Size, days, years and gravity
Mars is half Earth’s width, has a day just a bit longer than ours and a year almost twice as long. Here’s the planet in numbers.
How big?
With a radius of 3,390 km, Mars is about half the size of Earth. NASA Science: Mars facts 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
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 Mars has about a tenth of Earth’s mass (0.107 times). NASA NSSDC: Mars fact sheet
How far?
Mars is the fourth planet from the Sun. NASA Space Place: All about Mars 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
Sunlight takes 13 minutes to travel from the Sun to Mars. NASA Science: Mars facts 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
A day is a sol
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
The average length of a Mars solar day is 24.6597 hours. NASA NSSDC: Mars fact sheet
A long year
A year on Mars lasts 669.6 sols, which is the same as 687 Earth days. NASA Science: Mars facts To be exact, Mars takes 686.980 Earth days to go once around the Sun. NASA NSSDC: Mars fact sheet
Want your age in Mars years? Stamp your Mars passport →
Seasons
Mars is tilted 25 degrees, close to Earth’s 23.4 degrees, so it has seasons like ours. NASA Science: Mars facts Martian seasons are different lengths, because Mars has an egg-shaped orbit. Northern spring is the longest at 194 sols. NASA Science: Mars facts
Gravity
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 Mars’s mean surface gravity is 3.73 m/s², 0.380 times Earth’s. NASA NSSDC: Mars fact sheet
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
Thin air
Mars has a thin atmosphere made mostly of carbon dioxide, nitrogen and argon. NASA Science: Mars facts Mars’s air is 95.1% carbon dioxide and only 0.16% oxygen. NASA NSSDC: Mars fact sheet
The air pressure at the surface of Mars averages just 6.36 millibars. NASA NSSDC: Mars fact sheet
Inside Mars
Mars formed about 4.5 billion years ago, when gravity pulled swirling gas and dust together. NASA Science: Mars facts 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
Its crust is between 10 and 50 km deep. NASA Science: Mars facts Mars’s volcanoes are dead. NASA Space Place: All about Mars
A lost magnetic field
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
Most Mars numbers here come straight from NASA’s Mars facts page and NASA’s Mars fact sheet. Different NASA pages sometimes round differently (for example, Mars’s air is “95.1%” carbon dioxide on the fact sheet and “96%” on another page). Records and mission counts change, so they carry the date we checked them.
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