During his talk, McCleese briefly presented a whole table of proposals for future Mars spacecraft in 2003 and beyond -- and he quoted the Polar Lander failure review board as taking one look at this list and telling JPL, "No wonder you're having failures -- you're spreading your design efforts much too thin. You must focus firmly on one specific goal of Mars exploration -- presumably the search for life -- and on designing a limited variety of spacecraft to achieve it."

If NASA does decide to reconnoiter a whole set of possible landing sites before dispatching sample-return spacecraft to a few of them, what's the best way to do it?

McCleese described one idea that has been mentioned at several recent conferences: the "Mars Scout".

This proposal -- currently under study at JPL -- would involve launching 5 to 10 small, cheap landers to various potential sample-return sites (and maybe other interesting areas) over several Mars launch opportunities, perhaps starting as early as 2003.

They would be similar to the Mars Pathfinder -- hard landers that would come down fast, use inflatable airbag cocoons to cushion the landing shock, and then prop themselves upright by unfolding side petals with solar cells -- but they would be much smaller, weighing perhaps only 30 kg or so. This is similar to the design already used by the UK for its "Beagle 2" lander that will be launched in 2003, or the past series of Russian Mars hard landers, (whose failures had nothing to do with their overall design).

They would carry limited science payloads: two cameras to photograph the area close-up both during descent and after landing to check its safety and scientific interest for more expensive landers, infrared spectrometers to map the local minerals and check for signs that they were water-deposited, and perhaps (like Beagle 2) a few other instruments to further check the area's suitability for the return of samples containing possible fossils -- and they would work for only a few weeks.

These might be small enough that they could be carried on the 100-kg "Mars Micromission" spacecraft that the U.S. plans to launch to Mars starting in 2003, as piggyback payloads on Europe's Ariane 5 launches of large satellites.

These Micromission spacecraft (developed by Ball Aerospace) have other uses.

A series of seven is already planned for 2003 to 2009 to set up a network of little Mars comsats that will greatly improve both the data return and the navigational accuracy of future Mars landers, while also serving to return data from the Mars Scouts or similar small landers.

Meanwhile there are numerous proposals to have Micromission spacecraft carry various science payloads both into Mars orbit and on tiny surface landers.

One idea drawing great interest is the "Mars Micromission Aerobot", in which a little helium balloon would drift for weeks or months at about 5 km altitude, transmitting thousands of pictures and carrying other instruments such as IR mineral spectrometers, soil-water detectors and magnetometers.

McCleese said that this would make a superb addition to the Mars Scout program, for obvious reasons.

Gliders -- and even low-powered tiny airplanes -- have also been suggested for that purpose.

And NASA will definitely make a serious effort to recover the science lost on the failed 1998 spacecraft (along with that on the 2001 Lander if it is not flown) -- although this will be done using new, miniaturized instruments.

Finally, if the decision is made to have sample-return spacecraft (and manned missions) manufacture their liftoff propellant out of Mars' own air, a series of engineering experiments will be necessary to determine its feasibility. Such an experiment was planned for the 2001 Lander.

If NASA decides to start focusing immediately on developing a sample return spacecraft, though, there will probably be little money left over to fly many (if any) of these little reconnaissance craft as well. But if they are flown, then the flip side would probably be a sample-return mission not being launched until early in the next decade.

The agency's Mars funds, after all, are sharply limited -- and the feeling now is that the remaining money had better be very wisely spent.

A similar new caution informs NASA's thoughts about future manned Mars missions: McCleese said that the Space Station's continuing problems are both sucking up the funds that a manned Mars program would need, and raising new cautions about its feasibility.

(Another factor was mentioned by Margaret S. Race in her Conference poster on the dangers of accidentally contaminating Mars with Earth germs. She agrees with me that, since any manned Mars landing will immediately and unavoidably contaminate its landing site, then -- even if life is found on Mars, manned trips may be limited for a long time to Mars-orbiting manned ships running surface rovers and sample-return vehicles by remote control.)

At any rate, sometime later this year NASA should decide how to proceed -- but with luck, we'll get some information on this earlier (starting with the fate of the 2001 Lander).

There were many other talks and posters on Mars at the Conference, dealing with the data we already have on the planet and what it may say about Mars' past and present habitability for life -- and in my next report, I'll describe them.