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From the Executive Director

A Plan for Mars Sample Return

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Click to enlarge > Louis D. Friedman Executive Director of The Planetary Society Credit: The Planetary Society

April 8 , 2008

Mars sample return (MSR) is receiving considerable attention by NASA and ESA these days. Alan Stern, the departing Associate Administrator for NASA's Science Mission Directorate resurrected MSR mission planning, with a 2020 flight goal, after NASA stopped work on it three years ago when the budget for Mars exploration was cut in the Agency.

ESA has been studying MSR mission development as their major mission to follow ExoMars (planned for 2013). In the early 2000s, the French and Italian space agencies participated with NASA in developing a MSR mission design that would span multiple launch opportunities. The current NASA and ESA studies promote international cooperation, and are being coordinated within the International Mars Exploration Working Group (of space agencies interested in Mars missions).

Mars sample return is often referred to by planetary science insiders as the "holy grail" of robotic space missions. It has been highly sought after for several decades but has always slipped away from being put into the program.

So why is Mars sample return so highly sought after? Mars is the only planet where we think there is a chance of accessing evidence of life, past or present. It is also the only planet where we have oxygen and water that can be extracted to sustain future life. These are fundamental drivers in space exploration and planetary science, and to pursue these goals, we want to know much more about the surface composition and to better understand its geologic and atmospheric history.

Imagine geologists and microbiologists on Earth having to do their analysis remotely without ever bringing samples back to the laboratory. The best analysis will be conducted on Earth -- and the best analysis is what we need to prepare for future human missions.

Many detailed analyses currently cannot be done by spacecraft -- from scanning electron microscope imaging, to advanced astrobiology instrumentation, to age dating of rocks. To do these and many other studies correctly requires analyzing well-documented Martian samples in Earth-based laboratories. (We cannot use Martian meteorites for these studies because we do not know from what part of Mars they came.) Earth-based instrumentation will be much more up-to-date and much more capable since it doesn't have to be miniaturized. Also many laboratories with various capabilities from around the world can be used.

I am very interested in MSR. In addition to the science value, MSR broadly advances space engineering. Planning MSR requires evaluation of many options, tradeoffs, and vehicles, as well as a wide range of potential requirements, from the simplest "grab" sample to extensive roving and multiple sample selection. I was leader of a JPL MSR mission design analysis in the late1970s. Since that time, there have been about a half-dozen other missions studied.

One characteristic of all the studies has been growth in the cost estimate for the project. Always, it gets larger, to the point where it breaks the bank and becomes unfeasible. This growth, I think, follows from the complexity of the mission -- one likes to start out simple and then keep adding to it; but in the case of MSR, there is just too much that can be added on, including such expensive things at the end of the mission design like planetary protection (of Mars and Earth) and sample handling and analysis. The latter requires, according to the scientists, major new facilities.

I have three major conclusions from these experiences:

1. There will never be enough money in the science budget for NASA to do a Mars Sample Return mission alone;
2. The MSR mission will require international cooperation: technically, politically, and economically;
3. MSR is not a single mission -- it is multiple missions, or in NASA-speak, a program.

Science Budget

The first conclusion strikes at the heart of the current debate going on in the Mars community. Alan Stern presented his plan to that community (the Mars Exploration Program Analysis Group, MEPAG), and they supported MSR, with some caveats. They concluded, "Without the assumption that the funding for Mars exploration will dramatically increase from the proposed level of $300-400 million per year (fiscal years 2011-2013) to levels of $600-900 million per year in the future, then MSR cannot happen." But the reduced funding for Mars in the near term (fiscal years 2009-2014) is at the heart of Stern's proposal for MSR. That reduced funding will prevent the necessary technology for Mars sample return to be developed.

MEPAG was also uncomfortable with eliminating Mars missions from the current plan and pushing them out beyond the 5-year planning period. Past experience shows this type of planning is repeatedly done -- push the missions and required funding far enough in the future so that they are no longer today's problem. Then when the time comes, repeat the process, or eliminate MSR as too expensive -- this has happened, as noted, at least a half-dozen times in the past 30 years (about twice per decade).

It is reasonable that MSR doesn't fit in a science-only budget -- it is much more than a science-only mission. It is a crucial engineering step in exploration, a precursor to human space flight; both for the tough sample return requirements of entry, descent, landing, ascent, and rendezvous, and for the crew safety requirements of characterizing the Martian surface composition. The "exploration" side of NASA (that is, the human space flight mission developers) should be contributing funds to MSR. That will provide extra funding and a broader base for the mission development. Automated MSR will also provide a publicly interesting set of interim mission milestones to sustain the long-range vision for human Mars exploration.

International Cooperation

International cooperation will also broaden the technical and political base of MSR. The U.S. has never attempted sample return. The only country that has ever done automated sample return from a planetary surface is Russia (first with Luna 20 in 1972). They are about to try it again from the Martian moon Phobos. The only other country that has attempted it is Japan (Hayabusa). We won't know for a few years yet whether they will succeed. In any case, international cooperation should be as broad as possible.

This type of cooperation also will be a valuable precursor to a human Mars mission -- for it will certainly need international team building, even more than has been done on the International Space Station. The MEPAG also concluded, "All MSR options will require significant international participation". International cooperation plus resources from the human space flight program could make the MSR budget much more feasible.

Multiple missions

A single sample of Earth would not be sufficient to understand our planet. Neither would a single sample of Mars describe that planet. We will need multiple samples for a more complete understanding.

If mission are designed as a series, they will be better designed and require lower cost in the long run. Furthermore, as the JPL/CNES/ASI studies of the 2000s showed, MSR can be more flexibly and robustly designed if the mission is designed over 2-3 opportunities. When that timescale is integrated into a series of missions, one finds themselves back in the strategy of one mission per launch opportunity -- a strategy we began following in 1997. With a series of missions, we can start with a flexible design that can permit simple grab samples at first, followed by steps of increasing complexity. It also admits international participation in a flexible manner.

In Conclusion

I support the goal inserting MSR back into the NASA plan. But the Agency's "exploration" community -- the human space flight folks -- must get behind and contribute to the mission development. Current studies must be broadened to include Russia and Japan at least, and to make it part of the world's space agencies' "global exploration strategy." This would provide the wheelbase to create the necessary resources for technology development over the next four years to give this mission a chance of finally being started.

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