NASA has decided it can do a Mars sample-return mission on its own, but it will continue to collaborate with the European Space Agency on Mars exploration despite dropping out of Europe's ExoMars program last year.

Even though Europe has shifted to working with Russia on ExoMars, the program's 2016 orbiter could help provide data and command relays between Earth and a 2018 NASA rover on the surface of Mars. However, it remains to be seen if there will be such a rover, and what it could do if NASA finds the funds to build it.

The U.S. space agency has 4-6 months to decide how it will proceed under its reduced Mars-exploration funding plan. That decision will be shaped by a new set of mission options from the agency's Mars Program Planning Group (MPPG) instrument landing system, and possibly by congressional signals on fiscal 2013 funding levels for Mars. Also in the mix is the role of potential collaborators outside NASA's Science Mission Directorate, including the European Space Agency (ESA).

“Now what we're trying to do is go out and work with the human exploration folks and the technology development folks and decide how we synergize the four areas of NASA and still enable the U.S.—along with our international partners—to put humans on Mars in the 2030s,” said NASA Administrator Charles Bolden, speaking Sept. 26 during a visit to Liege, Belgium.

ESA Director General Jean-Jacques Dordain says his agency was involved in the MPPG study, and that he expects ESA to play a role in any future effort to send humans to Mars. But first, Europe needs to rebound from NASA's almost total withdrawal last year from its ExoMars campaign, a two-pronged mission that would send robotic spacecraft to the red planet in 2016 and 2018.

Dordain says he plans to meet with Roscosmos Director Vladimir Popovkin at the International Astronautical Congress in Naples, Italy, this week to finalize a revamped ExoMars strategy. ExoMars prime contractor Thales Alenia Space of France and Italy already is making progress on the mission.

“We are cutting the metal for the 2016 mission,” Dordain says. “It's not yet a reality, but close to a reality.”

In Washington, the MPPG reported last week that NASA may be able to return samples from Mars without significant international cooperation, in part by eliminating stovepipes in the way it organizes for scientific and human space missions. Set up after the Obama administration dropped its plans to collaborate on ExoMars, the planning group found lower-cost—but less-capable—sample-return missions still are possible, particularly if NASA's space science and human exploration organizations work together more closely, using the agency's Office of the Chief Technologist to develop hardware that serves the needs of both.

“Sending a mission to go to Mars and return a sample looks a lot like sending a crew to Mars and returning them safely,” says John Grunsfeld, a former space shuttle mission specialist who is the associate administrator for science.

Headed by retired NASA “Mars czar” Orlando Figueroa, agency and outside scientists and engineers on the MPPG spent five months developing options for a U.S.-only mission that follows the sample-return priority set in the “decadal survey” of planetary scientists run by the National Research Council last year.

Briefing the NRC's Committee on Astrobiology and Planetary Science (CAPS) Sept. 25, Figueroa presented robotic Mars options that could fly in the planetary launch windows in 2018, 2020 and 2022. With U.S. spending for the next mission to Mars limited to a Discovery-class mission capped at $800 million, Figueroa said there is probably not enough funding to land another rover on Mars in the 2018 window to identify and cache samples for eventual return to Earth.

Congress may not agree, however. Both houses added back $100 million for Mars exploration in fiscal 2013 spending measures that are still pending, although superseded by continuing resolutions. At that level, some of the options presented by the MPPG could be affordable under the fairly rigorous cost estimates included in the MPPG report.

“Basically we're getting what the decadal survey wanted in terms of science, and now the cost numbers have been looked at much more carefully,” says Arizona State University geological sciences Prof. Philip R. Christensen, who is chairman of the CAPS panel that Figueroa briefed. “We know MSL [the Mars Science Laboratory] worked, so we can rely on build-to-print MSL elements, so I think the $1.5-1.7-billion estimate is far closer, far more accurate, and will do exactly the science that the decadal survey was asking for.”

Based on the $800 million cost cap the MPPG used, Figueroa left the impression that a rover in 2018 could supplement the aging “infrastructure” of Mars orbiters able to relay commands and data. The planning group lists four orbiter options of increasing complexity that could be flown within the $800 million constraint. They include a $200 million single-purpose relay satellite launched to Mars as a secondary payload, and a combined science and relay orbiter based on the Mars Reconnaissance Orbiter and the upcoming Mars Atmosphere and Volatile Evolution (Maven) mission that could probably stay under the cost cap if launched on private contractor SpaceX's Falcon 9. Other options were a $500 million solar-electric-propulsion sample-return orbiter built with commercial components and piggybacked on the launcher for a lander, and an orbiter that would conduct research while waiting for sample deliveries from the surface, at a cost of $700 million plus a Falcon 9 launch.

Sample-return also would require a Mars ascent vehicle that possibly could be carried by the most expensive rover option the planning group identified. Designated Rover D, the vehicle would be a solar-powered version of the nuclear-powered MSL to save money. It would carry an ascent rocket along with a robotic arm to collect samples. Other rover options are a solar-powered version of Rover D without the ascent vehicle, designated Rover C, and two solar-powered rovers—A and B—based on the twin Mars Exploration Rovers Spirit and Opportunity, both with the guided-entry capability that put Curiosity down in Gale Crater, and distinguished from each other by the level of heritage hardware incorporated in their mechanical systems.

Christensen says the Rover D concept probably is too complex and costly to hit the 2018 planetary launch window, which scientists favor because it is sooner rather than later and offers the best planetary alignment in two decades to put a heavy lander on the surface of Mars. Rover C makes more sense, he says.

Technologies needed for a lower-cost sample-return mission—atmospheric guidance as demonstrated on MSL, hypersonic decelerators and supersonic parachutes—would also serve a human landing in the 2030s, the MPPG reported. And NASA's human-exploration directorate may be able to collaborate on sample-return for scientific study, collecting the samples in Mars orbit or elsewhere and returning them to Earth, in the process “breaking the chain” of possible biological contamination by encapsulating them in the sterile environment away from the planet.

“A lot of this is a coordination problem, and I do believe it could be better coordinated, better integrated over time,” says Bobby Braun of Georgia Institute of Technology, a longtime engineering adviser on NASA's Mars program and the agency's immediate-past chief technologist. “A couple of things that the MPPG team pointed to that I thought were interesting examples of additional ways that the technology programs could be involved [include] even more advancements in entry, descent and landing technology [and] in situ propellant production.”

Braun notes that all the ideas are intriguing, but need further study.

While the science community sees a sample-return mission to Mars as the “Holy Grail” of planetary space exploration, Bolden is not so sure.

“One piece of NASA, and the National Research Council, say the international community is going to figure out how to capture the Holy Grail,” Bolden says. “The question for many of us is what the timing of accomplishing the Holy Grail is. Do you have to do it before you can send humans? Some would say 'Certainly.' But when Neil Armstrong landed on the Moon, we did not have a sample.”