ner_tags: O O O O O O O B-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O
tokens: the albedo of ice on M-dwarf hosted Earth-like planets () and the ice-albedo feedback becomes a negative, or stabilizing, feedback. We tested particular land distribution scenarios (i.e., configurations in which a nonuniform (by latitude) land fraction is used as input), including present-day Earth, and equatorial ocean and land belt configurations, that revealed some variation in surface temperature (∼5 K) and albedo (∼0.02), depending on the distribution of land in the model (see labeled markers in Figure 2 ). In particular, ocean-dominated planets and land planets with oceanic equatorial belts (with otherwise identical orbital parameters) have higher global mean surface temperatures when compared to a uniform land fraction distribution by latitude. Distinct zones of high and low albedo surfaces are shown in the simulations pertaining to planets orbiting F-, G-, and K-dwarfs (Figure 3 ), which represent frozen (yellow) and unfrozen surfaces, respectively. Note that these frozen surfaces exhibit different Bond albedos depending on SED, despite being comprised of the same 50% snow/ice mixture. Transitional boundaries between these zones are also evident, representing the maximum equator-ward extent of glacial conditions, i.e., a nominal “ice line” in latitude and F L parameter space, from which we can approximate the minimum land fraction required to force mid-latitude glaciations, assuming default model conditions: 0.46, 0.55, and 0.68 F L for planets around F-, G-, K-dwarfs, respectively. Figure 2. Mean global surface temperature (; left) and Bond albedo (; right) by average planetary land fraction ( F L ) for terrestrial planets orbiting FGK- and M-dwarf stars. The dashed lines labeled denote the albedos of the 50% ice-snow mixture on planets orbiting X -type star; the gray shaded area depicts a range of F L over which exceeds the blue shaded region illustrates temperatures below 271 K. Markers indicate some individual land fraction and latitudinal distribution configurations tested in the model: present-day “Earth” (E), a scenario in which a narrow band of equatorial ocean exists on an otherwise land-covered planet (Eq. O), an “oceanplanet” (O) configuration with some land at the poles, an equatorial land belt on an otherwise oceanic planet (Eq. L.), and a “landplanet” (L) distribution with some open ocean at the poles. See text for discussion. Figure 3. Contours of albedo (dimensionless) as a function of land fractional coverage ( F L ) and latitude ( φ ) for a planet orbiting an M-dwarf (top left), K-dwarf (top right), G-dwarf (bottom left), and F-dwarf (bottom right) stars. M-dwarf planets do not exhibit mid-latitude glaciations in any of these simulations, although albedos for high land fraction planets in orbit around these stars are proportionally higher in the mid-latitudes and equatorial regions than at the frozen polar regions. A general trend exists in that planetary broadband albedo increases with increasing F L regardless of