As soon as it did so, it would have concluded that it had already landed and immediately switched the engines off -- falling the remining 40 meters to the surface of Mars.

According to SpaceDaily's source this event has been repeatedly reproduced during the Failure Board's tests and strongly suggests that -- while we will never know for certain due to no telemetry -- it is the single most likely cause for MPL's failure.

It is possible, of course, that during the actual landing this event didn't occur, and that the failure was caused by something else -- such as rugged terrain or instabilities in the thrust levels of the landing engines -- but after the Mars Observer's failure in 1993, its failure review board also could only identify the leakage of oxidizer into the craft's fuel propellant line as the single "most likely" cause of the failure, with several other causes remaining still possible.

In any case, it seems likely that the MPL failure board will suggest a whole series of modifications in the design of future Mars landers to deal with all remaining possible causes of the MPL failure (as was done with Mars Observer).

For example, it may perhaps recommend that future landers go back to using smoothly throttleable landing engines rather then the "pulse-modulated" system of clusters of fixed thrusters used for the first time on MPL, which might have led to a "jerky" and vibrating kind of descent braking that could have destabilized the craft.

It is also possible that all future Mars landers will be equipped with obstacle avoidance systems to detect excessively rugged patches or dangerously steep slopes in the landing area, so that the lander can throttle its engines to steer sideways away from them.

This writer has been told by a JPL official that, even before the MPL failure, the plan was to test such a system on the 2003 Mars Lander -- the first of the much larger and more complex landers designed to return Martian surface samples to Earth.

This system -- which probably would use a scanning laser altimeter to build up a detailed 3-D map of the surface -- might simply be tested on that flight for reliability, rather than actually being hooked up to the Lander's steering system; but if it worked properly, it would definitely be used to control the next lander's autopilot in 2005.

Meanwhile, the MPL Failure Review Board's final report could be officially released on Wednesday -- the same day that NASA Administrator Dan Goldin is scheduled to testify before the House Committee, at which time he will surely be asked about America's future Mars plans (although the Young Committee detailed to recommend changes to the Mars Program will not officially report until March).

SpaceDaily's source also tells us that there is pressure on Goldin to request a major expansion of the "Mars Micromissions" part of the program, in which tiny spacecraft piggybacking on European Ariane 5 commercial missions would be used both to explore Mars and to set up a network of miniature communication satellites around the planet.

• Description of MPL landing sequence:
• Description of spacecraft (including landing equipment):
• Mars Polar Lander press kit: - landing sequence pp 21-25 : ~ equipment pp 31
  
• NASA Fiscal Year 2001 Space Science Enterprise budget request - pp 39-42