Abstract

The exploration of the Moon involves multiple and complex competing interests, including those of nation states and commercial entities. This article identifies important science questions whose answers may be obscured by human activities on the Moon. We aim to encourage follow-on work to produce environmental impact assessments for various lunar activities in order to understand the degree of contamination generated by different processes. We also encourage the preservation of scientifically important regions, as proposed by others (e.g., National Academies of Sciences & Medicine, 2020; Farrell et al., 2021; Krolikowski, 2023). In the following sections, we discuss what measurements are necessary to determine how and where science investigations and exploration (commercial or otherwise) can be carried out concurrently. We advocate a strategy of concurrent exploration and science where possible, and for a science-first approach in cases where exploration may obscure scientific evidence that is uniquely preserved on the Moon.

1. The scientific value of the Moon

The first question that has to be answered is “why go to the Moon”. Is the purpose to establish a permanent human presence on the Moon, as a stopping-off place for Mars exploration, for National Defense, for mining of valuable resources, for scientific discovery and as a platform for scientific endeavors, or just because we can? The Moon has been discussed as a base for scientific endeavors for decades, including for geology, basic physics and astronomy (Potter & Wilson, 1990; Wilson, 2005). Potter & Wilson stated that physics and astrophysics from a lunar base encompasses space physics, cosmic ray physics, neutrino physics, experiments in gravitation and general relativity, gravitational radiation physics, cosmic background radiation, particle astrophysics, surface physics, and the physics of gamma rays and X-rays. Specific issues include space-plasma physics research at a lunar base such as medium- and high-energy neutrino physics from a lunar base, muons on the Moon, a search for relic supernovae antineutrinos, and the use of clocks in satellites orbiting the moon to test general relativity. Also addressed are large X-ray-detector arrays for physics experiments on the Moon, and the measurement of proton decay, arcsec-source locations, halo dark matter and elemental abundances at a lunar base. It is clear that planning is necessary, as large-scale exploration can go hand-in-hand with science, or it can destroy the very evidence that scientists seek.

2. Science Questions whose answers are held in the lunar environment

The Committee on the Scientific Context for Exploration of the Moon (National Research Council, 2007) prioritized science goals that can be addressed during the early stages of lunar exploration. The LEAG (Lunar Exploration Analysis Group) report: Advancing Science of the Moon (2017) argues that answers to the following science questions (Table 1) are held in the lunar environment. Given that lunar exploration will inevitably affect the resources in which the answers to these questions are held, we have assigned a rating for the human effect on each. If the human effect is assumed to be none or unknown the rating is "none"; possible or uncertain human effect is "possible", and definite human effect is "definite". Those effects with either a possible or definite human effect are discussed further in subsections 2. Some of these processes, such as the study of weathering processes, on the one hand may be affected by human activity, but on the other hand are enabled by human activity. In addition to the concepts outlined in the LEAG report, we discuss the origin of life as evidenced by biotic and pre-biotic molecules found on the Moon. High-priority goals that are required to be accomplished while the environment remains in a pristine state involve processes with the atmosphere and dust environment of the Moon. In order to understand whether the volatiles sequestered at the lunar poles were emplaced by a one-time cataclysmic event or are in dynamic equilibrium with ongoing processes, we require measurements before the atmosphere and the polar volatiles are disturbed by human landings. Recent studies of the contamination of the lunar atmosphere and polar volatiles by human activity on the Moon quantify those statements (Farrell et al. 2024; Killen, Sprague, & Farrell, 2024).

We have classified these science concepts according to whether their perceived relevant scientific evidence will be affected by human activities on the Moon, giving a value of none, possible or definite. Those processes with possible or definite effects are further discussed in subsections of section 2.1 - 2.6.

2.1 Processes manifested in crustal rocks

The Moon holds a repository of the history of the Earth-Moon system, whereas that history has been largely erased on Earth by the very processes that render Earth livable: active geological processes. The Moon may have a reservoir of implanted frozen volatiles that gives clues to how the Earth formed and how organics were delivered. The current level of depletion of moderately volatile elements constrains both the history of the solar rotation rate and the early lunar magnetic field (Saxena et al., 2019). The depletion of moderately volatile elements that is observed in lunar samples is consistent with only certain scenarios of the influence of solar wind/CME driven loss over time. Organics have mostly accumulated from meteorites and thus provide a historic record of contributions from meteoroids. Will it be possible to identify cometary organics and meteoritic organics vs. human organics once humans enter the lunar space? Are they preserved or lost? Details of the lunar subsurface reservoir – its content and depth - are important, not just for science but also for future human habitation. These details can easily be lost - for instance by dust disturbed by human activity, by rocket plumes, and by mining activity. On the other hand, mining interests and scientific interests can work hand-in-hand to determine the details of the reservoirs. We therefore should carefully plan these activities so that we don't destroy the evidence we seek.

2.2 Lunar polar volatiles as witness to the history of volatile flux: The case for studying polar volatiles before mining operations begin.

Can human activity on the Moon affect the measurement of water and other C and S species in the lunar cold traps?

Water is essential for life. It is also a resource for rocket fuel. By splitting the H₂O molecules into hydrogen gas molecules (H₂) and oxygen gas molecules (O₂) with an electrolyzer, and then compressing and liquefying both of those gases separately, fuel can be synthesized. O₂ is the oxidizer most commonly used in liquid-fueled rocket engines (Leucht, 2018). On the other hand, lunar polar volatiles serve as a unique inventory of volatiles that made up the Earth-Moon system. Collection of data on pristine polar water and the polar regolith is a key science priority, and also the number one priority for exploration. Not only are polar volatiles important for human consumption and other uses like rocket fuel, but they retain a historical account of how ice deposits were emplaced over time (Hurley et al., 2012). This will tell us whether the ice is replaceable, and if not, how long will it last for human consumption under what scenarios? The pristine lunar atmosphere tells us about the interaction of the interplanetary environment with the lunar surface, including the formation of water from the impinging solar wind protons, and its subsequent sequestration at the lunar polar cold traps. The rate of formation, sequestration and loss of water tells us an important piece of information: are the water ice reservoirs growing, in steady state, or being slowly depleted? Were the ice deposits delivered suddenly and massively by a large comet impact, slowly by meteoroid bombardment, or steadily by solar wind radiolysis? If this water is not a renewable resource, the users must develop and employ efficient recycling of water for human consumption, lunar agriculture and, most importantly, industrial processes. We need to know whether there is a lunar subsurface reservoir and if so, what is in it along with ice, and how deep is it. How much has been lost over time and how fast will it be lost during extraction? Will drilling for ice destroy the history of its emplacement? We need to know how much there is, and how stable the deposits are, before we start mining. These details can easily be lost. Thus, it is essential to study the details of the polar ice deposits before large scale mining occurs (Farrell et al., 2021). However, science and exploration can exist side-by-side as scientists gain access to drill cores, especially exploratory drill cores at different sites.

The sequestration of water from human activities in polar regions, where it is added to the native water, might be a positive effect from the standpoint of long-term occupation. However, we argue that we need to understand the native lunar environment first in order to determine the relative amounts of native and anthropogenic volatiles, and to understand whether the native water is currently in equilibrium or being naturally depleted or compounded.

Figure 1a illustrates the current model of lunar polar ice: a surface veneer of pure ice or interstitial ice (e.g. Tai Udovicic et al., 2023). Figure 1b illustrates a very deep and stable ice layer that has been in place since near the Moon’s formation (e.g. Cannon, Deutsch, Head, & Britt, 2020), similar to the thick ice/brine layer found by the Phoenix lander on Mars (Martínez & Renno, 2013). A definitive test of the origin of water on the Moon, and by inference the Earth, is the D/H ratio of lunar ice. If the D/H ratio is cometary then that implies a one-time origin of the ice. If the D/H ratio is solar, that implies a solar wind origin of the ice and continued renewal. Intermediate ratios might point to a meteoritic origin. Calculations must be made on the basis of the D/H ratio and the ice thickness and distribution to determine whether the ice is in equilibrium, shows a net accumulation rate or a net loss rate. How deep is the ice layer? Where are the ices? Are there paleo deposits associated with the former lunar poles? Are the ices contaminated?

In addition, lunar prospectors will likely want to know what the ice is made of and whether it is of a high grade—that is, not too dusty or otherwise contaminated. What contaminants are there and in what amounts? Some comets may have on the order of 5 percent cyanide in their cores (Ulich & Conklin, 1974; Matthews & Minard, 2006). In addition, Mercury (Hg) is the second most volatile species on the Moon (Jovanovic & Reed, 1972; 1982) and will undoubtedly be sequestered in the same places as the water (Hodges, 1981; Reed, 1999). Many minor species were observed in the vapor plume from the LCROSS Impact, including Co, Zn, As, Ar, and Hg (Gladstone et al., 2010). These factors are critical to know in advance of large-scale mining operations.

Although human activities on the Moon have little or no effect on the lunar interior, the pristine lunar atmosphere holds information on the deep interior through radioactive decay products, such as ⁴⁰Ar and ⁴⁰Ca from ⁴⁰K. The isotopic ratios can give us information on the source(s) of lunar volatiles, for instance comets, meteoroids, the solar wind, and the interior of the Moon. The D/H ratio found on the Moon is key to the origin of the lunar hydrogen: is it cometary, solar or endogenous? Answers to these and other questions held by the pristine lunar atmosphere will be quickly lost as massive rocket exhaust as well as slow but steady leakage overwhelms the original exosphere and surface. It is therefore essential to measure the isotopic ratios as soon as possible and at every region visited.

From the lunar volatiles, we can learn not only about the Moon but also about the Sun and its variation both on the short term and over millennia. Information on the past solar activity is preserved on the Moon and this information is fragile. Short term variation of the solar and galactic radiation is vitally important to assess risk to astronauts as well as instruments on and around the Moon. This must be assessed, and predictive methods need to be improved before large scale habitation can be undertaken. A 5-meter core sample taken before large scale mining operations would be a vital resource to scientists interested in the origin and evolution of the solar system (Crider & Vondrak, 2003).

Prem and Hurley (2019) showed that a Chang’e 3-class lander can increase the local exosphere density by several orders of magnitude. The molecular concentrations in the exosphere and regolith will change progressively as the frequency and type of landers increase. Spacecraft outgassing observed by the Bepi Colombo in spectrometers was dominated by water molecules, and was observed not only during the Mercury flybys but also during cruise phase (Fränz et al., 2024). Outgassing by the Rosetta spacecraft (Schläppi et al., 2010) maintained a permanent thin gas cloud around the spacecraft for many years, dominated by water, but also containing hydrocarbon compounds, nitrogen-bearing compounds, halogen and sulfur-bearing molecules. As instruments warm, the outgassing increases. The rovers, landers, astronaut backpacks and clothing will all contribute background gas that will eventually be trapped in the regolith and ice. Farrell et al. (2024) reported that the Starship landing plume has the potential, in some cases, to deliver over 10 T of water to the Permanently Shadowed Regions (PSRs), which is a substantial fraction (possibly > 20%) of the existing intrinsic surficial water mass. This anthropogenic contribution could possibly overlay and mix with the naturally occurring icy-regolith at the uppermost surface.

2.3 The Moon as a platform for studying solar system history

Lunar landings result in dust and small rocks being blown away to great distances, as well as the production of small craters under the rocket plume (Metzger, 2020; Watkins et al., 2021). These results depend to a large extent on the size and configuration of the rocket nozzles, the timing of the thrust, and the underlying regolith density and structure. In addition to small impact craters, there are other chronological signatures of lunar evolution that may not be as obvious or accessible from Earth or orbiting platforms, and these may be at risk, not only from collateral damage from exploration in the interest of science but by exploitation of resources (Scotkin, Beard, & Kuhns, 2022). Signatures of lunar history that may be destroyed include bombardment, especially by small impactors (Holcomb, Mandel, & Wegmann, 2023), volcanism, CME (Coronal Mass Ejection) and SEP (Solar Energetic Particle) frequency with time (Phipps et al., 2022), and evidence of the history of the lunar paleo-magnetic field (Suavet et al., 2013; Saxena et al., 2019).

2.4 The Moon as a laboratory for studying regolith processes

The study of regolith processes can be accomplished through means of modeling, remote sensing observations, laboratory experiments, and returned sample analyses (from the Apollo era and other spacecraft) (Papike, Simon, & Laul, 1982; Schreiner, Dominguez, Sibille, & Hoffman, 2016; Metzger, Anderson, & Colaprete, 2018). The anthropogenic processes that may influence the volatiles and dust would certainly be another challenge when collecting regolith and volatile samples. Rovers, landers, ascent – descent vehicles, and human activity (e.g., mobility, tool usage, etc.) would have several influences on the lunar regolith environment: (i) dust transport; (ii) outgassing; (iii) electricity; (iv) regolith porosity.

Dust transport through rover and astronaut mobility and use of tools also pose an interesting challenge of electrical discharge. Such discharge may depend on the tool used, but influence of electrical and magnetic output from these tools (and scientific payloads in general) would need to be monitored at the lunar surface. The interactions between the ambient space plasma environment and crustal magnetic fields (Halekas, Saito, Delory, & Farrell, 2011; Halekas, Brain, & Holmström, 2015), as well as electrostatic fields at the lunar surface (Zimmerman, Farrell, Stubbs, Halekas, & Jackson, 2011; Stubbs et al., 2014; Fatemi et al., 2015) are still poorly understood, especially at the lunar poles or lunar swirls (which is also a region of interest for future exploration, Robinson et al., 2018). Such anthropogenic interactions of rovers and scientific equipment may disrupt the ambient, natural lunar environment. This may inadvertently disrupt solar wind interactions through varying degrees of charged dust enhanced by human and robotic activity, which in turn may transport energetic particles (from stated exploration activity) to the regolith, volatiles (causing more insulation from dust coverings), and potentially lunar swirls (Jackson et al., 2011; Futaana et al., 2013; Haviland, 2021; Cucinotta & Saganti, 2023; Lorenz, Basilevsky, Dolgopolov, & Kozlova, 2023).

Dust transport through anthropogenic activity is a challenge on several factors to exploration. Dust can be mobile through walking movements, roving, tools (such as drills), and ascent/descent vehicle activity (Cain, 2010; Pan, 2024). This includes hazards on many levels, such as to astronaut health, decrease in power (e.g., solar cell) efficiency (Katzan & Edwards, 1991), coverings (which can also be a tripping hazard) and decreasing efficiency in tool usage, and decrease in suit capabilities.

Outgassing of materials, whether through the ascent/descent stages of lunar vehicles, rover or astronaut suit depressurizing, may cause an effect of unwanted accumulation of volatiles at the surface. This is especially important at (or proximal) to PSRs at the lunar poles. Astronaut suits produce some level of oxygen outgassing (Helou, Wang, & Brieda, 2022), which may transport and condense in these PSRs, even in micro-cold traps (Glavin et al., 2010).

Regolith porosity is an important parameter in light scattering, and sputter yield with incidence angle. The highly porous extreme surface is easily destroyed by rovers, dust and rocks thrown out by landers, and astronaut maneuvers. Care should be taken especially at high latitude regions and near the lunar swirls where “fairy castle” surfaces are possible.

2.5 Processes involving the atmosphere and dust environment

Temporary atmospheres result from various anthropogenic sources. Table 2 below lists the anthropogenic sources and their compositions. Depending on the frequency of each type of source, the anthropogenic atmosphere will be temporary or permanent. In addition to the atmosphere, the European perspective on lunar exploration (Flahaut, van der Bogert, Crawford, & Vincent-Bonnieu, 2023) also prioritizes study of electrostatic lofting of dust associated with plasma anomalies and voids, and its changes due to surface activities.

Killen, Sprague, & Farrell, (2024) estimated the composition and column abundance of exospheres created by outgassing from human sources on the Moon (Table 3). These include astronaut backpacks, airlocks, mining of water ice to produce oxygen, trash incineration, rovers and landers. Water is the most abundant source from outgassing, but other sources include O₂ and N₂ from airlocks, and CO₂, CO, and CH₄ from trash. Large rocket plumes are either purely H₂O or a mix of H₂O , CO, and CO₂. Small rocket plumes include H₂O, N₂, CO₂ and CO. All of these sources produce temporary exospheres that may contaminate the search for the pristine exosphere, most notably the indigenous water. H₂O, O₂ and N₂ anthropogenic sources are much greater than the pristine exosphere, although they are local and transient. However, the exospheric species are presumed to temporarily stick to the surface, and will subsequently evaporate and random walk to the cold traps near the lunar poles (e.g. Jones, Aleksandrov, Hibbitts, Dyar, & Orlando, 2018).

At least five electrical phenomena are in need of further study before large scale human activity commences on the Moon. These include (1) natural solar wind-induced charging on the sunlit side caused by the photoelectric effect that produces a positive charge on the dayside; (2) natural charging of the dark side or in shadows; (3) anthropogenic triboelectric charging of equipment, structures and spacesuits (e.g. Stubbs, Vondrak, & Farrell, 2007) a known phenomenon but poorly understood for the lunar environment; and (4) the terminator expression of these charging effects, also a poorly understood phenomenon, especially with respect to the various changing solar conditions. There is no equivalent of Earth for grounding on the Moon, especially in cold regions (Rhodes, Farrell, & McLain, 2020).

Study of the electrostatic environment on the Moon is of vital importance, not only for the science content but because of the threat of charging – and discharging – to astronauts and their equipment (Zimmerman et al., 2011; Jackson et al., 2011; Rhodes, Farrell, & McLain, 2020). A comprehensive study of several locations near the polar regions is required to learn how to protect machinery and astronauts.

2.6 Science Questions: Organics

2.6.1 Lunar Organics Are Clues to the Origin of Life

The origin and proliferation of life in our solar system is a profound question that continues to be one of the most important avenues of scientific inquiry. On Earth, historical records of this process have been all but wiped out due to active geological processes and the wide reaches of biological activity (Fedo & Whitehouse, 2002; Lepland, van Zuilen, Arrhenius, Whitehouse, & Fedo, 2005). The Moon, however, holds a repository of the history of the Earth-Moon system (Armstrong, 2002; Crawford, Baldwin, Taylor, Bailey, & Tsembelis, 2008) preserved in dry vacuum conditions. At the poles, the Moon may have a reservoir of implanted frozen volatiles (Basilevsky, Abdrakhimov, & Dorofeeva, 2012) that gives clues to how the Earth formed and how organics could have proliferated throughout our solar system (Matthewman et al., 2015). Such knowledge is important in the search for the origin of life. A recent study reported the possible existence of niches
near the South Pole in which microbes can survive (Saxena et al., 2023a).

It is therefore of incredible importance that the evidence described above is available for careful study. Human activity on the Moon, if not performed with care, threatens to compromise the integrity of precious evidence that could point to the origin of life. Many profound scientific questions depend on the availability of pristine lunar samples: Did organics survive on the Moon and to what extent can they survive today? Is there a pre-biotic inventory sequestered in the ice? In 2008, COSPAR re-catagorized the Moon to Category II, for bodies where " there is significant interest relative to the process of chemical evolution and the origin of life, but where there is only a remote chance that contamination carried by a spacecraft could compromise future investigations." But is this the case? Are there niches where biotic and/or prebiotic molecules survive on the Moon? Will biota that do survive on the Moon prove to be harmful to astronauts, human, plant, and animal species, and does this imply that life can survive on the Moon? There are indeed conditions where biological and/or prebiotic molecules might persist on the surface of the Moon (Glavin et al., 2010; Saxena et al., 2023a). Likewise, spores could also survive (although not grow or be metabolically active) lunar conditions (Gronstal et al., 2007), representing a contamination risk for certain astrobiological investigations and perhaps one day pose a harm to astronauts. It must be stressed that survivability does not imply reproducibility. Lunar polar regions may provide an inventory of volatiles and possibly pre-biotic organic materials carrying evidence for the formation/evolution of life. Even the absence of significant amounts of organics would be a profound finding that will spur better understanding of the origins of life. We argue that keeping that evidence relatively uncontaminated by future lunar landings until the inventory can be measured is therefore crucial.

2.6.2 Important Historical Records in Lunar Organics

Besides holding key information about the proliferation of organic matter and even life in the Solar System, the detection of organic molecules on the Moon has important implication for other aspects of our Solar System’s history. The current level of depletion of moderately volatile elements constrains both the history of the solar rotation rate and the early lunar magnetic field (Saxena et al., 2019). Organics have been thought to have mostly arrived from meteorites and interplanetary dust (Alexander et al., 1998; Quirico, Raynal, & Bourot‐Denise, 2003; Thomas-Keprta et al., 2014) and thus provide a historic record of contributions from meteoroids. Will it be possible to identify cometary organics and meteoritic organics vs. human organics once humans enter the lunar space? Are they preserved or lost? Details of the lunar subsurface reservoir – its content and depth - are important, not just for science but also for future human habitation. These details can easily be lost - for instance by dust thrown up by human activity, by rocket plumes, and by mining activity. On the other hand, mining interests and scientific interests can work hand-in-hand to determine the details of the reservoirs. We therefore should carefully plan these activities so that we do not destroy the evidence we seek.

2.6.3 Implications for Human Habitation of the Moon

Will humans introduce bacteria or other organisms that will survive on the Moon and other planetary bodies? Studies designed to search for biologically-derived organic compounds could provide ground truth data and help define planetary protection requirements for future missions to the Moon and Mars (Glavin et al., 2010). Habitable niches for bacteria were proposed to exist at the lunar poles (Saxena et al., 2023a). A variety of microorganisms have been found to survive the harsh conditions outside the International Space Station (Deshevaya et al., 2024), further raising the stakes for possible cross-contamination. There is therefore a significant need to understand not only the possible impact that human presence can have on organics on the Moon, but also the impact that the survival of organics and even organisms on the Moon could have on human inhabitants. These are not only scientifically important, but also existential questions that we need to address prior to human habitation.

2.6.4 Space Policy

Before large scale contamination happens, it is necessary to address scientific questions, the answers to which are held at the surface and near surface of the Moon (National Academies of Sciences & Medicine, 2020). Who makes the priorities and who enforces them? In response to the burgeoning space race, the UN created the Committee on Peaceful Uses of Outer Space (COPUOS) in 1959, which has been the primary forum for international agreements relating to outer space. The Outer Space Treaty (i.e. Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies) was signed in 1967. Subsequently the United Nations so-called Moon Treaty (Agreement Governing the Activities of States on the Moon and Other Celestial Bodies) went into force in 1984.  However, as of January 2022, only 18 states are parties to the treaty and only 7 have ratified the treaty. The United States and other major Space Faring nations have not signed the treaty. That treaty exists to "maintain the Moon in pristine conditions for the common heritage of mankind".  However, it leaves it up to the 'Member States'—those nations who have adopted the treaty—to create a framework of laws to facilitate the 'safe and orderly' commercial use of space resources, "at such time when such regulations become necessary". The Moon Treaty does not mandate any specific regulation for space commerce. Continuing disagreements involve the rights of member states to the natural resources of the Moon. The latest treaty with respect to activities on the Moon was "The Declaration on International Cooperation in the Exploration and Use of Outer Space for the Benefit and in the Interest of All States, Taking into Particular Account the Needs of Developing Countries", adopted in 1996. These treaties have significant challenges, including compliance, international cooperation, the advent of commercial interests and scientific innovations, and conflicts of interests, specifically between commercial and scientific interests. The US Commercial Space Launch and Competitiveness Act of 2015, which would have legalized space mining, was never passed into law. Thus, this activity lies in a legal void.

3. Conclusions: Last Chance for the Moon

We define the beginning of the Anthropocene for planet Earth (Lewis & Maslin, 2015) as having a geological signature containing a radiation level in sediments worldwide created by nuclear bomb testing in the middle of the last century. The Moon is about to enter its own Anthropocene (Holcomb, Mandel, & Wegmann, 2023) which might be marked by one of our study areas. This could be a dust layer containing hydrazine chemistry that becomes ubiquitous on the Moon. Potential sources of contamination during the Apollo missions were noted by Simoneit and Flory (1971), including dimethyl hydrazine and nitrogen tetroxide, lunar module outgassing, astronaut spacesuit venting of life support backpacks, particulates from spacesuits, and venting from the lunar module fuel and oxidizer tanks. Water extracted from lunar soils collected by the Apollo astronauts was determined to be of terrestrial origin (Epstein & Taylor, 1972).

The Moon as a platform for scientific investigations has been widely discussed (e.g., Flahaut, van der Bogert, Crawford, & Vincent-Bonnieu, 2023). It has been suggested that activities on the Moon should prioritize the unique opportunities for science that exist there (Krolikowski, 2023). She states "We need rules to guide who does what." Crawford, Prem, Pieters, & Anand (2022) have suggested that the best compromise between scientific investigation and commercial exploration and utilization of resources would be to place a moratorium on activities at the North Pole until the full consequences of human activities at the South Pole are understood. In addition, we suggest that a moratorium be placed on use of frequencies on the far side of the Moon that would interfere with radio and astronomical observations. Important scientific questions whose answers are held in the pristine Moon include the early Earth history, organic reactions in ices, and the origin or organics brought in by meteoroids.

What should we seal off from human presence on the Moon, and how will that be different at Mars? Moon restrictions (Special Regions) need to be kept pristine (Kelso and O'Leary 2011). However, it is recognized that it is a matter of degree what it means to be pristine, and to what degree this is possible, since gases travel quickly around the globe and dust does something similar. Given that rapid deterioration is almost certain once spacecraft landings on the Moon become routine, lunar science missions such as VIPER should be prioritized.

We advocate planetary conservation for the Moon, meaning the proper use of natural resources. Actions that need to be limited or contained long enough to understand and mitigate threats to the science topics noted above include but are not limited to:

Short to medium term particulate contamination of the exosphere/spacecraft plumes (i.e. dust, pebbles and rocks) is caused by erosion of regolith by spacecraft engines, construction, mining and or quarrying. It physically alters the surface physics and chemistry of the region. The dust hazard is global, and the projectile hazard is local.

Rocket fuel contamination of the environment. Non-reversible chemical reactions with water and other surface compounds pollute the environment.

Physical disturbance of geological features and regolith by astronaut tramping, rovers, landers and other vehicles and machinery transform the geological environment and erase scientifically important data.

Chemical contamination of regolith and PSRs by rocket exhaust, machinery, vehicles, and human and industrial waste is an irreversible process.

In his Sept. 12, 1962, speech at Rice University, John F. Kennedy said, "We set sail on this new sea because there is new knowledge to be gained, and new rights to be won, and they must be won and used for the progress of all people."  Let us go forth in the spirit of acquiring knowledge to be used for the progress of all mankind.

Acknowledgments

This work was supported by the NASA Solar System Exploration Research Virtual Institute, United States (SSERVI LEADER: Lunar Environment and Dynamics for Exploration Research).Yeo's research was supported by an appointment to the NASA Postdoctoral Program at the NASA Goddard Space Flight Center, administered by Oak Ridge Associated Universities under contract with NASA. C. Ahrens and P. H. Phipps were supported by NASA's Lunar Reconnaissance Orbiter (LRO) award number 80GSFC21M0002.