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A guide to the fourth planet from the Sun

Mars, the rusty one.

The biggest volcano in the solar system, blue sunsets, a moon that’s slowly falling in and a helicopter that flew 72 times. Every fact checked against NASA, plus a Mars passport, a rover to drive and an eraser called Useless who has been put in charge of mission control.

Get your Mars passport Drive a rover

Mars seen from space: a reddish-orange globe with dark markings and a white polar cap
Mars photographed by the Hubble Space Telescope in August 2003.Photo: NASA, ESA, and The Hubble Heritage Team (STScI/AURA), Public domain, Commons
687Earth days in one Mars year NASA Science: Mars facts
24.6 hin one Mars day, called a sol NASA Science: Mars facts
38%of your Earth weight: what you’d weigh on Mars NASA: Humans to Mars
2small moons, Phobos and Deimos NASA Science: Mars moons · checked 25 Oct 2026
Your Mars passport

Who would you be on Mars?

Put in your weight and birthday. We’ll work out what you’d weigh on Mars, how old you’d be in Mars years and when your next Mars birthday is. Nothing leaves your browser.

Mars passportmars.planets.im
Fill in the form to stamp your passport
Weight on Mars
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Age in Mars years
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Sols lived
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Next Mars birthday
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Right now on Mars
--:--:--Airy Mean Time (Mars’s prime meridian)
--:--:--Earth time now (UTC), for comparison

How it works: weight × 0.38 NASA: Humans to Mars; a Mars year is 686.980 Earth days NASA NSSDC: Mars fact sheet; a sol is 24.6597 hours NASA NSSDC: Mars fact sheet; the clock uses NASA’s Mars24 formula NASA GISS: Mars24 sunclock algorithm. Ages and dates are worked out from those figures, so they are rounded results, not official dates.

The short version

Mars is the fourth planet from the Sun. NASA Space Place: All about Mars Mars is a terrestrial planet: small and rocky, with a thin atmosphere. NASA Space Place: All about Mars

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

The ancient Romans named Mars after their god of war, because its reddish colour reminded them of blood. NASA Science: Mars facts It’s called the Red Planet because iron minerals in the Martian dirt oxidise, or rust. NASA Science: Mars facts

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 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

A wide view of Mars with a huge canyon system stretching across the middle of the planet
Valles Marineris across the middle of Mars, in a mosaic of Viking 1 orbiter pictures.Photo: NASA / USGS (see PIA04304 catalog page), Public domain, Commons

Explore Mars

The planetSize, sols, seasons, gravity and what’s inside. Surface & skyThe biggest volcano, the longest canyon and blue sunsets. Phobos & DeimosTwo potato-shaped moons, one of them slowly falling. Missions & roversFrom Mariner 4 in 1965 to Perseverance and Ingenuity. Myths vs factsThe Face on Mars, the red sky and “Mars is hot”. The big facts pageEvery fact on the site, each one checked against NASA or ESA.

Tile images are credited on their pages and on the credits page.

Mission control is open

Things to play

All games →

A dim blue glow around the setting Sun over the rim of a crater on Mars
Sunset in Gale Crater, photographed by Curiosity on 15 April 2015.Photo: NASA/JPL-Caltech/MSSS, Public domain, Commons
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Free Mars printables sample, 6 pages. Pick your paper size:

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Mars printables

Fact-checked PDFs in A4 and US Letter, sold as instant downloads from the ReallyByte store.

  • Mars Mission Control Pack

    Plan your own Mars mission: pick a landing site, design a rover, programme a drive, keep a sol log and earn a certificate

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  • Mars vs Earth Worksheets

    Size, days, years, gravity and weather compared, with Mars-maths, labelling and answer keys

    $4.99

  • Mars Rovers & Missions Cards

    Twelve double-sided photo cards, from Mariner 4 to Perseverance, plus a timeline game

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  • Mars Activity & Colouring Pack

    Colouring scenes, mazes, word search and puzzles for ages 4 to 9

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  • Mars Facts Poster Set

    Six fact-checked posters, from blue sunsets to the biggest volcano in the solar system

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  • Mars Quiz & Word Puzzles Pack

    A crossword, code breaker, fill-the-gap facts, number match, myth busters and a 16-question quiz, with answer keys

    $3.49
Best value

The Complete Mars Printables Bundle

All six packs plus a guide, A4 and US Letter, in one download.

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