Scientific Opportunities in the Human Exploration of Space (1994)

The post-Apollo directions of a U.S. program of human exploration of the solar system have long been the subject of study, discussion, debate, and controversy. Most concepts for the next steps in the human exploration of space, including those going back as far as the mid-1960s, have focused on missions to the Moon and Mars and their immediate vicinity.¹, ², ³, ⁴, ⁵, ⁶, Those studies were conducted largely in the context of a future program of human exploration of the Moon and Mars that was assumed to be inevitable.

Political support, however, has not materialized for initiating a piloted return to the Moon or for journeying to Mars; in fact, it has been difficult to get a political consensus to support the funding of a space station, the prime goal of which is, arguably, to prepare for long-duration human space exploration. The arguments, pro and con, for continued human spaceflight have shifted as the basic rationale has changed. No longer is competition with the Soviet Union a compelling force as it was for Apollo, and the economic pressures faced by the nation are causing many to question whether this is the time for human exploration of the solar system.

Despite the current uncertainty, however, the possibility for future human exploration of the Moon and Mars remains. In this regard, the Committee on Human Exploration (CHEX) recognizes that political factors can change rapidly and can have profound effects on the pace and content of a human space exploration program, as they did when President Kennedy committed to the Apollo program. CHEX views the current interlude as an opportune time in which to calmly and methodically study and stipulate the

role of science in any future program of human exploration of the solar system.

Given the often lofty, but still ill-defined, human exploration aspirations, what is the role of science in a Moon/Mars program? CHEX started with the recognition that one of the major goals in the National Aeronautics and Space Administration's (NASA) original charter was the acquisition of new scientific knowledge about space and the terrestrial environment. Indeed, scientific goals have always played an important part in NASA's activities. Thus it is natural to expect that science will play a major role in any future program of human exploration, as it did in Apollo and in all subsequent piloted spaceflight programs. The specific nature of that role and the way in which the scientific community has historically interacted with human space exploration will be dealt with in the third CHEX report.

It is not surprising then, that many, if not all, concepts for human exploration of the Moon and Mars include scientific investigations. Many proponents also propose using the Moon as an observational platform from which to conduct astronomical and space physics studies.

Is science then the motivation for a Moon/Mars program? This question was answered in the negative by the National Academy of Sciences and National Academy of Engineering in a report on space policy prepared in 1988. It stated that “the ultimate decision to undertake further voyages of human exploration and to begin the process of expanding human activities into the solar system must be based on nontechnical factors. ”⁷ In other words, the expansion of human presence and activity into the solar system does not demand any a priori scientific research component beyond the enabling research needed to provide for the health and safety of the astronauts (see next section).

Nevertheless, recognizing the need for enabling research and that piloted flight can result in new or modified space science opportunities, the U.S. research community has the opportunity and obligation to provide the best and most constructive scientific advice it can to help shape the political and technical decisions regarding piloted flight.⁸ Accepting such a role commits scientists to participating in establishing human exploration strategy and goals, mission planning, management, implementation, and analysis of results. During mission design and operations, scientists must participate to ensure optimal scientific return. Part of that optimization is the inclusion in the crews not only of people trained to perform particular scientific tasks, but also of experienced scientists. Indeed, scientist-astronauts have an important role to play in planning, postmission analysis, and preparations for future exploration.

Since the end of the Apollo program in 1972, humans have not set foot on another body in the solar system. The Apollo experience involved hundreds of scientists in many disciplines. Although science was not empha-

sized or well planned at the beginning of the program, Apollo evolved a highly successful mechanism to include scientific input that ultimately produced important scientific results.

Participation of scientists in a program of human exploration is a sensitive subject in the broad scientific community. Some individuals fear that any involvement is an implicit endorsement of such a program. Others fear that science is or will be used as a justification or that low-priority and/or low-quality science will be funded under the umbrella of an expensive human spaceflight program. Indeed, experience shows that these concerns cannot be dismissed out of hand—thus part of the Space Studies Board's (SSB) rationale for establishing CHEX was to ensure that the scientific aspects of a Moon/Mars program are established in the proper context. That is, only science that truly takes unique advantage of human presence should be undertaken and then only if it is of competitive quality.

CHEX concluded in its first study that the most important responsibility facing the scientific community, in the initial stages of a program of human exploration, is to define the conditions necessary to maintain the health and safety and ensure the optimal performance of astronauts during exploration missions. Answers are urgently needed to such questions as, Can humans function effectively on the Moon for long periods? and, Can they survive the lengthy journey to Mars? CHEX identified these enabling science issues in its first report⁹ and classified them according to their degree of urgency.

Critical research issues were defined as those for which inadequate scientific data lead to unacceptably high risks to any program of extended space exploration by humans. They are the potential “showstoppers ” for a Moon/Mars project. Items in this first category include, for example, the effects of prolonged exposure of humans to the microgravity and space radiation environments.

Optimal performance issues, the second category, were defined as those that, based on current knowledge, do not appear to pose serious dangers to the health and well-being of humans in space. They could, however, reduce human performance in flight or on planetary surfaces and result in a less than optimal return from the mission. Research to understand these factors cannot be neglected, and some of them may become critical research issues relative to long-duration human spaceflight and return to terrestrial gravity, when extraterrestrial habitation is considered or when new research information is obtained.

Given an eventual political decision to undertake a Moon/Mars program, how might prolonged human space voyages enable or enhance the accomplishment of overall space science objectives? Before addressing this question, CHEX reiterates the earlier position of the Space Studies Board that a program of solar system exploration that includes only the Moon and Mars and their immediate vicinity is scientifically incomplete. ¹⁰ The obvious concern is that a program of human exploration, which by its very nature would be expensive, could dominate NASA budgetarily, managerially, and programmatically to the detriment of a balanced scientific program. The existence of a vigorous ongoing space science program can go a long way toward creating a receptive environment for a program of human exploration.

Many of the scientific objectives for the Moon and Mars are a subset of the general goals for the scientific exploration of the solar system outlined in past SSB reports. For the Moon and Mars in general, we seek to learn their thermal, magmatic, and tectonic evolution; their bombardment history; and the origin and evolution of their volatiles. We hope to learn about the origin of the Moon and its relationship to the Earth. For Mars we strive to understand the history of its climate, the processes of surface weathering and modification, and global aspects of the magnetic field and associated interactions with the interplanetary medium. Also of high priority is understanding the history of martian biogenic elements and determining whether life ever existed there.¹¹, ¹²,¹³

Human exploration of the Moon and Mars might also lead to the achievement of objectives in fields other than the planetary sciences. Studies of the lunar regolith and martian ice cores may, for example, reveal the long-term evolution of the particle and photon outputs of the Sun. Similarly, if a human exploration program includes the construction and operation of scientific observatories on the Moon, it might, for example, aid our understanding of the mechanisms operating in solar flares, the origin of very high energy cosmic rays, and the frequency of occurrence of planets around other stars.¹⁴, ¹⁵, ¹⁶

A Moon/Mars program might enable studies of the response of living organisms to microgravity and fractional gravity environments.¹⁷ In addition, crews on Mars exploration missions will experience a combination of circumstances, including prolonged sequestration with no immediate possibility of escape, that might enable unique studies of human behavior.¹⁸ It must be stressed, however, that these research opportunities in the life sciences are fundamentally different from those in the physical sciences (outlined above), because the latter are inherently of high scientific priority to

their relevant research communities, whereas the former are currently not, absent a program of human exploration.

Over the years the SSB has made many specific recommendations for scientific investigations in space, but none of the board's previous reports considered possible opportunities in the physical or biomedical sciences enabled by prolonged human space missions. For this report, CHEX considered ways in which human presence might enhance the accomplishment of previously recommended robotic scientific investigations and also considered what new investigations, consistent with the SSB's scientific strategies, might be enabled by a human exploration program. From this extended list, CHEX selected a number of specific examples that have valid scientific and technical reasons for being performed in conjunction with a Moon/Mars program and that would

• Be enhanced or enabled by prolonged human space missions, and

• Contribute in a major way to achieving the overall goals of space science.

The investigations in the physical sciences described in Chapter 3 meet these criteria. But, as is discussed below, some of those suggested in other reports do not. This observation raises a major concern of the scientific community—too often little or no competitive analysis and prioritization have been done, with respect to alternative modes or other science, to assess the merit of the proposed science for a Moon/Mars program.¹⁹

1. President's Science Advisory Committee, Joint Space Panels, The Space Program in the Post-Apollo Period, U.S. Government Printing Office, Washington, D.C., February 1967.

2. NASA, Beyond the Earth's Boundaries: Human Exploration of the Solar System in the 21st Century , NASA, Washington, D.C., 1988.

3. Advisory Committee on the Future of the U.S. Space Program, Report of the Advisory Committee on the Future of the U.S. Space Program (the “Augustine report”), U.S. Government Printing Office, Washington, D.C., 1990.

4. NASA, Leadership and America's Future in Space, NASA, Washington, D.C., 1987.

5. Synthesis Group, America at the Threshold, Report of the Synthesis Group on America's Space Exploration Initiative, U.S. Government Printing Office, Washington, D.C., 1991.

6. NASA, Report of the 90-day Study on Human Exploration of the Moon and Mars, NASA, Washington, D.C., 1989.

7. Committee on Space Policy, Toward a New Era in Space: Realigning Policies to New Realities (the “Stever report”), National Academy Press, Washington, D.C., 1988.

8. Space Studies Board, Scientific Prerequisites for the Human Exploration of Space, National Academy Press, Washington, D.C., 1993, page 2.

9. Space Studies Board, Scientific Prerequisites for the Human Exploration of Space, National Academy Press, Washington, D.C., 1993, pages 3-4.

10. Space Studies Board, 1990 Update to Strategy for the Exploration of the Inner Planets , National Academy Press, Washington, D.C., 1990.

11. Space Studies Board, Strategy for Exploration of the Inner Planets: 1977-1987, National Academy Press, Washington, D.C., 1978.

12. Space Studies Board, 1990 Update to Strategy for the Exploration of the Inner Planets, National Academy Press, Washington, D.C., 1990, Chapter 5 and Chapter 6.

13. Space Studies Board, The Search for Life's Origins: Progress and Future Directions in Planetary Biology and Chemical Evolution, National Academy Press, Washington, D.C., 1990.

14. Astronomy and Astrophysics Survey Committee, The Decade of Discovery in As tronomy and Astrophysics, National Academy Press, Washington, D.C., 1991.

15. Space Studies Board, Assessment of Programs in Solar and Space Physics 1991, National Academy Press, Washington, D.C., 1991.

16. European Space Agency, Mission to the Moon: Europe's Priorities for the Scientific Exploration and Utilization of the Moon, Report of the Lunar Study Steering Group, ESA SP-1150, European Space Agency, Noordwijk, The Netherlands, June 1992.

17. Space Studies Board, Assessment of Programs in Space Biology and Medicine 1991, National Academy Press, Washington, D.C., 1991.

18. Space Studies Board, Assessment of Programs in Space Biology and Medicine 1991, National Academy Press, Washington, D.C., 1991, Chapter 4.

19. See, for example, Nancy Ann Budden and Paul D. Spudis, “SEI Science: Measuring the Return,” Aerospace America, March 1993, page 22.