Two months ago, on 5 December 2014, NASA launched the first test flight—uncrewed—of its next-generation Orion crew vehicle, which was propelled to an altitude about 15 times higher than the International Space Station. Orion then returned to Earth at 80% of the speed of a spacecraft returning from the Moon.
The success of the mission, including Orion’s atmospheric reentry and recovery, provides an opportunity to revitalize an integrated robotic and human exploration program to the Moon and beyond.
Why Go Back to the Moon?
Current lunar orbiters, supplementing the insights from Apollo and the missions before it, indicate the Moon is the best and most accessible place to evaluate the origin and evolution of the entire solar system. This evaluation could include new insight on the earliest evolutionary phases of our own planet, which through plate tectonics, crustal recycling, and constant weathering, have since been erased from Earth’s rock record.
The Moon contains evidence of how it formed through accretion and differentiated into layers of crust, mantle, and core, which is a model for the origin and evolution of other solar system planets. It also records the history of asteroid and comet impacts on that crust, which is essential to evaluating the environmental and biological consequences of such events, both on Earth and on other potentially habitable worlds such as Mars.
Target: South Pole–Aitken Basin?
A 2007 report from the U.S. National Research Council (NRC)—one of the most comprehensive studies of lunar exploration objectives—outlined 35 prioritized investigations. A global landing site study [Kring and Durda, 2012] concluded that the majority of the objectives could be addressed in the Moon’s South Pole–Aitken basin.
At 2500 kilometers across, South Pole–Aitken is one of the largest impact basins in the solar system. Within it, the 320-kilometer-wide Schrödinger basin holds the most promise for finding scientific pay dirt. A sample return mission to Schrödinger has the potential to address the two highest science priorities from the NRC  report. First, it could determine the length of the basin-forming epoch—the geological period in the Moon’s early history when objects that formed enormous basins like South Pole–Aitken smashed to the surface. Second, samples from Schrödinger could help determine the age of South Pole–Aitken.
In addition, because the basin is so well preserved, it is a perfect target for discerning the geological processes of such impacts. Those processes also uplifted material from great depth, producing a ring of crystalline massifs. These exposed layers of rock may date back to when, according to a prevailing hypothesis, the Moon was covered by a magma ocean.
That material, when combined with material exposed in the basin walls, can be used to reconstruct a cross section of the lunar crust. The melted rock on the floor of Schrödinger basin can be used to derive the bulk composition of that crust.
Scientists think that long after the impact melt solidified, magmas rose through the basin and erupted on its floor, producing mare basalt flows and an immense vent spewing hot rock and gas. The basalt and pyroclastic vent can also be used to probe the thermal evolution of the lunar interior. The pyroclastic vent may also yield deposits of volatiles (such as sulfur and water) and fine-grained material that can easily be excavated, transported, and processed for use on the Moon to support a sustainable exploration effort.
Toward Sample Return Missions
To adequately address the NRC  lunar objectives, sample return missions are required. The best results and those that maximize the advantages of an integrated robotic and human exploration program would be obtained by a trained crew on the lunar surface.
In pursuit of that type of integrated program, robotic efforts from many nations are underway. China recently landed a robotic spacecraft in Mare Imbrium as a precursor to a human landing scheduled for 2025–2030. Russia is planning a series of five robotic spacecraft, including a sample return mission that may involve the European Space Agency. Those efforts are part of an international community road map [International Space Exploration Coordination Group, 2013] that includes a human-assisted robotic sample return mission circa 2024 and a human lunar surface mission circa 2028.
Unfortunately, new lunar landers have yet to be designed, meaning that the world no longer has the capability to land crew on the Moon’s surface. To accomplish sound science without this capacity, researchers are developing plans for an alternative (and hopefully interim) solution combining robotic and human capabilities.
A Robotic Moon Lander Complemented by a Hovering Orion?
Burns et al.  outlined a plan to deploy robotic vehicles—a Moon lander—to Schrödinger basin that could be operated remotely by a crew in the Orion spacecraft. In this plan, Orion would hover above the Moon’s farside around Earth–Moon Lagrange position L2.
Candidate landing sites with traverses, along which a rover would collect samples and return them to the ascent vehicle, have already been identified [Potts et al., 2015]. This vehicle would then rendezvous with Orion so that crew could return the samples to Earth.
This mission would present technical challenges that scientists and engineers will need to solve as part of the redevelopment and expansion of capabilities to explore beyond low-Earth orbit. It would also demonstrate Orion’s capabilities to conduct long-duration operations, traveling 15% farther than Apollo and spending three times longer in deep space. It would practice teleoperation of rovers, which is an anticipated skill for future missions to Mars. It would also simultaneously address a majority of the NRC  science objectives.
This mission or a similar one could deploy an astrophysical observatory, another high-priority NRC  objective, and a communications satellite for future robotic and human missions. Joint scientific and engineering studies continue with the hope that this integrated robotic and human mission will be the first of many milestones that enhance our ability to explore space.
For more details on the history of human and robotic partnerships to explore the Moon, read the companion Eos story, “How Robotic Probes Helped Humans Explore the Moon—And May Again.”
The author thanks two anonymous reviewers. The work was supported, in part, by NASA through the Lunar and Planetary Institute (LPI) and the LPI-JSC Center for Lunar Science and Exploration. This is LPI contribution 1834.
Burns, J. O., D. A. Kring, J. B. Hopkins, S. Norris, T. J. W. Lazio, and J. Kasper (2013), A lunar L2-farside exploration and science mission concept with the Orion multi-purpose crew vehicle and a teleoperated lander/rover, J. Adv. Space Res., 52, 306–320.
International Space Exploration Coordination Group (2013), The Global Exploration Roadmap, Rep. NP-2013-06-945-HQ, NASA, Washington, D. C.
Kring, D. A., and D. D. Durda (Eds.) (2012), A Global Lunar Landing Site Study to Provide the Scientific Context for Exploration of the Moon, Contrib. 1694, 688 pp., Lunar and Planet. Inst., Houston, Tex.
National Research Council (NRC) (2007), The Scientific Context for Exploration of the Moon, Natl. Acad. Press, Washington, D. C.
National Research Council (NRC) (2010), New Worlds, New Horizons in Astronomy and Astrophysics, Natl. Acad. Press, Washington, D. C.
Potts, N. J., A. L. Gullikson, N. M. Curran, J. K. Dhaliwal, M. K. Leader, R. N. Rege, K. K. Klaus, and D. A. Kring (2015), Robotic traverse and sample return strategies for a lunar farside mission to the Schrödinger basin, Adv. Space Res., 55, 1241–1254.
David A. Kring, Lunar and Planetary Institute, Universities Space Research Association, Houston, Texas; email: firstname.lastname@example.org
Citation: Kring, D. A. (2015), Human and robotic missions: To the Moon again and beyond, Eos, 96, doi:10.1029/2015EO024609. Published on 20 February 2015.
Text © 2015. The authors. CC BY-NC 3.0
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