Proposals for a multibillion-dollar Mars sample return mission — perhaps even a comprehensive sample return program — appear to be on the front burner again, but not without controversy.
It turns out, Alan Stern, NASA's new associate administrator for the Science Mission Directorate, is a big proponent of Mars sample return. But while many NASA planetary scientists share that sentiment, a number of others also worry that such an ambitious mission — Stern estimates it could cost from $3 billion to $4 billion — would suck up all the available money for most other Mars missions in the next decade and disrupt NASA's ability to send at least one robotic mission to Mars every two years.
The Mars sample return program and related proposals for the early caching of Mars samples were big topics at the Seventh International Conference on Mars, held here July 9-13 at the California Institute of Technology. The meeting brought together some 500 leading experts on the red planet to discuss current and future exploration plans.
In a July 10 long-distance telephone hookup between meeting attendees and Stern, he advised that the Mars sample return undertaking would require "focus and discipline" to locate requisite funds for the effort within the agency's budget.
Stern said he is personally looking at the 2018-2020 time period for Mars sample return activities. To help fund the initiative, he proposed skipping one Mars mission opportunity sometime during the next decade.
Stern also is backing use of the nuclear-powered Mars Science Laboratory to practice caching Mars specimens. That large rover is under development here at the Jet Propulsion Laboratory. Putting a caching capability on the Mars Science Laboratory rover, Stern said, would help build the foundation of support for future Mars sample return activities, not only in scientific and public circles, but also in Congress and the White House Office of Management and Budget.
"I think there's something concrete about putting your stake in the ground," Stern told the meeting attendees.
Stern has asked a tiger team at NASA's Ames Research Center in Mountain View, Calif., to design sample caching gear to be installed on the Mars Science Laboratory. A small, hockey puck-sized device is being studied, seen as a "secondary payload" to be attached to the rover.
The final study results from the Ames team on the caching hardware are due by the end of July or early August, reported Chris McKay, a planetary scientist at the space agency field center who is helping to assess the feasibility of the Mars Science Laboratory add-on. Preliminary discussions also are under way with officials in the European Space Agency's ExoMars rover project to carry similar sample caching equipment on board that 2013 mission.
These NASA and European Space Agency rovers would collect bits of Mars during their respective exploration treks — preparatory to the landing of a sample return craft designed to gather, then rocket back to Earth a variety of select specimens of soil and rock from the red planet.
"I think there are things that we have to keep in mind as we move toward a sample return program," McKay told Space.com. "It's not going to just be a sample return. We're going to have a series of sample returns. We have to think of it as a program. The first sample return ought to be a simple, pathfinder-like sample return ... a technology demonstration."
Utilizing the Mars Science Laboratory for caching samples collected by rovers would get people focused and thinking about sample return, McKay said. "It ties sample return to the ongoing program. There's a tendency to think of sample return as something 'out there' ... it doesn't need to be. It can be something in the Mars program," he said.
McKay also said the sample return program has to connect, ultimately, with human exploration of Mars.
A careful, delicate balance
At the Mars conference, placing an expensive sample return activity on the exploration agenda, perhaps at the expense of other projects, sparked some anxieties.
"I'm cautiously optimistic," said Philip Christensen, a leading Mars scientist and professor in the Department of Geological Science at Arizona State University in Tempe. "I am concerned that the sample return mission would take over the Mars program. If you put that mission too far into the future, with not much in between, then you lose a lot of momentum ... a lot of young talented scientists and engineers," he said.
Christensen added that he sees "a real serious challenge" in carving out enough money in the near-term to pay for Mars sample return and still maintain a dynamic program.
"It's going to take a careful, delicate balance to be able to afford the sample return and yet maintain some measure of a program," Christensen told Space.com at the Mars meeting in Pasadena. "I have no expectation that the program will be as dynamic and vigorous as it has been if we're going to pay for a sample return. Something's got to give. But at the same time you can't just give up everything."
Pragmatic sample return
In a July 17 phone interview, NASA's Stern told Space.com that he has asked the Mars Science Laboratory project to add sample caching to the mission rover's duties. "It's a late but viable opportunity" and would explore techniques for follow-on Mars sample return work, he said.
The full life-cycle cost of the Mars Science Laboratory is $1.6 billion, according to Guy Webster, a Jet Propulsion Laboratory spokesman. The price tag for the caching apparatus, Stern noted, is $2 million for hardware, plus integration costs to the Mars Science Laboratory.
"I want to get serious about Mars sample return and this is the way to do it," Stern said. "This has been going on all my life, waiting for Mars sample return and it never gets there. We're going to do a pragmatic, but competent sample return."
Stern said he also has requested that ESA consider adding the Mars Science Laboratory sample caching equipment to their ExoMars mission. He said that he will discuss the matter with Daniel Sacotte, ESA's director of human spaceflight, microgravity and exploration in a meeting later this month at NASA headquarters.
"I want to be able to point up into the sky and say I already have a sample waiting up there," Stern said. "I'm just opening possibilities."
It is not a given, however, that those pre-selected Mars samples would later be robotically picked up for return to Earth, Stern said.
Make some history
Stern emphasized that the NASA Mars exploration program currently occupies 46 percent of the space agency's $1.4 billion planetary division budget.
"It won't get larger ... and there's already pressure to make it smaller. We have to do something worthy of that 46 percent. The Mars community has to thread a needle. If they don't do Mars sample return, their budget is likely to shrink. They have to do a Mars sample return, or get smaller.
That's my analysis, not my wish ... that's my analysis of the way the politics will go," Stern said.
Stern said he thinks that a $3 billion to $4 billion Mars sample return effort in 2018 is affordable, although architecture studies that blueprint the concept must still be done before the agency can seek a formal start to a sample return program and budget for it.
"Let's get this done ... make some history," Stern concluded.