Mission Concepts of Unprecedented Zipangu Underworld of the Moon Exploration (UZUME) Project

1) 1) 1) 1) 1) 1) By Junichi HARUYAMA, Isao KAWANO, Takashi KUBOTA, Masatsugu OTSUKI, Hiroki KATO, Toshihiko NISHIBORI, 1) 1) 1) 1) 1) Takahiro IWATA, Yukio YAMAMOTO, Yoshiaki ISHIHARA, Aiko NAGAMATSU, Kazuhito SHIMADA, 2) 3) 3) 4) 4) 5) Toshiaki HASENAKA, Tomokatsu MOROTA, Masaki N. NISHINO, Ko HASHIZUME, Kazuto SAIKI, Motomaro SHIRA, 6) 7) 8) 8) 9) Goro KOMATSU, Nobuyuki HASEBE, Hisayoshi SHIMIZU, Hideaki MIYAMOTO, Kensei KOBAYASHI, 10) 11) 12) 12) 13) Shinichi YOKOBORI, Tatsuhiro MICHIKAMI, Satoru YAMAMOTO, Yasuhiro YOKOTA, Hitoshi ARISUMI, 14) 15) 16) Genya ISHIGAMI, Katsushi FURUTANI and Yuichi MICHIKAWA

1)Japan Aerospace Exploration Agency, Sagamihara, Japan 2)Kumamoto University, Kumamoto, Japan 3)Nagoya University, Nagoya, Japan 4)Osaka University, Osaka, Japan 5)Planetary Geology Institute, Tokyo, Japan 6)Università d’Annunzio Pescara, Italy 7)Waseda University, Tokyo, Japan 8)University of Tokyo, Tokyo, Japan 9)Yokohama National University Yokohama, Japan 10)Tokyo University of Pharmacy and Life Sciences, Hachioji, Japan 11)Kindai University, Hiroshima, Japan 12)National Institute for Environmental Studies, Tsukuba, Japan 13)National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan 14)Keio University, Yokohama, Japan 15)Toyota Technological Institute, Tokyo, Japan 16)National Institute of Radiological Sciences, Chiba, Japan

(Received July 31st, 2015)

We are planning to explore the caverns through the skylight holes on the Moon and Mars. The holes and their associated subsurface caverns are among the most important future exploration targets. The importance of the lunar and Martian holes and their associated caverns is categorized from two aspects: (1) fresh materials are easily observed and sampled there, and (2) the subsurface caverns provide a safe, quiet environment. The expectation of lunar and Martian hole and cavern exploration is increasing in Japan. We name the project as UZUME (Unprecedented Zipangu (Japan) Underworld of the Moon Exploration) whose name is after a Japanese mythology. The ultimate purpose of the UZUME project is to investigate how to expand human activity and survival in space and on extraterrestrial bodies.

Key Words: Moon, Exploration, UZUME, SELENE, Hole

1. Introduction SELENE TC. The images of LRO-NAC provided conclusive In 2009, three huge vertical holes were discovered in the evidence that large spaces are opening around the floor of the lunar Marius Hills, Mare Tranquillitatis, and Mare Ingenii in SELENE holes.5) The vertical walls of the holes were also the 10 m-resolution images taken by the Terrain Camera (TC) imaged by LRO oblique observations and they exhibit layered aboard SELenological and ENgineering Explore (SELENE, structures.5) The diameters and depths of the SELENE holes nicknamed KAGUYA) of Japan.1,2) The holes have aperture were re-measured/ re-estimated based on LRO-NAC data.2,5) diameters and depths of several tens of meters to one hundred The measured values of the Mare Tranquillitatis and Mare meters. Haruyama et al. (2009)1) hypothesized that they are Ingenii holes were almost the same as the measurement and possible “skylights” opened on subsurface caverns such as estimation results based on TC image data. However, the lava tubes. Lava tubes often form in basaltic lava areas on the depth of the Marius Hills Hole (MHH) was shallower than Earth. Many lava tubes exist at the foot of Mt. Fuji in Japan, that estimated from SELENE observation results. Haruyama for instance. Similar hole structures are also found on Mars.3,4) et al. (2009) 1) estimated the depth of the hole using SELENE The United States Lunar Reconnaissance Orbiter (LRO) Multiband Imager (MI) data because no appropriate TC data Narrow Angle Camera (NAC) later identified more pits on the were available to estimate it. The spatial resolution of MI is 20 Moon,5-7) including three holes that SELENE had discovered m/pixel; thus, the boundary of the illuminated and shadowed (hereafter, “SELENE holes”). The resolution of LRO-NAC is areas from which the depth was estimated was unclear, 0.5 to 2 m/pixel, which is ten times better than that of resulting in overestimation of the shadowed region and

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Underworld of the Moon/Mars Exploration (UZUME). This presentation outlines UZUME.

2. Significance of Lunar Holes

There is much scientific significance in exploring lunar holes and caverns,2) which may be categorized from two 150 m aspects: (1) fresh materials are easily observed and sampled in the holes and caverns, and (2) the holes are entrances to caverns that provide a safe, quiet environment. On the Moon, Fig. 1. Mare Tranquillitatis Hole (MTH). LRO NAC images taken numerous meteorites have impacted, radiation has constantly by an oblique observation (Left, id: M152662021R) and by a nadir showered, and wide temperature oscillation has caused observation (Right, id: M155016845R). Rocks circled by orange ovals for both images are same ones; a void space extending under a deformation of rocks. The surface of the Moon has been thick roof is confirmed. (Courtesy of R.Yasuda) suffered from brecciation, space weathering, and therefore depth. fragmentation. “Fresh” rocks and materials keeping original The pits in the LRO-NAC images were classified into three information are rare on the surface of the Moon. On the other categories based on their locations: floors of large craters such hand, “fresh” rocks and materials are found on the walls and as the King crater (80 km diameter), 6) mare, and highlands. floors of vertical holes and subsurface caverns. They provide The pits on the crater floors were apparently formed by information about past volcanic activity; dynamo magnetic depression and/or degassing of cooling impact-melt lavas. field generation; implanted materials from the Sun, comets, Most are smaller than a few tens of meters in diameter and are and asteroids; and stratification that occurred in the deep not skylights of subsurface caverns. Including the SELENE interior. The best places to set various observation instruments holes, eight pits have been identified in mare regions. Most are inside the safe, quiet holes and caverns. mare pits are smaller and shallower than the SELENE holes;7) The lunar holes are precious entrances to safe, quiet an exception is the pit on Lacus Mortis (Lake of Death), environment of caverns that is also useful for both observation which is as large as the SELENE holes, with a 140 m x 110 m instruments and human beings. Temperature oscillations are axis-length oval opening and 80 m depth. The Lacus Mortis very large on the lunar surface. At the equatorial region, temperatures range from -150 to +120 deg C. Haruyama et al. pit is located at 45 deg north latitude. For the pit, no 2) entrance to caverns has been confirmed.7) In other words, the (2012) estimated that the temperature oscillation at a existence of subsurface caverns connecting to the pit has not permanently shadowed location on the floor of the MHH is been confirmed. -20 to +30 deg C, based on a cylindrical model for the vertical hole. The radiation environment on the lunar surface is also severe. Occasionally, fatal radiation bursts strike the lunar surface. It should be noted that covering by lunar regolith of a few meters thickness on shelters does not protect the people inside the shelters from radiation damage;9) rather, it yields the opposite effect. The radiation entering the regolith covering would generate weaker but more secondary radiation that 300 m reaches inside the shelters and harms the residents. Radiation

risk exists even in the lunar polar region. Only lunar Fig. 2. Lacus Mortis Pit. LRO NAC images taken by a nadir subsurface areas are safe from radiation. Lunar caverns do not observation (Left, id: M126759036L) and by an oblique observation collapse easily.10) Actually, terrestrial lava tubes are tough. (Right, id: M1105701957R). No entrance to caverns has been 7) Most lava tubes at the foot of Mt. Fuji have not been collapsed confirmed. by the repeated large earthquakes in Japan. It was also “Pit” is a general term for depression8) structures. However, reported that a magnitude 7.5 earthquake did not effect a lava vertical holes such as the SELENE holes are apparently tube in Hawaii.11) Moonquakes have such a low energy level unique, different from other smaller and shallower depressions. that their hazardous risk for subsurface caverns is almost zero. Thus, we use the term “hole” to refer to gigantic pit structures, The possibility of meteorite impacts that hit and destroy lunar such as the MHH, Mare Tranquillitatis Hole (MTH), and Mare base caverns is also quite low. Ingenii Hole (MIH). Lunar and Martian holes/pits and associated subsurface 3. Increasing Expectations of Hole and Cavern Explorations caverns have much importance from the viewpoints of science and future utilization. Expectation of the exploration of lunar Because of the significances of lunar holes and caverns, and Martian holes/pits and caverns is increasing, especially in expectations to explore them are increasing. Since 2010, many Japan. Many studies of lunar and Martian holes and associated Japanese researchers have met to discuss science, exploration caverns have been presented in academic meetings. Some technology, and outreach activity associated with lunar and research groups are planning to explore these holes and Martian holes and subsurface caverns. For example, more than caverns. One such plan is the project Unprecedented Zipangu 100 researchers totally participated in a meeting entitled

Pk_148 J. HARUYAMA et al.: Mission Concepts of Unprecedented Zipangu Underworld of the Moon Exploration (UZUME) Project

“Conference: Exploration of vertical hole and subsurface hole, and the inside of the caverns will be observed. caverns on the Moon and Mars”, held in 2015 at Temperature, radiation, and micrometeorites hitting the Fuji-Kawaguchiko Town, where there are many lava tubes, at bottom of the hole and the inside of the caverns will be the foot of Mt. Fuji in Japan. SELENE-2 was a mission with measured. How to detect volatiles at the wall and bottom of an intension to send a landing module to the Moon, and a the hole and inside the caverns is being considered. The lunar hole was a candidate for the landing site. However, the UZUME group aims to complete this first stage in the early SELENE-2 mission was officially terminated in March 2015. 2020s. The mission of the second stage, to be completed in the In January 2015, the Institute of Space and Astronautical mid-2020s, will be a sample return from the exposed layers of Science (ISAS) of the Japan Aerospace Exploration Agency the inner wall of the hole, the floor of the hole, and the inside (JAXA) announced that it would start making road maps of of the caverns. The third stage will involve traveling to Mars future space mission programs, and required that space with the technologies developed in the first two stages. The science communities provide information about space science main mission of this stage is a search for life on Martian. The missions that were in preparation and those that were expected. interiors of the Martian caverns where ultraviolet rays, a In response, the chair of the Japanese Society for Planetary destroyer of highly compound molecules approaching to Sciences and a group named by the chair surveyed missions become a form of life, do not reach, is one of the most and presented a report. This report indicated that one of probable locations of life existence. Martian caverns may thus expected target of future space exploration is “underground” be appropriate residences where human beings can live on on the Moon and planets. Thus, holes and subsurface caverns Mars for long periods. could be considered appropriate targets for future space The key technology of the UZUME project is robotics. science programs. A surface area right next to MHH is a Wheel rovers are perhaps not appropriate for investigation on candidate for a landing site for the Smart Lander for the floor with scattered rocks of a few meters across. Multi-leg Investigating the Moon (SLIM), a mission that will and humanoid robots may be needed. Robots that use the same demonstrate pinpoint landing technology on the Moon and instruments as human astronauts will be good co-workers for that has been proposed as the third small science mission to be astronauts. A goal of the UZUME project is the development launched by an Epsilon rocket. However, SLIM will not of “tele-scientists,” robots that work on the Moon and Mars explore the inside of the hole because of limited launch mass. using telecommunications, as alternatives for scientists staying The Hakuto team that is competing in the Google Lunar X on the Earth. We expect that the robot technology developed race to send a lander to the Moon and make a rover move on in the UZUME project will be used also in extreme conditions the lunar surface is planning to land on an area near the Lacus such as erupting volcanoes, deep seas, or inside of nuclear Mortis pit. plants. The UZUME project has a third pillar besides science and 4. UZUME Project engineering. It is the public engagement of ordinary people. The knowledge and technologies acquired in lunar and As a result of increased expectations to explore lunar holes planetary missions should be returned to the public. Public and caverns, Japanese scientists and engineers formed a engagement does not need to wait for the realization of research group under the space engineering committee to missions. Even during the planning phase, outreach activities consider a project to explore lunar and planetary caverns. could be tried. Publicity using a set of Karuta (Japanese cards) They named the project UZUME, after a goddess appearing in associated the UZUME project is one such trial.12) the two oldest Japanese historical records, Kojiki and Nihon Shoki. These works tell us that “Once upon a time, the Sun 5. Conclusions Goddess hid into Amano-Iwato cave in a reason, and the light was lost from the world. Other gods were in trouble. Then In 2009, the Japanese lunar explorer SELENE (Kaguya) Uzume, a goddess, danced in front of the cave. Other gods discovered on the Moon huge holes whose aperture diameter enjoyed seeing her dance and laughed loudly. The Sun and depth exceeded several tens of meters. Later, evidence Goddess became interested in what was going on outside and that the lunar holes are “skylights” of subsurface caverns was slightly opened the door of the cave. At the moment, a obtained using the LRO-NAC. These holes have much powerful god completely opened the door of the cave. Then significance for science and future utilization of the Moon. the light was returned to the world.” The project name of Similar holes have been found on Mars. The Martian holes UZUME is the abbreviation of Unprecedented Zipangu may provide safe shelters allowing terrestrial beings to survive Underworld of the Moon/Mars Exploration. on the planet. In the future, human beings will have a base The UZUME research group is proposing a three-stage inside the Martian caverns. program over the next two decades. The mission concept of The expectations of exploration of lunar holes are the first stage is technology demonstrations approaching from increasing. A landing site candidate for the Smart Lander for the landing location to a hole, descending into the hole, Investigating Moon (SLIM) is right next to the Marius Hills performing observation at the floor of the hole, and entering Hole (MHH) that SELENE found. However it seems to be the cavern opening at the bottom of the hole. Details of the difficult for SLIM to explore inside the hole. topography and geology of the surface around the hole, the A group of Japanese scientists and engineers are layers exposed at the inner wall of the hole, the floor of the considering missions to enter and explore lunar holes and

Pk_149 Trans. JSASS Aerospace Tech. Japan Vol. 14, No. ists30 (2016) caverns of the Moon and Mars. The mission program is named 10) Blair, D.M., Chappaz, L., Sood, R., Milbury, C., Melosh, H.J., UZUME, after a Japanese goddess in historical literatures. Howell, K.C. and Freed, A.M.: Determining the structural stability of lunar lava tubes, 46th LPSC Abstract 2174, 2015. Researchers are planning three stages for UZUME in the next 11) Coombs, C.R. and Hawke, B.R.: A search for intact lava tubes on two decades. The mission of the first stage will involve the the Moon: possible lunar base habitats, Proceedings of the Second utilizing technology to approach and enter the holes and Conference on Lunar Bases and Space Activities of the 21st subsurface caverns. In the second stage, samples from walls Century, NASA Johnson Space Center SEEN93-1741405-91, and floors of a lunar hole and its connecting cavern will be 1992, pp. 219-229. 12) Haruyama, J., Kawano, I., Iwata, T., Yamamoto, Y., Shimada, K., returned. The targets of the third stage of UZUME will be Shigeto, S., Nishino, N.M., Shirao, M., Yamada, T., Arai, M., Martian holes and caverns where extraterrestrial beings may Nakajima, M., Kitamura, K. and Fujiwara, Y.: Promoting Public have existed or may exist even today. Understanding of Science and Technology through the The ultimate purpose of the UZUME project is to Unprecedented Zipangu Underworld of the Moon Exploration th investigate how to expand human activity and survival in (UZUME) Project, 30 ISTS 2015-k-36, 2015. space and on extraterrestrial bodies. To accumulate knowledge of the origin and evolution of the Moon, Mars, and our solar system, and the possibility of emergence and existence of extraterrestrial life is part of this purpose. The Earth may be destroyed in the far distant future, but worldwide natural disaster and/or environmental deterioration in the near future should not be excluded. The Earth may not always be kind to human beings. Nobody knows if the Moon and Mars are the best places for evacuation of human beings. Therefore, the possibility of human activity there should be investigated. UZUME seeks to investigate the possibilities.

Acknowledgments This work was supported by JSPS KAKENHI Grant Number 26400459.

References

1) Haruyama, J., Hioki, K., Shirao, M., Morota, T., Hiesinger, H., vander Bogert, H.C., Miyamoto, H., Iwasaki, A., Yokota, Y., Ohtake, M., Matsunaga, T., Hara, S., Nakanotani, S. and Pieters, C.M.: Possible lunar lava tube skylight observed by SELENE cameras, Geophy. Res. Lett., 36 (2009), L21206. 2) Haruyama, J., Morota, T., Kobayashi, S., Sawai, S., Lucey, P. G., Shirao, M. and Nishino, M.N.: Lunar Holes and Lava Tubes as Resources for Lunar Science and Exploration, Moon – Prospective Energy and Material Resources, Badescu, V. (ed.), Springer 2012, pp. 139-164. 3) Cushing, G.E., Titus, T.N., Wynne, J.J. and Christensen, P.R.: THEMIS observes possible cave skylights on Mars, Geophys. Res. Lett., 34 (2007), L17201. 4) Cushing, G.E.: Candidate cave entrances on Mars, J. Cave and Karst Studies, 74 no.1 (2012), pp. 33-47, doi: 10.4311/2010 EX0167. 5) Robinson, M.S., Ashley, J.W., Boyd, A.K., Wagner, R.V., Speyerer, E.J., Hawke, B.R., Hiesinger, H. and vander Bogert, C.H.: Confirmation of sublunarean voids and thin layer in mare deposits, Planet. Space Sci., 69 (2012), pp. 18-27. 6) Ashley, J.W., Robinson, M.S., Hawke, B.R., vander Bogert, C.H., Hiesinger, H., Sato, H., Speyerer, E.J., Enns, A.C., Wagner R.V., Young, K.E. and Burns, K.N.: Geology of the King crater region: New insights into impact melt dynamics on the Moon, J. Geophys. Rev. (planets), 117 (2012), E00H29, doi: 10.1029 /2011 JE003990. 7) Wagner, R.V. and Robinson M.S.: Distribution, Formation Mechanisms, and Significance of Lunar Pits, Icarus, 237 (2014), pp. 52-60, doi.org/10.1016/j.icarus.2014.04.002. 8) Martellato, E., Foing, B.H. and Benkhoff, J.: Numerical modeling of impact crater formation associated with isolated lunar skylight candidates on lava tubes, Planet. Space Sci., 86 (2013), pp. 33-44. 9) Denisov, A.N., Kuznetsov, N.V., Nymmik, R.A., Panasyuk, M.I. and Sobolevskii, N.M.: On the problem of lunar radiation environment, Cosmic Res., 48 no.6 (2010), pp. 509-516.

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