SOL SYSTEM / PLANETARY DOSSIER

Mars

Mars is a cold desert world with rusty soil and traces of ancient rivers.

Planetary view ↗

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Artist’s impression of Mars

Rust-colored dust and ancient landscapes beneath a thin sky.

Environment ↗

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DIAMETER / EARTH0.53×
EARTHMARS
ATMOSPHERE / COMPOSITION
CO₂Carbon dioxide≈ 95.1%
N₂Nitrogen≈ 2.59%
ArArgon≈ 1.94%
SURFACE TEMPERATURE
≈ −59°C mean surface
SURFACE PRESSURE
≈ 0.0064 bar, variable
HABITABILITYPast potential
UNPROTECTED HUMANSNot survivable

Interior ↗

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Mars interiorSchematic cutaway · layer thicknesses are not to scale. Crust, Rocky mantle, Metallic core.CrustRocky mantleMetallic core

Moons Orbit ↗

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Mars moon orbitsSelected moons, ordered outward. Orbit sizes and positions are schematic; relative periods are preserved.MARSPHOBOSDEIMOS

Landscape ↗

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A ground-level reconstruction of dusty basaltic terrain and distant layered hills. The muted tan sky and rusty soil draw on rover observations; this is not a photographed rover site.
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Rotation ↗

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Mars rotation compared with EarthA marked longitude moves between the day and night sides. Equal elapsed time and sidereal rotation rates. Polar schematic: sizes, axial tilt and seasons are not shown. Illumination uses a circular mean orbit, not a live sky prediction.SAME ELAPSED TIME · POLAR SCHEMATICMARS24.6 hoursSIDEREAL ROTATION24.7 hours · solar dayEARTH23.9 hoursSIDEREAL ROTATION≈ 24 h · solar day

Gravity ↗

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Mars gravityEqual launches at 2 m/s; shared metre scale; air resistance ignored.0.0 m0.2 m0.4 m0.6 mEARTH9.8 m/s²MARS3.7 m/s²

Orbit ↗

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Mars orbitElliptical orbit viewed along the orbital axis, relative to Sun. Motion is accelerated, not a live position. Distances are center to center.SUNMARS1.67 AU1.38 AU
Sources ↗
MARS

Instrument detail

Mars orbitElliptical orbit viewed along the orbital axis, relative to Sun. Motion is accelerated, not a live position. Distances are center to center.SUNMARS1.67 AU1.38 AU
ONE ORBIT687 Earth days
Closest to the Sun
1.38 AU
Farthest from the Sun
1.67 AU

The Sun sits at a focus of the orbit. Mars moves faster near the Sun and more slowly farther away.

Mars rotation compared with EarthA marked longitude moves between the day and night sides. Equal elapsed time and sidereal rotation rates. Polar schematic: sizes, axial tilt and seasons are not shown. Illumination uses a circular mean orbit, not a live sky prediction.SAME ELAPSED TIME · POLAR SCHEMATICMARS24.6 hoursSIDEREAL ROTATION24.7 hours · solar dayEARTH23.9 hoursSIDEREAL ROTATION≈ 24 h · solar day
Marked longitude · equal time on both worlds
ONE SIDEREAL ROTATION24.6 hours

Turning through space

A Martian rotation takes about 24.6 hours, close to Earth’s. A solar day, called a sol, lasts about 24 hours and 40 minutes.

Mean solar day
≈ 24.7 hours
One orbit
687 Earth days

A sidereal rotation is one turn relative to the stars. A solar day follows the Sun: the marked longitude crosses the illuminated and dark halves as rotation and orbital motion combine.

0 Earth hoursMarker · daylight

Mean clock model with a circular orbit. Axial tilt, seasons and local sunrise times are omitted. Sizes and starting longitudes are schematic, not live positions.

Satellite atlasMoons
Mars moon orbitsSelected moons, ordered outward. Orbit sizes and positions are schematic; relative periods are preserved.MARSPHOBOSDEIMOS
NATURAL MOONS02
  1. 01Phobos ↗0.3189 days
  2. 02Deimos ↗1.2625 days

Phobos and Deimos are Mars’s two small, irregular moons. Phobos orbits closer to the planet; Deimos circles farther out. Neither is massive enough for gravity to give it the rounded shape of a large moon.

Mars gravityEqual launches at 2 m/s; shared metre scale; air resistance ignored.0.0 m0.2 m0.4 m0.6 mEARTH9.8 m/s²MARS3.7 m/s²
MARS / EARTH GRAVITY0.38 ×

Same push, different gravity

Both balls launch at 2 m/s, using the same height and time scales. Weaker gravity gives a higher jump and a longer time in the air. Air resistance is ignored.

Earth · height / airtime
0.20 m / 0.41 s
Mars · height / airtime
0.54 m / 1.08 s
Mars interiorSchematic cutaway · layer thicknesses are not to scale. Crust, Rocky mantle, Metallic core. Select a layer below to highlight it.010203
Schematic cutaway · layer thicknesses are not to scale.
EXPLORE THE LAYERS
  1. 01

    The thin, solid outer layer of the planet.

  2. 02

    Silicate-rich rock lies between the crust and the metallic core.

  3. 03

    The central region is rich in iron, nickel and sulfur. Seismic measurements help constrain its structure.

Select a material to connect its description with the cutaway. Colors and textures identify regions; they do not show measured temperature.

Artist’s impression of Mars

The color of weathered iron.

Mars gets its reddish appearance from oxidized iron minerals in its soil. Today it is a cold desert with a thin atmosphere, but spacecraft have found evidence that parts of this world were once much wetter, with rivers and lakes.

A familiar view. Unfamiliar air.

The thin air matters as much as the color. Although carbon dioxide dominates its composition, there is very little atmosphere overall. A person standing in this apparently familiar desert would still need pressure protection and a supply of breathable air.

Familiar shapes. Different scale.

Dunes, canyons and extinct volcanoes shape the landscape. Mars has polar ice caps and seasons, too. Its rotation takes about 24.6 hours, close to Earth’s, while its longer orbit stretches a year to 687 Earth days.

Two small shapes overhead.

Phobos and Deimos are Mars’s two small, irregular moons. Phobos orbits closer to the planet; Deimos circles farther out. Neither is massive enough for gravity to give it the rounded shape of a large moon.

DIAMETER / EARTH0.53×
EARTHMARS
EARTH
12,756 km
MARS
6,780 km
approximate planet diameter / equatorial Earth diameter · rings excluded
ATMOSPHERE / COMPOSITION
CO₂Carbon dioxide≈ 95.1%
N₂Nitrogen≈ 2.59%
ArArgon≈ 1.94%

Approximate volume fractions; minor gases are omitted. A large carbon-dioxide fraction does not mean a thick atmosphere. Pressure near the mean surface level is less than one percent of Earth’s sea-level pressure.

SURFACE TEMPERATURE
≈ −59°C mean surface
SURFACE PRESSURE
≈ 0.0064 bar, variable
HABITABILITYPast potential

Ancient water-shaped terrain records environments that may once have supported microbes. That is evidence of potentially habitable conditions, not proof of life. The present surface is cold, dry and exposed to radiation.

UNPROTECTED HUMANSNot survivable

Very low pressure and too little oxygen prevent unprotected breathing. Cold and radiation add to the hazards; a familiar-looking landscape does not provide Earth-like conditions.

Planet and landscape images are artistic interpretations.

  • NASA ↗
    • Classification and orbital data
    • Simplified interior model
    • Natural conditions and human survival
    • Overview
    • Atmosphere
    • Landscape
    • Companions
  • NASA ↗
    • Rotation, gravity and orbital distances
  • NASA ↗
    • Gravity reference level and diagram definitions
  • NASA / JPL ↗
    • Satellite orbital periods
  • NASA ↗
    • Size, physical data and atmospheric constraints
A ground-level reconstruction of dusty basaltic terrain and distant layered hills. The muted tan sky and rusty soil draw on rover observations; this is not a photographed rover site.

Across the dusty plain

A ground-level reconstruction of dusty basaltic terrain and distant layered hills. The muted tan sky and rusty soil draw on rover observations; this is not a photographed rover site.

An imagined view of dark sand ripples and scattered sedimentary slabs. The dusty sky and subdued colors suggest ordinary Martian daylight.

Wind-written sand

An imagined view of dark sand ripples and scattered sedimentary slabs. The dusty sky and subdued colors suggest ordinary Martian daylight.

A tall eroded sedimentary wall with rusty and buff strata, talus at its foot and a narrow strip of dusty tan sky. An artistic reconstruction of Mars; local detail, lighting and viewpoint are imagined.

Layers in the crater wall

A tall eroded sedimentary wall with rusty and buff strata, talus at its foot and a narrow strip of dusty tan sky. An artistic reconstruction of Mars; local detail, lighting and viewpoint are imagined.