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Mars: Overview
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Color image of a thin atmosphere over reddish Mars. Link to MAVEN toolkit.
Mars lost much of its atmosphere over time. Where did the atmosphere--and the water--go? The MAVEN mission's hunt for answers will help us understand when and for how long Mars might have had an environment that could have supported microbial life in its ancient past.

Mars is a cold desert world. It is half the diameter of Earth and has the same amount of dry land. Like Earth, Mars has seasons, polar ice caps, volcanoes, canyons and weather, but its atmosphere is too thin for liquid water to exist for long on the surface. There are signs of ancient floods on Mars, but evidence for water now exists mainly in icy soil and thin clouds.

Link to Eyes on the Solar System simulator
Explore Mars in 3D

10 Need-to-Know Things About Mars

  1. If the sun were as tall as a typical front door, Earth would be the size of a nickel, and Mars would be about as big as an aspirin tablet.
  2. Mars orbits our sun, a star. Mars is the fourth planet from the sun at a distance of about 228 million km (142 million miles) or 1.52 AU.
  3. One day on Mars takes just a little over 24 hours (the time it takes for Mars to rotate or spin once). Mars makes a complete orbit around the sun (a year in Martian time) in 687 Earth days.
  4. Mars is a rocky planet, also known as a terrestrial planet. Mars' solid surface has been altered by volcanoes, impacts, crustal movement, and atmospheric effects such as dust storms.
  5. Mars has a thin atmosphere made up mostly of carbon dioxide (CO2), nitrogen (N2) and argon (Ar).
  6. Mars has two moons named Phobos and Deimos.
  7. There are no rings around Mars.
  8. More than 40 spacecraft have been launched for Mars, from flybys and orbiters to rovers and landers that touched surface of the Red Planet. The first true Mars mission success was Mariner 4 in 1965.
  9. At this time in the planet's history, Mars' surface cannot support life as we know it. A key science goal is determining Mars' past and future potential for life.
  10. Mars is known as the Red Planet because iron minerals in the Martian soil oxidize, or rust, causing the soil -- and the dusty atmosphere -- to look red.

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Homework? We can help. Link to Mars Homework Help.
Just the Facts
Orbit Size (semi-major axis):  227,943,824 km
Mean Radius:  3,389.5 km
Volume:  163,115,609,799 km3
Mass:  641,693,000,000,000,000,000,000 kg
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Al Hibbs Al Hibbs
Al Hibbs decided as a five-year-old that he wanted to go to the Moon. He did qualify as an astronaut, but his legacy is in robotic exploration. Read More...
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Last Updated: 30 Aug 2014