The Mars Global Surveyor is an American spacecraft which went into orbit around Mars on September 12, 1997 to conduct a detailed photographic survey of the planet beginning in March 1998. The spacecraft used a formerly untried technique called aerobraking to turn its initially highly elongated orbit into a circular orbit by dipping into the outer atmosphere of the planet. This was a $273 million project that began sending important data about the planet's surface at a quarter of the cost of the Mars Observer mission, which had failed in 1993 (Lawler, 2000).
Mars has long been a particular goal for space exploration. The planet has excited the human imagination, perhaps because of the many literary and dramatic works that suggested civilizations on Mars, and certainly because of the long-ago error of the idea of the Martian canals, which also suggested that there might be a civilization on this planet. More recently, the discovery of a rock in the Antarctic named Sample ALH84001, which started its existence when it crystallized out of hot magma on the planet Mars some 4.5 billion years ago. Half a billion years later it became a space traveler when an asteroid or comet struck the planet and sent chunks of Martian crust flying into space, and it was then caught by the gravity of the Sun so that it drifted toward the center of the solar system until 13,000 years ago when it collided with Earth and landed in Antarctica. In 1984 it was picked up by scientists who have found through various tests that this rock might possibly contain evidence that life existed at one time on Mars. While much of this remains speculative, it is also tantalizing enough so that we want to know much more about Mars than we do today.
For centuries, we have been trying to decide about the history of Mars, and now that we have sent a probe there and have much photographic and other evidence to study, we are finding that we still cannot see through t...