Magellan has mapped Venus. Galileo is weaving among Jupiter's moons. And the Hubble Space Telescope, in orbit around Earth, is revealing the universe in unprecedented detail. During much of that time, Martian exploration was on the back burner. And when NASA turned its attention back to Mars, the agency suffered some bad luck.
Scientists say that the more fuel a spacecraft has to store on board, the greater the risk.
When craft are destined for orbit around Earth, they may use their propellants within a day or two of launch. Planetary spacecraft, on the other hand, may have to wait months to burn that fuel. Global Surveyor has been redesigned to avoid the pitfalls of Mars Observer. It is smaller than its predecessor and thus carries less fuel. It has 10 times better resolution than the camera on the 1970s Viking spacecraft.