Cryolith

(This world idea is for a sci-fi mod for some sort of civilization type game, hopefully one with multiple map abilities.  I'm not sure if this will happen, but have come up with some general ideas for the mechanics and worlds for it.)

General Description

Cryolith is a roughly earth sized planet, but orbiting farther out from its star than earth does.  It has a moon about the size of Europa, and itself is largely similar in composition to Earth, though with a larger fraction of water, ammonia, and other such materials.   The planet rotates about once every 30 hours.

As the name suggests, Cryolith is split between ice and rock as the main terrain.  The planet is split between rocky areas (resembling continents on Earth, but covering a relatively smaller area), and areas of solid ice, which have their own mountains, plains, valleys, and other such terrain.  Though the planet is colder than needed to freeze pure water, odd chemical processes produce large amounts of ammonia, that mixes with water to form large oceans (Though not as large as Earth's oceans).

Large Scale Geology

Cryolith's rocky areas form a plate tectonic system very much like Earth.  Ocean ridge equivalents exist underneath icy areas, forming large basins where ices and liquids accumulate.  Volcano arcs and mountain ranges are visible, either within larger rocky areas, or rising from beneath ice.  Sliding boundaries are visible at points on the rocky continents, but are  harder to see underneath icy areas.

The Icy parts of cryolith have their own tectonic systems, formed from a combination of surface processes and heat from volcanic activity in the rocks below.  Above mid ocean ridges, depressions often occur in the ice, created as volcanic heat melts the bottom ice, which than flows downwards, away from the ridge.  These depressions, if warm enough, fill with ammonia-water oceans, which further erode and dissolve the ice, increasing the size of the depression.  This water eventually cools and freezes some distance away from the ridge, accumulating ice that slowly makes its way to the surface, to be eroded again.

Ice also builds up at the edges of rocky continents, forming a similar structure as a continental shelf on earth.  This ice flows from its weight downwards through the depression.  Unlike on Earth, where the ice flows until it eventually melts, ice on Cryolith flows until it is stopped by more ice.  These "colission areas" between different ice flows can sometimes produce tall mountains.

Soil and Smaller Scales

In addition to the large ice basins, smaller areas of ice fill lake basins, and form glaciers on high mountains of cryolith.  These ice areas act more like traditional earth glaciers, digging valleys and acting as a source for rivers, although they can flow for much longer before being eroded or melted.  This ice has greatly eroded the rocky part of the surface of cryolith, and much of the rocky planet is covered in a deep permafrost, though with less organic material than is found on Earth permafrosts.  the soil is easily carried by winds, and surface ice in some areas is colored grayish or brownish due to deposits of this soil.

Atmosphere

The atmosphere of Cryolith mostly contains Nitrogen, with about 10% oxygen, and about 2% carbon dioxide, with traces of various other gases, and a pressure about the same as Earth's pressure.  Temperatures on the equator are around -40 Celsius, temperatures at the poles get to about -80.

Clouds on Cryolith air made of either water ice, or ammonia and water mixtures in a small number of areas.  Snow from these clouds feeds glaciers, rivers, and ice flows throughout the surface.  Ice particles are also directly eroded from some regions and transported through the atmosphere, acting as an additional source of water vapor, and are also transported in a similar way to soil, to different locations on the planet.

Winds on Cryolith are an average faster than those on Earth, but storms are not nearly as common, due to the lack of vapor to form clouds.  The most common types of severe weather on the planets are blinding snow or dust storms, where fast winds pick up ice or rock particules and blow them around.  Some of these resemble dust devils, but most resemble the clouds of material familiar from Earth.

Oceans, Rivers, and Lakes

Cryolith's oceans, lakes, and rivers are formed from a water/ammonia mixture.  These rivers start in glaciers or permafrost patches, where ammonia generated by bacteria concentrates enough to liquify ice.  The rivers of cryolith can change significantly as they flow, depending on temperature, flow rate, and the amount of bacteria in surrounding regions.  Rivers flowing to colder areas, or through areas with little life, will loose ammonia to evaporation, and will freeze out water.  Larger rivers will freeze water in their surfaces or on the body of the river, sometimes forming pack ice, or clouds of ice dust within the river.  Rivers slowing through warmer areas, or areas with a lot of nearby life, will accumulate ammonia, and dissolve ice from surrounding terrain if it is available.  these types of rivers often carry soil released from ice, and have a dirty appearance, and expand greatly during their travels.

Cryolith lakes and rivers are more stable the rivers, as they contain colonies of bacteria that generate ammonia.  The production and evaporation of ammonia can influence convection within the oceans, in addition to wind generated and temperature generated currents.  Differences in ammonia concentration can also cause Oceans and Lakes to freeze out, or erode, the surrounding terrain, though these processes take place more slowly than those in rivers.

Life

Only bacteria life exists on cryolith, but these bacteria have an enormous effect on the terrain of the planet.  Bacterial colonies can be found in most places, but are most common in oceans, permafrost, or border areas between rock and ice.

Most bacteria are photosynthetic, using carbon dioxide and water in a similar manner as earth life.  their most important reactions for Cryolith's surface, though, is one that converts nitrogen and water to ammonia and oxygen.  The ammonia produced by this reaction seems to mainly be used as antifreeze, with bacteria in colder regions usually producing more ammonia, though some bacteria can use it as a fuel if energy is short.  The ammonia generated by this process either diffuses from bacteria, or is released when the bacteria die, and feeds the rivers and oceans on the planet.  While some ammonia is consumed by other types of bacteria, most evaporates, and is broken down within a few days in the atmosphere.

Most photosynthetic ammonia forming bacteria create a number of different pigments, which powers the two main photosynthetic reactions, and makes use of the limited sunlight, making most bacteria colonies appear a black or brown color.  However, a few bacteria in warmer areas use fewer numbers of pigments, resulting in more colorful colonies in some ocean areas near the equator.

Hydrothermal bacteria also exist, mostly isolated from those on the surface, due to ice layers existing over most under ice volcanic areas. Non-photosynthetic predatory bacteria are rare, though some photosynthetic bacteria will eat when nutrients are scarce or sunlight is weak for long periods of time.  Bacteria that can internally generate nitrogen very quickly adapt to photosynthesize organic materials as well, while pure non-photosynthetic bacteria can absorb too much environmental ammonia, and freeze themselves if no outside sources exist nearby.  Well mixed oceans or lakes are better able to support predatory bacteria, though even here, the colder conditions limit the amount of material available to support predatory bacteria.

Explanation

(Disclaimer:  I am not in fact any sort of geologist, atmospheric scientist, planetary scientist, or anything related.  While I do occasionally attempt to read some papers, and more complex books, about planets for fun, I'm nowhere near an expert on any of this, and am making up these planets to have interesting characteristics, whether or not they would be be possible, and the resulting attempts at planets will read appropriately.  If any one of the above types of scientists is reading this and pulling their hair out, I understand completely.  :)  )

This world is being created to combine features of Mars and some icy moons with some (hopefully cool) ideas of my own, and is also based somewhat off Naumachia from the Test of Time Sci-fi game.  The plan for the mod also leads to me wanting some sort of water like oceans on the planet.  This planet , along with Cauldron and Phobis Terra (will link to future posts), will be starting planets.  I'm planning on having sea technology, but in order to be useful on other planets, and still make sense, a water like ocean terrain will be needed.  I do know that ammonia/water mixtures can freeze at a lower temperature, and is something that is theorizerd to exist on some outer planet moons, but have also read that ammonia breaks down very quickly in an atmosphere.  The Life is added partly to make the planet more interesting, but also to explain what might be generating the ammonia for the oceans.

Apart from the cold, unusual life, and extra ice, the description assumes the planet is mostly earthlike, simply to keep the description simpler (and easier to work out.)  Weather, or upper atmospheric chemistry, is left out and left vague, as I'm not as sure of how these things might work as i am of the changes here.