Open questions in lunar science (invited talk)
Authors: Head James 
Published: July 2021

The Earth&#8217;s Moon is a cornerstone and keystone in the understanding of the origin and evolution of the terrestrial, Earth-like planets.&#160; It is a cornerstone in that most of the other paradigms for the origin, modes of crustal formation (primary, secondary and tertiary), bombardment history, role of impact craters and basins in shaping early planetary surfaces and fracturing and modifying the crust and upper mantle, volcanism and the formation of different types of secondary crust, and petrogenetic models where no samples are available, all have a fundamental foundation in lunar science.&#160; The Moon is a keystone in that knowledge of the Moon holds upright the arch of our understand of the terrestrial planets. It is thus imperative to dedicate significant resources to the continued robotic and human exploration of this most accessible of other terrestrial planetary bodies, and to use this cornerstone and keystone as a way to frame critical questions about the Solar System as a whole, and to explore other planetary bodies to modify and strengthen the lunar paradigm.&#160;&#160;&#160;What is the legacy, the long-term impact of our efforts? The Apollo Lunar Exploration Program revealed the Earth as a planet, showed the inextricable links of the Earth-Moon system, and made the Solar System our neighborhood. We now ask: What are our origins and where are we heading?: We seek to understand the origin and evolution of the Moon, the Moon&#8217;s links to the earliest history of Earth, and its lessons for exploration and understanding of Mars and other terrestrial planets. A basis for our motivation is the innate human qualities of curiosity and exploration, and the societal/species-level need to heed Apollo 16 Commander John Young&#8217;s warning that &#8220;Single-planet species don&#8217;t survive!&#8221;. These perspectives impel us to learn the lessons of off-Earth, long-term, long-distance resupply and self-sustaining presence, in order to prepare for the exploration of Mars and other Solar System destinations.&#160;Key questions in this lunar exploration endeavor based on a variety of studies and analyses (1-3) include:-How do planetary systems form and evolve over time and when did major events in our Solar System occur?How did planetary interiors differentiate and evolve through time, and how are interior processes expressed through surface-atmosphere interactions?-What processes shape planetary surfaces and how do these surfaces record Solar System history?-How do worlds become habitable and how is habitability sustained over time?-Why are the atmospheres and climates of planetary bodies so diverse, and how did they evolve over time?-Is there life elsewhere in the Solar System?Specific lunar goals and objectives will be outlined in this broad planetary science context.&#160;References: 1. Carle Pieters et al. (2018) http://www.planetary.brown.edu/pdfs/5480.pdf, 2. Lunar Exploration Analysis Group, https://www.lpi.usra.edu/leag/. 3) Erica Jawin et al. Planetary Science Priorities for the Moon in the Decade 2023-2033: Lunar Science is Planetary Science.