Despite a declaration from President Barack Obama that the moon is not a planned destination for American astronauts, senior NASA engineers have quietly begun reconsidering it as a staging point for an eventual mission to Mars.

William Gerstenmaier, the chief of human exploration for NASA, does not see the president's plan of a direct, 900-day mission to the red planet as achievable. Instead, Gerstenmaier believes large amounts of ice at the lunar poles may provide an important reservoir of oxygen and hydrogen fuel to propel rockets and spaceships across the 40 million miles of space to Mars.

"If propellant was available from the moon, this could dramatically lower the mass needed from the Earth for a NASA Mars mission," Gerstenmaier said.

NASA officials have begun talking about an "Evolvable Mars Campaign," which recognizes the technical and financial challenges of reaching Mars, and the likelihood that the United States would not support an all-out, Apollo-like plan.

But Gerstenmaier and senior NASA officials remain in a delicate position when it comes to speaking of the moon publicly.

Adrift: NASA's future in human spaceflight

Obama established his space policy for NASA during a 2010 speech at Kennedy Space Center in Florida, and it did not include stopping at the moon.

"I just have to say pretty bluntly here, we've been there before," the president said. Instead, Obama directed NASA to visit an asteroid in the 2020s and proceed directly to Mars in the 2030s. This marked a decisive split from President George W. Bush, who had NASA developing plans to live and work on the moon, testing technology and mining resources there, before shooting for Mars.

Attractive in near term

Gerstenmaier, a widely respected engineer who has overseen NASA's human spaceflight program since 2005, appears to be steering the agency back toward a program that would more fully utilize the moon.

The influential National Research Council strongly encouraged such a shift last summer in a report on human spaceflight, urging Obama and NASA to reconsider their lack of interest in the lunar surface.

"It was clear to the committee from its independent analysis of several pathways that a return to extended surface operations on the moon would make substantial contributions to a strategy ultimately aimed at landing people on Mars," the report stated.

The moon is attractive in the near term for NASA because it's much closer than Mars, allowing for little communication lag with astronauts and, in an emergency, a means to get them safely home in a few days.

As well as potential caches of fuel at its poles, the moon's surface would offer a key test bed for rovers, habitation modules and other technologies before sending astronauts deep into space with no hope of return for years. There would also be more opportunities for the burgeoning private space industry to participate.

And as many critics have said NASA's plans to shoot for Mars in the 2030s are completely unrealistic, the moon offers a more affordable destination.

Politically, using the moon as a stepping stone to Mars offers advantages to NASA. Its international partners, including many European countries, have expressed a desire to explore the moon, but faced with NASA's public disinterest in the moon since 2010 these partners have begin considering working with China. Given the overall success of the space station program, however, Europe, Canada and Japan would likely be eager participants in a U.S.-led venture to return to the moon.

Finally, the moon-then-Mars pathway would also find support in Congress, which has been reluctant to support NASA's asteroid-then-Mars pathway.

'Reach first base'

"It's logical to go first to the moon, to demonstrate an ability to reach and use the lunar environment first before you attempt to go further in a manned spacecraft," said U.S. Rep. John Culberson, a Houston Republican who chairs the House subcommittee that oversees NASA's budget. "It makes sense to reach first base, and hold it, before you go on to second base."

Gerstenmaier, who answered questions through e-mail while traveling to Kazakhstan and Russia for astronaut Scott Kelly's launch, stressed that NASA has not laid down any definitive plans for deep space exploration, or how it will reach Mars.

"We have seen and done several studies that look at Mars missions as a logistics and resupply problem," Gerstenmaier said. "These studies show that resources from the moon could be extremely beneficial for Mars missions."

The agency is grappling with how to sustain a major Mars exploration program within a limited budget. NASA's share of the federal budget today is less than one-half of one percent. During the Apollo program it received nearly 5 percent.

One of the biggest costs for a Mars mission is launching enough fuel into space to get astronauts to and from the red planet.

This is why the moon's availability as a gas station is so attractive, and NASA is already planning robotic missions to the lunar surface to further assess the availability of ice at the poles.

With this "evolvable" campaign, which should be publicly released later this year, NASA is moving away from a flags-and-footprints approach used during the Apollo era to a more step-by-step, sustainable path. NASA is considering how to launch assets into space that could be built upon by subsequent missions, and ways of using resources in space that would reduce the burden of launching them from Earth.









Benefits to Houston center

Until now much of NASA's renewed assessment of the moon has flown under the radar, but engineers familiar with the agency's work say the lunar option is being kept open for when it's more politically acceptable.

Using the moon would also probably benefit Johnson Space Center, in Houston, because under the brute-force approach to Mars there would be very few opportunities for astronauts to fly, or missions to plan, during the next 20 years. By contrast, flying to cislunar space - the area between Earth and the moon and around the body - and possibly to the moon's surface would offer much more work for the center devoted to human spaceflight.

Scott Pace, director of the Space Policy Institute at George Washington University, said the moon offers NASA the best opportunity to maintain a robust exploration program after the International Space Station, while also easing the formidable task of sending humans to Mars.

"I see NASA as trying to position itself to be flexible if there are, or are not, any changes in policy direction," Pace said. "I hope the United States will take a stronger leadership role in cislunar and lunar surface operations with international and private sector partners."