Introduction
The Mysterious Red Planet

For thousands of years, people have gazed into the night sky and wondered about the planet Mars. It was an object of particular fascination for ancient astrologers who looked to the heavens for guidance about the past and the future. When they first noticed the fiery red planet, they thought it was a star. But as they continued to study the sky, they discovered that stars appear in fixed patterns (now known as constellations) and traveled across the sky with predictable regularity. Mars, however, and the other "wandering stars" behaved differently. They drifted about the sky from constellation to constellation, as if they were following an invisible path. Because of how these celestial bodies differed from stars, the ancient Greeks named them planetes , a word meaning "wanderers."

Although Mars shared certain characteristics with the other planets, sky watchers observed that it was unique in several ways. One difference was its burnished red color, which made it stand out from the rest. Another important feature that made Mars appear different was the way it moved across the sky. Whereas the other planets appeared as a narrow band that traveled in a constant direction, this was not the case with Mars. Instead, after moving in the same direction for many months, Mars began to

flare brilliantly and then reverse its course and start traveling backward. Because of its peculiar behavior, along with its fiery red color, Mars was associated with war, violence, danger, and death. As a result, some ancient peoples named the planet after their gods of war. The Greeks called it Ares, and the Romans called it Mars.

Thousands of years have passed since Mars was thought to be a brilliant red star shining in the night sky, but the human fascination with the planet has far from diminished. Since the 1960s, sophisticated technology and modern space missions have provided scientists with a wealth of knowledge and information. Still, many questions remain unanswered. For instance, even though it is doubtful that life exists on Mars today, was there a time when it did? If so, what happened to it? The absence of living things is likely related to the lack of water on the planet, which is another unsolved mystery. Scientists have tangible proof that water once ran freely on Mars, but there appears to be no trace of surface water now. What caused it to disappear?

Why Explore Mars?

As space exploration continues, additional pieces of the Mars puzzle will fall into place. Yet some people question whether it is worthwhile to study Mars at all. Space missions are extremely expensive, costing billions of dollars every year, but scientists are convinced that Mars exploration is crucial and must continue. That is because Mars is quite similar to Earth, and about 4 billion years ago, when the two planets were formed, they may have been almost identical. Geologists believe there was a time when Mars had a warmer and wetter climate, vast quantities of surface water, and an atmosphere that was much like Earth's. Over the course of its history, however, Mars has undergone such drastic changes that it looks as though it is caught in the grip of a global ice age. Today, the planet's surface is dry and lifeless, its atmosphere is unfit for human life, and its average daily temperature is more bone-chilling than even the coldest place on Earth. What caused these drastic changes? And is Earth destined for the same fate? By continuing to explore Mars, scientists

can gain a much greater understanding of the red planet, as well as insight into what the future may hold for Earth.

Mars has always been, and continues to be, a planet shrouded in mystery and intrigue. No one knows with any certainty what future exploration will reveal. But with each new mission, and each piece of knowledge that is gained, Mars becomes even more compelling for those who are determined to uncover its secrets. Astronomer and author William Sheehan shares his thoughts about why ongoing Mars exploration is so important:

It is a region untenanted and waiting to be claimed and challenged by our ideas. . . . The trailblazers who have led us to Mars have had various sources for their obsessions with the planet. Their obsessions, in turn, have contributed to our ongoing fascination. Some of the Mars-intoxicated ones were heroic figures; others were flawed, though their grand romantic visions often proved to be more inspiring than the truths of narrower minds. All were pioneers, dreaming of a brave new world that was disclosed to their eyes long before they or anyone else could arrive bodily. And so it is that we continue to explore Mars in our hearts and minds, until, one day, we remove Mars from the imagination and make it real. ¹