Future lunar exploration will provide opportunities to expand the human scientific exploration of the Moon and, eventually, Mars. Planning for renewed field exploration of the Moon entails the selection, training, and capabilities of explorers; selection of landing sites; and adoption of an operational approach to extravehicular activity. Apollo program geological exploration, and subsequent analysis and interpretation of findings and collected samples underpin our current understanding of lunar origin and history. That understanding continues to provide new and important insights into the early histories of Earth and other bodies in the solar system, particularly during the period when life formed and began to evolve on Earth and possibly on Mars. Specific new lunar exploration objectives include: (1) testing the consensus “giant impact” hypothesis for the origin of the Moon; (2) testing the consensus impact “cataclysm” hypothesis; (3) determining the temporal flux of large impacts in the inner solar system; and (4) investigating the internal structure of the Moon. Apollo samples also identified significant and potentially commercial lunar resources that could help satisfy future demand for both terrestrial energy alternatives and space consumables. Equipment necessary for successful exploration includes that required for sampling, sample documentation and preservation, communications, mobility, and position knowledge. Easily used active geophysical, portable geochemical, and in situ petrographic equipment can greatly enhance the scientific and operational returns of extended exploration compared to that possible during the Apollo program.

Planning and implementation of astronaut observations and photography from lunar orbit during the Apollo program were based on two expectations: (1) orbiting astronauts would be able to add to our knowledge by describing lunar features from their unique vantage point, and, (2) as illustrated by the Gemini Earth-orbital missions, expertly obtained photographs would allow us to place detailed information from field exploration into a regional context. To achieve these goals, the astronauts had to be thoroughly familiar with concepts of lunar geology and intellectually prepared to note and document the unexpected. This required mission-specific training to add to their store of knowledge about the Moon. Because the activity was not part of the original program objectives, the training was conducted at the behest of the astronauts. The training time grew from occasional briefings on the early flights to extensive classroom sessions and flyover exercises for a formal “experiment” on the last three missions. This chapter summarizes the historical development and salient results of training the Moon-bound astronauts for these tasks. The astronaut-derived orbital observations and photographs increased our knowledge of the Moon beyond that possible from robotic sensors. Outstanding results include: realization of the limitations of photographic film to depict natural lunar surface colors; description and documentation of unknown features on the lunar farside; observation by Apollo 15 of dark-haloed craters that helped in the selection of the Apollo 17 landing site; and real-time confirmation that the “orange soil” discovered at the Apollo 17 site occurs elsewhere on the Moon.

The Gruithuisen region in northern Oceanus Procellarum on the Moon contains three distinctive domes interpreted as nonmare volcanic features of Imbrian age. A 4 d extravehicular activity (EVA), four-astronaut sortie mission to explore these enigmatic features and the surrounding terrain provides the opportunity to address key outstanding lunar science questions. The landing site is on the mare south of Gruithuisen 3 (36.22°N, 40.60°W). From this site, diverse geologic terrains and features are accessible, including highlands, dome material, mare basalts, multiple craters, small rilles, and a negative topographic feature of unknown origin. Preliminary mission planning is based on Clementine multispectral data, Lunar Prospector geochemical estimates, and high-resolution (0.5 m/pixel) stereo images from the Lunar Reconnaissance Orbiter Narrow Angle Camera. Science objectives for the mission include: (1) determining the nature of the domes, (2) identifying and measuring the distribution of any potassium, rare earth elements, and phosphorus (KREEP)- and thorium-rich materials, (3) collecting samples for age dating of key units to investigate the evolution of the region, and (4) deploying a passive seismic grid as part of a global lunar network. Satisfying the science objectives requires 7 h, ~20 km round-trip EVAs, and significant time driving on slopes up to ~15°.

In response to the need to develop science-conducive architectures for future human exploration of particularly interesting targets on lunar and planetary surfaces, we have developed scenarios for a geological expedition to Marius Hills within current constraints of week-long sortie missions. This area has a dense nest of volcano-tectonic features representing the range of mare volcanic structures, which is one of the reasons why it is so compelling. Two distinct episodes of flood basaltic volcanism are represented, along with volcanic shields, domes, cones, rilles, wrinkle ridges, floor fractures, and a magnetic swirl anomaly. We found two potential landing sites (constrained to 10 km radius) in the southwestern portion of Marius Hills that would allow access to examples of most of the features of interest. We describe the geological context, resulting investigations, daily traverses, and survey/sample sites along those routes, in detail, as well as the required tools, instruments, and surface activities. The resulting science requirements, for a minimum of two rovers plus a few hundred kilograms of science payload, along with implications for a science-conducive architecture, are considered.

The Schrödinger impact basin near the southern pole on the lunar farside (134°E, 75°S) is a young multiring impact basin, and it is well preserved and exposed for scientific study. A crewed sortie-reconnaissance mission to Schrödinger Basin would allow (1) collection of samples in order to obtain an absolute age date for the Schrödinger impact event and to constrain the ages of volcanic events, (2) detailed analysis of pyroclastic materials that mantle the basin's impact melt sheet, (3) study of lunar explosive volcanism mechanics, and (4) installation of a passive seismic array for study of interior activity. The region's diversity of geologic materials and features make it a prime target for human and robotic exploration. A landing site located within the pyroclastic deposit (139.6°E, 75.7°S) allows access to the volcanic vent and inner ring of the basin. Sampling the inner ring, which may be composed of South Pole–Aitken Basin uplift material, would allow absolute dating of the South Pole–Aitken Basin event. Engineering objectives necessary for extending surface stay time for sortie missions or a lunar outpost can be met at this locale. Pyroclastic material is optimal for in situ oxygen production. Demonstrating oxygen production and storage at the landing site would prove technologies for an outpost and leave a cache of consumables for use by future longer-term expeditions. Mission planning is based on Lunar Reconnaissance Orbiter , Lunar Orbiter , Clementine , and SELENE mission data. Extravehicular activities necessary for completing the science objectives require long traverses (24 km and 7.5 h per traverse) for a four-member crew over a 4 d mission.

The motivation for this study was to create lunar surface exploration scenarios that would support current science needs, as captured in the Lunar Exploration Analysis Group (LEAG) Roadmap for Lunar Exploration. A science-driven capability to meet those needs required enhanced capability, relative to the Apollo J missions, to provide a broader field context for (1) improved interpretation of samples and measurements; (2) greater flexibility in the selection and nature of activities at field stations; as well as (3) greater potential for breakthrough science. Here, we offer advanced regional-scale (hundreds of kilometers) surface exploration scenarios, essentially design reference missions, for three high-priority targets representing the broadest differences in the nature and distribution of geological features. South Pole–Aitken Basin is the largest and oldest confirmed lunar impact basin. Covering most of the farside southern hemisphere and >2000 km in diameter, it contains extraordinarily diverse features and geochemical anomalies that are widely scattered and thus would require several regional-scale missions. Tsiolkovsky is an anomaly among farside craters: It is mare-filled in the thickest portion of farside crust, young, and has well-preserved impact structures, yet it is surrounded by the ancient Tsiolkovsky-Stark Basin. Aristarchus Plateau is a tectonically uplifted plateau associated with the formation of Imbrium Basin, and it is found on a concentric ring of basin. Features encompassing the entire range of mare volcanism activity in style and age are found either on the relatively compact plateau or within hundreds of kilometers in surrounding western Oceanus Procellarum. Our regional-scale architecture would allow science objectives for study of Aristarchus Plateau or Tsiolkovsky to be addressed from one landing site conveniently located on the target, while South Pole–Aitken Basin would require several missions to achieve such objectives. We describe the geological context and resulting investigations, as well as the required tools, instruments, and activities. We assumed, as initially instructed, science need–driven capabilities at least a generation beyond the Apollo J missions, i.e., the availability of a minimum of two pressurized rovers capable of hundreds of kilometers driving range at average speeds of 10–15 kph (without recharge), four crew, and 700 kg of science payload. The implications of such science-conducive architecture in the context of other architectures under consideration are discussed.

To test the lunar cataclysm hypothesis and anchor the beginning of the basin-forming epoch on the Moon, which are high science priorities for lunar exploration, we evaluated potential landing sites within Schrödinger basin. This impact site is the second youngest basin-forming event and lies within the South Pole–Aitken basin, which is the oldest and largest impact basin on the Moon. Thus, landing sites within Schrödinger should provide access to impact lithologies with ages of each event, providing a bracket of the entire basin-forming epoch and resolving both of the leading science priorities. Additionally, the floor of Schrödinger basin has been partially covered by younger mare and pyroclastic units. The volcanic materials, as well as impact-excavated and uplifted units, will provide chemical and lithologic samples of the lunar crust and potentially the upper mantle. Collectively, the impact and volcanic lithologies will provide calibration points to the entire lunar stratigraphic column.