NASA is formulating a Mars exploration plan for the next decade, receiving advice from all quarters, from outside academic circles to internal NASA working groups, as well as from the White House.

And if all goes according to plan, Mars will speak for itself, giving up surface and subsurface secrets as ever-more capable spacecraft -- like the two rovers currently en route -- survey that mysterious world. How to respond to the expected fast-paced rush of new discoveries, enough so that outgoing missions can take advantage of just-in findings, is a challenge.

One scenario has been advocated by the Committee on Planetary and Lunar Exploration (COMPLEX) -- a study arm of the National Research Council. It calls for a legion of robotic return-sample craft that are needed to truly unravel the history of Mars and reveal whether life existed in the planet’s past or is present today.

Rocketing back to Earth samples of Martian soil and rock via automated means has been on NASA’s to-do list for decades. But it’s a difficult task, with cost being the lead impediment.

Over the years, NASA as well as industry teams have sketched out details for such an undertaking. So too have European Space Agency engineers, as well as independent groups in France and Russia.

Those grappling with ways to land, pick up, and then safely haul back the goods to Earth from Mars -- all by robotic hardware -- wind up with an acute case of Space Age sticker shock.

Typically, at a minimum, the price tag escalates to a billion dollar-plus mission -- and can skyrocket to many billions of dollars. To date, a "cash and carry" Mars return-sample concept has remained little more than a hazy, hoped-for project.

The new report by COMPLEX calls return-sample missions to Mars the most effective way to enhance our view of Mars’ history and its surface environment. "No other single strategy can answer so many of the questions about martian chemistry, geology, climatology, and the presence of or potential for life, past or present," the study observes.

To this end, the 14-person COMPLEX study group urges Mars returned samples be given high priority at NASA. It recommends that a sample return mission be launched at the 2011 launch opportunity.

Furthermore, COMPLEX estimates that roughly 10 sample return missions should be carried out over a protracted period of time. That length of time, the group suggests, might stretch out over "three or four decades to as much as a century", to learn the most important things researchers want to know about Mars.

The COMPLEX report points out -- like other study groups before it -- the science-gathering capabilities of robotic instruments dispatched to Mars are dwarfed by highly sensitive gear stuffed inside laboratories here on Earth.

As for picking the initial landing sites for return-sample spacecraft, the report contends no new data is necessary.

"The committee believes that enough information is at hand already…to chose the first sites to be sampled intelligently, and that sample return need not wait on additional reconnaissance missions." There is enough information already in hand to define a half-dozen or more sites that would be excellent starting points for a Mars return-sample program, the report states.

Even a "grab sample" of soil from a randomly chosen spot on Mars, the report adds, will yield a treasure-trove of data about the character of martian surface material.

In endorsing a 2011 liftoff for NASA’s first return-sample mission to Mars, COMPLEX stresses that "this date should not be allowed to slip", unless, of course, the prospective mission runs into some extraordinary technological problem. Given that 2011 liftoff date, the first specimens of Mars brought back by a robotic vehicle would land on Earth in 2014.

The first Mars return-sample mission will be modest in its surface duties. But lessons learned can be applied to follow-on craft, with later missions becoming far more elaborate.

Sampling technology is likely to mature whereby Mars robot landers can haul drilling equipment to punch down deep below the planet’s surface. Also, sampling operations might be expanded to include exploration of the red planet’s polar caps, with the collection and return to Earth of ice and dust cores, the report suggests.

"The only thing we can be absolutely sure of finding on Mars is something not expected now," the COMPLEX report explains.

The new study emphasizes the need for a special Mars Quarantine Facility. It will serve in many capacities, including checkout of Mars rock and soil to guard against any virulent "bugs" being released that are harmful to we Earthlings and our biosphere.

Within this facility, Mars samples would be processed, stored, and released for scientific study. It is estimated that seven years will be required to design, construct, and staff the facility.

Clearly, therefore, COMPLEX suggests that time needed to ready the facility is running out.

On this score, the message from COMPLEX is plain: "Preparations for sample return should not be delayed any longer than they already have been."

The COMPLEX message to NASA regarding Mars return-sample strikes a chord, said James Garvin, NASA Lead Scientist for Mars Exploration within the agency’s Office of Space Science in Washington, D.C. It is reflective of science community inputs NASA has received on and off for the past 20 years, he said.

"Namely, that returning samples from Mars is a type of scientific ‘holy grail’, likely to provide the context within which we can sharpen our approaches for exploring the habitability of Mars and ultimately fashion an optimized methodology for searching for evidence of life," Garvin told SPACE.com.

NASA has been busy, Garvin explained, outlining its approach for incorporating nuclear power into Solar System exploration via a new generation of radioisotope thermoelectric generators (RTGs). Also, there has been focus on technology investments for future fission-based propulsion and power systems to enable new classes of missions to the outer planets and, someday, to Mars too, he said.

Another active factor, Garvin said, is a Bush Administration request to re-look at NASA's plans for Mars Exploration beyond 2009, zeroing out all funds for next decade missions until an "options-driven approach" was outlined.

NASA has complied with this direction, Garvin said, and spent much of 2002 and the first half of 2003 developing a "pathways-driven" plan for Mars exploration beyond 2009, "with emphasis on a discovery-responsive strategy and with attention to the search for evidence of life," he said.

"It must be noted that the [Bush] Administration direction given NASA in February 2002 specifically stated that NASA must examine options for Mars exploration that do not all include sample return as an inevitable mission, at least in the upcoming decade," Garvin said.

NASA is shaping a "Next Decade Plan for Mars Exploration". This 2009-2020 strategy has benefited by the COMPLEX report, as well as from the rapid-paced work of NASA’s Mars Exploration Program Assessment Group (MEPAG) -- a confab of key Mars scientists, engineers and planners.

This plan includes four pathways, better tagged as lines of science inquiry.

Garvin said that three of those pathways suggest a precision-targeted, but limited mobility "ground-breaking Mars sample return" mission. It must occur as early as conceivable in the upcoming decade of Mars exploration, if scientific progress is to be made, he said.

Another pathway, as required by the Bush Administration directive, Garvin noted, delays sample returns until 2020 or beyond, instead focusing on revolutionary on-the-spot astrobiological investigations, some of which require advanced technologies that can access the subsurface of Mars to many meters of depth.

The COMPLEX report, in combination with the outputs from the grassroots MEPAG, Garvin said, have strengthened the science focus of the current NASA Mars Exploration Program. There is "full recognition of the essential nature of sample returns as a necessary element in any science-based strategy of Mars exploration," he concluded.