Guest Author - Lea Terry

Named for the Roman god of war, Mars has fascinated humankind for centuries. Could it be the origin of life on Earth? Or our future home? Perhaps it harbors a civilization that will one day overtake our own planet. Science fiction has cast Mars in all of these roles, but the planet’s true story has its own surprises.

Mars is believed to be similar to Earth, with polar ice caps, volcanoes, possibly even water. Though it is more like Earth than any other planet in the solar system, there are profound differences. The atmosphere is too thin to provide protection from the Sun’s rays, and temperatures usually hover below freezing, dropping as low as -220 degrees Fahrenheit.

The planet’s red color comes from iron in its surface soil, which reacted with oxygen and produced rust. The planet may have undergone other drastic changes during its life. It is believed that about 3.5 billion years ago, Mars experienced the largest known floods in the solar system, with the water possibly forming lakes or shallow oceans. Little of that water remains on the surface, however; certainly not enough to account for the planet’s many flood plains and channels. The planet’s atmosphere is so thin that water can’t exist on the surface for long, but there may be underground reserves of water. If so, this water might support simple life forms like those found in ice in Earth’s Antarctic region, although the possibility is remote.

Mars's surface is one of the most unusual in the solar system, and there is a striking difference in the planet’s northern and southern hemispheres. In the south, the surface is similar to that of Earth’s moon--dotted with ancient craters. The north, however, is younger and flatter and has a lower elevation. There is a prominent boundary between the two, marked by a sudden change in elevation. The reason for the difference is not known, but it has been speculated it may be due to a large impact early in the planet’s history.

The planet has several distinctive geologic features, most notably Olympus Mons, the largest volcano in the solar system. It towers over the surrounding plain, measuring about 17 miles high and encircled by a cliff that stands about 20,000 feet high. In the north, a group of volcanoes in the Tharsis region are so massive they form a huge bulge in the planet’s surface.