Frequently Asked Questions

about Humans Orbiting Mars

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Programmatic Questions

I don't want to read the report, what's the short version?

Mars is the goal for human spaceflight. But because money is tight, NASA should minimize the development of new hardware and articulate a clear strategy for a long term exploration of Mars to build a broad coalition of support. To help keep things affordable, break the first crewed mission to Mars into two pieces: the first mission would stay in Mars orbit and explore the Martian moon Phobos; a follow-up mission mission would be the first to land.

Where can I get more the details of the JPL study team's Mars architecture concept?

There's a lot of additional information in our Further Reading section on our website. Our report features a good run-down as well.

Why go all the way to Mars and not land? Why orbit-first?

The reasons to orbit first are pragmatic in response to the limited budgets NASA has to work with. By splitting the first crewed mission to Mars into two pieces, NASA can spread the risk and cost associated with landing over time while still making progress in human exploration.

Landing on Mars is hard. The heaviest thing NASA has ever landed on Mars thus far is the Curiosity rover—about one ton. A human mission to Mars will require multiple tens of tons of mass on the surface, to say nothing of the technology development required to sustain humans for a short stay and return them safely to orbit. Designing, validating, and building this new hardware takes money and time.

Orbiting first allows you to demonstrate and validate the operational techniques needed for all future crewed Mars missions. People have never traveled as far as the first humans who go to Mars will travel, so reducing the risks of that journey is imperative.

Mission planners have used this stepwise approach for decades. For example, Apollo 8 and Apollo 10 orbited first to validate Moon landing techniques and operations before NASA attempted to land.

Isn't Mars too expensive? How can we afford this?

There are many misperceptions about the cost of a human Mars mission. We debunk of lot of them in Section 3 of our report.

NASA currently spends about $8 billion per year on its human spaceflight program. At our workshop, it was argued that NASA should define a Mars strategy that fits within this budget, allowing it to only grow with inflation.

If we doubled NASA's budget, we could get to Mars a lot sooner.

Yes, we could.

Isn't radiation a showstopper?

The threat of radiation on the health of astronauts is a manageable problem. NASA has stated that “there are no crew health risks at this time that are considered ‘mission-stoppers'” [April 2015 presentation to the NASA Advisory Council, PDF, slide 3] for a human mission to Mars.

Radiation is now an ethical question: how much of a percentage increase in cancer risk is NASA willing to ask of its astronauts?

Why wait until the 2030s? Isn't that too far in the future?

Selecting 2033 as the goal for orbiting Mars is a pragmatic response to limited budgets. NASA and any potential partners would find it difficult to to meet the technical challenges in a shorter timeframe without a significant (and unlikely) increase to the human spaceflight budget.

Human spaceflight programs, historically, are multi-decadal efforts. The space shuttle program began in 1972 and ended in 2011. The International Space Station program began in the early 1990s (with roots going back to the mid-1980s) and will continue to at least 2024. The compressed schedule of Apollo was an aberration—an outcome of the vast resources allocated to the project by the U.S. government.

2033 is only 18 years away. Is that enough time?

Maybe. The concept plan presented at our workshop would use a significant amount of hardware already under study or in active development (the SLS rocket, Orion crew capsule, and Solar Electric Propulsion). This would theoretically help to mitigate schedule overruns since some of the unknowns are already being confronted.

As we emphasize in the report, work needs to begin now in order to successfully develop and test the rest of the hardware yet to be developed, like deep space habitats and the Exploration Upper Stage of the SLS, as well as the techniques and operations to sustain human life for the long duration of the trip. But space, as they say, is hard, and there are all sorts of difficult problems lurking in the details. The sooner we start, the better.

An important factor in keeping any program on schedule is the availability of funding when it's needed. This will require Congress and the White House to ensure NASA's human spaceflight budget receives adequate annual funding for the mission (no easy task) but also that the program's budget structure is flexible enough to rebound from potential setbacks. Program managers usually take this into account by maintaining funds dedicated to addressing unexpected problems. The availability of those funds is a critical piece in any successful mission development timeline.

What's so great about 2033 anyway?

The orbits of Earth and Mars provide periodic launch opportunities that are favorable in terms of the fuel required to travel from one planet to another. These come around roughly every 26 months. Humans launching to Mars would necessarily be limited to these opportunities. The year 2033 has a particularly favorable Mars launch opportunity to send lots of mass to the Red Planet.

Why use the Space Launch System and Orion?

NASA designed the Space Launch System (SLS) rocket and Orion crew capsule to provide the capability to send humans into deep space. Congress mandated the creation of SLS in the 2010 NASA Authorization Act, though they didn't specify how exactly SLS and Orion were to be used or precisely where and when NASA should send astronauts. It makes sense to take advantage of these new capabilities that are years into their development. What kind of human spaceflight program can you put together using the current infrastructure NASA is developing? Orbit-first is one potential answer.

Canceling both programs now and developing the political consensus around their successors would require a massive restructuring of several major field centers and likely face considerable congressional opposition (see the 2010 battle between the Obama Administration and Congress when the White House canceled the Moon-focused Constellation program). It seems to us that directing both the SLS and Orion to support the human exploration of Mars is a better use of time and effort than fighting again to cancel them.

This isn't to brush aside the major concerns related to the cost of developing, maintaining, and flying both SLS and Orion. These programs must find ways to increase their flight rate and decrease their overhead costs to make these programs sustainable over decades. Using SLS to launch robotic probes into deep space (which dramatically reduces their transit times) is one way to increase the launch rate of the SLS during the 2020s, but the other issues remain.

Many commercial enterprises are now attempting to travel in space using different technical and financial strategies than companies have traditionally pursued. As these companies are able to prove their new capabilities, NASA will find itself presented with new opportunities to enhance or refine its human spaceflight strategy. It will be important to understand the differences in the capabilities of new spacecraft and launch vehicles as they become available, and also to accurately assess when these capabilities will reach a level of maturity at which the risks of the vehicles are fully understood. Nevertheless, as we discuss in the report, NASA should actively pursue the best assets available to successfully enact all the phases of a human spaceflight program to Mars, but to do so the space agency needs to better define its goals and strategy.

Won't SpaceX get to Mars first?

How great would that be? If SpaceX, in addition to or along with NASA, makes it to Mars, so much the better. We're all for anyone and everyone getting to Mars.

Section 6 of our report briefly discusses the role of SpaceX and other companies could have in providing services in support of a NASA-led mission to Mars. The workshop generally agreed that if NASA is the organization to lead an effort to Mars, it must articulate its strategy so industry and international partners can define their places within that effort. It would make a lot of sense for SpaceX and other companies to provide fixed-cost services as part of the Mars effort.

Won't the public be disappointed by an orbital/Phobos-only mission?

We address public engagement in Section 5 of our workshop report. The workshop participants generally agreed that any plan to Mars would have to keep the overall narrative of a “boots-on-the-ground” goal during the implementation of intermediate steps such as cis-lunar test missions in the 2020s and a potential 2033 Phobos mission. But that narrative is pretty easy to explain as humans gradually increase their presence in space. If anything, we think that a Phobos mission would whet the appetite of the public for the next step of landing.

Don't forget that the intermediate step of a Phobos mission would still require that humans travel farther in space than at any point in history. It would arguably be the most daring, risky, and ambitious space exploration mission in human history. And that seems like it a pretty engaging public outreach moment to us.

Why not just go to the Moon instead?

The Planetary Society believes that Mars should be the goal of NASA's human spaceflight program. Its rich and intriguing history makes it a prime destination to search for signs of past life. Its environment supports humans more naturally than any other accessible destination in space.

It is likely, however, that any long-term program to get humans to Mars will use the space around the Moon (cis-lunar space) as a proving ground. The JPL study team's concept we discuss in our report proposes multiple missions to the vicinity of the Moon throughout the 2020s and a crewed demonstration landing on the lunar surface in the mid-2030s.

The important item to note here is that going to the Moon without the context of a clear, Mars-directed strategy has the pitfall of long-term infrastructure costs. This would siphon funds that could otherwise be directed toward the Mars effort. That said, NASA's precursor program at the Moon could provide an opportunity for international or commercial partners to build off of NASA's test missions and engage in independent lunar endeavors. Again, this is an area that could benefit from NASA clarifying its strategy and plan.

Isn't NASA already on a “Journey to Mars”?

Yes, and that's important. The agency is clearly acknowledging Mars as its goal in human spaceflight. That hasn't happened before, and it's commendable.

However, NASA has yet to define a clear strategy to get humans to Mars by the 2030s. The next major human spaceflight mission proposed by NASA is the Asteroid Redirect Mission (ARM) which involves astronauts rendezvousing with a boulder robotically plucked off an asteroid and placed in lunar orbit. The mission promotes the development of solar electric propulsion (which can be used to pre-position cargo in Mars orbit). But beyond ARM, NASA has made no commitments, possibly to avoid criticism of the associated costs or schedule expectations. Our workshop and report was a in part a response to this lack of definition.

Is The Planetary Society advocating for JPL's Mars plan?

Not in the sense that it should be “the plan” for Mars exploration. That's because the study concept provided by JPL is meant to serve as a proof-of-concept demonstration that a program could be affordable within budget constraints. It's a response to the sobering findings of the National Research Council's 2014 Pathways to Exploration report, which found that NASA's existing plans for Mars could not be realized until the mid 2040s. The JPL study team, using the exact same cost and schedule analysis, proposed a concept plan that could get humans to Mars vicinity by 2033 and on the surface by 2039. Orbiting first provides a significant number of advantages in a cost-constrained scenario, and that's something we believe is worth consideration by NASA.

We acknowledge that the details of any Mars plan will necessarily change as engineers sit down and deal with all of the difficulties inherent in any space exploration program. NASA doesn't need to commit to every detail up front.

We do believe, however, that NASA should at least articulate its strategy to get to Mars. There are many good reasons to do this: providing a metric to judge progress and affordability; helping prioritize investments in technology development; and enabling the creation of a coalition to sustain the endeavor over the decades. The JPL study teams' concept provides a good starting point for defining this strategy.

Why does this depend on NASA divesting from the International Space Station? Are you against the ISS?

Again, this is a practical concession to constrained budgets. At the moment, NASA cannot afford an exploratory human spaceflight program and a low-Earth orbit human spaceflight program (at least as currently defined).

The ISS costs roughly $3 billion per year to supply and operate. That's nearly half of NASA's entire budget for human spaceflight. If NASA expects a budget that, at best, grows with inflation, the ISS must be handed off or divested from before significant resources can be spent on a human mission to Mars. If NASA's budget increases beyond inflation, this may no longer be an either-or scenario.

NASA's current policy is to operate the ISS through 2024. Many supporters of ISS want to extend operations to 2028. The Aerospace Corporation examined both scenarios in their cost and schedule analysis of the JPL study group's Mars concept. The scenario in which NASA ends its leadership role in ISS in 2024, as you might expect, makes affording a Mars mission easier. Ending the leadership role in 2028 still allows for a Mars mission, but will require clever phasing and far narrower budget margins. It is a higher risk scenario from a cost and schedule standpoint.


What is Phobos?

Phobos is the larger of Mars's two moons (the smaller moon is named Deimos). It is exponentially smaller than Earth's moon, with a diameter of 27 × 22 × 18 kilometers (16 by 14 by 11 miles).

Why is Phobos worth visiting?

There are a number of compelling scientific reasons to explore Phobos. We detail some of them in our workshop report (Section 4.4: The Scientific Potential of Mars Orbit and Phobos).

No one actually knows the origin of Phobos (or Deimos). Was it originally accreted from the debris of a major impact on Mars (like our Moon)? Or is it a captured asteroid? There are arguments for both, and either outcome would provide valuable science.

Additionally, Phobos is close enough to Mars that it can collect debris kicked up by major impacts on the Red Planet. Phobos flies through these debris fields and accumulates bits of Mars like so many bugs splattering on a windshield during August in the midwest. These samples are likely embedded in the top meter or so of Phobos's surface—a difficult location for robots to sample, but easier for humans. In essence, since astronauts could collect samples from Phobos and samples from Mars in one location, Phobos is a two-for-one sample return opportunity.

There's a lot more science to understand about the Martian moons. NASA and Brown University are presenting a free online course exploring the science of both:

Science and Exploration of Phobos and Deimos
A free, online course exploring the science potential of Mars's moons. Provided by NASA's Solar System Exploration Research Virtual Institute:

Isn't Phobos deep in Mars's gravity well and not an ideal place to use as a base for exploration?

In the JPL team's concept architecture, astronauts would not return to Phobos in subsequent missions. Phobos doesn't serve as a base for future operations but as a prime science target for the first mission.

Is it easier to get into orbit around Mars than to go to Phobos?

Yes. Orbit-only would require less hardware. Astronauts would likely avoid traveling deep into Mars's gravity well in the manner required for a mission to Phobos. It would provide fewer opportunities for science, though.