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10 Things You Should Know About Mars


Named for the Roman god of War, Mars probably got this name due to its red color. It is sometimes referred to as the Red Planet. The name of the month March derives from Mars.

1. Mars is the fourth planet from the sun

Planet Mars, Earth visible in background (Digital Composite)
World Perspectives/ Photographer's Choice/ Getty Images
Mars orbits the sun at an average distance of 141 million miles (approximately 1.5 AU), taking 686.93 Earth days or 1.8807 Earth years to complete a revolution.

2. Mars is the seventh largest planet

Pictures of Mars - Mars Daily Global Image
Copyright 1995-2003, California Institute of Technology
At about half the diameter of Earth (about 4212 miles), with one tenth Earth's mass, Mars's gravity is about one third that of Earth. The density of Mars is about 30 percent less than that of Earth (3.94 g/cm3 vs. 5.52 g/cm3). Its core is probably similar to Earth's, mostly iron, with small amounts of nickel, but spacecraft mapping of its gravity field seem to indicate that its iron-rich core and mantle are a smaller portion of its volume than on Earth. Also, its smaller magnetic field than Earth, indicates a solid, rather than liquid core.

3. Mars is a small rocky body

Pictures of Mars - Lander 2 Site
Copyright 1995-2003, California Institute of Technology
Like the other "terrestrial" planets - Mercury, Venus, and Earth - its surface has been changed by volcanism, impacts from other bodies, movements of its crust, and atmospheric effects such as dust storms.

4. Mars's surface is closest to that of Earth of any of the planets

Pictures of Mars - Western Tithonium Chasma - Ius Chasma
Copyright 1995-2003, California Institute of Technology
Still, it would still be a very harsh place to live, with temperature extremes between -225 and +60 degrees Fahrenheit, with an average of -67 degrees.

5. Mars may be the best hope for finding life away from Earth

Pictures of Mars - Martian Solar Eclipses
Copyright 1995-2003, California Institute of Technology
Mars has a very thin atmosphere made up mostly of a tiny amount of carbon dioxide (95.3%) plus nitrogen (2.7%), argon (1.6%) and traces of oxygen (0.15%) and water (0.03%). Also, water has been found to exist in liquid form on the planet.

6. Mars has inspired wild flights of imagination over the centuries

Pictures of Mars - Enormous Volcano
Copyright 1995-2003, California Institute of Technology
Italian astronomer Giovanni Schiaparelli observed Mars during the opposition of 1877 making note of what he called canali or channels. This was misinterpreted to mean canals, which many thought to indicate intelligent life.

In 1939, Orson Welles's radio theater company performed a production based on HG Wells's book "War of the Worlds" and caused a panic in many people who did not realize the event was merely a play.

7. Mars has two tiny satellites which orbit very close to the surface

Phobos from 6,800 Kilometers
NASA/JPL-Caltech/University of Arizona
Phobos at a distance of 9000 km has a radius of 11 km and a mass of 1.08e16 kg. It was discovered by American astronomer Asaph Hall, Sr., in 1877, at the US Naval Observatory in Washington, DC.

Deimos Distance at a distance of 23 has a radius of 6 km and a mass 1.80e15 kg. It was discovered by American astronomer Asaph Hall, Sr., in 1877, at the US Naval Observatory in Washington, DC.

8. Mars has some remarkable geological characteristics

Pictures of Mars - Ophir Chasma
Copyright 1995-2003, California Institute of Technology
These include the largest volcanic mountain in the solar system, Olympus Mons (27 km high and 600 km across): volcanoes in the northern Tharsis region that are so huge they deform the planet's roundness; and a gigantic equatorial rift valley, the Valles Marineris. This canyon system stretches a distance equivalent to the distance from New York to Los Angeles; Arizona's Grand Canyon could easily fit into one of the side canyons of this great chasm.

9. Mars has been visited by several probes

Mars Global Surveyor Mission
In 2004, a pair of rovers landed on Mars and started providing pictures and data. The Twin Mars Rovers, Spirit and Opportunity are providing NASA with some fascinating information about the red planet. In 2008, the Phoenix Lander touched down near the north pole and is also providing answers to other big questions.

10. One day, humans will walk on Mars

NASA's new Crew Exploration Vehicle (CEV) with solar panels deployed, docked with a lunar lander.
NASA & John Frassanito and Associates
NASA currently is planning a return to the moon in what is being called the first step towards a manned expedition to Mars.
Mars Facts Related Resources

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