We know more about many aspects of the Moon than any world beyond our own, and yet we have barely begun to solve its countless mysteries. The Moon is, above all, a witness to 4.5 billion years of solar system history, and it has recorded that history more completely and more clearly than any other planetary body. Nowhere else can we see back with such clarity to the time when Earth and the other terrestrial planets were formed.
Planetary scientists have long understood the Moon’s unique place in the evolution of rocky worlds. Many of the processes that have modified the terrestrial planets have been absent on the Moon. The lunar interior retains a record of the initial stages of planetary evolution. Its crust has never been altered by plate tectonics, which continually recycle Earth’s crust, or planetwide volcanism, which resurfaced Venus only half a billion years ago, or by the action of wind and water, which have transformed the surfaces of both Earth and Mars. The Moon today presents a record of geologic processes of early planetary evolution in the purest form.
For these reasons, the Moon is priceless to planetary scientists: It remains a cornerstone for deciphering the histories of those more complex worlds. But because of the limitations of current data, researchers cannot be sure that they have translated the message correctly. Now, thanks to the legacy of the Apollo program, and looking forward to the Vision for Space Exploration, it is possible to pose sophisticated questions that are more relevant and focused than those that could be asked over three decades ago. Only by returning to the Moon to carry out new scientific explorations can we hope to close the gaps in understanding and learn the secrets that the Moon alone has kept for eons.
NASA asked the National Research Council (NRC) to provide guidance on the scientific challenges and opportunities enabled by a sustained program of robotic and human exploration of the Moon during the period 2008-2023+ as the Vision for Space Exploration evolves. This interim report was prepared by the Committee on the Scientific Context for Exploration of the Moon. The committee will present additional material and more details in its full report, to be released in mid-2007.
PRIORITIES, FINDINGS, AND RECOMMENDATIONS
Within a balanced science program the committee provides the following prioritization of lunar science goals that can be accomplished by lunar measurements and analyses during the early phases of the Vision for Space Exploration. It has used the prioritization criteria adopted by the decadal survey New Frontiers in the Solar System: An Integrated Exploration Strategy (NRC, 2003) as a guideline: scientific merit, opportunity, and technological readiness. Each of these priorities has related orbital, in situ, returned sample, and human-tended measurement goals.
Fundamental Solar System Science
Characterize and date the impact flux (early and recent) of the inner solar system.
Determine the internal structure and composition of a differentiated planetary body.
Determine the compositional diversity (lateral and vertical) of the ancient crust formed by a differentiated planetary body.
Characterize the volatile compounds of polar regions on an airless body and determine their importance for the history of volatiles in the solar system.
Determine the time scales and compositional and physical diversity of volcanic processes.
Characterize the cratering process on a scale relevant to planets.
Constrain processes involved in regolith evolution and decipher ancient environments from regolith samples.
Understand processes involved with the atmosphere (exosphere) of airless bodies in the inner solar system.
Other Opportunities (additional information is required for these)
Utilize data from the Moon to characterize Earth’s early history.
Determine the utility of the Moon for astrophysics observations.
Determine the utility of the Moon as a platform for observations of Earth.
Determine the utility of the Moon as a platform for observations of solar-terrestrial processes.
FINDINGS AND RECOMMENDATIONS
Lunar science has much broader implications than simply studying the Moon. There are strong linkages between the science goals recommended for the lunar exploration program and diverse scientific and applied concerns.
Principal Finding: Lunar activities apply to broad scientific and exploration concerns.
Finding 1: Enabling activities are critical in the near term.1
In order to take advantage of the information expected to be returned from missions flown before 2010 by the United States and other nations, the committee finds that enabling, preparatory activities will be critical in the near term.
Recommendation 1: The committee urges NASA to make a strategic commitment to stimulate lunar research and engage the broad scientific community2 by establishing two enabling programs, one for fundamental lunar research and one for lunar data analysis. Information from these two efforts, the Lunar Fundamental Research Program and the Lunar Data Analysis Program, will speed and revolutionize understanding of the Moon as the Vision for Space Exploration proceeds.
Finding 2: Explore the South Pole-Aitken basin.
As the oldest and largest basin in the solar system, the South Pole-Aitken Basin on the Moon is a unique location.
Recommendation 2: NASA should develop plans and options to accomplish the scientific goals set out in the New Frontiers in the Solar System: An Integrated Exploration Strategy’s3 high-priority recommendation, through single or multiple missions that increase understanding of the
South Pole-Aitken basin and by extension all of the terrestrial planets in our solar system (including the timing and character of the early heavy bombardment).
Finding 3: Determine the composition and structure of the lunar interior.
Determination of the interior structure and composition of the Moon are high-priority scientific goals.
Recommendation 3: Because a globally distributed network of many geophysical stations is critical for these investigations, an international effort should be pursued to coordinate the development of a standard, small set of key instruments (e.g., seismometer, thermal profiler, retro-reflector, etc.) and to cooperate in providing for its wide deployment across the Moon.
Finding 4: Maximize the diversity of lunar samples.
The Moon is a complex, heterogeneous body. Samples of the Moon from diverse sites are necessary to reach science goals.
Recommendation 4: Landing sites should be selected that can fill in the gaps in diversity of lunar samples. To improve the probability of finding new, ejecta-derived diversity, every landed mission that will return to Earth should retrieve at a minimum two special samples: (a) a bulk undisturbed soil sample (200 g minimum) and (b) at least 1 kg of rock fragments 2 to 6 mm in diameter sieved from bulk soil. These samples would be in addition to those collected at specific high-priority sampling targets within the landing site.
Finding 5: Proceed with lunar surface mission development and the site selection process.
Plans to return to the Moon will involve the selection of surface exploration sites. Many of the science goals the committee set out depend critically on site selection.
Recommendation 5: Development of a comprehensive process for lunar landing site selection that addresses the science goals of Table 14 should be started by a science definition team. The choice of specific sites should be permitted to evolve as understanding of lunar science progresses through the refinement of science goals and the analysis of existing and newly acquired data. Final selection should be done with full input of the science community in order to optimize science return while meeting engineering and safety constraints.
Finding 6: Understand the lunar polar deposits and environment.
Almost nothing is known about the sources of volatiles at the lunar poles and the processes operating on these volatiles. Lunar polar deposits and the lunar polar environment are probably fragile.
Recommendation 6: NASA should carry out activities to understand the inventory, lateral distribution, composition (chemical, isotopic, mineralogic), physical state, and stratigraphy of the lunar polar deposits. This understanding will be gained through analyses of orbital data and in situ data from landed missions in the permanently shaded regions. In situ studies should occur early enough in the lunar program to prevent substantial change in the polar environment due to robotic and human activities.
Finding 7: Understand and characterize the lunar atmosphere.
The lunar atmosphere is tenuous and therefore fragile. Its pristine state is vulnerable to alteration from robotic and human activities.
Recommendation 7: To document the lunar atmosphere in its pristine state, early observational studies of the lunar atmosphere should be made, along with studies of the sources of the atmosphere and the processes responsible for its loss. These include a full compositional survey of all major and trace components of the lunar atmosphere down to a 1 percent mixing ratio, determination of the volatile transport to the poles, documentation of sunrise/sunset dynamics, determination of the variability of indigenous and exogenous sources, and determination of atmospheric loss rates by various processes.
Finding 8: Evaluate the Moon’s potential as an observation platform.
The Moon may be a suitable site for various scientific observations of Earth, Sun-Earth connections, astronomy, and astrophysics.
Recommendation 8: The committee recommends that a thorough study be done by NASA to evaluate the suitability of the Moon as an observational site for studies of Earth, Sun-Earth connections, astronomy, and astrophysics.
Finding 9: Establish strong ties with international programs.
The participation of other nations in lunar exploration is a fact. Coordinated and cooperative international activities would benefit all participants.
Recommendation 9: NASA is encouraged to explicitly plan and carry out activities with the international community for scientific exploration of the Moon in a coordinated and cooperative manner. The committee endorses the concept of international activities as exemplified by the recent “Beijing Declaration” of the 8th International Conference on Exploration and Utilization of the Moon.
The committee also presents several related findings and recommendations intended to facilitate a balanced program to reach the scientific goals:
Finding 1R: Optimize the partnership between NASA’s Exploration Systems Mission and Science Mission Directorates.
Recommendation 1R: Prior Space Studies Board reports examined management approaches to the integration of human exploration and space science. They found that an optimum approach consisted of establishing a science management office within (today) the Exploration Systems Mission Directorate, reporting jointly to the Science Mission and Exploration Systems Mission Directorates. Such an office should be established as soon as possible to ensure the productive involvement of science planning and implementation ab initio.
Finding 2R: Identify and develop lunar-specific advanced technology and instrumentation.
Recommendation 2R: NASA should create an advanced technology program to develop lunar-specific capabilities that are critical to successful implementation of the lunar science strategy outlined in Table 1. This program should tap the creativity of the engineering and science communities to address development of robotic and instrumentation capability to meet needs that at present are unmet.
Finding 3R: Plan curatorial and principal investigator facilities for new lunar samples.
Recommendation 3R: NASA should evaluate the future needs of curatorial facilities for the collection of new lunar samples. The state and availability of instrumentation for both curation
and analyses should be assessed. Such a study should include representatives of the science community in detailed planning of an appropriate strategy.
Finding 4R: Optimize astronaut lunar field investigations—an integrated human/robotic approach.
Recommendation 4R: NASA should provide astronauts with the best possible technical systems for conducting science traverses and emplacing instruments. An integrated human/robotic program should be developed using robotic assistants and independent autonomous/teleoperated robotic systems. The capabilities of these systems should be designed in cooperation with the science community and operations planning teams that will design lunar surface operations. Extensive training and simulation should be initiated early to help devise optimum exploration strategies.