Mars has always held a fascination for us Earthlings. It is our immediate neighbour out from the Sun and the outermost of the hard, rocky terrestrial planets before the asteroid belt and the gas giants, such as Jupiter and Saturn. Since the first telescope observations of Mars in the early 1600s, we have suspected that it is more Earth-like than any other planet.
Our desire to know it better has been driven by our need to learn more about our own planet and its place in the Solar System and by our fertile imaginations. Is Mars inhabited? Could it be a home for mankind in some distant future?
These and other questions have spurred scientists and engineers to meet the enormous challenge of sending a mission to Mars. A Mars-bound spacecraft must survive a six-month journey, approach Mars from just the right angle and at the right velocity to enter orbit, and then work well enough to return valuable observations. Some missions have failed, but the successes have more than repaid the effort and risk.
It is hard to believe, for example, that just 40 years ago, some serious observers still thought thick vegetation grew on Mars. That myth was finally dispelled only in the late 1960s when NASA's Mariner 6 and 7 spacecraft flew past the planet and sent back images of a barren, but fascinating, landscape. Since then, our knowledge about Mars has grown dramatically with every subsequent visit by a successful space mission. Just two or three decades of space-based observation produced more information and knowledge than earlier astronomers with Earth-bound telescopes could have imagined.