THE NEED TO CLASSIFY MOON SOILS: PROPOSAL FOR A FIRST STEP FOR PLANETARY PEDOLOGY

The first step in the process of utilizing space resources is to identify them, localize them and assess the distribution, composition, and quantity of extra-terrestrial terrigenous material available [1] , in other words the mapping of the so-called regolith or real soil according to others [2,3]. The latter will probably play an analogous role as soil does for our civilization on Earth for future extra-terrestrial human settlements. The creation of a lunar resource cartography requires to reach a consensus on the language used to communicate on the soil layers or “horizons”of the upper regolith. Such agreement is a prerequisite for communication, interpretation and classification of soils. On Earth, pedologists have developed an international nomenclature of soil horizons based on interpretative symbols which allow to immediately link soil description to properties and/or genesis of the described layers [4]. Its development during the 20th permits to develop pedological classification in parallel of the soil mapping process. For the Moon, we propose to use characteristics of the lunar regolith such as the Is/FeO maturity index of Morris [5] and the agglutinate content as a first attempt to differentiate soil horizons (see figure 1). Base on those, we propose a labelling system inspired on Earth’s pedology concept but adapted to the Moon context. We expect this work to serve as a starting point for discussions between the planetary scientists community and soil scientists with the aim of building the foundation and concepts of extra-terrestrial soil science for space resources, as already advocated by Cameron in 1963 [6] . References: [1] Abbud-Madrid, A. (2018). Space and Planetary Resources. In: Rossi, A., van Gasselt, S. (eds) Planetary Geology. Springer Praxis Books. Springer, Cham. [2] Certini, G., Scalenghe R., and Amundson, R. (2009) “A view of extraterrestrial soils,” European. Journal of Soil Science. 60 (6), 1078–1092. [3] Certini, G., Scalenghe, R., 2010. Do soils exist outside Earth? Planet. Space Sci. 58, 1767–1770 [4] IUSS Working Group WRB. 2022. World Reference Base for Soil Resources. International soil classification system for naming soils and creating legends for soil maps. 4th edition. International Union of Soil Sciences (IUSS), Vienna, Austria. [5] Morris, R.V. (1978) Proc. LPSC 9th, 2287- 2297 [6] Cameron, R.E. 1963. (1963) The role of Soil Science in Space Exploration. Space Reviews 2: 297 – 312. [7] Laul J.C. and Papike J.J. (1980) The Apollo 17 drill core:Chemistry of size fractions and the nature of the fused soil. Proc. 11th Lunar Planet. Sci. Conf. 1395-1413 [8] Taylor G.J., Warner R.D. and Keil K. (1979) Stratigraphyand depositional history of the Apollo 17 drill core. Proc.10th Lunar Planet. Sci. Conf. 1159-1184