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... to develop a mission architecture for an initial settlement on Mars by assessing the feasibility of cave habitation as an alternative to proposed surface-based solutions.

Mission Statement

Introduction

Human Cave Program

Alternative Program

Mars Caves

Governing Frameworks

Future Considerations

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ACCESS Mars will assess habitation scenarios that maintain crew health and safety in the Martian environment, while allowing them to perform key science and exploration tasks. Aside from the engineering and technological challenges of such a mission, the assessment of cave-based solutions will also address issues related to social impact, international cooperation, policy, law, and planetary protection.

Scope

Overview

Introduction

A human mission to Mars will be a bold endeavor and will launch humankind into a new era of space exploration. Given the complex technical and ethical dimensions in-volved in exploring another planet, it will be necessary to manage and optimize the associated benefits while reducing the risks and hazards to crewmembers on Mars.

This requires consideration and analysis of diverse subsur-face habitation options such as lava tubes. The advantages of lava tubes include, but are not limited to, shielding against radiation, protection from surface environmental hazards, the possible discovery of unexplored scientific opportuni-ties.

“Two thousand years from now, their descendants might walk into this chamber … the first hu-man dwelling built on Mars! ... They were like Cro-Magnons in a cave, living a life that was certain to be pored over by the archae-ologists of subsequent genera-tions… ”

Kim Stanley Robinson, Red Mars

The Lava Caves National Monument, California, yielding unexpected plant growth.Image: National Park Service

1Never before in the history of humankind have people left their home planet to settle permanently on another celestial body. Present generations must extend the work accomplished during the Apollo era and commit to a new vision of exploration to include an initial settlement on Mars.

Caves have been and still are natural protection against hostile environments. They also represent the cradle of human culture and society and are still in use today. It is therefore likely that caves on Mars may provide the protec-tion and security necessary for crew members to establish an initial settlement.

The first humans on Mars can use the knowledge of terrestrial cave dwellings to adapt more easily to a hostile environment, paving the way for a permanent human settle-ment on the planet. ACCESS Mars focuses on caves because of their known presence and potential benefits, including hazard protection against the extreme Martian environ-ment, and engineering advantages. A precursor mission to the Moon can help investigate future Mars mission aspects such as crew size, mission duration, exploration strategies, level of complexity and capability of tools, the application of light-weight and inflatable structures, the reliance on robots, and the dependence on local resources.

Rationale

Introduction

Natural and man-made caves have traditionally served as human dwellings, housing both simple wine cellars and complex temples. Image: John C. Pint

Exploring the Harrat Lavatube: An analog for future EVAs.Image: John C. Pint

“There is a free resource that exists on the Martian surface – caves.”

Penny Boston

Mars Caves

Why cave habitation?Lava tubes have recently been found on Mars. Due to their known presence in volcanic areas and their size, shape, and sound structural stability, their use as human habi-tats is promising. The potentially smooth flat floor and accessible entrances near the surface reinforce this concept. The low radiation levels, protection from dust storms and stable temperatures within these caves provide a safe natural environment for both humans and robots. The notion of a long-term settlement on Mars is supported by the presence of natural hazard protection.

How do we detect caves?

The detection of cave entrances and determining the key cave parameters through remote sensing is required before robotic and human missions can take place. A promising technological option for this task is thermal sensing from a satellite platform. By measuring the thermal variations of the cave entrance in comparison with the surface, caves can be differentiated from mere holes in the ground and key properties of the cave such as length and diameter can be deduced. However, to find caves, we must know what to look for. Measurements of analog sites on both Earth and the Moon will provide the necessary knowledge to more accurately identify caves on Mars. Once caves have been identified through remote sensing detection, surface robotic precursor missions will be required to investigate the caves of interest to assess cave usability and available resources, as well as astrobiological signatures. This will ultimately permit the appropriate selection of a cave as a human habitat.

Various volcanic regions on Mars have evidence of lava tubes and available resources for use. Accessing these regions will open the possibility of rich science and allow long term settlement. Image: NASA (Background terrain)

The smooth floor surface and uniform shape of lava tubes as found on Earth provides ideal spaces for an artificial habitat structure and mobility. Image: Line Drube

2Mars Caves

What makes a good landing site?

Selecting the proper cave requires careful planning. It must meet physical requirements for habitat design, and be suit-ably located such that both survival and mission return can be assured. Nearby water ice, mineral sources and the scien-tific value of the local environment also determine wheth-er the site is appropriate. Although shallow ground ice is known in polar regions, it is anticipated that ice is globally present deep under the subsurface. Access to this resource is not only essential for human survival, but might be facili-tated through the use of caves. The scientific interest of a particular site is also a main driver. The presence of meth-ane, remnant magnetism and the evidence of life could dra-matically change our understanding of Mars.

What resources exist there? Water ice on Mars is central for human exploration. It will allow autonomy from Earth and thus facilitate long term settlement. The significant weight reduction in required stored consumables may in fact render the mission techni-cally feasible. Both the ambient air and the Martian regolith may be converted to oxygen, an essential ingredient for the life support system and fuel. For secondary power genera-tion, both solar and geothermal sources may be used. Iden-tifying new resources and learning their retrieval and uses will lead to sustainability and self sufficiency. Although the restriction to lava tubes for site selection could be limiting compared to a surface habitat, they offer an entry to cur-rently unknown subsurface resources such as ice, energy sources and minerals.

This shows an observed partially collapsed lava tube on Mars with a diameter of several hundred meters. Un-collapsed portions could be ideal for habitation Image: NASA

Human Cave Program

Will caves affect mission planning?

Using Martian caves will pose challenges regarding human mission planning, in that it implies some changes in the car-go launching campaign defined in the latest NASA Design Reference Mission. Operating a cave habitat will require ex-tra cargo shipments in addition to subsurface communica-tion capabilities and underground robotic support.

How would they serve as habitats?Caves on Earth provided shelter in the early stages of human history. This time around Martian caves can play a decisive role in providing humans with shelter and logistic support for human exploration of Mars, replacing heavy structures and shielding required for a surface habitat.

Human habitats will still have to be constructed and de-ployed inside caves. However, requirements will be much less strict, as many caves provide extensive protection from meteorites, radiation, and dust storms. This provides prime conditions for inflatable structures technologies to be used for habitats inside caves. Mass reduction allows us to take full advantage of our launch capacities and enables faster expansion of a modular habitation infrastructure. Tempera-ture fluctuations in caves are less severe and therefore put less strain onto thermal and power systems.

Dynamic lighting systems can be employed to simulate day-light, which is fundamental to human wellbeing in an envi-ronment with low natural light, as well as for horticultural applications.

Illustration of an Inside Cave Habitat (ICH) with two inflatable modules. Image: ACCESS Mars

“We are children of Earth,” Hiroko said, loud enough for all to hear. “And yet here we stand, in a lava tunnel on the planet Mars. We should not forget how strange a fate that is. Life any-where is an enigma and a pre-cious miracle…” Kim Stanley Robinson, Green Mars

3Human Cave Program

Can caves help Mars Exploration?

Caves are both prime candidates for supporting human ex-ploration of Mars and also test beds for scientific explo-ration. Given the strong astrobiological potential of caves, sub-surface environments, and the characteristic environ-mental conditions inside caves, are typically different from surface conditions.

Crews will be expected to act highly autonomously, as no real-time support possibility exists between Earth and Mars. Consequently, crews must become medically autonomous. The crew should be trained as field scientists in Mars cave analog environments to guarantee a good performance for the necessary Mars cave-specific operations.

Reducing overall radiation, which will allow the mission crew to extend EVA time and perform more scientific ex-ploration of the planet surface as well as the cave interior. Temperature conditions inside and at the entrance of caves may also allow implementation of new closed loop life sup-port system, and an increase in the performance of existing technologies.

Some technical capabilities and scientific information that would be required to allow humans to live in caves on Mars are missing. Therefore, precursor missions will be needed, in order to test planetary technology and in-situ resource utili-zation (ISRU) or sending robots to explore potential caves.

A multi-functional Mars base could include a greenhouse. Image: NASA

Future exobiology and geology research on Mars — on the surface, and below.Image: NASA

Access Mars

A Vision of Exploration

Permanent Presence

Robotic Reconnaissance

Human Exploration

The Search for Life

Cave Habitats

Access Mars

A Vision of Exploration

Permanent Presence

Robotic Reconnaissance

Human Exploration

The Search for Life

Cave Habitats

Capacity USA Russia China Europe Japan IndiaMANNED

Access To LEO Yes Yes Yes No No NoEarth Re-Entry Yes Yes Yes Anticipated Anticipated NoLife Support System Yes Yes Yes Anticipated No NoLEO Rendez Vous Yes Yes No No No NoTransfer to Moon/Mars Orbit Yes No Anticipated No No NoMars EDL Anticipated No No No No NoMoon Landing Yes No No No No NoSurface Habitat Anticipated No No No No NoRover/Mobility Capability Yes No No No No NoMoon Surface to LLO Yes No No No No NoMars Surface to LMO No No No No No No

UNMANNEDAccess To LEO Yes Yes Yes Yes Yes YesTransfer to Moon/Mars Orbit Yes Yes Yes Yes Yes YesEarth Re-entry Yes Yes Yes Anticipated Anticipated NoMoon Landing Yes Yes Anticipated Anticipated Anticipated NoMars EDL Yes Yes No Anticipated Anticipated NoRover/Mobility Capability Yes Yes No Anticipated No NoAutonomous Rendez-vous Anticipated Anticipated No Yes No NoMoon Surface to LLO Yes Yes No No No NoMars Surface to LMO No No No No No No

Yearly Foreseable Budget ($ Billions) 18 1.5 n/a 7 2 1

Governing Frameworks

What role does law play?

A human mission to Mars raises certain legal issues for com-pliance under both international and national law. In fact, the four main space law treaties delineate the rights and ob-ligations of states in conducting space activities. The current legal regime applies equally to both surface-based or cave-based habitat solutions. Important legal concepts include:

■ No national appropriation of Martian territory is al-lowed; no private or public entity can claim a piece of Mars territory.

■ States have an equal right under the Outer Space Trea-ty to explore, exploit, and use Martian resources. This includes mining on Mars, water extraction, and other ISRU activities.

■ States must authorize and supervise national and private entities involved in space activities. This includes enact-ing law and licensing regimes to ensure compliance with the treaties.

■ States are internationally responsible and could be liable for damage caused as a result of their national space activities.

■ In pursuing activities on Mars surface and subsurface, States must take appropriate measures to avoid harm-fully contaminating the Martian environment. Likewise, precautions should be taken to avoid adversely affecting the Earth as a result of Martian exploration.

Overview of international State space capabilities as of 2009

Stakeholder matrix illustrating areas of focus for gaining global public, private and governmental support

Capacity USA Russia China Europe Japan IndiaMANNED

Access To LEO Yes Yes Yes No No NoEarth Re-Entry Yes Yes Yes Anticipated Anticipated NoLife Support System Yes Yes Yes Anticipated No NoLEO Rendez Vous Yes Yes No No No NoTransfer to Moon/Mars Orbit Yes No Anticipated No No NoMars EDL Anticipated No No No No NoMoon Landing Yes No No No No NoSurface Habitat Anticipated No No No No NoRover/Mobility Capability Yes No No No No NoMoon Surface to LLO Yes No No No No NoMars Surface to LMO No No No No No No

UNMANNEDAccess To LEO Yes Yes Yes Yes Yes YesTransfer to Moon/Mars Orbit Yes Yes Yes Yes Yes YesEarth Re-entry Yes Yes Yes Anticipated Anticipated NoMoon Landing Yes Yes Anticipated Anticipated Anticipated NoMars EDL Yes Yes No Anticipated Anticipated NoRover/Mobility Capability Yes Yes No Anticipated No NoAutonomous Rendez-vous Anticipated Anticipated No Yes No NoMoon Surface to LLO Yes Yes No No No NoMars Surface to LMO No No No No No No

Yearly Foreseable Budget ($ Billions) 18 1.5 n/a 7 2 1

4Governing Frameworks

Policy Considerations

A human Mars mission involves several major policy con-siderations. They include the capacity for international co-operation and contribution, an analysis of the significance or benefits of a Moon/Mars exploration strategy, and as an analysis of the benefits of precursor missions.

As international cooperation is essential for such a mission, consideration should be taken for each country’s specific technical capabilities and yearly budget.

Looking at precursor missions, it appears that there is a solid case for a combined exploration strategy, first using the In-ternational Space Station (ISS), then landing on the Moon, and eventually setting foot on Mars. Indeed, such a program would allow gaining the necessary confidence in the required technologies in a progressive, and affordable, manner.

Society

Overview of international State space capabilities as of 2009

Stakeholder matrix illustrating areas of focus for gaining global public, private and governmental support

The main stakeholders that should be targeted on are gov-ernments, space agencies, large aerospace companies, and the public (taxpayers, mass media & social media) espe-cially in the area of interest of social impact, technology, engineering, and economical prosperity. These results show these areas of society that have the most influential impact on the Mars mission; thus, time and effort need to be dedi-cated to these stakeholders to maximize the ability for a suc-cessful mission.

Alternative Program

As a result of our investigation, an alternative scenario for a permanent human presence is proposed in addition to the ACCESS Mars Design Reference Mission. Six crew members stay for two rotations (~1300 days), creating an overlap of twelve people in the habitat for eighteen months.

Doubling the number of crewmembers and time spent on the Mars surface introduces both benefits and risks. A permanent presence on Mars will provide valuable contri-butions to science and technological innovation. At the same time, the increase in mission duration and crew size will affect the mission parameters. Consequently, recom-mendations and suggestions are provided to mitigate the associated risks.

Impact of Mission Duration

Overview

Extending the presence of a crew on the surface from 18 to 48 months will lead to a reduction in mission hardware life time due to wear and tear. Therefore, the designs should be adapted to ensure continuous operability of the settlement. Using caves as an equipment shelter may decrease the harm-ful impacts of the Martian environment.

Likewise, radiation can be reduced by using caves as protec-tive shields for the habitats. In fact, a surface habitat for long duration missions may not otherwise be possible due to the extreme radiation on Mars.

While longer missions may increase the risk of health is-sues such as acute respiratory infections, urinary calculus, and psychological implications, countermeasures are being developed in technology, in training, and in selection pro-cedures to reduce risks. For instance, technology exists for designing dust repelling suits and surfaces, as well as dust filtration systems.

ACCESS Mars Extended DRMImage: ACCESS Mars

T-14 months, 1st Cargo, Cave Habitat and Surface Habitat Mars Transfer Ve-hicle (MTV) arrive. Cargo and Cave Habitat MTV Land on Mars. Surface Habi-tat MTV stays in orbit.

T+6 months, Crew 1 MTV arrives. Crew transfers to Surface Habi-tat MTV and land on Mars. Crew 1 MTV stays in orbit.

T+10 months, 2nd Cargo, Cave Habitat and Descend-ing MTV ar-rive. Cargo and Cave Habitat MTV Land on Mars. Descending MTV stays in orbit.

1 2 3

5Alternative Program

Impact of Crew Size

Increased crew size allows more specialization amongst the crew in medicine, engineering, and science, thereby enhanc-ing their ability to solve problems that may arise; however, personal and cultural diversity among the crew introduces social interaction difficulties. Other considerations for mission planning include changes in workload, safety, habitat occupancy, and level of privacy, based on occupancy level. For example, while the habitat is fully occupied, the crew will have increased personnel redundancy (in case of sickness or injury), but decreased equipment redundancy.An enlarged crew increases international participation, as in the ISS model.Further research/studies are required to identify other im-plications of increased crew size. For example, planetary protection issues cannot be properly assessed until the im-pact of a single crewmember on an extraterrestrial environ-ment is quantified.

Impact of Human PresenceEstablishing a permanent human presence on Mars will al-low continuous operations and maintenance of the explora-tion infrastructure. In addition, operations are simplified by knowledge han-dovers between crews. Conversely, crew training, including ‘inter-crew’ training, should be modified to enhance inter-personal relationships. International community responsibility for continued hu-man missions on Mars will increase mission success, as was demonstrated on the International Space Station (ISS) after the Columbia accident in 2003. The international communi-ty preferred reducing the crew size over abandoning the ISS.As prolonged human presence and Mars colonization takes place, Mars international nationality may be created. This will affect Earth culture and the necessity for Martian law.

T+32 months, Crew 2 MTV arrives. Crew transfers to Descending MTV and land on Mars. Crew 2 MTV stays in orbit.

T+36 months, 3rd Cargo and Descending MTV arrive. Cargo MTV Land on Mars. Descending MTV stays in orbit.

T+50 months, Crew 1 depar-ture to Earth and arrives at T+56 months.

54 6

General Recommendations

Astrobiology & Planetary Protection

ISS and Lunar bases should be used as stepping stones in establishing a permanent Martian habitat.

A need exists for an in-depth study of Martian caves to fur-ther our understanding of potential hazards such as small meteoroid flux, surface radiation, cave stability (materials, fractures, structure), electrical environment and lighting sys-tems etc.:

■ By using Earth and lunar analogues ■ Through precursor robotic missions and research.

Further consideration of alternate mission scenarios are needed in order to achieve a long-term sustainable human presence on Mars.

Extravehicular activities and the exploration of the un-known in the foreign environment of Mars are a natural progression of the curiosity of humankind. However, plan-etary protection policies are inextricably linked to planetary exploration. ACCESS Mars recommends better and more cost-effective instrument-sterilization and anti-contamina-tion procedures to satisfy these policies. Improved technol-ogies may also help facilitate more astrobiology exploration missions, which should adhere to the COSPAR Planetary Protection Policy. Further debate pertaining to the evolution of planetary protection policies on a global scale (should a consensus be reached) will be beneficial given a multilateral desire to explore beyond Earth. Finally, if planetary explora-tion rights are thought of as earned privileges, a policy sce-nario might reward advances in the sterilization of robotic instrumentation with increasing planetary exploration privi-leges, perhaps using the moon as a test bed for practicing protection procedures.

Future Considerations

International Space Station seen from STS-127.Image: NASA

Now was their chance, for all of them together in this present — ghosts could watch, from before and after, but that was the moment when what wisdom they could muster had to be woven together, to be passed on to all the future generations.

Kim Stanley Robinson, Blue Mars

6

Conclusions

As humanity endeavors to become a two-planet civilization, the use of Martian caves can provide an excellent initial so-lution to some of the problems posed by the various haz-ards on the planet. With time, it is possible that new tech-nologies will lead to more discoveries on how to thrive on Mars, thereby fully realizing a new era of space exploration. By continuing to Assess Cave Capabilities and Evaluating Specific Solutions, we will leave the cradle of Earth, effec-tively accepting the challenge of exploring the unknown and pushing the limits of knowledge beyond our home planet.

Future Considerations

Future TechnologiesMany hazards and surface constraints on Mars are mitigated by cave habitats, which will be very important until future technologies are developed. Recommendations include:

■ The recovery of materials necessary for human life and habitat construction out of the Martian regolith and at-mosphere;

■ Using materials with an atomic number less than alumi-num for radiation shielding to reduce secondary radia-tion, e.g. liquid hydrogen;

■ Improving EVA suit mobility, possibly in the form of mechanical counter-pressure suits;

■ Implementing technology to protect humans and equip-ment from dust storms;

■ Developing advanced propulsion systems, which may make Earth-Mars transits faster and less costly;

■ Advancing ISRU technology for recovering materials necessary for human life and habitat construction from the Martian regolith and atmosphere;

■ Studying futuristic concepts such as nuclear fusion reac-tors

Possible concept of surface exploration on Mars.Image: NASA

The authors gratefully acknowledge the generous guidance, support and direction provided by the following individuals during the course of this work:

Project FacultyRené LauferAlfonso DavilaJhony ZaveletaBeatriz Gallardo

Design & ContentACCESS Mars Effort.

The authors are also grateful for the advice and support of all faculty, teaching associates, staff, advisors and visiting experts of the Interna-tional Space University.

AuthorsA. Al Husseini, L. Álvarez Sánchez, K. Antonakopoulos, J. Apeldoorn, K. Ashford, Jr., D. Atabay, I. Barrios, Y. Baydaroglu, K. M. Bennell, J. Chen, X. Chen, D. Cormier, P. Crowley, G. de Carufel, B. Deper, L. Drube, P. Duffy, P. Edwards, E. Gutiérrez Fernandez, O. Haider, G. Kumar, C. Henselowsky, D. Hirano, T. Hirmer, B. Hogan, A. Jaime Al-balat, E. Jens, I. Jivănescu, A. Jojaghaian, M. Kerrigan, Y. Kodachi, S. Langston, R. MacIntosh, X. Miguélez, N. Panek, C. Pegg, R. Peldszus, X. Peng, A. Pérez-Poch, A. Perron, J. Qiu, P. Renten, J. Ricardo, T. Sarace-no, F. Sauceda, A. Shaghaghi Varzeghani, R. Shimmin, R. Solaz, A. Solé, R. Suresh, T. Mar Vaquero Escribano, M. Vargas Muñoz, P. D. Vaujour, D. Veilette, Y. Winetraub, O. Zeile

SponsorsNASA Ames Research CenterNASA Exploration Systems Mission Directorate (ESMD)

Additional copies of the Executive Summary, Final Report and Project DVD may be ordered directly from the ISU Central Campus: International Space UniversityParc d’Innovation1, rue Jean-Dominique Cassini67400 Illkirch-Graffenstaden, FranceEmail: publications@isu.isunet.edu

Credits & Acknowledgements