{"id":656,"date":"2026-03-08T15:34:36","date_gmt":"2026-03-08T05:34:36","guid":{"rendered":"https:\/\/stevewatson.info\/blog\/?p=656"},"modified":"2026-03-11T18:16:09","modified_gmt":"2026-03-11T08:16:09","slug":"encounter-classifications-for-terran-worlds","status":"publish","type":"post","link":"https:\/\/stevewatson.info\/blog\/2026\/03\/08\/encounter-classifications-for-terran-worlds\/","title":{"rendered":"Encounter Classifications for Terran Worlds"},"content":{"rendered":"
    \n
  1. Size<\/span>\n
      \n
    1. S\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Small<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0r < 0.8rE<\/sub>,\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 m < 0.5mE<\/sub>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 g<\/span>[1]<\/a> < 0.8<\/span><\/li>\n
    2. M\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0Medium<\/em>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/em>8rE<\/sub> < r < 1.7rE<\/sub>\u00a0 \u00a0 \u00a0 \u00a00.5mE<\/sub> < m < 6mE<\/sub>\u00a0 \u00a0 \u00a0 \u00a0 \u00a00.8 < g < 2.0<\/span><\/li>\n
    3. L\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Large<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 6mE<\/sub> < m < 10mE<\/sub>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 0 < g < 2.2<\/span><\/li>\n
    4. G\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Giant<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 10mE<\/sub> < m\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 2 < g<\/span><\/li>\n<\/ol>\n<\/li>\n
    5. Dominant Hard Surface Type<\/span>\n
        \n
      1. V\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Vulcanic<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Dominant surface is due to vulcanism<\/span><\/li>\n
      2. R\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Rocky\u00a0\u00a0\u00a0 <\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0Heavy minerals, silicates, carbonates, varieties of regolith<\/span><\/li>\n
      3. I\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0Icy\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0<\/em>Frozen volatiles (eg. water, ammonia, methane)<\/span><\/li>\n<\/ol>\n<\/li>\n
      4. Persistent Surface Liquid Types<\/span>\n
          \n
        1. N\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Anhygric<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0None \u2013 indicating liquid cannot<\/em> persist on the surface<\/span><\/li>\n
        2. W\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Hydrohygric<\/em>\u00a0 \u00a0 \u00a0 \u00a0 Water<\/span><\/li>\n
        3. C\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Anthracohygric<\/em>\u00a0 \u00a0 Methane, ethane, etc<\/span><\/li>\n
        4. A\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Allohygric<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Other<\/span><\/li>\n<\/ol>\n<\/li>\n
        5. Surface Liquid Coverage<\/span>\n
            \n
          1. X\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Xeric<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 No surface liquid<\/span><\/li>\n
          2. D\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Drosic<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Insignificant or transient liquidity<\/span><\/li>\n
          3. L\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Limnic<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Significant but not extensive liquid coverage<\/span><\/li>\n
          4. T\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Thalassic<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Extensive but not total liquid coverage<\/span><\/li>\n
          5. O\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Oceanic<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Total liquid cover.<\/span><\/li>\n<\/ol>\n<\/li>\n
          6. Effective Surface Radiation (R, mSv per annum<\/em>)<\/span>\n
              \n
            1. M\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Radiominimal<\/em>\u00a0 \u00a0 \u00a0R < 0.1<\/span><\/li>\n
            2. S\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Radionormal<\/em>\u00a0 \u00a0 \u00a0 \u00a0 0.1 < R < 10\u00a0 \u00a0 \u00a0 \u00a0 \u00a01 is the ICRP recommended max<\/span><\/li>\n
            3. C\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Radiocritical\u00a0 \u00a0 \u00a0 \u00a0 <\/em>10 < R < 1000\u00a0\u00a0\u00a0<\/span><\/li>\n
            4. T\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Radiotoxic\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/em>1000 < R<\/span><\/li>\n<\/ol>\n<\/li>\n
            5. Surface Temperature (T, o<\/sup>C)<\/span>\n
                \n
              1. 1\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Super-Cold<\/em>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 -273 < T < -100<\/span><\/li>\n
              2. 2\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Cold<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 -100 < T < 4<\/span><\/li>\n
              3. 3\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Temperate<\/em>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 4 < T < 40\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Approximate human habitable zone<\/span><\/li>\n
              4. 4\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Hot<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a040 < T < 100<\/span><\/li>\n
              5. 5\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Super-<\/em>Hot<\/em> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 100 < T<\/span><\/li>\n<\/ol>\n<\/li>\n
              6. Surface Atmospheric Pressure (P, b)<\/span>\n
                  \n
                1. 1\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Microbaric<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0P < 0.001b<\/span><\/li>\n
                2. 2\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Hypobaric<\/em>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 001b < P < 0.3b<\/span><\/li>\n
                3. 3\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Mesobaric<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a00.3b < P < 3b\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Approximate human habitable zone<\/span><\/li>\n
                4. 4\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Hyperbaric<\/em>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 3b < P < 100b<\/span><\/li>\n
                5. 5\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Megabaric<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0100b < P<\/span><\/li>\n<\/ol>\n<\/li>\n
                6. Surface Atmospheric Composition (by dominant<\/span>[2]<\/a> component)<\/span>\n
                    \n
                  1. A\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Airless<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Microbaric worlds with an exosphere<\/em><\/span><\/li>\n
                  2. P\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Primordial air<\/em>\u00a0 \u00a0 \u00a0 H2<\/sub>, He2<\/sub><\/span><\/li>\n
                  3. C\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Compound air\u00a0 \u00a0 \u00a0<\/em>Common compound: CO2<\/sub>, CH4<\/sub>, NH3<\/sub>, H2<\/sub>O<\/span><\/li>\n
                  4. N\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Nitrogen air<\/em>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 N2<\/sub>\u00a0<\/span><\/li>\n
                  5. O<\/span>[3]<\/a> \u00a0 \u00a0 \u00a0 \u00a0 <\/span>Oxygen<\/em> air<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Breathable levels of O2<\/sub><\/span><\/li>\n
                  6. L\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Complex air<\/em>\u00a0 \u00a0 \u00a0 \u00a0 No dominant component<\/span><\/li>\n
                  7. X\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Exotic air<\/em>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><\/li>\n<\/ol>\n<\/li>\n
                  8. Biocomplexity<\/span>[4]<\/a>, [5]<\/a>,[6]<\/a><\/sup> (K, 10K<\/sup>bytes)<\/span>\n
                      \n
                    1. 0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Abiotic<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 K = 0<\/span><\/li>\n
                    2. 1\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 <\/span>Protobiotic<\/span><\/em>[7]<\/a>\u00a0 \u00a0 \u00a0 4 < K < 5\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><\/li>\n
                    3. 2\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Deuterobiotic<\/em>\u00a0 \u00a0 \u00a0 5 < K < 6\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 5 = approximate minimal level for a cell<\/span><\/li>\n
                    4. 3\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Triobiotic\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/em>6 < K < 7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Coli<\/span><\/li>\n
                    5. 4\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Tetrobiotic<\/em>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 7 < K < 8\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Fungus, Fruit fly<\/span><\/li>\n
                    6. 5\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Pentobiotic<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 8 < K < 9\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Mouse, Human<\/span><\/li>\n
                    7. 6\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Hexobiotic<\/em> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 9 < K\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Pine<\/span><\/li>\n<\/ol>\n<\/li>\n
                    8. Biodensity<\/span>[8]<\/a> (D, Gt\/m2<\/sup>)<\/span>\n
                        \n
                      1. 0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Nonvital<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 D = 0<\/span><\/li>\n
                      2. 1\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Rarivital<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 0 < D < 0.001<\/span><\/li>\n
                      3. 3\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Paulivital<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a00.001 < D < 0.1<\/span><\/li>\n
                      4. 4\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Plenivital<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a00.1 < D < 10\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0Earth = 1<\/span><\/li>\n
                      5. 5\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Supervital<\/em>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a010 < D<\/span><\/li>\n<\/ol>\n<\/li>\n<\/ol>\n

                        [1]<\/a> Rough estimates only for values of surface gravity (g, gE<\/sub>) based on r and m.
                        \n<\/span>                        [2]<\/a> Dominant means > 75%
                        \n<\/span>                        [3]<\/a> This classification takes priority over any other applicable classification
                        \n<\/span>                        [4]<\/a> Kolmogorov system complexity for biological organisms. Note that such organisms are distinguishable at any level of K by their reciprocal entropy. See C. Mayer (2020)<\/span> Life in The Context of Order and Complexity – PMC<\/a>. They may alternatively be distinguished as just the complex systems historically evolutionarily<\/em> responsive to environmental pressures.
                        \n<\/span>                        [5]<\/a> The biocomplexity of a world is marked as the complexity of the highest scoring biological organism on the world.
                        \n<\/span>                        [6]<\/a> The examples use the genome size of terrestrial organisms (rather than genes identified) to calculate their complexity. The genome is a first approximation only to a proxy for complexity.
                        \n<\/span>                        [7]<\/a> Since the scale only applies to biological organisms, 0 is assigned to all non-biological entities. It is assumed, on the basis of plausibility and the evidence of terrestrial life, that complexity below 4 is not possible for biological organisms.
                        \n<\/span>                        [8]<\/a> Total biomass \/ surface area of world. A rough measure of the degree to which life has occupied the world. See Bar-On, Yinon M.; Philips, Rob; Milo, Ron (2017).\u00a0<\/span>“The biomass distribution on Earth”<\/a>.\u00a0Proceedings of the National Academy of Sciences<\/em>.\u00a0115<\/strong>\u00a0(25): 1. Note that the current definition references only the mass of carbon contained in living things. This definition may or may not be adequate in considering alien ecologies. Note also the comment in the Abstract to the referenced article:<\/span><\/p>\n

                        We find that the kingdoms of life concentrate at different locations on the planet; plants (\u2248450 Gt C, the dominant kingdom) are primarily terrestrial, whereas animals (\u22482 Gt C) are mainly marine, and bacteria (\u224870 Gt C) and archaea (\u22487 Gt C) are predominantly located in deep subsurface environments. We show that terrestrial biomass is about two orders of magnitude higher than marine biomass and estimate a total of \u22486 Gt C of marine biota, doubling the previous estimated quantity.\u00a0<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

                        Size S\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Small\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0r < 0.8rE,\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 m < 0.5mE\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 g[1] < 0.8 M\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0Medium\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 8rE < r […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[54],"tags":[],"class_list":["post-656","post","type-post","status-publish","format-standard","hentry","category-space"],"_links":{"self":[{"href":"https:\/\/stevewatson.info\/blog\/wp-json\/wp\/v2\/posts\/656","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/stevewatson.info\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/stevewatson.info\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/stevewatson.info\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/stevewatson.info\/blog\/wp-json\/wp\/v2\/comments?post=656"}],"version-history":[{"count":27,"href":"https:\/\/stevewatson.info\/blog\/wp-json\/wp\/v2\/posts\/656\/revisions"}],"predecessor-version":[{"id":683,"href":"https:\/\/stevewatson.info\/blog\/wp-json\/wp\/v2\/posts\/656\/revisions\/683"}],"wp:attachment":[{"href":"https:\/\/stevewatson.info\/blog\/wp-json\/wp\/v2\/media?parent=656"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/stevewatson.info\/blog\/wp-json\/wp\/v2\/categories?post=656"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/stevewatson.info\/blog\/wp-json\/wp\/v2\/tags?post=656"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}