PASADENA, Calif. - Its all, Frank Jordan will tell you, a work in progress.

Stung by the recent back-to-back losses of two robotic spacecraft at Mars, NASA has embarked on an exhaustive retooling of its entire program to explore the Red Planet.

Some missions may be delayed, swapped, beefed up or stripped down. Others may be cancelled outright.

NASA vs Mars

Wanted: Mars Money A growing choir of Mars cheerleaders see theday is fast approaching when humankind will jump the gulf of vacuum that existsbetween Earth and the Red Planet. However, part of that jumping off process involves hurtling over politics and other budget demands, as well as a myriad of technical unknowns that haunt a human mission to Mars.

NASA Needs More Time to Re-think Mars Program: As an independent review panel looking into recent Mars failures prepares to announce its findings next week, NASA decided last week to extend its internal discussions about Mars indefinitely.

The International Mars Society Champions Human Missions: Undaunted by the setbacks that seem to have NASA in turmoil, the International Mars Society is pressing forward with its activities to gain support for human exploration of the Red Planet.

But the aim, said Jordan, the program architect for the Space and Earth Sciences Directorate at NASAs Jet Propulsion Laboratory (JPL) here, is to tweak the program so it makes technical, scientific and financial sense.

Nearly two weeks ago, nearly 50 scientists gathered at JPL to hash over the Mars program and to study how best it be shuffled.

"There was an explicit interest in Lets not be bound by the thinking before," Jordan said. "Its a positive thing, in that its got our head out of the box, but with all the things there, we really have to think about what is really the best thing to do."

For the time being, there will be no definitive answers.

Ed Weiler, the NASA Administrator for Space Science, told the National Academy of Sciences Space Studies board on Monday that the American space agencys "failed architecture" for Mars could take months more to rectify.

NASA had originally targeted mid-March to announce its planned changes, along with the results of the various panels investigating the twin losses of the Mars Climate Orbiter and Polar Lander.

What wont change are NASAs primary goals in exploring Mars: To gain knowledge of evidence of past or present life; its weather processes and history; and its resources and how they might be used, scientists said. Common to all three goals is the search for water.

"Those are the objectives and they are good and valid for the future exploratory program," said Dan McCleese, chief scientist in JPLs Mars Exploration Directorate.

To satisfy those goals, NASA had embarked on an ambitious plan to send a lander-orbiter pair to Mars every 26 months over the next decade. The Climate Obiter, lost in September 1999, and the Polar Lander, lost later in December, were one such pair.

"I certainly see no backing away, I see no shift in general priorities. If anything, it will be a question of how, not what."

The way NASA will pick up that thread again is now the million billion, really dollar question.

"I certainly see no backing away, I see no shift in general priorities. If anything, it will be a question of how, not what," said Bruce Murray, a former JPL director and current consultant to NASA on its efforts to assess its Mars program.

The following are among those options being considered to answer the "how":

• 2001 - NASA has all but scrapped plans to send a lander to Mars at this opportunity. "It seems quite sensible to let that mission slip to 03," McCleese said. However, NASA will likely press ahead with its original plans to send an orbiter to the planet. "An 01 orbiter is fairly certain," McCleese said.
• 2002 - Scientists have proposed flying the 2001 lander a year later to repeat much of the science experiments lost with the Polar Lander. The spacecraft would take longer to make it to Mars, flying by Venus to gain a slingshot-like gravity boost. "Thats very, very improbable. Were not willing to take on a Herculean effort to recuperate the science," McCleese said.
• 2003 - Until recently, this launch opportunity was to have kicked off NASAs plans to collect and return to Earth samples of martian soil and rock. That will now slip to at least 2005. The 2003 opportunity could still include a lander-orbiter pair. The lander could carry the 2001 package of instruments, plus Marie Curie, a rover nearly identical to Pathfinders Sojourner.
• However, the mass and bulk of added telecommunications gear including a so-called "black box" that could transmit data even if the lander crash landed would likely leave no room for a rover.
• The 2003 shot could even skip over a major orbiter in favor of the first Mars micromission, which would piggyback aboard a French Ariane 5 for the trip to the red planet.
• JPLs Jordan said that in 2003 two micromission orbiters could be sent to Mars, or a sole micromission orbiter and one "scout." The scout would be a tiny lander similar to the Deep Space 2 spacecraft that the Polar Lander ferried to Mars, or the Beagle 2 the European Space Agency will land on Mars in late 2003.
• But with the launch of a 2003 mission a scant 39 months away, a decision will have to be made this spring on what it will entail, Jordan said.
• 2005 - What this opportunity will look like depends on 2003. It will likely kick off NASAs efforts to return martian samples to Earth, although it could merely involve laying the groundwork to do so.
• McCleese said baseline plans for a 2005 lander do not presently call for samples to be actually collected and placed into orbit for pickup by a French orbiter. Instead, the mission could involve a lander or two, but with just one carrying a rover to do reconnaissance work for sample return.
• A minority of Mars scientists is pushing to skip the lander altogether for the reconnaissance work, and use orbiters instead to do the job, McCleese said.
• 2007 - The likely beginning of Mars sample return, with perhaps a large lander deploying Athena a mammoth 154-pound (70-kilogram) rover to select and collect an estimated 1.1 pounds (500 grams) of martian soil and rock. The samples would then be blasted into Mars orbit for later collection and return to Earth.

NASA is currently budgeting about $250 million a year for Mars exploration, a number projected to rise to $350 million a year by 2005.

"The question is what fits under the cost profile? Nothing, but some are very close," said Mark Adler, the Mars sample return chief engineer at JPL, of the various mission scenarios.

Jordan said the reshaping exercise might even broaden NASAs scientific horizons in its efforts to explore Mars. That could include missions targeting Mars climate, atmosphere and geology.

"In general, the way the space science enterprise is looking at this, the older architecture seemed to be driven by the single goal of sample return by a certain date," Jordan said. "Now its a broadening of the whole program to include not only sample return but other ways of increasing our scientific knowledge of the planet."