Mars | Facts, Surface, Moons, Temperature, & Atmosphere | Britannica

You are using an outdated browser. Please upgrade your browser to improve your experience and security. Ask the Chatbot Games & Quizzes History & Society Science & Tech Biographies Animals & Nature Geography & Travel Arts & Culture ProCon Money Videos Mars

• Introduction & Top Questions
• Basic astronomical data
• Early telescopic observations
• Mars as seen from Earth
  • Surface features
  • Polar regions
  • Transient atmospheric phenomena
• The atmosphere
  • Basic atmospheric data
  • Composition and surface pressure
  • Atmospheric structure
  • Meteorology and atmospheric dynamics
• Character of the surface
  • Southern cratered highlands
  • Sparsely cratered plains
  • Surface composition
  • Valleys and lakes
  • Outflow channels and oceans
  • Valles Marineris
  • Tharsis and Elysium
  • Polar sediments, ground ice, and glaciers
• The interior
• Meteorites from Mars
• Martian moons
• Spacecraft exploration
• The question of life on Mars
• Human exploration

References & Edit History Related Topics Images, Videos & Interactives For Students Mars summary Quizzes Astronomy and Space Quiz Space Odyssey Planets and the Earth’s Moon Brightest Star in the Solar System All About Astronomy Related Questions

• What do Mars and Earth have in common?
• What is the temperature on Mars?
• When did Viking 1 and Viking 2 land on Mars?

Science Astronomy

Mars planet Quick Summary Ask the Chatbot Print print Print Please select which sections you would like to print:

• Table Of Contents

Cite verifiedCite While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. Select Citation Style MLA APA Chicago Manual of Style Copy Citation Share Share Share to social media Facebook X URL https://www.britannica.com/place/Mars-planet Feedback External Websites Feedback Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login). Feedback Type Select a type (Required) Factual Correction Spelling/Grammar Correction Link Correction Additional Information Other Your Feedback Submit Feedback Thank you for your feedback

Our editors will review what you’ve submitted and determine whether to revise the article.

External Websites

• The Planets - Mars Facts
• NASA - Science - Mars
• Live Science - Mars: The red planet
• The Nine Planets - Mars
• Space.com - Mars: Everything you need to know about the Red Planet
• Physics LibreTexts - Mars

Britannica Websites Articles from Britannica Encyclopedias for elementary and high school students.

• Mars - Children's Encyclopedia (Ages 8-11)
• Mars - Student Encyclopedia (Ages 11 and up)

Quick Summary Ask the Chatbot a Question Also known as: Ares, Nergal Written by Michael C. Malin President and Chief Scientist, Malin Space Science Systems, Inc., San Diego, California. Professor of Geology, Arizona State University, Tempe, 1987–91. Coauthor of Earthlike Planets. Michael C. MalinAll Fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Last updated Dec. 28, 2025 •History Table of Contents Table of Contents Quick Summary Ask the Chatbot a Question Top Questions

How far is Mars from Earth?

Mars is less than 56 million km (35 million miles) from Earth at its closest approach, but it recedes to almost 400 million km (250 million miles) when the two planets are on opposite sides of the solar system.

What is the size of Mars?

Mars is the second smallest planet in the solar system, only larger than Mercury and slightly more than half the size of Earth. It has an equatorial radius of 3,396 km (2,110 miles) and a mean polar radius of 3,379 km (2,100 miles).

What do Mars and Earth have in common?

Mars is similar to Earth in many ways. Like Earth, it has clouds, winds, a roughly 24-hour day, seasonal weather patterns, polar ice caps, volcanoes, canyons, and other familiar features. There are clues that billions of years ago Mars was even more like Earth, with a denser, warmer atmosphere, rivers, lakes, flood channels, and perhaps oceans.

What is the temperature on Mars?

The characteristic temperature on Mars in the lower atmosphere is about 200 kelvins (K; −100 °F, −70 °C), which is generally colder than the average daytime surface temperature of 250 K (−10 °F, −20 °C). In the summer daytime temperatures can peak at about 290 K (62 °F, 17 °C).

When did Viking 1 and Viking 2 land on Mars?

The Viking landers are two robotic U.S. spacecraft launched by the National Aeronautics and Space Administration (NASA) for the study of the planet Mars. Viking 1 landed in the region of Chryse Planitia (22° N, 48° W) on July 20, 1976, and Viking 2 landed 6,500 km (4,000 miles) away in Utopia Planitia (48° N, 226° W) several weeks later on September 3.

News •

Scientists may have found the best place for humans to land on Mars • Dec. 26, 2025, 8:02 PM ET (ScienceDaily) ...(Show more) Beijing extends Mars mission lead; stranded crew returns: China’s year in space • Dec. 25, 2025, 11:16 PM ET (South China Morning Post) See the 100,000th photo of Mars taken by NASA's groundbreaking Red Planet orbiter • Dec. 24, 2025, 2:47 AM ET (Live Science) NASA loses contact with MAVEN, which reached Mars with Mangalyaan • Dec. 21, 2025, 4:56 PM ET (The Hindu) NASA reveals why Mars changed from a blue world into a red desert • Dec. 18, 2025, 10:41 AM ET (Earth.com) Show less

Mars, fourth planet in the solar system in order of distance from the Sun and seventh in size and mass. It is a periodically conspicuous reddish object in the night sky. Mars is designated by the symbol ♂.

Sometimes called the Red Planet, Mars has long been associated with warfare and slaughter. It is named for the Roman god of war. As long as 3,000 years ago, Babylonian astronomer-astrologers called the planet Nergal for their god of death and pestilence. The planet’s two moons, Phobos (Greek: “Fear”) and Deimos (“Terror”), were named for two of the sons of Ares and Aphrodite (the counterparts of Mars and Venus, respectively, in Greek mythology).

Planetary data for Mars
*Time required for the planet to return to the same position in the sky relative to the Sun as seen from Earth.
mean distance from Sun	227,943,824 km (1.5 AU)
eccentricity of orbit	0.093
inclination of orbit to ecliptic	1.85°
Martian year (sidereal period of revolution)	686.98 Earth days
visual magnitude at mean opposition	−2.01
mean synodic period*	779.94 Earth days
mean orbital velocity	24.1 km/sec
equatorial radius	3,396.2 km
north polar radius	3,376.2 km
south polar radius	3,382.6 km
surface area	1.44 × 108 km2
mass	6.417 × 1023 kg
mean density	3.93 g/cm3
mean surface gravity	371 cm/sec2
escape velocity	5.03 km/sec
rotation period (Martian sidereal day)	24 hr 37 min 22.663 sec
Martian mean solar day (sol)	24 hr 39 min 36 sec
inclination of equator to orbit	25.2°
mean surface temperature	210 K (−82 °F, −63 °C)
typical surface pressure	0.006 bar
number of known moons	2

In recent times Mars has intrigued people for more-substantial reasons than its baleful appearance. The planet is the second closest to Earth, after Venus, and it is usually easy to observe in the night sky because its orbit lies outside Earth’s. It is also the only planet whose solid surface and atmospheric phenomena can be seen in telescopes from Earth. Centuries of assiduous studies by earthbound observers, extended by spacecraft observations since the 1960s, have revealed that Mars is similar to Earth in many ways. Like Earth, Mars has clouds, winds, a roughly 24-hour day, seasonal weather patterns, polar ice caps, volcanoes, canyons, and other familiar features.

There are intriguing clues that billions of years ago Mars was even more Earth-like than today, with a denser, warmer atmosphere and much more water—rivers, lakes, flood channels, and perhaps oceans. By all indications Mars is now a sterile frozen desert. However, close-up images of dark streaks on the slopes of some craters during Martian spring and summer suggest that at least small amounts of water may flow seasonally on the planet’s surface. The InSight lander found that the region of Mars’s crust between 11.5 and 20 km (7.1 and 12 miles) under the surface is saturated with water.

Britannica Quiz 27 True-or-False Questions from Britannica’s Most Difficult Science Quizzes

The presence of water on Mars is considered a critical issue because life as it is presently understood cannot exist without water. If microscopic life-forms ever did originate on Mars, there remains a chance, albeit a remote one, that they may yet survive in these hidden watery niches. (In 1996 a team of scientists reported what they concluded to be evidence for ancient microbial life in a piece of meteorite that had come from Mars, but most scientists have disputed their interpretation.) NASA announced in 2025 that the Perseverance rover had found two minerals, vivianite and greigite, that on Earth form in the presence of microbial life. However, NASA also announced that ruling out that life had not formed the minerals required returning the mineral samples to Earth for a more thorough analysis than could be done by Perseverance’s instruments.

Since at least the end of the 19th century, Mars has been considered the most hospitable place in the solar system beyond Earth both for indigenous life and for human exploration and habitation. At that time, speculation was rife that the so-called canals of Mars—complex systems of long, straight surface lines that very few astronomers had claimed to see in telescopic observations—were the creations of intelligent beings. Seasonal changes in the planet’s appearance, attributed to the spread and retreat of vegetation, added further to the purported evidence for biological activity. Although the canals later proved to be illusory and the seasonal changes geologic rather than biological, scientific and public interest in the possibility of Martian life and in exploration of the planet has not faded.

Access for the whole family! Bundle Britannica Premium and Kids for the ultimate resource destination. Subscribe

During the past century Mars has taken on a special place in popular culture. It has served as inspiration for generations of fiction writers from H.G. Wells and Edgar Rice Burroughs in the heyday of the Martian canals to Ray Bradbury in the 1950s and Kim Stanley Robinson in the ’90s. Mars has also been a central theme in radio, television, and film, perhaps the most notorious case being Orson Welles’s radio-play production of H.G. Wells’s novel War of the Worlds, which convinced thousands of unwitting listeners on the evening of October 30, 1938, that beings from Mars were invading Earth. The planet’s mystique and many real mysteries remain a stimulus to both scientific inquiry and human imagination to this day.