ESSC-ESF Position Paper—Science-Driven Scenario For

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ASTROBIOLOGY Volume 9, Number 1, 2009 © Mary Ann Liebert, Inc. DOI: 10.1089/ast.2007.1226

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ESSC-ESF Position Paper Science-Driven Scenario for Space Exploration: Report from the European Space Sciences Committee (ESSC)

Jean-Claude Worms,1 Helmut Lammer,2 Antonella Barucci,3 Reta Beebe,4 Jean-Pierre Bibring,5 Jacques Blamont,6 Michel Blanc,7 Roger Bonnet,8 John R. Brucato,9 Eric Chassefière,10 Angioletta Coradini,11 Ian Crawford,12 Pascale Ehrenfreund,13 Heino Falcke,14 Rupert Gerzer,15 Monica Grady,16 Manuel Grande,17 Gerhard Haerendel,18 Gerda Horneck,15 Bernhard Koch,15 Andreï Lobanov,19 José J. Lopez-Moreno,20 Roberto Marco,21 Peter Norsk,22 Dave Rothery,16 Jean-Pierre Swings,1,25 Cam Tropea,23 Stephan Ulamec,15 Frances Westall,24 and John Zarnecki16

Abstract

In 2005 the then ESA Directorate for Human Spaceflight, Microgravity and Exploration (D-HME) commissioned a study from the European Science Foundation’s (ESF) European Space Sciences Committee (ESSC) to exam- ine the science aspects of the Aurora Programme in preparation for the December 2005 Ministerial Conference of ESA Member States, held in Berlin. A first interim report was presented to ESA at the second stakeholders meeting on 30 and 31 May 2005. A second draft report was made available at the time of the final science stakeholders meeting on 16 September 2005 in order for ESA to use its recommendations to prepare the Executive proposal to the Ministerial Conference. The final ESSC report on that activity came a few months after the Min- isterial Conference (June 2006) and attempted to capture some elements of the new situation after Berlin, and in the context of the reduction in NASA’s budget that was taking place at that time; e.g., the postponement sine

1ESSC-ESF, Strasbourg, France. 2IWF/ÖAW, Graz, Austria. 3LESIA, Meudon, France. 4New Mexico State University, USA. 5IAS, Paris, France. 6CNES, France. 7École Polytechnique, France. 8ISSI, Bern, Switzerland. 9Osservatorio Capodimonte, Italy. 10IPSL, Paris, France. 11IFSI-CNR, Rome, Italy. 12Birkbeck College, UK. 13University of Leiden, the Netherlands. 14ASTRON, the Netherlands. 15DLR, Germany. 16Open University, UK. 17University of Wales, UK. 18MPE Garching, Germany. 19MPI, Germany. 20IAA-CSIC, Granada, Spain. 21formerly University of Madrid, Spain—deceased. 22University of Copenhagen, Denmark. 23Technical University, Darmstadt, Germany. 24CBM-CNRS, France. 25IAG, Liège, Belgium.

23 24 WORMS ET AL. die of the Mars Sample Return mission. At the time of this study, ESSC made it clear to ESA that the timeline imposed prior to the Berlin Conference had not allowed for a proper consultation of the relevant science community and that this should be corrected in the near future. In response to that recommendation, ESSC was asked again in the summer of 2006 to initiate a broad consultation to define a science-driven scenario for the Aurora Programme. This exercise ran between October 2006 and May 2007. ESA provided the funding for staff support, publication costs, and costs related to meetings of a Steering Group, two meetings of a larger ad hoc group (7 and 8 December 2006 and 8 February 2007), and a final scientific workshop on 15 and 16 May 2007 in Athens. As a result of these meetings a draft report was produced and examined by the Ad Hoc Group. Fol- lowing their endorsement of the report and its approval by the plenary meeting of the ESSC, the draft report was externally refereed, as is now normal practice with all ESSC-ESF reports, and amended accordingly. The Ad Hoc Group defined overarching scientific goals for Europe’s exploration programme, dubbed “Emergence and co-evolution of life with its planetary environments,” focusing on those targets that can ultimately be reached by humans, i.e., Mars, the Moon, and Near Earth Objects. Mars was further recognized as the focus of that programme, with Mars sample return as the recognized primary goal; furthermore the report clearly states that Europe should position itself as a major actor in defining and leading Mars sample return missions. The report is reproduced in this article. On 26 November 2008 the Ministers of ESA Member States decided to give a high strategic priority to the robotic exploration programme of Mars by funding the enhanced ExoMars mission component, in line therefore with the recommendations from this ESSC-ESF report. Key Words: European exploration programme—Robotic exploration—Human lunar missions—Human Mars missions—NEOs—Sam- ple return missions—Planetary protection—International cooperation. Astrobiology 9, 23–41.

1. Introduction This draft report features the recommendations from the AHG to ESA’s Human Spaceflight, Microgravity and Ex- HE INTERNATIONAL SPACE EXPLORATION PROGRAMME fore- ploration Directorate (D-HME), supplemented by the find- Tsees multiple robotic and human missions in the Solar ings laid out by the participants in the Athens workshop. System in the coming decades. A global strategy is being de- Part of this outcome has already been taken into account by veloped jointly by a large number of space-faring nations ESA’s D-HME as input to their architecture studies.

and organisations. In Europe a major planning effort is on- going in the framework of the ESA Aurora Programme (see 2. General Scientific Goals of Europe’s Fig. 1), Europe’s Exploration Programme (EEP) that envis- Exploration Programme ages the launch of ExoMars in 2013 as a first step towards a robust and renewed effort for exploration. Whether done robotically or with humans, or both, science A roadmap for Aurora started to be developed in 2001. and the search for knowledge are an essential part of explo- Furthermore a strong heritage exists in Europe within both ration. Exploration without human spaceflight does lack an the mandatory programme, with several Solar System mis- important societal and even scientific interest and perspec- sions having been launched, as well as the various ELIPS- tive. Hence human spaceflight should be integrated in Eu- funded research programmes. This allows Europe and ESA rope’s Exploration Programme (EEP) in a synergistic way at to face new explorative challenges making use of solid and all stages of development of the programme. However the successful experiences. first phases of this programme should be robotic. In view of the evolving international context, ESA has initiated further analysis and definition of Europe’s potential A vision for Europe should therefore be to prepare for a long-term role in the exploration initiative by identifying scientific, European participation in a global endeavour of human exploration technological, and societal priorities. For the science part ESA of the Solar System with a focus on Mars and the necessary in- has asked the ESSC-ESF to conduct a broad consultation in termediate steps, initiated by robotic exploration programmes with support of the definition of a science-driven European sce- a strong scientific content. nario for space exploration. To this end the ESSC has ap- Drivers for human exploratory missions include science, pointed a Steering Committee to supervise the whole eval- technology, culture, and economic aspects. Above all the uation exercise and an Ad Hoc Group (AHG) to conduct the search for habitability and, hence, for life beyond the Earth, evaluation itself. The final report to ESA received the agree- has been considered as one of the intellectual driving forces ment of the AHG before it was approved by the ESSC and in the endeavour to explore our Solar System. This aspect ESF. The AHG met twice, on 7 and 8 December 2006 and 8 was central in establishing the overarching science goal of February 2007. At their second meeting the AHG decided to the EEP. split the work among five sub-groups: Near Earth Objects (NEOs), Mars robotic missions, Mars human missions, Moon 2.1. General recommendations robotic missions, and Moon human missions (Appendix 3). In addition a workshop was organised by ESF to consult • The overarching scientific goal of EEP should be called: with the relevant scientific community. Eighty-eight scien- “Emergence and co-evolution of life with its planetary en- tists and national representatives from ESA Member States vironments,” with two sub-themes pertaining to the emer- met in Athens on 15 and 16 May 2007 in a workshop or- gence of life and to the co-evolution of life with their en- ganised by ESF and sponsored by ESA (Appendix 2). vironments. EUROPE’S EXPLORATION PROGRAMME 25

FIG. 1. Artist’s impression of the Aurora programme roadmap (© ESA—AOES Medialab).

• EEP should focus on targets that can ultimately be reached text of an international lunar exploration programme. ESA by humans. needs to ensure the continuity of the necessary expertise • The first steps of EEP should be done robotically. in the longer term by supporting the relevant groups. • International cooperation among agencies engaged in • Europe should develop a sample reception and curation fa- planetary exploration should be a major feature of EEP, cility, of joint interest to ESA’s science and exploration pro- materialised by concrete joint ventures, such as some of grammes. A sample distribution policy needs to be estab- the elements mentioned in the 14 space agencies’ Global lished between international partners early in the process. Exploration Strategy document. • Understanding the processes involved in the emergence • Mars is recognised as the focus of EEP, with Mars sample of life in the Solar System, e.g., through in-depth explo- return as the driving programme; furthermore Europe ration of Mars, is crucial to understanding the habitabil- should position itself as a major actor in defining and lead- ity of exoplanets and remains a high scientific priority that ing Mars Sample Return missions. should be supported by ground-based laboratory studies • There is unique science to be done on, of, and from the and specific experiments in space. Moon and of/on Near Earth Objects or Asteroids • Once EEP is funded and running it is suggested that a se- (NEOs/NEAs). Therefore, if these bodies are to be used ries of international science and technology exploration as a component of EEP, further science should be pursued; workshops be set up in the near future, which for Europe the Moon could thus be used as a component of a robust could be organised by ESF and the community and co- exploration programme, including among others: geolog- sponsored by ESA, in order to better define the mission ical exploration, sample return, and low-frequency radio- concepts and technological choices relevant to the above astronomy, technology, and protocol test-bed. goals as this multi-decadal programme develops. • The role of humans as a unique tool in conducting research on the Moon and on Mars must be assessed in further de- 3. European Capabilities and Achievements tail. • Since EEP’s ultimate goal is to send humans to Mars in In order to remain a key player with its unique expertise, the longer term, research on humans in a space environ- Europe needs to maintain and further develop its indepen- ment must be strengthened. Beyond the necessary ongo- dent capabilities for planetary exploration so that it can pre- ing and planned biological research and human presence pare independent access to planetary exploration. This on, e.g., the International Space Station (ISS) or in Antarc- should be done by developing its key enabling technologies tica, opportunities to this end might also arise in the con- and scientific domains of expertise. Niches already exist, e.g., 26 WORMS ET AL. for hardware development in the field of life sciences, geo- were made in the final report of that evaluation process, per- physical sciences, and planetary sciences. Europe has already taining to the detection of signatures of life on other planets developed scientific capabilities benefiting human space- or bodies and to the understanding of the limits of life on flight in human physiology, countermeasures, and radiation Earth. health. Hence Europe certainly does not start from scratch Several recommendations in that report address the core compe- on this exploration programme. Examples of these niche de- tences of Europe in that domain and list specific contributions by velopments and achievements are the exo/astrobiology and planetary exploration communities, including • Mars Express, which on the one hand has demonstrated Europe’s technical capabilities to fly an independent plan- • development of life-support systems including bio-regenerative etary orbiter mission (Huygens and Rosetta lander are ex- approaches, amples of landing devices) and on the other hand has pro- • early detection, control, and prevention of microbial contami- vided ample information on the geology, mineralogy, and nation, atmosphere of Mars, which is important for its further ex- • investigation of the radiation field in space and its biological ef- ploration (e.g., Lundin et al., 2004; Murray et al., 2005; Bib- fects. ring et al., 2005). • Concerning our understanding of the adaptation of the These studies require preparatory robotic space missions, human body and its functions to the conditions of space- supportive ground-based studies, and use of the ISS and flight, above all weightlessness, Europe has a leading role Concordia. from studies in space as well as in long-term simulation experiments. This is also valid for psycho-physiological 4. The Robotic Exploration of Mars aspects of human spaceflight (e.g., Horneck et al., 2003; Clé- ment, 2005). The study of other planets has told us how Earth is unique. • Regarding our understanding of the regulations at the cel- Clearly, life, even if it formed elsewhere in our Solar System, lular and sub-cellular level (signal transduction and gene has developed significantly only on Earth. Moreover, Earth expression) and their responses to the gravity stimulus Eu- presents a unique combination of geological characteristics: ropean researchers are very strong in this field (e.g., Seib- plate tectonics and a global magnetic field, an oxygen-rich ert et al., 2001; Clément and Slenzka, 2006; Brinckmann, atmosphere (for the last two billion years, produced by life 2007). itself) and a hydrosphere, and a satellite (the Moon) that sta- • There is a long heritage in Europe relating to the biologi- bilises the obliquity and thus the climate.

cal effects of cosmic radiation and its dosimetry. The first, A habitable planet appears to be a complex and perhaps and so far only, radiobiological experiments outside our rare object. But how are geological evolution and habitabil- magnetosphere were done with the European Biostack ex- ity coupled? Will life interact with the host planet to make periments during the Apollo missions (e.g., Bücker and it all the more habitable? On Earth, life has interacted with Horneck, 1975; Horneck, 2007; Reitz and Berger, 2006). global geological processes to make it habitable for large, • European scientists have developed a prototype for a self- multi-cellular life forms. sustained bio-regenerative life-support system Melissa We may thus see life as a geological process. On Mars, it (Mergeay et al., 1989). may have once appeared and eventually have lost the race • SMART-1, the first European mission to the Moon has against faster-developing adverse geological processes. For demonstrated new technologies for propulsion, naviga- instance, one hypothesis is that Mars had a warmer and wet- tion, and miniaturisation. It performed reconnaissance of ter environment protected by a magnetic field. But the pro- geology, composition, polar regions, and possible landing tecting field died before life had significantly evolved, and sites as a precursor to future international exploration.1 the atmosphere was eroded and went into a negative green- • Just as the International Space Station is a key element for house cycle that resulted in the cold desert planet we see to- some of these achievements, the French-Italian Concordia day.3 base in Antarctica is an asset in preparatory studies on One may thus envisage Mars as a “paleo-habitable” long-term isolation, water and waste recycling, and other planet. What are the links between geology and life? Has relevant aspects. Mars ever hosted life? If so, for how long, and under what conditions, was Mars able to sustain life? There is a deep A very strong synergy will need to exist between Aurora need to understand how the geological evolution and hab- and ELIPS, ESAs programme for life and physical sciences itability are coupled, and Mars offers a unique opportunity in space. ELIPS was reviewed, and its second phase was eval- to investigate this crucial question on a second planet. uated by the ESSC-ESF through a very large user consulta- One of the most significant and important aims of robotic tion process, which took place in 2005.2 A similar exercise exploration of Mars is therefore to assess the habitability of took place in the first half of 2008. Specific recommendations Mars and its capability to have sustained life, if it ever

1By Sunpower to the Moon—SMART-1, ESA Publication BR-191, 3Recent observations made by the OMEGA spectrometer of ESA’s 2003. Mars Express probe seem to point to a quite different scenario, that 2 Scientific perspectives for ESA’s future programme in life and Mars never had enough CO2 and methane to generate such an ef- physical sciences in space, ESSC-ESF recommendations, ISBN 2- fect. If confirmed this would mean that the Red Planet has always 912049-51-2, European Science Foundation Strasbourg, September been cold and dry, even if major impacts could have modified this 2005. situation for brief periods of time (Bibring et al., 2006). EUROPE’S EXPLORATION PROGRAMME 27 emerged, and for how long. This in turn is crucial to understanding the habitability of exoplanets.

Another essential aspect is to continue a relevant research on Earth to enable the determination of possible habitats, the mode of preser- vation of expected bio-signatures (differentiate traces of life from abiotic processes) in these habitats, and the unambiguous recogni- tion of life beyond Earth. Indeed, characterising bio-signatures in- volves studies of early traces of life in the Precambrian Earth and taphonomy4 of cells in various preservational environments of present Earth.

The search for extinct and extant life on Mars refers to the “Emergence of life” theme of EEP, whereas the search for extant life and characterisation of past and present habitability conditions deal with the “Co-evolution of life with their environments” theme of EEP. If a robotic mission should dis- cover traces of extinct or even extant life on Mars, this would stimulate the interest of scientists and of society at large for a continued human exploration of a second inhabited planet. Therefore, a further important goal of robotic exploration is its ability to demonstrate the necessity for a detailed human exploration of Mars in order to answer the question of whether or not there is extant life at various locations on Mars.

Mars is recognised as the focus of EEP, which should first be led robotically, with sample return(s) from the red planet as its dri- FIG. 2. ExoMars rover (© ESA). ving series of programmes; furthermore Europe should position itself as a major actor in defining and leading Mars sample return missions. To participate in this endeavour with a major role, Europe

has a number of assets but needs to develop or improve Recent evaluations conducted with international partners them, or identify the assets that international partners could are pointing towards the possibility of implementing a contribute to its programme, such as “caching” system for future Mars landers, to be retrieved by MSR missions. Such a caching system could then be de- • improving and expanding Europe’s world-class instru- veloped by Europe for ExoMars (see Fig. 2), which would mentation capability; then include samples obtained by drilling. This approach • Europe’s industrial capability to build an infrastructure on could both increase the science return from future Mars lan- Mars; ders and also, spread over several missions and a longer • international collaboration history of Europe; period of time, the technological risk attached to potential • development in Europe of 5–10 W radioisotope-based, multiple point failures of a single mission. Hence one pos- long-lived (e.g., over 5 years) power devices to open new sible option would be for Europe to develop such a caching opportunities for European-led international collabora- system for ExoMars. This option must be weighted, how- tion. ever, against the added complexity of the mission, which could easily generate unacceptable delays and/or budget There are two separate but equally important purposes for increase. the exploration of Mars using robots. One purpose is science Beyond the experience gained with Mars Express a driven, the achievement of specific goals that will aid in the roadmap for EEP should articulate the following steps: understanding of the potential origin of life beyond Earth and the evolution of a rocky planet. Another purpose is • Step 1: Exomars will be the first and therefore critical step preparation, in terms of technology development and in EEP; it will offer the European community a leading demonstration, for the human exploration of space. Scien- position by exploring Mars with scientific objectives as tific drivers for the exploration of Mars are diverse as exobiology, geology, environment, and geo- physics. Securing this mission for a 2013 launch must • Is, or was, Mars inhabited? Were conditions for long-term therefore be the top priority of Europe’s robotic explo- life sustainability ever reached on Mars? ration programme; • How has Mars evolved as a planet? This will include ori- • Step 2: Mars sample return programme (see Fig. 3); gin and evolution of the martian atmosphere, hydros- • Step 3: Human mission programme, for which Europe phere, cryosphere, lithosphere, magnetosphere, and deep needs to prepare itself to be a major partner. interior. • To what extent are the present surface conditions of Mars supportive or hazardous to life (to putative indigenous or 4Study of a decaying organism over time. terrestrial life forms, including humans)? 28 WORMS ET AL.

FIG. 3. Artist’s view of the Mars sample return ascent module lifting off from Mars (© ESA).

To explore Mars with robots, the approach must consider composition, surface radiation levels, depth profile of ra- both the science goals and human exploration requirements diation penetration, etc. of any programme. • Setting up a weather station network in conjunction with seismology stations. 4.1. Exploration of Mars from orbit • High-resolution imagery, spectroscopy, and any other rel- 4.3. Exploration of Mars with returned samples evant techniques of remote sensing of planetary surfaces; • Very high precision analysis at sub-micron level; • Planetary geodesy and all relevant techniques of probing • Enabling technology demonstration for human explo- of planetary sub-surface and interior; ration. • Identification of potential landing sites (recent changes in morphology; landslips); Finally, the Ad Hoc Group has discussed limitations of ex- • Monitoring and measuring atmosphere, climate, and ploring Mars with robots. Sections 6 and 7 address these as- weather (dust storms) over the solar (activity) cycle for re- pects in more detail. constructing the evolution of the martian atmosphere and early martian environment. 5. Robotic Lunar Exploration 4.2. Exploration of Mars with landers Europe should actively participate in the manned explo- • Probing of deep interior by seismology and other relevant ration of the Moon and Mars. The first step is to continue techniques such as deep drilling (metres to tens of metres); with robotic missions and prepare for manned missions to • Life detection; Mars. An intermediate step could be to contribute to an in- • Ability to undertake direct imagery and any other rele- ternational venture to establish a human base on the Moon; vant analysis of surface and sub-surface regions. This will the third step would be to contribute to the implementation require precision landing; of manned missions to Mars and back to Earth again. • Analysis of different rocks and ice. This will require the The Moon as a target for exploration missions offers a ability to move; number of outstanding opportunities for science of, on, and • Assessment of In Situ Resource Utilisation (ISRU): regolith from, the Moon. The main objective would be the discovery, EUROPE’S EXPLORATION PROGRAMME 29 exploration, and use of the “8th continent” (Crawford 2004), There is a consensus among astrophysicists today that initially the and the harvesting of unique information from the Moon as Moon should be used only for projects uniquely requiring the Moon. an archive of the formation and evolution of the Solar Sys- A prime example of such a unique experiment is a digitally steered tem. Furthermore EEP should consider the use of the Moon low-frequency radio interferometer consisting of an array of non- as a large laboratory in free space. moving dipole antennas (Basart et al., 1997; Kuiper and Jones, 2000; While the Moon is geologically less active than Mars, its Jones et al., 2007; Lockwood, 2007). The low-frequency window to structure (core/mantle, chemical stratification) and geo- the universe has never been explored with imaging telescopes before physical processes are far from being understood and require because of the Earth’s ionosphere and the lack of any lunar infra- in situ measurements (rover, seismic network, heat-flow structure; hence unique and novel science can be done. Scientific probes, etc.) at various locations. goals of a first explorative mission would be the local interstellar environment of the Solar System, the solar-terrestrial relationship, and We also require analysis and sample return for geochemi- in situ the history thereof. Ultimately this technique can be developed into cal analyses of regions not yet sampled ( South Pole Aitken e.g., a large telescope for targeting precision measurements of the condi- basin, far-side high lands, young basalts in Procellarum, far-side tions in the early Universe and its inflationary phase. maria). Experience gained in developing precision landing, sample collection and return, and rover techniques for the Moon will In addition a number of space-based interferometers at be advantageous for subsequent martian missions. other wavelengths (sub-millimetre, infrared, optical) have been proposed (Monnier, 2003; Helmich and Ivison, 2007; A particularly interesting aspect of the “science of the Léger et al., 2007). Should a realisation of these large inter- Moon” is that lunar evolution is closely related to the evo- ferometers as free-flyers prove to be technically or financially lution of the Earth. All external effects that have acted on life more difficult than expected, lunar options may be revisited. on Earth in the past will have acted on the Moon as well. This too will require a detailed knowledge of lunar surface Like a “museum” the Moon has acted as a “witness plate” properties (dust, seismicity, etc.) and potentially some actual of past meteorite bombardments of the Earth-Moon system astronomical site-testing. Site-testing would include the re- and will harbour traces of past activity of the Sun.5 sponse of construction materials and lubricants to extreme Identifying promising locations for reading these archives/records temperature variations. could first be done robotically, although the full scientific ex- There are a number of enabling technologies to realise this ploitation of them is likely to require renewed human operations roadmap, such as air-less entry and descent, hazard avoid- on the lunar surface. ance control, precise point landing, generic soft-landing platform, instrument development, context and environment Robotic exploration of the Moon should also provide the characterisation, sample acquisition and screening (robotics), prerequisite information for a safe presence of humans on intelligent rover sample fetcher and permanent robotic as- the Moon. Important issues to be understood are the bio- sets deployment, planetary protection demonstration, lunar logical adaptation to reduced gravity, the assessment of ra- ascent rocket, rendezvous, Earth re-entry, Earth descent and diation risks in missions outside the geomagnetic shield, the landing, sample curation, radioisotope power sources de- establishment of closed artificial ecosystems, and the devel- velopment. In summary a European roadmap for lunar ex- opment of technologies for the use of in situ resources. Be- ploration would include cause planetary protection policy considers the Moon as part of the Earth-Moon system, relevant studies on microorgan- • SMART 1 (see Fig. 4) exploitation and orbiter follow-up; isms, plants, and animals can be performed on the Moon • Surface missions-mobile laboratory; without planetary protection restrictions. • Sample return; Apart from being a research target itself, the Moon is also • Contribution to a human-tended science laboratory; an ideal platform for a number of scientific experiments, es- • Low-frequency radio astronomy, especially from the far pecially in astrophysics, because of its large stable ground,6 side. the absence of any significant atmosphere, and its large mass for shielding against cosmic radiation and particles. A sys- tematic lunar programme, with balanced contributions from 6. The Case for Human Missions to Mars science, exploration, and technology demonstration, will in- and the Moon clude orbiters, landers (equipped with rovers, environment Science is driven by rationality, excitement, curiosity, co- package, seismometers), sample return missions, life science operation, competition, and boldness. What is more exciting experiments, precursors for human exploration, and science than to send human beings to Mars and bring them safely investigations conducted with astronauts. back to Earth again? What stimulates our curiosity more than to explore, whether there can be or has ever been life on a 5Space Studies Board, US National Research Council, The Scien- planet other than Earth? What is bolder than to test whether tific Context for the Exploration of the Moon—Final Report, © NAS humans can sustain the environment of long-term space- 2007, www.nap.edu/catalog/11954.html. flight in the Solar System and live on another planet? 6This statement must be qualified: from the Apollo seismic data, Manned missions to the Moon and Mars are the natural the Moon has more than 1 seismic event of body wave magnitude next steps to explore the conditions for the origin and evo- larger than 5 on the Richter scale. We also know that the Moon has a high Q and maximum ground movements that last between 10 lution of life, and how it has interacted with its planetary en- and 60 minutes. Hence the Moon’s surface is stable only insofar as vironment(s) (see Fig. 5). such seismic events can be accounted for (Schreiber, 1977; Tittmann et al., 1978; Nakamura and Koyama, 1982; Oberst and Nakamura, Thus, missions to Mars, and especially those involving humans 1992). are, from an exploration, science, and technology perspective, an 30 WORMS ET AL.

FIG. 4. SMART-1 mission at the Moon (© ESA—AOES Medialab). extremely exciting challenge of our time. A broad range of scien- bly out of the question, so in situ studies by human spe- tific disciplines from physics, chemistry, and geology to biology cialists would be desirable. and medicine will benefit from it by addressing the following questions: How does gravity affect life, from molecules to integrated physiology, and what is the significance of the gravitational Can Mars sustain life? Are there any signs of past or pres- environment for evolution? To explore these issues, biolog- ent forms of life on Mars, and could it be made habitable? ical material from molecules and cells to organisms should Only by sending human-made instruments (robots) there be subjected to long-term variations in exposure to gravita- with, at some stage, a human presence to fully expand their tional stress (g) such as 0 g (spaceflight, e.g., on the ISS), 0.17 capability, will we be able to answer these questions. g (Moon), and 0.38 g (Mars). Without sample return and humans on Mars at an appropriate stage, the scientific and technological return will In addition to answering these questions, manned missions to Mars be incomplete, and the confirmation of the hypothesis that are expected to increase public awareness of science and expand life exists or has existed in some form on Mars will remain funding and activities in many related scientific and technological open. Specifically, a human presence will greatly facilitate fields. This will lead to an increase in scientific knowledge and an the following: expansion in the economy at a global level. Prior to manned missions to Mars, appropriate guidelines • Deep (100 m to km) drilling through the cryosphere need to be developed to protect the planet from human ac- to seek possible habitable environments in martian tivities that may be harmful to its environment and also to aquifers—probably the most likely environments for ex- protect human explorers from the environment (i.e., that of tant life on Mars today. the spaceflight and that of Mars). Finally, we need to protect • Searches for microfossils in martian sedimentary materi- the Earth from potentially harmful agents brought back from als. Experience on Earth shows that large quantities of ma- Mars with the return of the explorers. Answers to these is- terials from carefully selected locations will need to be sues concerning planetary protection and countermeasures searched with microscopes. Shipping the required quan- against the effects on humans of weightlessness, radiation tities of martian materials to Earth for analysis is proba- and the planetary environment need to be available well EUROPE’S EXPLORATION PROGRAMME 31

FIG. 5. Artist’s impression of the Aurora Moon base (© ESA—AOES Medialab). ahead of manned missions to Mars. Section 7 deals with this activities on the Moon such as life sciences investigations issue in more detail. under reduced gravity conditions, and maintenance and The human exploration of the Moon would be an obvious upgrading of astronomical instruments placed on the lu- means of developing techniques for later exploration of Mars nar surface. and would add greatly to our knowledge of the early history of the inner Solar System. Specifically, human lunar ex- It can be noted that human versatility is such that a num- ploration would have the following scientific advantages: ber of these objectives can be met simultaneously. For European scientists to continue exploring the frontiers of new research, Europe should actively participate in the • Much more efficient collection of a more diverse range of manned exploration of the Moon and Mars. The first step is samples from larger geographical areas than is possible to continue with robotic missions and prepare for manned by tele-operated robotic exploration; missions to Mars. An intermediate step could be to contrib- • Facilitation of large-scale exploratory activities such as ute to an international venture to establish a human base on deep (approximately 100 m) drilling to determine geolog- the Moon; the third step would be to contribute to the im- ical details of the surface of the Moon (e.g., paleo-regolith plementation of manned missions to Mars and back to Earth deposits); again. • Facilitation of landing much more complex geophysical and other equipment than is likely to be feasible roboti- Therefore, this programme should start as soon as possible with a cally; dual-track roadmap: (1) robotic and non-manned missions to Mars • Increase of opportunities for serendipitous discoveries; and, in parallel, (2) the continued biological research and human • Gaining operational experience on a planetary surface that presence on the ISS, in Antarctica, atmospheric balloons, etc. in will be of value for later exploration of Mars; preparation for the manned missions to the Moon and, eventually, • Facilitation of a number of other, non-planetary science Mars. 32 WORMS ET AL.

FIG. 6. Inspection of the STARDUST canister and sample collector (© NASA/JSC).

7. Planetary Protection brought back from Mars or even sample return missions upon return of the explorers. Whereas from the planetary protection point of view, the Moon is considered as part of the Earth-Moon system and Answers to these planetary protection issues need to be therefore no special planetary protection measures are re- available well ahead of manned missions to Mars, e.g., by quired for lunar missions, Mars on the other hand is a target testing this protocol and guidelines during lunar missions. of special concern with regard to possible forward, as well as backward, contamination, as laid down in the planetary protection guidelines7 of COSPAR. (Horneck et al., 2007). 8. Impact of Human Presence on the Scientific ESA is encouraged to continue the development and adop- Exploration of Mars tion of its own Planetary Protection policy in compliance In the endeavour to search for signatures of life on Mars, it with the COSPAR guidelines. European involvement must is expected that several robotic missions will and have to pre- be investigated further, for example with respect to Mars cede any human landing on Mars (see Fig. 7). Overall, human sample return missions, defining the role that Europe should and robotic missions should be complementary. Finally, as- play in developing Earth-based quarantined sample curation trobiology can immensely benefit from a human presence on facilities (see Fig. 6). A sample distribution policy also needs Mars. The advantages of human presence include to be established between international partners early in the process. • the adaptability and dexterity of humans, thereby pro- With this involvement in planetary protection activities, viding a better capacity in dealing with the unpredictable; Europe will develop further competence to be able to actively • possibility of carrying out field geology, such as deep- contribute to the planetary protection discussions with re- drilling (metres to tens, or even hundreds, of metres), crit- gard to human exploratory missions that are just starting. As ical in situ inspection and decision-taking, and long-term already indicated, prior to manned missions to Mars, ap- in situ analysis of a wide variety of samples (rocks, ice, propriate guidelines need to be developed: atmosphere), thereby also enabling a skilful pre-selection of samples to be returned to Earth; • to protect the planet from human activities that may be • remote control of on-site robotic activities, such as search harmful to its environment; this includes preventing the for life in special regions; introduction of biological agents and human microbes that • adaptability and flexibility of the research experiment could hamper the search for indigenous martian life; portfolio; • to protect the Earth from potentially harmful agents • in situ repair of explorative and analytical facilities and instruments, as has already been demonstrated with the 7http://cosparhq.cnes.fr/Scistr/Pppolicy.htm. Hubble Space Telescope repair by astronauts. EUROPE’S EXPLORATION PROGRAMME 33

FIG. 7. Artist’s impression of a base on Mars (© ESA).

On the other hand, one should bear in mind that human 9. The Case for NEO Sample Return Missions involvement may also impede the scientific exploration of Small bodies, as primitive leftover building blocks of the the planet. Those cases where human presence could become Solar System formation process, offer clues to the chemical an impediment pertain to the following areas: mixture from which the planets formed some 4.6 billion years ago. Near Earth Objects (NEOs) as shown in Fig. 8, represen- • Science: planetary protection requirements might hinder tative of the population of asteroids and dead comets, are access of humans to astrobiologically interesting sites. thought to be similar in many ways to the ancient planetesi- Bearing these constraints in mind a rigorous sequence of mal swarms that accreted to form the planets. NEOs are in- events must be established well in advance, e.g., by test- teresting and highly accessible targets for scientific research. ing them on the Moon. In addition it may become neces- The chemical investigation of NEOs having primitive sary to establish “human-free” areas on Mars; characteristics is thus essential in the understanding of the • Human health issues: a detailed environmental risk assess- planetary formation. They carry records of the Solar System’s ment is required before humans are sent to Mars; birth and early phases and the geological evolution of small • Technology: human presence requires much higher de- bodies in the interplanetary regions. Moreover, collisions of mands on reliability of the mission than robotic missions; NEOs with Earth pose a possible hazard to present life and, there are additional requirements with regard to life sup- additionally, they could have been one of the major deliver- port and safety; ers of water and organic molecules on the primitive Earth. • Economics: high costs of a human mission; Characterisation of multiple small bodies is important in that • Societal issues: risk of potential back-contamination when context for threat evaluation, mitigation and, potentially in returning to the Earth. the longer term, for identification of resources. Therefore, a careful planning of the overall scenario of the For all these reasons the exploration of NEOs is particularly in- EEP is required to make maximum use of the synergy be- teresting, urgent, and compelling. The main goal is to set, for the tween robotic and human exploration of Mars. Adequate first time, strong constraints on the link between asteroids and me- guidelines, both scientific/technological and legal, will need teorites, to achieve insight on the processes of planetary accretion to be established with the different stakeholders involved. and on the origin of life on Earth and its distribution in the Solar 34 WORMS ET AL.

FIG. 8. Asteroid 243 Ida & Dactyl (© NASA/JPL Caltech).

System. In the short term, and after flyby and landing missions • What are the properties of the building blocks of the ter- on NEOs (ca. 2014), the next goal should be sample return, en- restrial planets? abling a detailed investigation of primitive and organic matter from • How have major events (e.g., agglomeration, heating, one selected, small body. aqueous alteration, solar wind) influenced the history of planetesimals? A sample return mission to an NEO can be a precursor, • What are the elemental and mineralogical properties of low-cost mission to Mars sample return missions, and it is NEO samples, and how do they vary with geological con- possible with a short planning phase (before 2020). Priority text on the surface? shall be given to pristine small bodies; e.g., C- or D-type as- • Do primitive classes of NEOs contain pre-solar material teroids or comets. It is generally agreed that NEOs are among yet unknown in meteoritic samples? the most accessible bodies of the Solar System and that some • How did NEO and meteorite classes form and acquire of them could even turn out to be more accessible than the their present properties? Moon. A sample return mission to an NEO could be realised with new technological developments. Furthermore, sample return missions on primitive NEOs Based on the present knowledge of the NEO population, will give insights into major scientific questions related to it is possible to find 320 objects, reachable with a Delta-V exobiology, such as 7km/s, and about 180 with Delta-V 6 km/s (Perozzi et al., 2001; Christou, 2003; Binzel et al., 2004). Target selection strategy must take into account both compositional properties • What are the nature and origin of organic compounds on and Delta-V. At a later stage, the diversity of objects should an asteroid? be investigated by missions to different types of objects. Fi- • How can asteroids shed light on the origin of organic mol- nally, characterisation of potentially hazardous objects is ecules necessary for life? considered vital. • What is the role of asteroid impact for the origin and evolution of life on Earth? Europe should implement an NEO technological demonstration mission, where the cosmogonical and exobiological contexts would Although challenged by several recent articles one im- be explored. portant observation to date is the chiral asymmetry in or- The leading aim is to answer the following fundamental ganics such as amino acids in meteorites. It has been sug- questions: gested that this left-handedness may be related to the left-handedness that is the signature of life on Earth (Cronin • What are the initial conditions and evolutionary history and Pizarello, 1997; Cronin and Reisse, 2005). The planets of of the solar nebula? the inner Solar System experienced an intense influx of EUROPE’S EXPLORATION PROGRAMME 35 cometary and asteroidal material for several hundred mil- mandate, for instance on an international exploration pro- lion years after they formed. gramme, would greatly facilitate this coordination of efforts. The earliest evidence for life on Earth coincides with the There are two ways to international collaboration: multilat- decline of this enhanced bombardment. The fact that the in- eral or bilateral; in the latter there is a minor partner, which flux contained vast amounts of complex organic material of- is rarely a satisfactory option. International Traffic in Arms fers a tantalising possibility that it may be related to the ori- Regulations (ITAR) rules are also very detrimental to inter- gin of life. national cooperation. Therefore we propose A detailed study of the material at the surface or sub-surface of an asteroid is therefore needed. The information that • to give a strong international cooperation side to the EEP, is required demands complex pre-analysis processing and identifying relevant partners for each building block of the very high levels of analytical precision. programme; • to base this cooperation on “planetary assets” that part- Therefore, it is essential that the sample is returned to Earth for ners can bring in: systems deployed on planetary bodies detailed laboratory investigations where the range of analytical to be used by everybody; e.g., GPS on Mars. tools, their spatial resolution and analytical precision are generally orders of magnitude superior to what can be achieved from re- This is a different philosophy, not one guided by national- mote sensing or in situ analyses. ism, but one of cooperation, which should appeal more to Eu- Such information can be achieved only by large, complex ropean citizens. In addition the Global Exploration Strategy instruments; e.g., high mass resolution instruments (large Group composed of 14 space agencies has met a number of magnets, high voltage), bright sources (e.g., synchrotron), times in the past year and a half to try and better coordinate and usually requires multi-approach studies in order to un- the exploration goals and objectives of the various space agen- derstand the nature and history of specific components. cies, including NASA, ESA, and a number of European part- In summary, a mission with sample return to a primitive ners (The Global Exploration Strategy: the framework for co- NEO of C or D type will help in understanding the chemi- ordination, http://www.globalspaceexploration.org). cal and biological aspect of the formation and the evolution of our and other planetary systems. Acknowledgments Such an innovative mission will be very important This work was carried out under ESA contract No. 21012. We acknowledge image credits by ESA, P. Carril. Finally we • to test new technology developments: precision landing, au- would like to thank gratefully Professor Gerhard Haerendel, tonomous sampling (sample transfer, containment, drilling), ad- who was chairing the ESSC-ESF during most of this evalu- vanced propulsion, Earth re-entry capsule, in-orbit docking, ation and who contributed to a very large extent to its suc- telecommunication, in situ energy, planetary protection; cessful completion as well as the European Science Founda- • to prepare new adequate laboratory facilities for extraterrestrial tion and Jean-Pierre Swings, Chairman, European Space sample analysis; Sciences Committee. This strategy report has been reviewed • for scientists, and particularly young scientists, for a program- by individuals chosen for their diverse perspectives and ex- matic vision of exploration, huge scientific interest, large inter- pertise, in accordance with procedures used by the European est for the media and European citizens. Science Foundation (ESF). The purpose of this independent review was to provide additional critical comments to assist Moreover, robotic sample return missions to NEOs can ESF and the European Space Sciences Committee’s (ESSC) serve as pathfinders for sample returns from high-gravity Ad Hoc Group in making the published report as sound as bodies, e.g., Mars and, much later on, for human missions possible and to ensure that it meets standards for objectiv- that might use asteroid resources to facilitate human explo- ity, evidence, and responsiveness to the study charge. The ration and the development of space. contents of the review comments and draft manuscript remain confidential to protect the integrity of the deliberative 10. International Cooperation process. We wish to thank the following individuals for their participation in the review of this report: Philippe Masson, All space agencies agree that international cooperation University of Orsay, Orsay, France. Clive R. Neal, Univer- will be essential to accomplish advanced missions such as sity of Notre Dame, Notre Dame, Indiana, USA. An anony- Mars sample returns. One of Europe’s strengths is its col- mous reviewer. The ESSC and the ESF are also very grate- lection of member states, making it naturally open to inter- ful to all Steering Committee members and participants to national cooperation. Apart from a prioritized mission list, the Athens workshop for their dedication and hard work in Europe’s exploration programme could have two compo- support of this evaluation activity. The contribution of nents. One is architecture for Mars: if one agrees to concen- Agustin Chicarro in compiling the table appearing in Ap- trate on Mars sample return missions, this architecture could pendix 1 of this report is gratefully acknowledged. be based on telecom and navigation (“GPS on Mars”). The other one—bolder—is to engage other partners to join Eu- rope in developing instruments or other aspects and coor- Appendix 1 dinating their approach. Science goals for the scientific exploration of Mars and Indeed the current situation sees duplication of similar ini- the Moon tiatives by various international partners; e.g., Moon missions by India, China, Japan. It has been argued that an In- The following table summarises the remaining science ter-Agency Consultative Group (IACG) with a renewed goals for future European exploration of the Moon and Mars, 36 WORMS ET AL.

APPENDIX 1 TABLE.SCIENCE GOALS FOR THE SCIENTIFIC EXPLORATION OF MARS AND THE MOON

Planet MARS MOON EARTH