When it was initiated after the 1993 failure of Mars Observer, the Surveyor program had three overall goals of equal importance: understanding Mars' potential for past or present life, its climate history, and the "natural resources" of the planet (which included both the resources that might support future manned expeditions, and -- rather awkwardly -- the overall geological history of Mars).

Indeed, both the 1998 spacecraft were designed to focus on the climate question.

But in 1996, following the revelation of possible micro fossils in Mars meteorite ALH84001 (which many suspect was deliberately overplayed by NASA to bolster its funding requests), the program's central goal was changed by NASA Administrator Dan Goldin to focus on the hunt for present or (more likely) past life on Mars -- and sample return, which had been a longer-range goal, was suddenly emphasized for the near future, without adequate consideration of just how expensive it might turn out to be.

Now the question of whether life ever existed on Mars will still be the guiding question in designing the Mars program -- but there has been a return to a multi-pronged investigative approach to answer that question.

As McCleese says, answering that question one way or the other convincingly "will take decades, require an understanding of the climatological history of Mars, and probably require deep drilling into its surface" -- several meters deep in the short run, and maybe eventually kilometers deep, into or below the thick buried "cryospheric" layer of permafrost that most scientists believe underlies the surface of Mars.

To complicate matters further, the results so far from Mars Global Surveyor -- the first really detailed scientific survey of the planet since the Seventies -- have been confusing.

Its super-detailed photos of Mars's surface have revealed many unexpected and still puzzling surface processes, and yet has left dangling the central question of whether Mars -- during its more hospitable early days and had a dense atmosphere -- had large amounts of liquid water flowing across its surface, or whether it was always so cold as to be frozen at the surface, with its "valley networks" forged instead by slower trickles of liquid water (perhaps geothermally heated) a short distance underneath that frozen surface.

And MGS' thermal IR spectrometer has so far failed to discover the expected large deposits of carbonate minerals that should exist if (as believed) Mars' ancient dense carbon dioxide atmosphere disappeared because it reacted with that liquid water and the surface rocks to form carbonates.

McCleese said that this could mean either that wind-deposited materials (which have turned out to dominate virtually all parts of Mars) are covering up the clues of its ancient surface, or that our current theories about the history of Mars are significantly wrong.

McCleese suspects the latter.

In either case, he says that we are left with a major question: if surveys by Mars orbiters continue to fail to reveal convincing evidence of water-deposited minerals or sedimentary rocks on Mars' surface, do we assume that they really don't exist -- or do we send some landers down for a more thorough search?

And that question, of course, ties in with the failures of the 1998 Mars missions.

The reports of the Failure Review Boards for both missions have made it clear that the failures' central cause was very simple: grossly inadequate funding.

For $8 million less than the cost of the single Mars Pathfinder mission, JPL and Lockheed Martin tried to develop and fly two smaller but comparably complex spacecraft with entirely new designs.