Introduction

Over the next twenty years, the National Aeronautics and Space Administration plans to send at least seven different unmanned missions to Mars. These missions include the Mars Express, the 2003 Mars Exploration Rovers, the 2005 Mars Reconnaissance Orbiter, several aerial scout missions, a smart lander, and a sample return mission. They will cost NASA and ultimately, the American taxpayer billions of dollars over the next two decades. Therefore, it is important for the public to understand the wide scope of the missions and to fully realize the benefits to all of mankind that will result from NASA's Mars Program. When the public is presented with the full picture of NASA's Mars Program, it will become clear that the benefits to technology, science, and society far outweigh the costs. Because NASA's interest in the Red Planet has at its roots mankind's long history of fascination with its mysterious red neighbor, it is essential to begin by examining the past.
Mankind's first step toward the exploration of Mars was made through the work of a single man. In the Seventeenth Century, Galileo Galilei designed and constructed the world's first telescope and used this telescope to make more detailed observations of Mars than had ever been possible before. Though Mars did not appear much largerthan the blood-red dot that captivated previous civilizations, Galileo recorded that hecould barely discern Mars passing through its phase. As word of Galileo's telescope spread, others began improving its design. Thanks to variations in size and differences in lens shape, the red dot slowly grew larger and sharper in our eyes. With even greater magnification came the discovery of spots covering the surface of Mars. In 1655, only forty-five years after Galileo's first glimpse of the planet, Christiaan Huygens, a great researcher of the 17th Century and one of the founders of mechanics and optical physics was able to track these spots and produce the first recorded sketch of Mars. He followed the spots over time, deducing in his journal: "The rotation of Mars, like that of the Earth, seems to have a period of 24 hours."

In the years that followed, astronomers and hobbyists alike worked to piece together data on Mars. Although the amount of visual and mathematical data regarding Mars continued to grow, the planet never seemed to shed its mystique.
In the middle of the seventeenth century, Giovanni Cassini, a professor of astronomy at the University of Bologna, noted white spots at the poles of Mars. A half century later, his nephew Giacomo Maraldi suggested that these white spots were polar ice caps similar to Earth's and implied that the southern caps would melt and evaporate during Mars' summer months. This discovery, combined with similarities in observed rotational period and distance from the sun, created the sense of fraternal relationship between Earth and Mars.

While the world was discovering the striking similarities between Mars and Earth, however, Mars remained a planet whose true nature was not completely known. As astronomers struggled to get better views of the planet, they could only speculate about what might lie on its surface. In 1686, Bernard de Fontenelle argued that the diminutive size of Mars made it impossible to sustain intelligent life. "In short," he wrote, "Mars is not worth the trouble of stopping at. A much prettier choice would be Jupiter with her four moons!"

Two centuries later, however, the world was abound with speculation about the possibility of intelligent life on Mars. Tales of "Martians" were published with increasing frequency throughout the beginning of the nineteenth century, but the real explosion in Martian mania did not occur until after the completion of the Suez Canal in 1869. In 1877, the astronomer Giovanni Schiaparelli described the streaks he observed on Mars as "canali," or channels. English publications mistranslated his findings and reported the discovery of "canals" on Mars.

The public mind was soon preoccupied with the possibility of life on Mars. The effect of this planetary explosion in culture is felt even today: the word 'Martian' is nearly synonymous with extraterrestrial life.

Humanity now has a more intimate knowledge of Mars than at any other time in history but also a larger number of questions about the nature of Mars. Galileo's observations of Mars through a telescope were a major stepping-stone in our exploration of the red planet. We have taken two more such leaps within the past fifty years: orbiting Mars and landing unmanned spacecraft on its surface. These milestones were not the work of one scientist, however, but the product of a society determined to learn about the planet that has intrigued it for centuries. The National Aeronautics and Space Administration (NASA) has been the foremost player in these accomplishments.

NASA's exploration of Mars began in 1964 with the launch of the Mariner program. Mariner 4 returned the first close-up pictures of Mars in 1965. The probe observed magnificent impact craters touched with frost from the chilled Martian evening as it sailed silently through space. Mariner 6 and 7 completed fly-bys of Mars four years later, returning a total of 201 pictures. Their instruments provided insight into the composition of the Martian atmosphere, and the returned images showed that the "canals" formerly believed to exist on Mars were natural geological features.

With the newfound ability to view Mars up close, NASA sent Mariner 9 in 1971 to map the planet's surface. Dust storms raged across Mars' surface upon the orbiter's arrival, obscuring the ground below. Mariner 9 patiently waited in orbit for its chance to begin piecing together a mosaic of the Martian terrain. Finally its chance came. What the world saw was astonishing. The large dark spots that had always puzzled observers turned out to be enormous volcanoes. Despite Mars' smaller size, the magnificent volcanoes dwarf any mountain on the surface of the Earth. The photos revealed impact craters strewn about the crust from the ancient bombardment of asteroids. Perhaps the most interesting feature, however, was the presence of dried river beds and tributaries. These remnants of ancient oceans and streams that once dominated the surface of the now-barren planet give scientists clues about Martian geographical history.

Four years after Mariner 9 returned its 7,329 photos to the world, NASA's Viking missions resulted in the first successful spacecraft landing on Mars. After touching down on the alien planet, the Viking lander began transmitting images of the rocky planet back to Earth. The first pictures of another planet ever to be taken directly from that planet's surface pleased eager observers. The lander then began testing the Martian soil for traces of life. Scientists found the results of these experiments confusing because unexpected chemical reactions were taking place in the Martian soil. The absence of strong data supporting the presence of life suggested that its existence on Mars was unlikely.

After the excitement of the Mariner and Viking programs, it was still many years before NASA would again explore Mars. In July 1997, NASA successfully landed another probe on the Martian surface. The Pathfinder project performed excellently. Using a parachute and an extensive airbag cushioning system, NASA landed a robotic rover named Sojourner in the middle of an ancient Martian floodplain. Sojourner was able to traverse the Martian surface and deliver chemical analyses, weather data, and stunning photographs. The rover observed dunes suggesting the presence of sand and rounded pebbles which in turn seemed to indicate the presence of running water in the past.

The scientific data returned by NASA's Mariner, Viking, and Pathfinder missions has contributed to geological and biological sciences on Earth. "If you want to learn about how a planet lived and died, then you've got to go to Mars," said Donna Shirley, manager of the Mars Exploration Program at NASA's Jet Propulsion Laboratory.