Indeed, throughout all of 2002 NASA has been engaged in a radical rewrite of the post-2009 program, with the assistance of two advisory groups: MEPAG (Mars Exploration Program Analysis Group), a group of 75 scientists who provide advice on desirable scientific goals, and MERT (Mars Exploration Review Team), a group of 15 program managers, engineers and scientists who provide NASA with advice on the actual design of the program to achieve these goals.

Each group has already completed two full-scale reviews this year, with the second pair of reviews preceded by a set of reports from three subgroups of MEPAG dealing with the most important subtopics. The new U.S. plan for longer-range Mars exploration should be completed and released by the end of this year.

The previous U.S. Mars exploration plan centered around the launch of the first U.S. Mars sample return lander in 2011-13, equipped with a piggyback rover -- generally similar to the 2003 MER rovers -- which would make a series of increasingly long looping explorations from the lander out to a range of one kilometer or so.

The rover would use a set of onboard instruments to carry out a preliminary analysis of various rocks and soil patches, collecting a total of several dozen small samples from those targets that looked most promising on the basis of the in-situ analyses and photos.

In this situation, a short rock drill would collect 3-centimeter-long plugs from interesting rocks to ensure that much of the sample was from below the rocks' weathered crusts. After each loop, it would return its latest load of samples to the lander.

Meanwhile the lander would use its own drill to collect soil samples from about two meters below the surface -- maximizing the chances of collecting both near-surface permafrost and soil samples from below the thin surface layer where powerful oxidant chemicals manufactured by solar UV light are thought to destroy any Martian organic compounds.

The total sample collection -- weighing about half a kilogram -- would then be launched into low orbit around Mars on a two-stage solid rocket weighing about 250 kg.

Several months later, a French-built Mars orbiter would rendezvous and docking with the tiny orbiting sample canister, using a system of radar and optical sensors mostly built by the U.S., and place the canister into an attached Earth-return capsule.

When the next Mars-to-Earth launch window presented itself, the orbiter would use its onboard engine to launch itself out of Mars orbit and sail back to Earth, flying by our planet and dropping off the reentry capsule -- which would land in the Utah desert using either a parachute or simply a thick layer of shock-absorbent plastic foam.

Finally, the reentry capsule and its still-carefully-sealed can of Mars samples would be hustled back to a "Mars Quarantine Facility" which would carefully examine the samples for any sign of Martian microbes.

If any evidence of life -- either living or fossil -- was found, the samples would continue to be rigidly protected inside the Facility, probably for years, while very careful tests were run to rule out any slim chance that they might be harmful to any organisms in Earth's ecosystem.

In fact, a whole expensive second lab facility might well have to be built to study any such actual evidence of Martian life, with only carefully radiation-sterilized portions of the samples being released to any outside labs in the meantime.

But if no evidence of life was discovered, the samples -- having been equally carefully shielded inside the Facility from any Earth contaminants that could foul up the delicate search for fossil evidence of past Martian life -- would be immediately parceled out to labs worldwide for genuinely detailed scientific study.

It's obviously a very ambitious mission -- the most complex unmanned space mission the U.S. has ever attempted. And it was running into serious problems even before the French indicated a few months ago that they were seriously considering canceling their development of the sample return orbiter so that the U.S. would have to build its own.