FLAGSTAFF, ARIZONA -- Move over Mars, researchers say Jupiter's icy moon Europa is a possible biological hot spot that's in need of close-up study.

Space scientists see the moon as deserving of inspection from top to bottom - charting Europa's fractured face with ice-penetrating radar as well as deep diving below surface to probe a likely liquid ocean that could be teeming with life.

Currently, a new strategy is being hammered out that calls for Europa to become a high-priority on NASA's exploration roadmap. A Europa Focus Group of leading specialists -- from biologists and planetary scientists to ice experts and technologists -- met here May 14-15 at the U.S. Geological Survey to discuss the prospects for an extensive survey of the Galilean satellite.

But never mind finding life on Europa. It is more a matter of putting life back into a mission to explore the moon in the first place. NASA plans for returning to the enigmatic moon anytime soon seem to have slid into oblivion.

"We are in a state of being undernourished mushrooms," said one disgruntled scientist at the meeting. "You grow mushrooms by keeping them in the dark and feeding them manure. We now find ourselves in the situation where we're not even getting the manure."

Nonetheless, the passion to reach Europa remains high.

"It's an opportunity to look at it fresh," Greeley said. "The cancellation has caused a lot of rethinking," he told SPACE.com.

Experts at the Focus Group are seemingly caught between a rock and a hard ice flow on Europa.

Some say taking a go-for-broke approach is advisable. That is, flying a "flagship mission" to the Jovian moon -- a Viking-style orbiter that deploys a lander -- will best serve science. Others sense that a first-things-first Europa Orbiter would better characterize the ice-covered world, to be followed in later years by a lander, a rover and subsurface probe.

Specially outfitted orbiters, ice penetrators, a lander outfitted with airbags, hydrophones scattered across Europa's surface - all these ideas are once again talking points worth talking about.

"It's kind of bad news, good news," said Torrence Johnson, chief scientist for the Solar System Directorate at the Jet Propulsion Laboratory (JPL) in Pasadena, California. "We don't have a Europa mission at the moment. On the other hand, perhaps if there's going to be a phoenix rising from these ashes, it may be in the form of a more ambitious Europa mission around 2010 or thereabouts," he said.

One point is clear. Any robotic return to Europa worth its scientific salt is likely to carry with it a hefty price tag. Perhaps the cash register would tally to $1 billion-plus, at a minimum. Whatever the cost, there is universal concern that the budget masters at the White House, the Office of Management and Budget, and at NASA Headquarters won't seize the moment, but more likely will have a seizure.

For the scientific community to take a step back and argue even more strongly for a better mission to Europa is the sense of William Moore, a researcher at the University of California, Los Angeles, in the Department of Earth and Space Sciences.

"From an astrobiological standpoint, Europa is really an interesting target and especially important," Moore said. "You just can't do it cheap. There is no faster, better, cheaper in the outer solar system. It's so much of an investment just to get there that you'd better do it rightyou can't take riskswhich means it's going to be expensive," Moore said.

For one, radiation hardening of Europa spacecraft hardware requires top-dollar treatment. Secondly, meeting strict sterilization standards will be costly. After all, you don't want to transport Earth bugs to Europan real estate.

It does seem apparent that the only way to return to Europa is with a relatively large mission, suggests Robert Pappalardo, assistant professor in the Astrophysical and Planetary Sciences Department at the University of Colorado at Boulder.

"In my view and that of many in the planetary science community, exploration of Europa remains a very high priority," Pappalardo said. Europa's astrobiological potential is a science driver, he noted, as is the moon's geophysical uniqueness in our solar system as a world believed to have a relatively shallow ocean.

"Whether or not Europa's ocean contains life, exploring and characterizing that ocean will provide a scientific windfall in our understanding of natural satellites and their astrobiological potential. If that ocean is ultimately found to contain life, Europa could prompt both scientific and societal revolutions," Pappalardo said.

Past and present life on Europa might be evident suggested Dirk Schulze-Makuch, a researcher at the Department of Geological Sciences at the University of Texas at El Paso. There are a number of plausible sources of energy for living systems to thrive at Europa, he said.

"If life can be detected there, it most likely developed independent from Earth," Schulze-Makuch said. In Europa's early history, the moon probably had water on its surface as well as a water vapor atmosphere - a far different world than we now see, he said.

A top priority is determining the composition of Europa's near surface material, a measurement that can help gauge the moon's past and present habitability, Schulze-Makuch said. "With Europa we really can have a search for past and present life. If we do find life there, it will probably be something unique," he said.

Europa might be giving us a colorful clue as to its potential for exobiology. Could patches of reddish-brown material seen in Galileo spacecraft images be deposits of bacteria?

It is worth considering, said J. Brad Dalton, a National Research Council resident research associate at NASA's Ames Research Center, near San Francisco, California.

While the exact composition of the reddish-brown material is not yet known, Dalton said, it is clear from the Galileo data that its primary components are strongly hydrated - that is, they are compounds that contain water bound into their molecular structure.

"This occurs in a number of minerals and salts which form on Earth in the presence of water. Living organisms also contain water bound in several forms," Dalton said.

If the reddish-brown material is representative of Europa's interior composition, also a point of conjecture, Dalton said, then the possible presence of salts is exciting because it implies that the ocean could be hospitable to life. "An even more speculative argument, which cannot be ruled out at present, is that there could be remnants of formerly living cells in the reddish-brown deposits themselves," he said.

Because of the high radiation environment at Jupiter, Dalton continued, scientists do not expect to find extant life or even complex biological compounds exposed at the surface of Europa. Only heavily processed and broken down remnants could survive under those conditions, he noted.

"However, within a few centimeters of the surface, many complex compounds could persist. And within a few meters, biological material and even hardy extremophilic microorganisms might remain viable for millions of years, even to the present epoch," Dalton said.

Always up for debate is the true depth of the icy shell that encapsulates Europa's still speculative liquid ocean. Those arguments seem to mimic squabbling pizza lovers who swear by either thick or thin crust.

Yet knowing how thin or thick Europa's ice shell is may shed light on the implications for life forms existing subsurface. Also, if that ice is really thick -- perhaps many miles in depth -- it may be tough sledding for any robot to make its way downward into any ocean.

Keen on picking a touchdown site for a future Europa lander is Louise Prockter, senior professional staff scientist at the Applied Physics Laboratory in Laurel, Maryland. She has her eye on Castalia Macula, an unusually dark region over 60 miles (100 kilometers) north to south, near Europa's equator. That area consists of two sky high domes, separated by what appears to be a flat frozen pond of dark material. This pond appears flat and smooth - an ideal and relatively safe place to set down a lander.

"We know that darker places tend to be younger on Europa, and that the domes formed when subsurface material moved upwards and smashed the surface apart. Therefore, if we want to sample the Castalia Macula region, we have a good chance of collecting material that used to be below the surface until recently. So that material is probably not too damaged or altered by Europa's harsh radiation environment," Prockter said.

Moreover, it is also possible that some of the dark material was once part of an ocean thought to lie beneath Europa's surface. "So this would be a potential way of sampling that ocean without having the problems associated with drilling through many kilometers of ice," Prockter said.

The allure of Europa is discovering whether life has ever taken root there. However, reaching out to that distant moon of Jupiter is a daunting technological challenge in its own right.

"Exploration of Europa as a possible habitat for life, either at the onset of the evolutionary process or well into the production of life-like entities, is a complicated adventure requiring thoughtful applications of current and near-to-be technologies," said Arthur Lane, Deputy Leader for JPL's Center for Life Detection.

Lane said progress is being made on radiation resistant electronics and sensors. "We're getting better. Give us a little time. We're getting there," he told the Europa Focus Group. Similarly, research is underway in "cold electronics" and in fabricating ultra-small devices, such as cameras, drills, microscopes, temperature probes and spectrometers.

For example, Lane detailed joint Caltech-JPL work on a robotic probe, a Cryobot, designed to bore through ice. Such a device, replete with tiny side-looking and down-looking cameras and signal relay gear, may find its way to Europa in the future.

A wide range of technologies can be designed, built, and flown to unveil outer and inner workings of Europa. "Whether they can fit within the timeframe of the human 'itch to learn' is another matter," Lane said.

Greeley, as leader of the Europa Focus Group, remains resolute in the need to put political and budgetary realities to the side. "We're about sciencewe want to learn something about Europa and want to define the ultimate missions to this intriguing moon. It's a fresh piece of paper."