With the exception of Earth, Mars is the most popular planet for science-fiction writers. Today, it is now the most popular planet on the Internet as well. The current NASA mission has turned everyone eyes to the “Red Planet” in hopes that it can answer some of our questions. Luckily, there is already a great deal that we know about Mars through previous missions.
Mars is the fourth planet from the sun and the third smallest. It is approximately half the size of Earth but has only one tenth the mass. Because of this, the force of gravity on Mars is less than that on Earth. Going to Mars would be a quick way to lose weight, as a 150-pound person would only weigh 56.5 pounds standing on the surface of Mars. (Check out www.exploratorium.edu/ronh/weight to find out what you’d weigh on other planets!)
Here on Earth, plate tectonics cause the crust to slowly move on top of the mantle. This is why we have earthquakes and island chains, like Hawaii. On Mars, there is currently no evidence for tectonic motion. Combined with the lower gravity, this is why Mars is home to the largest mountains in the solar system. The Tharsis region on Mars is an area almost 2500 miles across and reaches over 6 miles high. The title of largest mountain in the solar system goes to Olympus Mons. This single mountain is 310 miles across and almost 15 miles tall. As a point of reference, Mt. Everest, the tallest peak on Earth, is only 5.5 miles high.

Besides Olympus Mons, another striking feature is Valles Marineris. Visible from Earth, this giant canyon stretches for 2500 miles and can be as much as 5 miles deep. Originally Valles Marineris was viewed as part of a gigantic system of manmade, or should I say Martian-made structures. Giovanni Schiaparelli, an Italian astronomer first observed Mars in 1877 and observed “canali”- the Italian word for “channels.” The word made some people think that they were canals used by a Martian civilization. Percival Lowell did some of the most extensive observations of Mars and discovered over 500 canals, which he wrote about in his 1903 book Mars and it’s Canals. Unfortunately, when our spacecraft reached Mars, we discovered that there were no canals.

Canals actually would not have been very useful on Mars. It’s located 142 million miles away from the sun, (one and a half times farther than the Earth) and has a very thin atmosphere. The average temperature on the surface of Mars is –81°F, far below the freezing point of water. The atmosphere also cools very quickly as temperatures during the day reach can often reach 60°F but then drop to –135°F during the night. While Mars currently cannot support liquid water on the surface, there are trace amounts of water vapor in the atmosphere as well as ice in the Martian poles. There appears to be evidence that there once was water on the surface and that there may still be liquid water below. One of the Mars Exploration Rovers jobs will be to find evidence of water on Mars.

Some Basic Facts about Mars Compared to the Earth...

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