The Allure of Mars Through History

Jan. 2 -- Before people even knew what planets were, Mars was an alluring glow in the night sky.

As early as the 1500s B.C., Egyptians refer to Mars as "Horus of the Horizon," a god whom they depicted as a human with the head of a hawk. Ancient Romans saw the fiery red light in the heavens and named it after their mythical god of war.

Early astronomers saw channels and suggested a dying society had dug canals to irrigate water from the planet's poles. Modern scientists claim to have found signs of Martian life in meteorites. Endless books and movies have detailed the lives of "little green men."

Three rovers — one that may have crashed upon landing, another due to reach Mars late Saturday and a third due down on Jan. 25 — are poised to reignite a fascination that has persisted since the ancients first noted the planet's glow.

Harsh, But Habitable?

Why Mars? There are, after all, nine planets in our solar system. One reason may be the planet's similarity to our own home. A day on Mars is only 37 minutes longer than a day on Earth. The temperatures are harsh (ranging from -100 degrees Fahrenheit to 75 above), but may be at least bearable at some locations. The air is thin in oxygen (0.13 percent) and rich in carbon dioxide (95.3 percent). The air pressure is low at 7 millibars versus Earth's 1,000 millibars.

That may not sound all that habitable, but it is — compared to the competition. The air pressure on Venus, for example, would crush any visitor in seconds. And if the pressure didn't kill you, the searing temperatures would. The gaseous planets, Jupiter, Neptune, Uranus and Saturn, couldn't support you, Pluto is just a rock and Mercury is way too hot.

"There are only a couple, maybe a few places in the solar systems where people could conceivably go," explains Roger Launius, chair of space history at the Smithsonian National Air and Space Museum. "We've been to the moon and found out there's no life there. But there are a lot of questions remaining about Mars."