Spooked by back-to-back failures at Mars in 1999, NASA is considering alternate launch plans that would delay the missions until fully assured the landers have the maximum chance of successfully landing on Mars using the Pathfinder hard landing technique of cushioning the lander for final touchdown within a cocoon of shock absorbing balloons.

SpaceDaily learned of these concerns at the latest quarterly meeting of NASA's Advisory Council, held last week at the Jet Propulsion Laboratory in Pasadena. Generally the Council focuses on two or three main subjects at each of these meetings.

For this meeting the main topics of discussion were, firstly, NASA's most serious problem - the International Space Station - and, secondly, the current form of America's Mars Exploration Program.

Separately from concerns about the 2003 rovers, NASA's Mars program continues to undergo changes as the difficulty of flying a sample return mission from Mars becomes more and more apparent. In retrospect, the absurdity of plans that until just a few years ago envisaged a sample return mission to Mars by 2008 has become painfully clear.

Last year, NASA assigned contracts to four aerospace firms to design and appraise possible Mars sample return missions, and they agreed that the first such mission would cost $1.3 to 2 billion - and probably near the higher end of the spectrum.

Meanwhile, it has become quite clear that any chance of launching the first Mars sample return mission in 2011 has now disappeared, just like NASA's earlier plan to start the sample-return mission in 2003 and finish it in 2008. Indeed, it now seems impossible for NASA to start the mission until 2016 -- unless it radically revises it, which it is now in the process of doing.

Although the Mars program is not about to collapse in disaster, it has become clear that a radical redesign of the program for next decade will be necessary. Recognizing the inevitable, NASA has spent the past year working up a new program for the next decade that it expects to have finalized by the end of this year.

The Dog Days Of Mars Continue
Separately, problems are emerging in NASA's Mars exploration plan through 2009, requiring substantial redesign efforts for some of this decade's missions.

At last week's Advisory Council meeting, NASA's Mars Exploration Program director Orlando Figueroa and JPL's Mars program manager Firouz Naderi delivered a status report, which included details on some of the problems connected with the very next U.S. Mars mission: the two Mars Exploration Rovers scheduled for launch next May and June.

These two 170-kg rovers - based on the "Athena" design created by Cornell University - are slated to land on Mars three weeks apart in January 2004, and spend at least three months crawling anywhere from 600 meters to a kilometer along the surface.

They are designed to travel as far as 100 meters per day, receiving instructions from Earth the night before on their next stop, and then crawling across the surface while analyzing stereo photos from their navigation cameras to automatically identify dangerous obstacles ahead, swerve around them, and then resume moving toward their original preset goal.

They will, however, actually spend most of their time studying individual patches of landscape in detail with their onboard cameras and infrared spectrometers, locating interesting rocks, and edging up directly to them, before examining them in greater detail with an instrumented arm carrying two more spectrometers, a magnifying imager, and a grinding wheel to remove weathering from the rock's surface.

Their purpose is to study the geology and mineralogy of Mars' surface rocks and soil in unprecedented detail, trying in particular to determine the extent to which those rocks and minerals have been exposed to - or actually formed by - liquid water and associated processes during the planet's earlier and perhaps more hospitable days. Such rocks and minerals might also be a possible location for fossilized evidence of microscopic life that could have evolved on ancient Mars, although the MER rovers themselves cannot detect such fossils.

The MERs will also be crucial in "ground-truthing" the observations made by the cameras and spectrometers on Mars orbiters, providing the information necessary to allow correct interpretation of the extensive orbital observations conducted in recent years by Mars Global Surveyor and Mars Odyssey.

The MER twin rovers are ambitious missions, but as any engineer will tell you, the God of Engineering has a perverse sense of humor.

The most genuinely complex and original part of the MER mission - the Athena rovers themselves - have run into very few problems in design, building, or testing.

The major problem, it turns out, is almost entirely from that part of the MER mission which was supposed to be the simplest and cheapest: namely, the rovers' landing systems which are based on the "hard landing" technique pioneered by the famous 1997 Mars Pathfinder mission.

In fact, the supposed ease of adapting the Pathfinder landing system for getting the rovers down safely on to Mars was the key factor in their selection as a mission.

After the failure of both 1998 U.S. Mars missions, NASA was forced to cancel the stationary lander which was part of its 2001 Mars mission, and to radically revise the later program - something which would have been necessary even if the 1998 missions had succeeded, since it had already become clear that its original hopes of launching the first lander component of its planned sample return mission in 2003, and completing the mission by 2008, was utterly absurd.

NASA therefore had to select a new 2003 Mars mission in 2000, as opposed to the usual four- or five-year gap between selecting and flying a mission.

Several alternatives - including a modified version of the 2001 lander, and a sophisticated new Mars orbiter which has since been selected as the 2005 mission - were rejected in favor of a single MER rover, because a hastily done two-month-long preliminary study made it appear that an Athena rover (already intended as part of the payload for the cancelled bigger 2003 sample-return lander) could be fit into an almost unchanged copy of the Pathfinder hard lander, greatly cutting mission development costs.