When will humans get to Mars? What path should they take? And can we afford the trip? These questions have been percolating since Project Apollo, but they're coming into sharper focus — partly because NASA is reviewing its long-term space exploration plans, and partly because there's a presidential election ahead.
At this week's meeting of the NASA Advisory Council, space agency officials provided the outline of their "Evolvable Mars Campaign," a long-term effort to develop the technologies needed for human missions to Mars. Some of the choices for that campaign have to be made sooner rather than later, said Bill Gerstenmaier, NASA's associate administrator for human exploration and operations.
"We've got to make life-support systems decisions fairly soon, probably this year or next year," he said in an account of the meeting from Space News.
Even more fundamental decisions may be in the offing. For instance, a plan to snag a piece of a near-Earth asteroid and bring it into lunar orbit for study in the mid-2020s is a key element of NASA's current exploration vision. But the Asteroid Redirect Mission, or ARM, has its critics — and on Friday, the advisory council approved a non-binding statement telling NASA planners to forget about the asteroid sample and instead send a next-generation spacecraft to Mars orbit and back.
Some advisers are even talking about grabbing a rock from one of Mars' moons, Phobos or Deimos, and bringing it back for study.
NASA says its Mars campaign is aimed at sending humans to the Red Planet and its moons by the 2030s — but Robert Zubrin, president of the Mars Society, says there's a downside to having such a stretched-out timeline.
"You can't do this on a 24-year timeline," he told NBC News, "because God's patience is not infinite, and the U.S. Congress is considerably worse."
Just as the Obama administration shifted NASA's vision from the moon to a near-Earth asteroid to be named later, the next presidential administration could change course again. "The upcoming one could well be hell-bent for Mars, or decide to stop messing around with this because we don't know what we're doing," Space News quoted retired aerospace executive Tom Young as saying.
For the benefit of the next president — and the electorate, too — here are three potential visions for missions to Mars:
Evolvable Mars Campaign
NASA's current strategy sees the Asteroid Redirect Mission as a test bed for technologies ranging from solar electric propulsion to the use of a particular kind of orbit around the moon, known as distant retrograde lunar orbit, as a staging ground for deep-space missions.
Gerstenmaier said NASA isn't contemplating human landings on the moon, but could test ways to use resources from it. For example, robots or commercial operations could mine lunar soil and water and turn those materials into the fuel and supplies that would be needed for trips to Mars. Spacecraft components could be sent into lunar orbit for assembly.
Meanwhile, beefed-up versions of the yet-to-be-built Space Launch System could pre-position cargo in lunar or Martian orbit, for use by the crews heading to Mars and its moons.
NASA is planning to issue an updated version of its strategy for human exploration strategy this summer, said Greg Williams, the agency's deputy associate administrator for human exploration and operations. But Gerstenmaier said it would take years to nail down the detailed timeline for Mars missions.
Humans Orbiting Mars
Last week, a group of space experts worked out a more specific timetable. The "Humans Orbiting Mars" workshop was organized by the Planetary Society, drawing upon expertise from The Aerospace Corp., NASA's Jet Propulsion Laboratory and others.
The group's key milestone was a 30-month mission to Martian orbit that would be launched in 2033: The mission plan called for a nine-month cruise to Mars; 12 months in orbit, with a potential landing on Phobos or Deimos; and nine months back to Earth.
The buildup to that mission could include NASA's asteroid mission in the mid-2020s as well as follow-up missions to lunar orbit, also known as cislunar space. Those would set the stage for the 2033 mission to Mars orbit.
Workshop chairman Scott Hubbard, a former NASA executive who is now a professor at Stanford University, said the orbital odysseys could open the way for sending a two-person crew for a 30-day stay on the Martian surface in 2039 — and then putting four astronauts on Mars for a yearlong stay in 2043.
Hubbard told NBC News that such a timetable was affordable, based on a cost assessment conducted by The Aerospace Corp. and JPL. But the scenario assumes that NASA ends its roughly $4 billion annual contribution to the International Space Station project in 2024, he said.
NASA is committed to supporting the space station through 2024, and the agency has not yet spelled out what will happen after that. Last month, Russian space officials suggested that they would work with NASA on a new space station to replace the current one. In response, NASA turned the focus of the discussion to its plans "to lead a human mission to Mars in the 2030s."
The Planetary Society said the details of the "Humans Orbiting Mars" vision would be issued as a report later this year.
Hell-bent for Mars
The Mars Society's Robert Zubrin voiced impatience with any plans that put off Red Planet odysseys to the late 2030s. "This is not a plan to send humans to Mars," he said of the "Humans Orbiting Mars" scenario. "This is a plan to pretend to be thinking about sending humans to Mars."
In addition to developing the heavy-lift Space Launch System and the Orion crew capsule, NASA should be designing the hardware required for making the transit to Martian orbit and landing on the Red Planet's surface, Zubrin said. "What we need to do is develop, right now, the flight systems to allow astronauts to do useful missions," he said.
He acknowledged that speeding up the timetable might mean more up-front costs, but would be more efficient than a campaign that stretched out over more than 20 years.
Zubrin noted that other visions of Mars are taking shape. The prospects for some of those visions, such as the scenarios advanced by Mars One and Inspiration Mars, may be debatable. But SpaceX's billionaire founder, Elon Musk, is due to unveil his own long-term plan for Mars odysseys by the end of the year.
"SpaceX is the most hopeful development going," Zubrin said. "I wouldn't be surprised at all if SpaceX did a two-person [Mars] flyby in the 2020s."
The bigger question about all these visions is why any of them should fly. If the next president decides to make Mars a priority, selling the multibillion-dollar project to Congress and the American taxpayers could be as challenging as any of the technical hurdles.
Bill Nye, who's known as "the Science Guy" as well as the CEO of the Planetary Society, argued that the long-term vision is worth the short-term price tag. "What does it say about you, if you are a society that does not look up and out?" Nye told reporters last week. "What does it say about you if you stop exploring? I'm not really sure what it says, but it's not good."