Combined with NASA's other problems this year and in earlier years, this is predictably leading to a lot of debate about where the agency -- and specifically the Mars exploration program -- should go from here. Let me, in this series, contribute my own views on the three most important topics.

First of all: What happened? There has been a lot of talk from the JPL mission team about the three landers perhaps failing for different coincidental reasons (perhaps related to the local terrain).

For instance, the two Deep Space-2 probes apparently landed in or near a large crater, which might have blocked their communications or contained unusually rugged terrain which the probes could not survive an impact into, while the main MPL lander failed for some other reason.

However, the two probes were designed to survive a high-speed crash into many different types of terrain, and they supposedly landed about 2 kilometers apart. And as many observers have pointed out, when you have three simultaneous failures, common sense suggests that you first look for a single common cause.

Since there apparently were no abnormal telemetry indications from the MPL spacecraft during its cruise to Mars, up to the time 6 1/2 minutes before entry when the cruise state broke off contact with Earth and started to change its attitude in order to eject the three landers, the events of that brief period are the prime suspect.

And one story reported in Keith Cowing's "NASA Watch" Website on Nov. 7 comes immediately to mind: According to a rumor he had heard from JPL, it had been discovered that the pyrotechnic separation charges for the three landers had been designed without heaters -- and since the pyrotechnics weren't designed to operate below 4 deg C, this might lead to all three probes remaining attached to the cruise stage, unable to align themselves for entry, so that the entire craft would either have burned up during entry or crashed.

Shortly thereafter, the Mishap Investigation Board for the Mars Climate Orbiter released its official report. It mentioned no such possible problem with MPL, but did state that the Board was concerned about the possibility that the Lander's rocket descent engines might be too cold for the catalyst beds that ignited their hydrazine fuel to function properly, and that the hydrazine might even freeze in their fuel lines.

JPL responded by changing its plans and turning on the fuel-line heaters several hours earlier -- raising the engines' estimated temperature at startup to 8 deg C -- and it also conducted a hasty series of ground tests which concluded that the engines would fire properly even if their catalyst beds were at minus 20 deg C.

I concluded that the rumor which "NASA Watch" had heard had actually been a garbled version of this problem -- and indeed, JPL spokewoman Mary Hardin told me flatly that there was "no apparent problem" with the cruise stage pyrotechnics.

I find myself wondering, however, whether -- for whatever reason -- there might have been a failure of all the pyrotechnics. Such a problem could certainly explain the simultaneous failure of all three landers.

The only other single problem that might have caused such a loss would be a disastrous attitude-control failure while the cruise stage was reorienting itself to release them -- but nothing of that sort happened during the long cruise to Mars or any of the five trajectory corrrection maneuvers (the last of which was made less than 7 hours before the landing, apparently with a remarkable accuracy of only 10 km).

There is, however, another possibility. One industry source reports that many engineering observers thought that the failure of the two Deep Space-2 probes was a near-certainty, simply because there had not been enough funding to develop and test them properly.

(Indeed, our source says that new transmittters had to be installed in the probes while they were actually on the launch pad.)

If so, then the one really mysterious failure is that of the main Lander -- and it could have been due to a multitude of causes, including simply bad-luck with a final landing on top of a boulder.

It could, for instance, have been caused by vibrational instabilities resulting from the fact that its descent engines were clusters of fixed-thrust pulse-modulated thrusters rather than smoothly throttleable engines -- a soft-landing technique never used before -- which is a possibility that the MCO failure review board had already expressed concern about. Or it may be that the cold descent engine problem was not as fully corrected as JPL said.

The problem is that -- thanks to the total lack of communications during the landing sequence -- we simply do not know. The new failure review board's investigation will therefore have to focus on reinspecting the records of the spacecraft's design and construction to look for errors, and on conducting ground tests of the craft's parts, more thorough than those that JPL and Lockheed Martin carried out during its construction, in order to look for problems they missed.

Very possibly they will have to conclude that a number of different possible causes exist, and that measures will have to be taken against all of them -- as was the case with the 1993 Mars Observer failure, and with the notorious 1964 failure of the cameras on the Ranger 6 Moon probe. It should be kept in mind, though, that both of those efforts were ultimately successful in eliminating that kind of failure on future probes.

But there are bigger issues in this failure, particularly when you combine it with the Mars Climate Orbiter failure and with the other failures that have recently afflicted NASA in general and its spacecraft built in accord with the "better-faster-cheaper" philosophy in particular. In Part 2, I'll take a look at those issues.