Planetary geology is a scientific field to study surface evolution processes of the Moon and other planetary bodies. Its development began with the initiation of the space race between the United States of America and the Soviet Union to the Moon in the 20th century. Geological processes are wide ranging, but they can be classified roughly into impact cratering, tectonics, volcanism, transport of materials due to water, atmosphere and gravity, and weathering/alteration/metamorphism. Furthermore, since the origin, evolution and presence of life depend on the environment in which it thrives, it is extremely important to understand the planetary geological environments for astrobiological studies. Data acquisition by planetary probes is the main approach for direct observation of planetary bodies, but ground-based and space telescope observations are also conducted. On the other hand, as a comparative planetology approach, numerous terrestrial analog studies have been performed for contributing to the understanding of the planetary geological processes. In fact, previous studies indicate that there are many terrestrial geological processes resembling those on planetary bodies.
The Planetary Exploration Research Center has been conducting planetary geology research from its founding, and the results have been published in scientific journals and other venues. As a main research project performed in the past, we can list the investigation of the Lonar impact crater located in the Deccan Traps of India. Ongoing projects include one focusing on mud volcanoes, and another about methane in the atmosphere of Mars analyzing its relation to geology and conducting theoretical research to explain its observations.
Mud volcanoes are different from “normal” volcanoes that are formed by magma extrusion. They form because of eruption of the mud enriched in water and gases such as methane from the subsurface. Like the normal volcanoes, they form edifices, but the difference is that mud volcano edifices are made mainly of unconsolidated clayish materials. In general, the mud is considered to originate from fine-grained sedimentary layers at deep subsurface levels, and by investigating the mud, we can infer the past depositional environment or how the sediment has been altered over time. On Mars, there are many surface features hypothesized to be mud volcanoes, and by studying them we expect to be able to deepen the understanding of water circulation and past depositional environments on the red planet. In addition, since mud volcanoes’ sediment is related to water or methane, components generally linked with the presence of life, mud volcanoes can become potentially interesting targets for the future Mars landing missions. At the Planetary Exploration Research Center, we have been conducting terrestrial analog site researches of mud volcanoes in Azerbaijan, and in Japan at Tokamachi (Niigata Prefecture), Goshogake (Akita Prefecture), and in Wakayama Prefecture. These mud volcanoes are either active vents of mud and methane or fossilized traces. On these sites, we have been investigating a variety of topics such as geology, mineralogy, gas components, and in some cases microbiology.
Lonar impact crater
The 1.8-km wide Lonar impact crater is located in the basaltic Deccan Traps of India. A shallow alkaline lake resides in the bottom of the crater. Today, the Martian surface environment is extremely dry and liquid water is considered to be almost non existing, but there is a hypothesis of past water-rich epochs on the planet. In fact, many pieces of evidence for the past existence of lakes in impact craters (called crater lakes) have been found. For the purpose of deepening the understanding of the Martian crater lakes, Lonar is a great place to provide useful information about the scales of the crater lakes, and circulations of surface and ground waters. Lonar is well preserved for a terrestrial impact crater and its age is considered to be relatively young. We estimated the age of its formation by measuring cosmic-ray exposure ages and estimated the degree of erosion it has experienced to date.
Methane of Mars
The presence of methane in the Martian atmosphere has been reported by multiple observational methods including spacecraft orbiting Mars and ground-based telescopes, and the Curiosity rover on the surface. The presence of reducing methane in the oxidizing environment of Mars is surprising in the sense that it might invoke active biological or geological processes. However, the quantities of the detected methane are extremely low and we have not obtained clues that lead to finding out about their definitive origins. The Planetary Exploration Research Center has been conducting assessment of instruments to detect methane on the Martian surface and theoretical studies for explaining its presence on Mars.
Lonar impact crater
Komatsu, G., Senthil Kumar, P., Goto, K., Sekine, Y., Giri, C., Matsui, T ., 2014. Drainage systems of Lonar Crater, India: Contributions to Lonar Lake hydrology and crater degradation. Planetary and Space Science, 95, 45–55,
Nakamura, A., Yokoyama, Y., Sekine, Y., Goto, K., Komatsu, G., Senthil Kumar, P., Matsuzaki, H., Kaneoka, I., Matsui, T., 2014. Formation and geomorphologic history of the Lonar impact crater deduced from in situ cosmogenic 10Be and 26Al. Geochemistry, Geophysics, Geosystems, 15(8), 3190-3197, doi: 10.1002/2014GC005376.
Komatsu, G., Ishimaru, R., Miyake, N., Kawai, K., Kobayashi, M., Sakuma, H., Matsui, T., 2019. The Goshogake mud volcano field, Tohoku, northern Japan: an acidic, high-temperature system related to magmatic volcanism. Geomorphology, 329, 32-45, https://doi.org/10.1016/j.geomorph.2018.12.035.
Komatsu, G., C.H. Okubo, J.J. Wray, L. Ojha, M. Cardinale, A. Murana, R. Orosei, M.A. Chan, J. Ormö, R. Gallagher, 2016. Small edifice features in Chryse Planitia, Mars: Assessment of a mud volcano hypothesis. Icarus, 268, 56-75, doi: 10.1016/j.icarus.2015.12.032.
Methane of Mars
Komatsu, G., G.G. Ori, M. Cardinale, J.M. Dohm, V.R. Baker, D.A. Vaz, R. Ishimaru, N. Namiki, T. Matsui, 2011. Roles of methane and carbon dioxide in geological processes on Mars. Planetary and Space Science, 59, 169–181, 10.1016/j.pss.2010.07.002.
- 2011 PERC Planetary Geology Field Symposium
- Planetary and Space Science special issue
- Komatsu, G., Goto, K., Tanaka, K.L., 2014. Preface. Planetary Geology Field Symposium, Kitakyushu, Japan, 2011: Planetary Geology and Terrestrial Analogs. Planetary and Space Science, 95, 1-4
(Guest Principal Scientist of Planetary Exploration Research Center, Chiba Institute of Technology)
International Research School of Planetary Sciences
Dipartimento di Ingegneria e Geologia (INGEO)
Università d’Annunzio, Italy