 would tend to migrate closer to the equator. On planets with a very high degree of axial inclination and mild temperatures, we would find most plant species specialized with both frost resistance and heat tolerance. On such worlds, we might find plants going through a growing cycle where their cells are partially filled with an electrolyte during the winter, forming a biological antifreeze. As winter gives way to spring and spring to summer, the electrolyte might gel into a paste, reducing water loss. Then as the climate cooled, the paste would dissolve back into antifreeze.
Ice Caps, Tundra and Snow Fields
On many of our model worlds, we should expect to find the existence of ice caps. On the cooler worlds we will find thicker ice caps in the polar regions, with snow fields extending in various coverage down to mid latitudes. Cooler planets with a low degree of axial inclination will have permanent ice caps. Warmer planets, with a high degree of axial inclination, will have ice sheets and snow fields that migrate with the season, similar to winter snow across northern latitudes on Earth. On planets with a high degree of axial inclination the plant and animal life with have a high degree of cold and heat tolerance, species migration may be an important part of many large animal life forms and hibernation a retreat from the cold for most of the smaller less mobile creatures.
Ice caps are bordered by Tundra in terrestrial environments. As we move up through the APST range, we could find the Tundra and Ice Caps at progressively higher latitudes. Eventually the ice cap is replaced by diminished snow fields. As the APST approaches 60ºC, the Snow fields melt away and are replaced by a low illumination environment.
If we compared two planets of the same mass and axial inclination, the planet with the higher APST would have the smallest ice cap. If we compared two planets of same mass and APST, the planet with the smallest axial inclination would have the largest permanent snow fields.
On warm planets with moderate to high axial inclination, the ice cap may completely disappear during that hemisphere’s summer. The activity of the biotic community on alien worlds will be similar to that on Earth as each season is experienced. The hemisphere entering Spring, a time of increases sunlight and warmth, will come out of winter dormancy and experience growth.
In the hemisphere entering Fall, the biotic community will be gearing down for the approaching Winter. The plants will winterizes, the animals will migrate, build up energy reserves, prepare for hibernation and/or utilize other adaptive mechanisms.
On planets with approximately a 30ºC APST, we may find the absence of true ice caps. In their place may exist the relatively more temperate permafrost fields with perennially frozen ground or nearly permanent frost.
Frost caps require an annual temperature of about -3ºC (26ºF) or less in order to exist; however, the temperature range over the entire area may run from -36ºC to 4ºC (-32ºF to 39ºF). Precipitation in these regions is under 15 inches per year. Climatic conditions in the permafrost zone is are cold and dry, with long winters and cool summers.
[Illustration at right: Ice Cap & Snow Field expansion on a cool planet with varying degrees of axial inclination.]
On any world with a permafrost region either covering the poles or circumventing the icecap, an explorer would find large expanses of flat land and rounded hilly terrain, where the effects of freezing and thawing would have reduced rocks to small particles. The soils of these regions would be poorly drained and poorly aerated on planets with low axial inclination and just the opposite planets with high axial inclination.
Remember, if the planet were orbiting a relatively cool G9 or K0 spectral class star, it’s orbit would be near the star, providing a short year. If the planet orbited a much hotter, F24 or F4 star, its orbit would fall further from the star giving it a year perhaps twice as long as our own, hence a ‘quarter year’ of about 6 months- plenty of time for small 