Despite the compelling scientific arguments for the return of martian samples to Earth and irrespective of how such an endeavor is implemented, sample return will be a technically challenging, high-risk, high-cost endeavor. Although the committee was not composed appropriately to independently estimate the cost of such a mission, figures in the range of $3 billion to $5 billion are frequently quoted.12 Thus, the decision to implement such an undertaking would have an impact on NASA’s science program extending far beyond the Astrobiology Program or the Mars Exploration Program. As such, the decision to implement a Mars sample-return mission will hinge on factors such as the relative balance of NASA’s flight activities between the various scientific programs, the state of the agency’s budget, and opportunities presented by international cooperation—all factors whose examination is beyond the scope of this study. As such, it behooves the astrobiology community to plan for the possibility that a Mars sample-return mission is not an integral component of current mission plans.
If a commitment is not made for sample return, then high-quality and high-priority science still can be done at the surface of Mars, for example from an astrobiology field laboratory. Such an advanced rover mission should have significant analytical capabilities beyond those of MSL and should address science questions complementary to those of MSL. Alternatively, two Mid Rovers could investigate the geological and geochemical diversity of carefully selected sites on Mars. Either approach would provide high science value and would be compelling in itself.
Although a compelling Astrobiology Field Laboratory (AFL) mission could be defined today that would complement MSL, the launch of an AFL mission should be phased to take into account the results obtained from MSL. Such a mission would be most effective as part of an overall program that also addressed the broad range of issues related to astrobiology, including planetary habitability. However, it must be recognized that, although they would address some astrobiology science goals, such missions would have a much more limited ability than sample return to make fundamental discoveries and to respond to them. They would be incapable of addressing the most fundamental astrobiology and other science goals in the same substantive ways as sample return. An AFL mission would be complementary to a sample-return mission in that it would allow some extension of the detailed results from sample return to other locations via in situ analyses.
International collaboration in Mars missions has the potential to make expensive missions such as Mars Sample Return affordable. The benefit, however, has to be balanced against the political difficulties of working with multiple countries and multiple space agencies. The European Space Agency (ESA), for example, already values the role that astrobiology plays in Mars science. One area of relatively straightforward collaboration would involve encouraging ESA to include a sample-caching capability on its rovers currently under development that would be analogous or equivalent to that being encouraged by this committee for NASA rovers.
Recommendation. International collaboration in Mars missions should be pursued in order to make expensive missions affordable, especially in the areas of sample caching and sample return.
1. See, for example, M.J. Drake, W.V. Boynton, and D.P. Blanchard, “The Case for Planetary Sample Return Missions: 1. Origin of the Solar System,” Eos 68:105, 111-113, 1987.
2. See, for example, J.L. Gooding, M.H. Carr, and C.P. McKay, “The Case for Planetary Sample Return Missions: 2. History of Mars,” Eos 70:745, 754-755, 1989.
3. G. Ryder, P.D. Spudis, and G.J. Taylor, “The Case for Planetary Sample Return Missions: 3. The Origin and Evolution of the Moon and Its Environment,” Eos 70:1495, 1505-1509, 1989.
4. T.D. Swindle, J.S. Lewis, and L.A. McFadden, “The Case for Planetary Sample Return Missions: 4. Near-Earth Asteroids and the History of Planetary Formation,” Eos 72:473, 479-480, 1991.
5. National Research Council, Assessment of Mars Science and Mission Priorities, The National Academies Press, Washington, D.C., 2001, pp. 83-88.