted life is the question the rovers were sent to answer; results so far are 'consistent with habitability in the deep past, no biosignatures yet.'
Who's been there
| Mission | Encounter | Year | Status | Primary objective |
|---|---|---|---|---|
|
Mariner 4 NASA |
Flyby | 1965 | Completed | First close-up images of Mars; revealed a cratered, Moon-like surface. |
|
Mariner 9 NASA |
Orbiter | 1971 | Completed | First Mars orbiter; revealed Olympus Mons and Valles Marineris through a planet-wide dust storm. |
|
Viking 1 NASA |
Lander | 1976 | Completed | First successful Mars lander; operated until 1982. |
|
Viking 2 NASA |
Lander | 1976 | Completed | Second successful Mars lander; operated until 1980. |
|
Mars Pathfinder & Sojourner NASA |
Rover | 1997 | Completed | First Mars rover; operated for three months on Ares Vallis. |
|
Mars Global Surveyor NASA |
Orbiter | 1997 | Completed | Long-duration global mapping; operated until 2006. |
|
Mars Odyssey NASA |
Orbiter | 2001 | Active | Longest-running Mars orbiter; mapped subsurface water ice. |
|
Mars Express ESA |
Orbiter | 2003 | Active | Mineralogical and atmospheric mapping; subsurface radar. |
|
Spirit & Opportunity NASA |
Rover | 2004 | Completed | Twin Mars rovers; confirmed past liquid water at both sites. Spirit operated to 2010, Opportunity to 2018. |
|
Mars Reconnaissance Orbiter NASA |
Orbiter | 2006 | Active | High-resolution imaging (HiRISE); subsurface radar; communications relay. |
|
Phoenix NASA |
Lander | 2008 | Completed | Confirmed water ice in the Martian arctic; operated 5 months. |
|
Curiosity NASA |
Rover | 2012 | Active | Gale Crater; assessing past habitability; nuclear-powered. Still operating. |
|
MAVEN NASA |
Orbiter | 2014 | Active | Atmospheric escape and solar-wind interaction. |
|
Mangalyaan ISRO |
Orbiter | 2014 | Completed | India's first Mars mission; succeeded on first attempt. Mission ended 2022. |
|
ExoMars TGO ESA/Roscosmos |
Orbiter | 2016 | Active | Trace gas characterization; methane mystery. |
|
InSight NASA |
Lander | 2018 | Completed | Seismometry; detected hundreds of marsquakes. Mission ended 2022. |
|
Perseverance & Ingenuity NASA |
Rover | 2021 | Active | Jezero Crater; sample-caching for Mars Sample Return; first powered helicopter flight on another world. |
|
Tianwen-1 & Zhurong CNSA |
Rover | 2021 | Completed | China's first Mars mission; orbiter active. Rover operated until 2022. |
|
Hope UAE |
Orbiter | 2021 | Active | Atmospheric study; first Arab interplanetary mission. |
Moons
Naming etymology
Mars takes its name from the Roman god of war — the red color, suggestive of blood and battle, was the trigger. The Greeks called it Ares; the Babylonians called it Nergal (god of pestilence). Across cultures, the consistent thread is that the reddish planet was associated with violence, war, or destruction. The Roman name stuck in Western astronomy and gave its name to its two moons (Phobos and Deimos — fear and dread, the personified attendants of Ares in Homer's Iliad), to the month of March (named for Mars), and to the iron oxide pigment 'Mars red.'
Methodology & sources
Numerical data drawn from the NASA Planetary Fact Sheets; satellite parameters from JPL Solar System Dynamics — Physical Parameters and the JPL Satellite Discovery Circumstances table. Mission history cross-referenced against NASA's mission catalog and individual mission pages. Naming etymology from the IAU Working Group for Planetary System Nomenclature. Hero rendering is a stylized SVG composed from primary-source visual reference (NASA / JPL imagery) — no photographs are reproduced.