Lunar Astrobiology: a Review and Suggested Laboratory Equipment
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ASTROBIOLOGY Volume 7, Number 5, 2007 © Mary Ann Liebert, Inc. DOI: 10.1089/ast.2006.0082 Special Review Lunar Astrobiology: A Review and Suggested Laboratory Equipment AARON GRONSTAL,1 CHARLES S. COCKELL,1 MARIA ANTONIETTA PERINO,2 TOBIAS BITTNER,3 ERIK CLACEY,4 OLATHE CLARK,5 OLIVIER INGOLD,6 CATARINA ALVES DE OLIVEIRA,7 and STEVEN WATHIONG6 ABSTRACT In October of 2005, the European Space Agency (ESA) and Alcatel Alenia Spazio released a “call to academia for innovative concepts and technologies for lunar exploration.” In recent years, interest in lunar exploration has increased in numerous space programs around the globe, and the purpose of our study, in response to the ESA call, was to draw on the exper- tise of researchers and university students to examine science questions and technologies that could support human astrobiology activity on the Moon. In this mini review, we discuss as- trobiology science questions of importance for a human presence on the surface of the Moon and we provide a summary of key instrumentation requirements to support a lunar astrobi- ology laboratory. Keywords: Lunar astrobiology—Human lunar exploration—Instrumenta- tion—Microbiology—Planetary protection. Astrobiology 7, 767–782. INTRODUCTION Moon would provide experience that could be applied in similarly hostile planetary environ- HE MOON IS NOT EXPECTED to harbor indige- ments, such as Mars, and even in extreme envi- Tnous life, yet human explorers and their ro- ronments on Earth (Mendell, 2005). Therefore, botic precursors will likely carry out a range of defining the scientific objectives of lunar astrobi- important astrobiology studies on the lunar sur- ology and the suite of instruments necessary to face that include the search for ancient meteorites, accomplish them is an important objective of the testing of planetary protection protocols, and planetary science. the monitoring of crew life-support systems. In In this review paper, we discuss the primary addition to offering important insights in their research questions for lunar astrobiology. Based own right, astrobiology investigations on the on a three-month design study for a lunar astro- 1Planetary and Space Sciences Research Institute, Open University, Milton Keynes, United Kingdom. 2Thales Alenia Space Italia, Torino, Italy. 3Zentrum für Neuropathologie und Prionforschung, Ludwig-Maximilians-Universität, München, Germany. 4Swedish Space Corporation, Stockholm, Sweden. 5Environmental Biology, University of Guelph, Guelph, Canada. 6International Space University, Strasbourg, France. 7European Southern Observatory, München, Germany. 767 768 GRONSTAL ET AL. biology laboratory conducted at the Open Uni- ological information about Earth, Mars, and other versity in the United Kingdom (performed in re- planets or celestial bodies whose material may sponse to a call for innovative concepts and tech- have been deposited on the Moon (Taylor, 2005; nologies released by the European Space Agency Korotev, 2005). During the Late Heavy Bom- (ESA) and Alcatel Alenia Spazio Italia*), our re- bardment, a great deal of material was ejected search also provides definition of the instrumen- from Earth, some of which would have been tation that human explorers could use to conduct caught by the gravity well of the Moon and, con- experiments in these scientific areas. sequently, deposited on the lunar surface (Koe- berl, 2003; Armstrong et al., 2002). It is unknown how much of this material is present on the Moon, LUNAR ASTROBIOLOGY: KEY though some estimates indicate that as much as Ϫ SCIENTIFIC QUESTIONS 200 kg km 2 of terrestrial material ejected from Earth during the period of 3.9 to 3.8 Gyr could be In recent years, interest in lunar missions has exposed at the surface today (Armstrong et al., increased immensely in space agencies around 2002; Crawford, 2006). In addition, robotic remote the world. In 2004, NASA released the President’s sensing missions prior to human exploration Vision for Space Exploration, which includes spe- could aid in narrowing down the search for me- cific goals for returning humans to the Moon teorites by taking advantage of the differences in (NASA, 2004). The European Space Agency com- absorption spectra seen between the hydrated sil- pleted its first dedicated lunar mission, SMART- icates and carbonates of Earth rocks and lunar 1, in September of 2006 and is currently examin- rocks, which contain no water or carbonates ing options for participating in lunar explorations (Crawford, 2006). These rocks would likely yield that go beyond robotics (Messina and Venne- information about the bombardment history of mann, 2005; Laurance, 1996; Horneck et al., 2001). Earth and improve our understanding as to the As interest in human missions to the Moon rate of impact and the size of impactors. A fuller grows, it is important to look at the scientific rea- understanding of conditions on Earth during the sons for returning there and, in particular, the Hadean will help to answer key questions as to reasons that warrant the establishment of a more how the habitability of Earth evolved (Chyba, permanent presence than that achieved during 1993; Ryder, 2002). Plate tectonics and surface the Apollo era. weathering processes have wiped away most of In this review, we examine astrobiology ques- the evidence of past impacts on our planet. The tions specifically of interest to human researchers Moon, however, with its lack of plate tectonics on the lunar surface. Human settlement would and lack of aeolian and aqueous weathering provide a means by which to conduct novel sci- processes, could be described as a “witness plate” ence that cannot be performed on Earth. As well of what Earth has experienced throughout its his- as consulting the primary literature, we carried tory (Spudis, 2001). The chemical and physical out a survey of numerous researchers in fields re- features of lunar material subjected to melting lated to astrobiology with the intent to define the and brecciation during heavy bombardment re- scientific goals that will be pursued during future veal details about the nature of impacts during human missions to the Moon. What resulted was this early critical phase of terrestrial evolution a list that ranged from the abiotic studies of ge- (Petro and Pieters, 2004; Gomes et al., 2005) and ology and meteoritics to more biology-oriented the possible scenario within which life emerged areas of human physiology and planetary pro- (Arrhenius and Lepland, 2000). tection. Specific topics within each area of study The analysis of meteorites from other planetary are discussed. bodies, such as Mercury, Mars, and Venus, would also contribute to our understanding of the geo- Geology/Meteoritics logical history of these planets. If rocks from Venus, for example, have been transported to the Meteorites on the Moon will be of great inter- Moon and currently reside there, they would be est to astrobiology researchers and will yield ge- the only existing evidence of Venus’s early geol- ogy (Armstrong et al., 2002). The identification of *In 2007, Alcatel Alenia Spazio became Thales Alenia such meteorites on the Moon would contribute to Space Italia. the study of the exchange rate of material be- LUNAR ASTROBIOLOGY AND INSTRUMENTATION 769 tween bodies in our Solar System. This informa- rectly address these types of questions, a refined tion could also be used to validate computer knowledge of lunar history, brought about by an models of exchange rates within the Solar System analysis of an improved sample set, can help to (Gladman et al., 1996). constrain the early history of the Earth-Moon sys- The geology of the Moon itself will be an im- tem and, thus, the role of the Moon in influenc- portant area of future study. It is thought that the ing the habitability of Earth. Moon was likely formed when a large Sun-orbit- ing object or planetesimal struck Earth and jetti- Prebiotic chemistry soned debris into orbit that later coalesced (Hart- The Moon may not support indigenous life, but mann, 1986; Stevenson, 1987; Shearer et al., 2006). it is possible that chemicals native to its surface The orbital evolution of the Moon subsequent to could provide important information about how its formation remains an intriguing mystery (Gar- life develops. Two important concerns with re- rick-Bethell et al., 2006). Study of the geology of gard to astrobiology on the Moon are the extent the Moon, along with a substantial addition to the of ice deposits or hydrated minerals in the polar diversity of samples from different locations on shadows (Seife, 2004; Vasavada et al., 1999) and the Moon, would help to elucidate this geologi- whether ices preserved in these regions could cal and astronomical history (e.g., Kleine et al., contain evidence of prebiotic chemistry. When 2005). Although the Apollo program provided us the Apollo astronauts returned samples of the lu- with lunar surface samples from which much of nar regolith to Earth, no evidence of organics was our understanding of the Moon’s composition discovered in the samples. All of the Apollo sam- and structure has been gained, remote sensing ples, however, were taken from the equatorial re- missions such as Clementine and Lunar Prospec- gions; other areas of the Moon support vastly dif- tor have shown that there is a great deal of vari- ferent conditions. ation in materials at the lunar surface (Shearer et Both indigenous and exogenous organics could al., 2006; Wieczorek et al., 2006). Obviously, the be sought: knowledge drawn from Apollo samples with re- 1) Indigenous: It has been proposed that pre- gard to the origin and geologic evolution of the biotic materials, such as amino acids, may have Moon is incomplete (Crawford, 2004, 2006; formed from inorganic molecules in volcanic con- Okada et al., 2006). Studying the history of geo- ditions on the early Moon and may remain pre- logical processes such as volcanism and crust de- served to this day in permanently shadowed ice formation would not only reveal information (Lucey, 2000).