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The big facts page

105 Mars facts, all checked

Every fact on this site in one place, each linked to its NASA or ESA source. Our build checks each one against the source text; see the sources page. Things that can change carry the date we checked them.

Jump to: The basics | Size and distance | Days, years and seasons | Gravity | Air, weather and sky | Inside Mars | The surface | The moons | Missions and rovers | Myths

The basics

  1. 1 Mars is the fourth planet from the Sun. NASA Space Place: All about Mars
  2. 2 Mars is a terrestrial planet: small and rocky, with a thin atmosphere. NASA Space Place: All about Mars
  3. 3 The ancient Romans named Mars after their god of war, because its reddish colour reminded them of blood. NASA Science: Mars facts
  4. 4 The ancient Egyptians called it “Her Desher”, meaning “the red one”. NASA Science: Mars facts
  5. 5 It’s called the Red Planet because iron minerals in the Martian dirt oxidise, or rust. NASA Science: Mars facts
  6. 6 Mars has been known since ancient times, because you can see it without a telescope. NASA Space Place: All about Mars
  7. 7 Mars is one of the most explored places in the solar system, and the only planet where we’ve sent rovers to roam. NASA Science: Mars facts
  8. 8 NASA missions have found lots of evidence that Mars was much wetter and warmer, with a thicker atmosphere, billions of years ago. NASA Science: Mars facts
  9. 9 Mars formed about 4.5 billion years ago, when gravity pulled swirling gas and dust together. NASA Science: Mars facts

Size and distance

  1. 10 With a radius of 3,390 km, Mars is about half the size of Earth. NASA Science: Mars facts
  2. 11 If Earth were the size of a nickel (a US 5-cent coin), Mars would be about as big as a raspberry. NASA Science: Mars facts
  3. 12 Mars is only about half Earth’s width, but its surface has nearly the same area as all of Earth’s dry land. NASA Science: Mars facts
  4. 13 Mars orbits at an average distance of 228 million km from the Sun, which is 1.5 times Earth’s distance (1.5 AU). NASA Science: Mars facts
  5. 14 Sunlight takes 13 minutes to travel from the Sun to Mars. NASA Science: Mars facts
  6. 15 Mars and Earth are never closer than 54.6 million km, and they can be as far apart as 401.4 million km. NASA NSSDC: Mars fact sheet
  7. 16 Mars has about a tenth of Earth’s mass (0.107 times). NASA NSSDC: Mars fact sheet
  8. 17 Mars’s mean radius is 3,389.5 km. Earth’s is 6,371.0 km. NASA NSSDC: Mars fact sheet
  9. 18 Mars’s average distance from the Sun is 227.956 million km, compared with Earth’s 149.598 million km. NASA NSSDC: Mars fact sheet

Days, years and seasons

  1. 19 A day on Mars lasts 24.6 hours, a little longer than Earth’s. Martian days are called sols, short for “solar day”. NASA Science: Mars facts
  2. 20 The average length of a Mars solar day is 24.6597 hours. NASA NSSDC: Mars fact sheet
  3. 21 A year on Mars lasts 669.6 sols, which is the same as 687 Earth days. NASA Science: Mars facts
  4. 22 To be exact, Mars takes 686.980 Earth days to go once around the Sun. NASA NSSDC: Mars fact sheet
  5. 23 Mars is tilted 25 degrees, close to Earth’s 23.4 degrees, so it has seasons like ours. NASA Science: Mars facts
  6. 24 Martian seasons are different lengths, because Mars has an egg-shaped orbit. Northern spring is the longest at 194 sols. NASA Science: Mars facts
  7. 25 In Mars’s northern hemisphere, spring lasts 194 sols, summer 178 sols and winter 154 sols. Autumn is the shortest season: NASA lists it at 142 days. NASA Science: Mars facts
  8. 26 NASA’s Mars24 sunclock works out the time on Mars from the time on Earth. Its formula gives the “mean solar time” at Mars’s prime meridian, called Airy Mean Time. NASA GISS: Mars24 sunclock algorithm
  9. 27 Measured from noon to noon, a Mars day averages 24.6597 hours and an Earth day 24.0000 hours. NASA NSSDC: Mars fact sheet

Gravity

  1. 28 Gravity on Mars is about a third of Earth’s. If you weigh 100 pounds on Earth, you would weigh 38 pounds on Mars. NASA: Humans to Mars
  2. 29 Mars’s mean surface gravity is 3.73 m/s², 0.380 times Earth’s. NASA NSSDC: Mars fact sheet
  3. 30 To escape Mars’s gravity a rocket needs 5.03 km per second, less than half the 11.19 km/s needed on Earth. NASA NSSDC: Mars fact sheet
  4. 31 Mean surface gravity is 3.73 m/s² on Mars and 9.82 m/s² on Earth. NASA NSSDC: Mars fact sheet

Air, weather and sky

  1. 32 Mars has a thin atmosphere made mostly of carbon dioxide, nitrogen and argon. NASA Science: Mars facts
  2. 33 Mars’s air is 95.1% carbon dioxide and only 0.16% oxygen. NASA NSSDC: Mars fact sheet
  3. 34 The air pressure at the surface of Mars averages just 6.36 millibars. NASA NSSDC: Mars fact sheet
  4. 35 Temperatures on Mars can reach 20 °C or drop to about −153 °C. NASA Science: Mars facts
  5. 36 The average temperature on Mars is about −59 °C. NASA NSSDC: Mars fact sheet
  6. 37 Stand on the equator at noon and it would feel like spring at your feet (24 °C) and winter at your head (0 °C). NASA Science: Mars facts
  7. 38 To our eyes the Martian sky would look hazy and red, because of dust floating in the air, not blue like Earth’s. NASA Science: Mars facts
  8. 39 Sunsets on Mars glow blue. Fine dust lets blue light through more easily, so the blue stays close to the Sun. NASA Photojournal: Sunset in Mars’ Gale Crater
  9. 40 Curiosity photographed its first colour sunset on sol 956 of its mission, 15 April 2015, in Gale Crater. NASA Photojournal: Sunset in Mars’ Gale Crater
  10. 41 Winds on Mars sometimes whip up dust storms that cover much of the planet. Afterwards it can take months for the dust to settle. NASA Science: Mars facts
  11. 42 Clouds are rare on Mars. Most float no higher than about 60 km and are made of water ice, but some very high ones are probably dry ice. NASA JPL: Curiosity captures shining clouds
  12. 43 Mars has no global magnetic field today, but magnetised rocks in its southern crust show it had one about 4 billion years ago. NASA Science: Mars facts

Inside Mars

  1. 44 At the centre of Mars is a dense core of iron, nickel and sulfur, 1,500 to 2,100 km in radius. NASA Science: Mars facts
  2. 45 Its crust is between 10 and 50 km deep. NASA Science: Mars facts
  3. 46 Mars’s volcanoes are dead. NASA Space Place: All about Mars

The surface

  1. 47 The Red Planet is actually many colours. Up close the ground is brown, gold and tan. NASA Science: Mars facts
  2. 48 Mars has the largest volcano in the solar system, Olympus Mons. It is more than 40 km tall from base to summit. NASA Science: Mars facts
  3. 49 That’s more than four times the height of Mount Everest, which rises 8,848 m. NASA Science: Mars facts
  4. 50 The base of Olympus Mons covers an area as large as the US state of Arizona. NASA Science: Mars facts
  5. 51 Valles Marineris, the largest canyon in the solar system, is about 3,870 km long, 600 km wide and 9.3 km deep. It would stretch from California to New York. NASA Science: Mars facts
  6. 52 Valles Marineris is more than 10 times longer and wider than Earth’s Grand Canyon. NASA Science: Mars facts
  7. 53 Mars has ancient river valleys, deltas and lakebeds, and rocks that could only have formed in liquid water. NASA Science: Mars facts
  8. 54 Some features suggest Mars had huge floods about 3.5 billion years ago. NASA Science: Mars facts
  9. 55 There is water on Mars today, mostly as ice just under the surface near the poles. The air is too thin for liquid water to last long on the surface. NASA Science: Mars facts
  10. 56 There’s evidence of liquid salty water in the ground on some Martian hillsides. NASA Space Place: All about Mars
  11. 57 Scientists don’t expect to find anything living on Mars today. They are looking for signs of life from long ago, when Mars was warmer and wetter. NASA Science: Mars facts · checked 25 Oct 2026
  12. 58 Mars has no rings. NASA Science: Mars facts

The moons

  1. 59 Mars has two small moons, Phobos and Deimos. NASA Science: Mars moons · checked 25 Oct 2026
  2. 60 Asaph Hall discovered both moons in 1877. NASA Science: Phobos
  3. 61 They are named after the horses that pulled the chariot of Ares, the Greek god of war. NASA Science: Mars facts
  4. 62 Both moons are potato-shaped, because they have too little mass for gravity to pull them into balls. They may be captured asteroids. NASA Science: Mars facts
  5. 63 Phobos, the larger moon, goes round Mars three times a day. NASA Science: Mars moons
  6. 64 Phobos is only 27 by 22 by 18 km. NASA Science: Phobos
  7. 65 Phobos is creeping closer to Mars by 1.8 m every hundred years. In about 50 million years it will crash into Mars or break up into a ring. NASA Science: Mars moons
  8. 66 Phobos’s biggest crater, Stickney, is named after Chloe Angeline Stickney Hall, a mathematician and the wife of Asaph Hall. NASA Science: Phobos
  9. 67 Deimos, the smaller moon, is just 15 by 12 by 11 km and goes round Mars every 30 hours. NASA Science: Deimos
  10. 68 Deimos looks smoother than Phobos because loose dirt fills many of its craters. NASA Science: Mars facts
  11. 69 NASA’s fact sheet lists 2 natural satellites for Mars and 1 for Earth. NASA NSSDC: Mars fact sheet · checked 25 Oct 2026

Missions and rovers

  1. 70 Mariner 4 flew past Mars on 14 July 1965. It was the first successful mission to Mars, and took the first close-up pictures of any planet beyond Earth. NASA Science: Mariner 4
  2. 71 The Mariner 4 team were too excited to wait for computers to process the first picture, so they printed the numbers on paper strips and coloured them in by hand. NASA Science: Mariner 4
  3. 72 NASA’s Viking 1 lander touched down on 20 July 1976 and sent back the first pictures from the surface of Mars. NASA Science: Viking 1
  4. 73 Viking 1 made the first truly successful landing on Mars. The Soviet Mars 3 lander landed in 1971, but contact was lost seconds after touchdown. NASA Science: Viking 1
  5. 74 The two Viking orbiters returned 52,663 pictures and mapped about 97 percent of Mars. NASA Science: Viking 1
  6. 75 Viking 2’s lander touched down on 3 September 1976, about 6,460 km from Viking 1. NASA Science: Viking 2
  7. 76 Mars Pathfinder landed on 4 July 1997 and delivered Sojourner, the first robotic rover ever sent to Mars. NASA Science: Mars Pathfinder
  8. 77 Sojourner weighed just 10.6 kg. NASA Science: Mars Pathfinder
  9. 78 Pathfinder landed inside giant airbags and bounced like a beach ball about 15 times, as high as 15 m. NASA Science: Mars Pathfinder
  10. 79 Twin rovers Spirit and Opportunity landed in January 2004, on opposite sides of Mars, to look for signs of past water. NASA Science: Spirit and Opportunity
  11. 80 Opportunity last talked to Earth on 10 June 2018, when a planet-wide dust storm covered the solar-powered rover. NASA Science: Spirit and Opportunity
  12. 81 By studying the rocks, Spirit and Opportunity confirmed that water stood on the surface of Mars for a long time in ancient times. NASA Science: Spirit and Opportunity
  13. 82 NASA’s Mars Reconnaissance Orbiter launched in 2005 to search for evidence that water lasted on the surface of Mars for a long time. NASA Science: Mars Reconnaissance Orbiter
  14. 83 ESA’s Mars Express launched on 2 June 2003 and reached Mars in December 2003. ESA: Mars Express
  15. 84 Mars Express has mapped the chemistry of Mars’s atmosphere and studied the moon Phobos in unprecedented detail. ESA: Mars Express
  16. 85 Curiosity landed on 6 August 2012. When it launched it was the largest and most capable rover ever sent to Mars. NASA Science: Curiosity rover
  17. 86 Curiosity is about the size of a small SUV, and its wheels are 20 inches (51 cm) across. NASA Space Place: Curiosity
  18. 87 Curiosity took 17 cameras to Mars, more than any other rover. NASA Space Place: Curiosity · checked 25 Oct 2026
  19. 88 Curiosity found chemical and mineral evidence that Mars once had places where tiny microbes could have lived. NASA Science: Curiosity rover · checked 25 Oct 2026
  20. 89 Perseverance launched on 30 July 2020 and landed in Jezero Crater on 18 February 2021. NASA Science: Perseverance rover
  21. 90 Perseverance is searching for signs of ancient microbial life and collecting rock samples that a future mission could bring to Earth. NASA Science: Perseverance rover · checked 25 Oct 2026
  22. 91 On 11 October 2026 Perseverance’s odometer reached 45.22 km, beating Opportunity’s record of 45.16 km for the farthest anyone has driven on another world. NASA Science: Perseverance rover · checked 25 Oct 2026
  23. 92 In 2025 the journal Nature published results showing that a Perseverance sample from a rock nicknamed “Cheyava Falls” contains potential biosignatures: clues that need more study before anyone can say whether life was there. NASA Science: Perseverance rover · checked 25 Oct 2026
  24. 93 Perseverance’s top speed on flat, hard ground is just under 0.1 mph: 152 metres per hour. NASA Science: Perseverance rover components
  25. 94 Perseverance has six wheels, each with its own motor. NASA Science: Perseverance rover components
  26. 95 Perseverance has six Hazard Cameras (HazCams), four at the front and two at the back, to spot rocks, trenches and sand dunes. NASA Science: Perseverance rover components
  27. 96 Engineering cameras help human operators on Earth drive Perseverance more precisely. NASA Science: Perseverance rover components
  28. 97 On 19 April 2021 the Ingenuity helicopter made the first powered, controlled flight on another planet. NASA Science: Ingenuity Mars Helicopter
  29. 98 Ingenuity was meant to make no more than five test flights in 30 days. It made 72 flights in nearly three years, the last on 18 January 2024. NASA Science: Ingenuity Mars Helicopter
  30. 99 Perseverance’s MOXIE experiment made 122 grams of oxygen from Martian air, about what a small dog breathes in 10 hours. NASA Science: Perseverance instruments
  31. 100 NASA has sent five rovers to Mars: Sojourner, Spirit, Opportunity, Curiosity and Perseverance. NASA Space Place: The Mars rovers · checked 25 Oct 2026
  32. 101 NASA is working on technology to send astronauts to Mars as early as the 2030s. NASA: Humans to Mars · checked 25 Oct 2026
  33. 102 Dust storms on Mars can last for months, so NASA says nuclear fission power is a more reliable choice than solar power for human missions. NASA: Humans to Mars
  34. 103 Pathfinder’s landing site was Ares Vallis. NASA Science: Mars Pathfinder

Myths

  1. 104 In 1976 the Viking 1 orbiter photographed a hill that looked like a human face. NASA explained at the time that shadows gave the illusion of eyes, nose and mouth. NASA Science: The “Face on Mars”
  2. 105 In 1998 Mars Global Surveyor photographed the “Face” again, ten times sharper than the best Viking picture. NASA Science: Face on Mars (1998 image)