But why have so many Mars missions fallen short of their goal? Is there something special about Mars that leads spacecraft and the teams that guide them like moths to a flame? The answer partly has to do with the sheer number of attempts launched from Earth to the red planet. "We've sent more things to Mars than any other body except the Moon, so we've had more opportunities to fail," says Whetsel.

Some compare the record of Mars exploration to that of the early Moon shots that preceded the astronauts. Many failures occurred early in the program, but the record improved with experience.

In addition, says Whetsel, many people incorrectly assume Mars is an easy target to reach because of its relative proximity and many Earthlike qualities. But just because it's closer to Earth than Jupiter or Saturn doesn't necessarily make Mars a simpler destination.

Lessons Learned: The Silver Lining

A mix of excitement touched with trepidation is building at JPL, where, in about a month, engineers will direct NASA's Mars Odyssey spacecraft to enter orbit around Mars. At the time, Odyssey will be about 150 million kilometers (93 million miles) from Earth. Communicating through its 15-watt radio, the spacecraft will be at one of the most critical junctures of its mission.

It is the first spacecraft to be sent to Mars since the dual loss of the Mars Surveyor orbiter and lander two years ago. Fresh in the collective mind of the space exploration engineering community are recent lessons learned the hard way as the Odyssey team heads toward its orbit insertion maneuver. Those tough lessons, however, are considered by many at JPL and at Odyssey contractor Lockheed Martin Astronautics in Denver, Colo., to be the silver lining ending a cloudy period for Mars exploration in particular and JPL in general.

The team is acutely aware that thousands of engineering details have to proceed correctly for the spacecraft to begin its first successful orbit around Mars. If only one of those details goes wrong, it may unleash a cascade of events that could cause Odyssey to fail its entry into Mars' orbit.

Not that the public should expect anything short of a mission accomplished, says Mars Odyssey Project Manager Matt Landano of JPL:

"I think they ought to be expecting a success. We are doing everything we reasonably could on Odyssey to reduce risk and maximize our prospects for success. We clearly aren't going into this thinking that anything short of success is acceptable. In our minds, it's not ok to fail. We must succeed."