MOON VILLAGE Why we should build a Moon village

Ian Crawford explains how science would benefit from a human outpost on the Moon.

he director general of the European kind of transportation and other infrastruc- Specific planetary science activities that Space Agency, Jan Wörner, has sug- ture required to establish a Moon village would benefit from such a lunar surface Tgested that the creation of a human– would likely facilitate human and robotic infrastructure include (see e.g. NRC 2007, robotic lunar outpost would be a logical operations at locations that may not be local Crawford & Joy 2014, Neal et al. 2014, and next step in human space exploration to the village itself. Moreover, references cited therein) (e.g. Wörner & Foing 2016). The creation in the fullness of time, just as “The lunar geological inner solar system bom- of such a Moon village (figure 1) would in Antarctica today, we might record still has much to bardment history, impact offer significant scientific opportunities by envisage multiple such out- tell us about the early cratering processes, the lunar providing an infrastructure on the lunar posts at different locations. solar system” interior including volatile surface, analogous to the way that human With these caveats in mind, content, regolith processes outposts in Antarctica (figure 2) facilitate we here address the major areas of science and serendipitous discoveries. research activities across multiple scien- that would benefit from the scientific infra- The lunar cratering rate is used to tific disciplines on that continent. In the structure represented by a Moon village. estimate the ages of cratered surfaces case of a Moon village, scientific fields that throughout the solar system, but it is not might benefit include planetary science, Planetary science well calibrated (e.g. Robbins 2014). Improv- astronomy, astrobiology, life sciences and As discussed by Crawford & Joy (2014), ing this calibration is a key objective of fundamental physics (e.g. Taylor 1985, the lunar geological record still has much planetary science, and requires sampling Ehrenfreund et al. 2012, McKay 2013, Craw- to tell us about the earliest history of the impact melt deposits from multiple (ideally ford & Joy 2014). In addition, a Moon village solar system, the origin and evolution of the hundreds) of impact craters of a wide range would help assess the economic potential Earth–Moon system, the geological evolu- of ages. In addition, recovering fragments of lunar resources, while also acting as a tion of rocky planets, and the near-Earth of the impacting bodies would reveal how market for them (e.g. Crawford 2015). cosmic environment throughout solar sys- and if the population of impactors has The extent to which different scientific tem history. Having humans operating on changed with time (Joy et al. 2012, 2016). fields would benefit from a lunar outpost the lunar surface would enable much better Accessing these materials requires a signifi- would, in part, depend on its location and access to this record, especially if supported cant transportation infrastructure (such as on the length of time for which it is occu- by a scientific infrastructure such as that pressurized rovers; figure 3) on the lunar pied. Some of the scientific areas discussed envisaged for the Moon village. A much surface, a significant sample return capacity below are more dependent on these factors wider range of rock and soil samples could and, ideally, in situ analytical instruments. than others. For example, science questions be collected, analysed (and, if necessary, Impact cratering is a fundamental plan- related to the lunar poles would clearly shipped to Earth), and the base would sup- etary process, but our understanding of it is benefit more from a polar Moon village port implementation of complex explora- limited by lack of access to pristine craters than an equatorial one. Nevertheless, the tory activities such as subsurface drilling. of a wide range of sizes. The lunar surface

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1 (Left) Artist’s impression of a Moon village. (ESA) facilitated by a human and 2 (Below) The Amundsen–Scott research station at Earth’s South Pole. robotic infrastructure on the Such outposts provide a scientific infrastructure that supports research Moon. Key aspects include in multiple disciplines (e.g. astronomy, atmospheric science, biology, low-frequency radio astron- glaciology, geology, magnetospheric physics, meteoritics and zoology) on omy, optical and infrared the Antarctic continent that would be difficult or impossible to sustain astronomy, high-energy otherwise. Lunar research stations will fulfil the same function astrophysics and funda- on the Moon. (NSF) mental physics. 3 (Right) The Lunar Electric Rover, under development by Radio wavelengths NASA. Many lunar science activities will require the ability to longer than about 10 m move away from the outpost, requiring pressurized rovers, cannot penetrate the but conversely a lunar outpost will provide the facilities to Earth’s ionosphere, yet maintain, recharge and upgrade such vehicles. (NASA) much valuable scientific information is expected to lie in this low-frequency range (e.g. Jester & Falcke 2009). The lunar farside, which is permanently shielded from the Earth, is probably the best location in the inner solar system for such observations and a human infrastructure on the Moon would assist in the setting up of the neces- sary equipment (although care would also be required to ensure that human opera- tions do not degrade the natural radio- quietness of the location). Although the Moon could in principle provide a platform for optical and infrared telescopes, there is a consensus that free- flying satellites (e.g. at the Earth–Sun L2 point) probably provide better platforms for such activities (Lester et al. 2004). It is certainly true that some aspects of the lunar surface environment (e.g. dust and, in most locations, extreme diurnal temperature clearly exhibits the required diversity of meteorites have played in delivering vola- ranges) are not ideal for astronomical obser- craters. Using these craters to improve our tile substances to the terrestrial planets. vations at these wavelengths. Nevertheless, knowledge of impact cratering processes Determining the nature and extent of these access to a scientific infrastructure able requires visiting many craters of a wide volatiles requires surface activities (includ- to emplace, maintain and upgrade such range of sizes and ages to conduct sam- ing sampling and near-surface drilling) at instruments (the value of which has been pling, geophysical surveys and, possibly, polar and high-latitude locations. demonstrated by multiple HST servicing subsurface drilling. The lunar surface is a natural labora- missions) might compensate for these dis- The Moon provides an excellent example tory for understanding space weathering advantages. Moreover, the stability of the of a small rocky body that largely preserves and regolith processes throughout the lunar surface may be enabling in the con- its internal structure from solar system, through time. text of building optical/IR interferometric shortly after its formation. As “The Moon could be Access to regoliths of differ- arrays, and permanently shadowed polar such it can provide insights a useful platform ent composition, thickness craters might enable passive cooling of IR into the early geological for astronomical and latitude are required to instruments. The pros and cons of the lunar evolution of larger and more observations” improve our knowledge of surface for optical/IR astronomy still need complicated planets. To bet- these processes. to be properly assessed and a lunar outpost ter understand the structure, composition Humans are unique in our ability to would at least facilitate such an assessment. and evolution of the lunar interior requires recognize the significance of new observa- As the lunar surface is not shielded by emplacement of geophysical tools (e.g. tions or phen­om­ena, even if they were not either an atmosphere or a magnetic field seismic networks and magnetic surveys), anticipated. Having humans living and (other than the Sun’s heliospheric mag- as well as sampling a wide range of lunar working on the lunar surface for long peri- netic field) it is an attractive location from crustal and volcanic rocks of diverse ages ods is likely to result in unanticipated dis- which to study the flux and composition and compositions. Such studies would also coveries that might not otherwise be made. of primary cosmic rays. This can also be help constrain theories of lunar origin. Although unquantifiable, such discoveries done in free space, but the existence of a There is now convincing evidence may ultimately prove to be among the most human and robotic infrastructure on the that water ice exists within permanently significant to result from a lunar outpost. lunar surface may facilitate the installation shadowed polar craters, and that hydrated of the required instrumentation. Similar materials also exist at high-latitude (but Astronomy arguments apply for gamma-ray and X-ray not permanently shadowed) localities (see The lunar surface is a potentially useful observations. Anand 2010 for a review). In addition to platform for astronomical observations Although not a major driver for lunar their possible value as resources (dis- (e.g. Burns et al. 1990, Crawford & Zarnecki exploration, several areas of fundamental cussed below), such deposits would inform 2008), and establishing the equipment physics research may benefit from the sci- our knowledge of the role comets and required for such observations would be entific infrastructure represented by a lunar

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4 Several lunar science objectives require accessing the subsurface and may require drilling to depths of tens or hundreds of metres (e.g. Crawford et al. 2010). A lunar outpost would provide the background supporting infrastructure required to enable such activities, just as Antarctic research stations are required to support scientific drilling on that continent. (NASA)

outpost. These include testing General palaeoregoliths would require extensive extent to which this process occurs and its Relativity through improved lunar laser fieldwork and, possibly, drilling to depths relevance to abiotic syntheses of organic ranging measurements (Currie et al. 2010), of tens or hundreds of metres (figure 4). molecules in planetary and interstellar ices. tests of quantum entanglement over the This is the kind of large-scale exploratory In addition, microbial spores, and con- Earth–Moon baseline (Schneider 2010), and activity that would be greatly facilitated by ceivably even live microorganisms, may searches for exotic particles (e.g. strange a human infrastructure on the Moon, just as still be present within the remains of space quark matter, dark matter, etc) interacting Antarctic research stations are required to vehicles (including Apollo lunar module with the lunar surface (Banerdt et al. 2007). support scientific drilling on that continent, ascent stages) that have crashed onto the for example, to sample biological diversity Moon (Glavin et al. 2010). Sampling such Astrobiology in subglacial lakes. localities, and determining Astrobiology is usually defined as the In addition, as pointed out “Microorganisms may what, if any, viable organic study of the origin, evolution, distribu- by Armstrong et al. (2002) and still be present within material has survived for tion and future of life in the universe. As Gutiérrez (2002), the lunar the remains of crashed decades on the lunar surface the Moon has presumably never had any surface may contain frag- space vehicles” would provide key informa- indigenous life of its own, at first sight a sci- ments of the early Earth, and tion regarding the survival entific lunar infrastructure might not seem possibly also of Mars and Venus, that pre- of life in the space environment relevant to especially relevant to astrobiology. How- date the oldest existing surfaces on those fundamental biology, planetary protection ever, we can identify the following areas of planets. Finding such material, especially and panspermia. astrobiological research that would benefit for the early Earth, could help constrain the At the other end of the astrobiology from lunar surface operations (e.g. Craw- timing of the origin and early evolution of spectrum, a scientific infrastructure on ford 2006, Cockell 2010, and references cited life on our planet and would be of consider- the Moon could help constrain the preva- therein): the early impact regime at the time able astrobiological significance. Finding lence of technological civilizations in our when life began on Earth, the evolution of such materials on the Moon would likely galaxy. There are two main routes to this: Earth’s space environment, samples of early require extensive exploratory activities and SETI could make use of radio astronomical terrestrial planet materials, and the search would be aided by a Moon village. facilities established on the Moon (e.g. Mac- for extraterrestrial intelligence. There is also the possibility that mol- cone 2004) or, more speculatively, the lunar Understanding the extent to which large ecules derived from the Earth’s atmosphere surface might be searched for artefacts of meteorite impacts may have affected the may be preserved in the lunar regolith extraterrestrial origin (Arkhipov 1998, Rose origin and early evolution of life on Earth (Ozima et al. 2008, Terada et al. 2017). If these & Wright 2004). Both would benefit from a is a key aspect of astrobiology. It would be can be identified in, and extracted from, human-tended infrastructure, but the latter addressed on the Moon as part of the wider ancient palaeoregolith layers, then they (speculative though it is) would probably calibration of inner solar system cratering have the potential to provide insights into require such an infrastructure because of rate discussed above, and would require the evolution of Earth’s atmosphere with the large surface areas that would need to sampling of ancient impact melt deposits in time. Accessing them will require the same be searched to place any meaningful limits the age range 4.5–3.8 Gyr. sort of capabilities required for extracting on the existence of any such artefacts. As discussed by Crawford et al. (2010), solar wind and GCR records from palaeo­ buried ancient regoliths are expected to regolith layers as discussed above. Life sciences contain records of the solar wind and Lunar ices also have astrobiological The lunar surface provides multiple oppor- galactic cosmic ray (GCR) fluxes throughout significance. Lunar polar ices exposed to tunities for research in the life sciences (e.g. solar system history, both of which would GCRs may be expected to form organic Gronstal et al. 2007, Cockell 2010, Carpen- inform our understanding of the past molecules (Lucey 2000). Sampling of polar ter et al. 2010, Green 2010). Most of these habitability of the Earth. Accessing such ices, as described above, would indicate the studies are not dependent on the physical

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5 Tim Peake operates rely on lunar resources such as locally the Muscle Atrophy derived water and oxygen (Anand et al. Research and Exercise 2012, Crawford 2015), but equally the infra- System (MARES) on structure provided by an outpost of this the ISS. MARES is kind would facilitate prospecting for addi- an ESA experiment tional resources. Indeed, a Moon village for research on could help kick-start a space economy by human physiology in providing a market for commercial space microgravity. A lunar resource companies while at the same time outpost would extend providing infrastructure to support their such experiments to activities. Although not strictly a scientific low, but non-zero, benefit of a Moon village per se, there is little gravity, potentially doubt that, in the longer term, science will providing insights benefit from the development of a space relevant to human economy built on the use of space resources health on Earth (e.g. (e.g. Elvis 2016, Metzger 2016). Green 2010) as well as long-term goals Conclusion for future space By analogy with scientific outposts in exploration. (ESA/ Antarctica, a human–robotic outpost on NASA) the Moon would enable multiple scientific opportunities owing to the lunar surface infrastructure that it would provide. Scientific fields expected to benefit from location of a human-tended outpost, that may be beneficial for human health such an infrastructure include planetary although some would require a prolonged on Earth (e.g. Green 2010) and the future science, astronomy, astrobiology, the life presence. Gronstal et al. (2007) have exploration of space. sciences and fundamental physics. In addi- reviewed the kind of laboratory equipment In addition to the low gravity, the lunar tion, a Moon village would help initiate the that would be required for such investiga- surface presents a challenging radiation utilization of lunar resources, and perhaps tions, from which it is clear that a human- and dust environment, and life science help kick-start a space economy. Although tended outpost would greatly facilitate this studies in this environment would also beyond the scope of this paper, a Moon work (and would, of course, be essential for be expected to yield both fundamental village would also offer important societal human studies). Specific areas of lunar life biological knowledge and knowledge and cultural benefits to humanity, espe- science investigations include life in lunar with potential medical applications (e.g. cially if, as envisaged, it is developed as a gravity and within the lunar radiation and Cockell 2010, Carpenter et al. 2010, Green truly global endeavour (e.g. White 2014). dust environment. 2010, Loftus et al. 2010, Durante 2012). And Moreover, although not explicitly identi- Although a lot of research has now if humans are to have a long-term future on fied as an objective in the current Global been performed on the response of life, the Moon, and on other planetary surfaces, Exploration Roadmap (ISECG 2013), an including human beings, to micrograv- then growing food will at some stage international Moon village would clearly ity (e.g. Seibert et al. 2001, Horneck et become necessary. A lunar outpost would be consistent with this roadmap, and more al. 2003; figure 5), no comparable data facilitate the necessary research. especially with the over-arching aims of exist for prolonged exposure to low, but the Global Exploration Strategy (ISECG non-zero, gravity. A lunar outpost would Lunar resources 2007). The whole scientific community, and permit such studies on life forms ranging There is growing interest in the future use indeed the world community more gener- from individual cells to entire organisms of lunar resources, both to support lunar ally, has the greatest possible interest in

(Cockell 2010). Fundamental insights into exploration itself and as a contribution seeing this initiative succeed. ● biological processes may be expected from to a developing space economy. A self- such studies, in addition to knowledge sustaining Moon village would very likely

AUTHOR Banerdt W B et al. 2007 Nuclear Physics B Proc. on Exo-Astrobiology ESA SP-518 187 NRC 2007 The Scientific Context for Exploration of Ian Crawford is based in the Department of Supp. 166 203 Horneck G et al. (eds) 2003 HUMEX: Study on the the Moon (National Research Council, National Earth and Planetary Sciences at Birkbeck College, Burns J O et al. 1990 Scientific American 262(3) 18 Survivability and Adaptation of Humans to Long- Academies Press, Washington DC) University of London, UK. Carpenter J et al. 2010 Earth Moon Planets 107 11 Duration Exploratory Missions ESA SP-1264 Ozima M et al. 2008 Proc. Nat. Acad. Sci. 105 17654 Cockell C S 2010 Earth Moon Planets 107 3 ISECG 2007 The Global Exploration Strategy: Frame- Robbins S J 2014 Earth Planet. Sci. Lett. 403 188 ACKNOWLEDGMENTs Crawford I A 2006 Internat. J. Astrobiology 5 191 work for Coordination http://esamultimedia.esa.int/ Rose C & Wright G 2004 Nature 431 47 This article is based on a paper presented at the Crawford I A 2015 Prog. Phys. Geog. 39 137 docs/GES_Framework_final.pdf Schneider J 2010 EPSC abstract 202 10th IAA Symposium on “The Future of Space Crawford I A & Joy K H 2014 Phil. Trans. Royal Soc. ISECG 2013 The Global Exploration Roadmap http:// Seibert G et al. (eds) 2001 A World Without Gravity Exploration: Towards the Moon Village and A372 20130315 www.globalspaceexploration.org/web/isecg/ ESA SP-1251 Beyond”, Turin, Italy, June 2017. I thank Giancarlo Crawford I A & Zarnecki J 2008 Astron. & Geophys. news/2013-08-20 Taylor G J 1985 The need for a lunar base: answer- Genta and Giuseppe Reibaldi for the opportunity 49 2.17 Jester S & Falcke H 2009 New Astron. Rev. 53 1 ing basic questions about planetary science, in to present these ideas at that meeting. I also thank Crawford I A et al. 2010 Earth Moon Planets 107 75 Joy K H et al. 2012 Science 336 1426 Lunar Bases and Space Activities of the 21st Century all my lunar science colleagues, too numerous to Currie D G et al. 2010 AGU Fall Meeting 2010, Joy K H et al. 2016 Earth Moon Planets 118 133 Mendell W W (ed.) (Houston, TX) 189 identify, for many stimulating conversations over abstract P51C-1467 Lester D F et al. 2004 Space Policy 20 99 Terada K et al. 2017 Nature Astronomy 1 26 the years. Durante M 2012 Planet. Space Sci. 74 72 Loftus D J et al. 2010 Earth Moon Planets 107 95 White F 2014 The Overview Effect: Space Exploration Ehrenfreund P et al. 2012 Adv. Space Res. 49 2 Lucey P G 2000 Proc. SPIE 4137 84 and Human Evolution, 3rd edition (AIAA) references Elvis M 2016 Space Policy 37 65 Maccone C 2004 in Life in the Universe Seckbach J Wörner J & Foing B 2016 The “Moon Village” Anand M 2010 Earth Moon Planets 107 65 Glavin D P et al. 2010 Earth Moon Planets 107 87 et al. (eds) (Springer) 303 concept and initiative, Annual Meeting of the Lunar Anand M et al. 2012 Planet. Space Sci. 74 42 Green D A 2010 Earth Moon Planets 107 127 McKay C 2013 New Space 1 162 Exploration Analysis Group, LPI Contribution no. Arkhipov A V 1998 J. Brit. Interplanetary Soc. 51 181 Gronstal A et al. 2007 Astrobiology 7 767 Metzger P T 2016 Space Policy 37 77 1960, id.5084 Armstrong J C et al. 2002 Icarus 160 183 Gutiérrez J L 2002 Proc. First European Workshop Neal C R et al. 2014 Space Policy 30 156

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