About Mars

10 Need-to-Know Things About Mars

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.

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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    Discovered By		Known by the Ancients
    Date of Discovery		Unknown
    Orbit Size Around Sun (semi-major axis)		Metric: 227,943,824 km English: 141,637,725 miles Scientific Notation: 2.2794382 x 108 km (1.523662 A.U.) By Comparison: 1.524 x Earth
    Perihelion (closest)		Metric: 206,655,215 km English: 128,409,598 miles Scientific Notation: 2.06655 x 108 km (1.381 A.U.) By Comparison: 1.405 x Earth
    Aphelion (farthest)		Metric: 249,232,432 km English: 154,865,853 miles Scientific Notation: 2.49232 x 108 km (1.666 A.U.) By Comparison: 1.639 x Earth
    Orbit Circumference		Metric: 1,429,085,052 km English: 887,992,283 miles Scientific Notation: 1.429 x 109 km By Comparison: 1.520 x Earth
    Average Orbit Velocity		Metric: 86,677 km/h English: 53,858 mph Scientific Notation: 2.4077 x 104 m/s By Comparison: 0.808 x Earth
    Orbit Eccentricity		0.0933941 By Comparison: 5.589 x Earth
    Orbit Inclination		1.85 degrees
    Equatorial Inclination to Orbit		25.2
    Mean Radius		Metric: 3,389.5 km English: 2,106.1 miles Scientific Notation: 3.3895 x 103 km By Comparison: 0.5320 x Earth
    Equatorial Circumference		Metric: 21,296.9 km English: 13,233.3 miles Scientific Notation: 2.12969 x 104 km
    Volume		Metric: 163,115,609,799 km3 English: 39,133,515,914 mi3 Scientific Notation: 1.63116 X 1011 km3 By Comparison: 0.151 x Earth
    Mass		Metric: 641,693,000,000,000,000,000,000 kg Scientific Notation: 6.4169 x 1023 kg By Comparison: 0.107 x Earth
    Density		Metric: 3.934 g/cm3 By Comparison: 0.714 x Earth
    Surface Area		Metric: 144,371,391 km2 English: 55,742,106 square miles Scientific Notation: 1.4437 x 108 km2 By Comparison: 0.283 x Earth
    Surface Gravity		Metric: 3.71 m/s2 English: 12.2 ft/s2 By Comparison: If you weigh 100 pounds on Earth, you would weigh 38 pounds on Mars.
    Escape Velocity		Metric: 18,108 km/h English: 11,252 mph Scientific Notation: 5.030 x 103 m/s By Comparison: Escape velocity of Earth is 25,030 mph.
    Sidereal Rotation Period (Length of Day)		1.026 Earth days 24.623 hours By Comparison: Earth's rotation period is 23.934 hours.
    Minimum/Maximum Surface Temperature		Metric: -87 to -5 °C English: -125 to 23 °F Scientific Notation: 186 to 268 K
    Atmospheric Constituents		Carbon Dioxide, Nitrogen, Argon Scientific Notation: CO2, N2, Ar By Comparison: CO2 is responsible for the Greenhouse Effect and is used for carbonation in beverages. N2 is 80% of Earth's air and is a crucial element in DNA. Ar is used to make blue neon light bulbs.