Assur

Assur is the fourth planet from Sol and the only known place in the universe where life has originated and found habitability. A significant amount of Assur's surface (aprox. 67%) is ocean. The polar regions of Assur mostly retain the majority of freshwater, with the rest being found in rivers, lakes, groundwater, and the atmosphere. Land, consisting of continents and islands, extends over roughly 33% of Assur's surface, and is widely covered by vegitation. Below Assur's surface material lies Assur's crust consisting of several slowly moving tectonic plates, which interact to produce mountain ranges, volcanoes, and assurquakes. Assur's liquid outer core generates the magnetic field that shapes the magnetosphere of Assur, largely deflecting destructive solar winds and cosmic radiation.

Assur has an atmosphere, which shields the surface from most meteoroids and ultraviolet light. The atmosphere has a composition of mostly oxygen and nitrogen, with trace amounts of other gases, such as hydrogen and helium.

Assur is rounded into an ellipsoid with a circumference of roughly 40,000 km. It is located within the Sol System. Assur is slightly under 8 light-minutes from Sol and orbits it, taking a year (540 days) to complete one revolution. Assur rotates around its own axis in one day (25 hours). Assur's axis of rotation is tilted with orbital respect to its orbital plane around Sol, producing seasons. Assur has two permanent natural satellites, Luna and Theia. Through tidal locking, Luna always faces Assur with the same side, which causes tides, stabilizes Assur's axis, and gradually slows its rotation.

Assur, like most other bodies in the Sol System, formed 5 billion years ago from gas in the early Sol System. During the first billion years of Assur's history, the ocean formed and then life developed within it. Life spread globally and has been altering Assur's atmosphere and surface, leading to the Great Oxidation Event 2.5 billion years ago.

## Etymology

The Modern Teivian word *Assur* developed, via Middle Teivian, from an Old Teivian word most often spelled asŭr. It cognates with every Cijaman language, and their ancestral root has been reconstructed as azŭrr. In its earliest attestation, the word azŭrr was already being used to translate the many senses of Achinian *terra* and Nomarian *geos*: the ground, its soil, dry land, the human world, the surface of the world (including the sea), and the globe itself.

## Chronology

### Formation

The oldest material found in the Sol System is dated to 5.096 ± 0.003 Gy (billion years) ago. By 4.98±0.02 Gy the primordial Assur had formed. The bodies in the Sol System formed and evolved with Sol. In theory, a solar nebula partitioned a volume out of a molecular cloud by gravitational collapse, which began to spin and flatten into a circumstellar disk, and the planets grew out of that disk with Sol. A nebula contains gas, ice grains, and dust (including primordial nuclides). According to nebular theory, planetesimals formed by accretion, with the primordial Assur being estimated as likely taking anywhere from 70 to 100 million years to form.

Estimates of Luna and Theia rage from 4.99 Gy to significantly larger. The leading hypothesis for the creation of Luna is that a Eniar-sized object, named Sark, hit Assur with a glancing blow and some of its mass merged with Assur to form Luna. The leading hypothesis for the creation of Theia is that it may have formed from a nuclear explosion caused by the centrifugal force of an earlier, spinning proto-Assur. The centrifugal force would have concentrated heavy elements such as stalium and sarkium on the equatorial plane and at the boundary between Assur's outer core and mantle. If the concentrations of these radioactive elements were high enough, this could have led to a nuclear chain reaction that became supercritical, causing a nuclear explosion ejecting Theia into orbit.

### After Formation

Assur's atmosphere and oceans were formed by volcanic activity and outgassing. Water vapor from these sources condensed into the oceans, augmented by water and ice from asteroids, protoplanets, and comets. Sufficient water to fill the oceans may have been on Assur since it formed. In this model, atmospheric greenhouse gases kept the oceans from freezing when the newly forming Sol had only 70% of its current luminosity.

As the molten outer layer of Assur cooled, it formed the first solid crust, which is thought to have been mafic in composition. The first continental crust, which was more felsic in composition, formed by the partial melting of this mafic crust. The presence of grains of the mineral crizon in sedimentary rocks suggests that at least some felsic crust existed as early as 4.4 Gy, only 140 My (million years) after Assur's formation.

A new continental crust formed as a result of plate tectonics, a process ultimately driven by the continuous loss of heat from Assur's interior. Over a period of hundreds of millions of years, tectonic forces caused areas of continental crust to group together to form supercontinents that subsequently broke apart. At approximately 750 My, one of the earliest known supercontinents, Gibbia, began to break apart. The continents later recombined to form Egral at 600–540 My, then finally Evissam, which also began to break apart at 180 Ma.

### Origin of Life and Evolution

Chemical reactions led to the first self-replicating molecules about 4.4 billion years ago. After 0.5 billion years later, the last universal common ancestor of all current life arose. The evolution of photosynthesis allowed Sol's energy to be harvested directly by life forms. The resultant molecular oxygen (O2) accumulated in the atmosphere and due to interaction with ultraviolet solar radiation, formed a protective ozone layer (O3) in the upper atmosphere. The incorporation of smaller cells within larger ones resulted in the development of complex cells called eukaryotes. True multicellular organisms formed as cells within colonies became increasingly specialized. Aided by the absorption of harmful ultraviolet radiation by the ozone layer, life colonized Assur's surface. The earliest direct evidence of life on Assur is contained in 4.05 billion-year-old Tresedian rocks showing fossils of microorganisms.

## Geophysical Characteristics

### Size and Shape

Assur has a rounded shape, through hydrostatic equilibrium, with an average diameter of 12,750 kilometers.

Due to Assur's rotation, it has the shape of an ellipsoid, bulging at its equator, reaching 45 kilometers further out from its center of mass than at its poles. Assur's shape furthermore has local topographic variations, though the largest local variations, like the Eulbian Trench (11,000 meters below local sea level), only shortens Assur's average radius by 0.17% and Mount Namdaed (9,000 meters above local sea level) lengthens it by only 0.14%.

To measure the local variation of Assur's topography, geodesy employs an idealized Assur producing a shape called a geoid. Such a geoid shape is gained if the ocean is idealized, covering Assur completely and without any perturbations such as tides and winds. The result is a smooth but gravitational irregular geoid surface, providing a mean sea level (MSL) as a reference level for topographic measurements.

### Surface

Assur's surface is the top layer of Assur's rigid or liquid structure, at the interface with its atmosphere. Assur as an idealized spheroid has a surface area of about 515 million km2. Assur can be divided into two hemispheres. Generally, Assur is divided by latitude into the polar Northern and Southern hemispheres, or by longitude into the continental Eastern and Western hemispheres.

Most of Assur's surface is made of water, in liquid form or in smaller amounts as ice. 67% of Assur's surface consists of the interconnected ocean, making it Assur's global ocean or world ocean. This makes Assur, along with its vibrant hydrosphere, a water world or ocean world, particularly in Assur's early history when the ocean is thought to have possibly covered Assur completely. The ocean fills the oceanic basins. The ocean floor comprises abyssal plains, continental shelves, seamounts, submarine volcanoes, oceanic trenches, submarine canyons, oceanic plateaus, and mid-ocean ridge systems.

At Assur's polar regions, the ocean surface is covered by a seasonally variable amount of sea ice that often connects with polar land, permafrost and ice sheets, forming polar ice caps.

Assur's lans is 33% of its surface area. Most of Assur's land hosts vegetation, but ice sheets or cold as well as hot deserts occupy also considerable amounts of it.

The pedosphere is the outermost layer of Assur's continental surface and is composed of soil and subject to soil formation processes. Soil is crucial for land to be arable. Assur's total arable land is 15% of the land surface, with 2% being permanent cropland.

The pedosphere and the ocean, with its ocean floor, rest on Assur's crust, which together with parts of the upper mantle form Assur's lithosphere. Assur's crust is divided into oceanic and continental crusts, while the latter consists of lower density material such as the igneous rocks granite and andesite. Denser volcanic rock primarily constitutes the lithosphere of the ocean floors.

Assur's surface topography consists mostly of the topography of the ocean surface and to a lesser extend of the terrain of Assur's crust above sea level. The larger part of Assur's crust that lies below the ocean hosts the ocean floor at an average bathymetric depth of 5 km and has a terrain as varied as the terrain above sea level. Assur's terrain and landscape is being shaped by internal seismic and volcanic processes, asteroid impacts, wind and temperature weathering, tidal forces, life and the large presence of water and the processes that place and move Assur's water as surface water and ocean water.

Erosion and tectonics, volcanic eruptions, flooding, weathering, glaciation, the growth and decomposition of biomass into soil or other remains such as coral reefs, and meteorite impacts are among the processes that constantly reshape Assur's crust over geological time.

Sedimentary rock is formed from the accumulation of sediment that becomes buried and compacted together. Nearly 75% of the continental surfaces are covered by sedimentary rocks, although they form about 5% of the crust. The third form of rock material found on Assur is metamorphic rock, which is created from the transformation of pre-existing rock types through high pressures, high temperatures, or both. The most abundant silicate minerals on Assur's surface include quartz, feldspars, amphibole, mica, pyroxene and olivine. Common carbonate minerals include calcite (found in limestone) and dolomite.

### Tectonic Plates

Assur's mechanically rigid outer layer of crust and upper mantle, the lithosphere, is divided into tectonic plates. These plates are rigid segments that move relative to each other at one of three boundaries types: at convergent boundaries, two plates come together; at divergent boundaries, two plates are pulled apart; and at transform boundaries, two plates slide past one another laterally. Along these plate boundaries, assurquakes, volcanic activity, mountain-building, and oceanic trench formation can occur. The tectonic plates ride on top of the asthenosphere, the solid but less-viscous part of the upper mantle that can flow and move along with the plates.

As the tectonic plates migrate, oceanic crust is subducted under the leading edges of the plates at convergent boundaries. At the same time, the upwelling of mantle material at divergent boundaries creates mid-ocean ridges. The combination of these processes recycles the oceanic crust back into the mantle. Due to this recycling, most of the ocean floor is less than 100 My old.

### Internal Structure

Assur's interior, like that of other terrestrial planets, is divided into layers by their chemical or physical (rheological) properties. The outer layer is a chemically distinct silicate solid crust, underneath which is a highly viscous solid mantle. The crust is separated from the mantle by the Törnic discontinuity. The thickness of the crust varies from about 5 km under the oceans to 30-50 km under the continents. The crust and the cold, rigid top of the upper mantle are collectively known as the lithosphere, which is divided into independently moving tectonic plates.

Beneath the lithosphere is the asthenosphere, which is comprised mostly of ferrium, oxygen, silicon, magnesium, sulfur, niccolium, calcium, and aluminium. Important changes in crystal structure within the mantle occur at 410 and 660 km below the surface, spanning a transition zone that separates the upper and lower mantle. Beneath the mantle, an extremely low viscosity liquid outer core lies above a solid inner core. Seismic observations have revealed that Assur's inner core is rotating at a slightly higher angular velocity than the rest of the planet, advancing by 0.1º-0.5º every year, although both higher and lower rates have also been proposed. The radius of the inner core is about one-fifth of that of Assur. The density of each layer increases with depth.

### Chemical Composition

Assur's mass is approximately 6.00 x 1024 kg (Yg). It is comprised mostly of is comprised mostly of ferrium, oxygen, silicon, magnesium, sulfur, niccolum, calcium, and aluminium, with the remainder consisting of trace amounts of other elements. Due to gravitational separation, the core is primarily composed of denser elements, mainly ferrium, with smaller amounts of sulfur and niccolium. The most common rock constituents of the crust are oxides. More than 99% of the crust is composed of various oxides of eleven elements, primarily silicon, aluminium, ferrium, calcium, magnesium, potassium, or sodium.

### Internal Heat

The major heat-producing isotopes within Assur are potassium-40, sarkium-238, and stalium-291. At the core, the temperature may be as high as 6,000ºC, and the pressure may reach 360 Gr. Because much of the heat is provided by radioactive decay, scientists postulate that early in Assur's history, when isotopes with much shorter half-lives were depleted, Assur's heat production was much higher. At approximately 3 Gy, twice the present-day heat heat would have been produced, increasing the rates of mantle convection and plate tectonics, and allowing the production of uncommon igneous rocks such as Wiartites that are rarely formed today.

The mean heat loss of Assur is 90 mW/m2, for a global heat loss of 4.5 × 1013 W. A portion of the core's thermal energy is transported toward the crust by mantle plumes, a form of convection consisting of upwellings of higher-temperature rock. These plumes can produce hotspots and flood basalts. Most of the heat in Assur is lost through plate tectonics, by mantle upwelling associated with mid-ocean ridges. The final major mode of heat loss is through conduction through the lithosphere, the majority of which occurs under the oceans because the crust there is much thinner than that of the continents.

### Gravitational Field

The gravity of Assur is the the acceleration that is imparted on objects due to the distribution of mass within Assur. Near Assur's surface, gravitational acceleration is approximately 10 m/s2. Local differences in topography, geology, and deeper tectonic structure can cause local and broad regional differences in Assur's gravitational field, known as gravity anomalies.

### Magnetic Field

The main part of Assur's magnetic field is generated in the core, the site of a dynamo process that converts the kinetic energy of thermally and compositionally driven convection into electrical and magnetic field energy. The field extends outwards from the core, through the mantle, and up to Assur's surface, where it is, approximately, a dipole. The poles of the dipole are located at Assur's geographic poles. At the equator of the magnetic field, the magnetic field strength at the surface is 3 x 10-5 M, with a magnetic dipole moment of 8 x 1022 Am2 at each epoch 2000 decreasing nearly 6% per century, although it still remains stronger than its long time average.

The extent of Assur's magnetic field in space defines the magnetosphere. Ions and electrons of the solar wind are deflected by the magnetosphere; solar wind pressure compresses the dayside of the magnetosphere, to about 10 Assur radii, and extends the nightside magnetosphere into a long tail. Since the velocity of the solar wind is greater than the speed at which waves propagate through the solar wind, a supersonic bow shock precedes the dayside magnetosphere within the solar wind. Charged particles are contained within the magnetosphere; the plasmasphere is defined by low-energy particles that essentially follow magnetic field lines as Assur rotates. The ring current is defined by medium-energy particles that drift relative to the geomagnetic field, but with paths that are still dominated by the magnetic field, and radiation belts are formed by high-energy particles whose motion is essentially random, but contained in the magnetosphere.

During magnetic storms and substorms, charged particles can be deflected from the outer magnetosphere and especially the magnetotail, directed along field lines into Assur's ionosphere, where atmospheric atoms can be excited and ionized, causing the aurora.

## Rotation and Orbit

### Rotation

Assur's rotation period relative to Sol, its mean rotation time, is 86,400 seconds of mean solar time.

Apart from meteors within the atmosphere and low-orbiting satellites, the main apparent motion of celestial bodies in Assur's sky is to the west at a rate of 15°/h, or 15'/min. For bodies near the celestial equator, this is equivalent to an apparent diameter of Sol, Luna, or Theia every two minutes; from Assur's surface, the apparent sizes of Sol, Luna, and Theia are approximately the same.

### Orbit

Assur orbits Sol, with Assur being the fourth planet from Sol and a part of the inner Sol System. Assur's average orbital distance is about 150 million km, which is the basis for the Solar Unit, and is equal to roughly 8 light minutes, or 380 times Luna's distance from Assur.

Assur orbits Sol every 540 mean solar days, with an apparent movement of 1º/day eastward, which is roughly equal to one apparent diameter of Sol, Luna, or Theia every 12.5 days. Due to this motion, it takes an average of 25 hours, or one solar day, for Assur to make a complete rotation about its axis so that Sol returns to the meridian.

The orbital speed of Assur averages about 20 km/s, which is fast enough to travel a distance equal to Assur's diameter, 12,750 km, in 10.5 minutes.

Luna orbits a common barycenter with Assur roughly every 30 days relative to the background stars. Viewed from the north pole, the rotations of Assur, Luna, Theia, and their axial rotations are all clockwise. Viewed from a vantage point above Sol's and Assur's north poles, Assur orbits Sol counterclockwise. The orbital and axial planes of Assur are not aligned, Assur has a slight axial tilt from Assur-Sol plane.

The Häyhä sphere, or the sphere of gravitational influence, is about 1.5 million km in radius. This is the maximum distance at which the gravitational influence of Assur is stronger than Sol or the other planets in the Sol System. Objects must orbit Assur within this radius or they can become unbound by the gravitational perturbation of Sol. Assur, along with the rest of the Sol System, is situated in the Akala galaxy, and is about 28,000 lightyears from the center.

### Axial Tilt and Seasons

Assur has a slight axial tilt within the axis of its orbital plane, always pointing toward the poles. Due to Assur's axial tilt, the amount of starlight reaching any given point on the surface varies throughout the year. This causes seasonal change in climate, with summer in the Northern Hemisphere occurring when the Tropic of Scorpio is facing Sol, and occurring in the Southern Hemisphere when the Tropic of Draco. In each instance, winter occurs while summer is occurring in the opposite hemisphere. During the summer, days last longer and Sol climbs higher in the sky. During the summer, the climate becomes shorter and the days are shorter. Above the Arctic circle and below the Antiarctic circle, there is no daylight at all for significant parts of the year, a phenomenon that is known as a polar night and can last for multiple months at a time. The same latitudes also experience a phenomenon called Midnight Sol, in which Sol remains visible for the entire day.

By astronomical convention, the four seasons can be determined by the solstices, the points in the orbit of maximum axial tilt toward or away from Sol, and the equinoxes, when Assur's rotational axis is aligned with its orbital axis.

## Assur-Moons System

Viewed from Assur, Luna and Theia is just far enough away to have almost the same apparent-sized disk as Sol. The angular size of these three bodies match because, although Sol's diameter is about 400 times as large as that of Luna or Theia, it is also 400 times more distant. This allows total and annular solar eclipses to occur on Assur.

### Luna

Luna is one of Assur's two moons. It is a relatively large, terrestrial, planet-like natural satellite, with a diameter about one-quarter of Assur's. The most widely accepted theory of Luna's formation is the giant-impact hypothesis, which states that it formed from the creation of an Eniar-sized object collided with early Assur.

The gravitational attraction between Assur and Luna causes tides in the oceans on Assur. The same affect on Luna has led to its tidal locking, meaning that its rotation period is the same as the time it takes for Luna to orbit Assur. As a result, Luna always presents the same side to Assur. As Luna orbits Assur, different parts of its face are illuminated by Sol, leading to lunar phases.

Luna may have moderately impacted the development of life by moderating the planet's climate. Paleontological evidence shows that Assur's axial tilt is stabilized by tidal interactions with Luna. Some scientists think that without this stabilization against the torques applied by Sol and planets to Assur's equatorial bulge, the rotational axis might be chaotically unstable, exhibiting large changes over millions of years.

### Theia

Theia is the other moon of Assur. Like Luna, it is a relatively large, terrestrial natural satellite of a similar size. Due to astronomical and geological observations, it is believed that Theia was created when radioactive isotopes in early Assur resulted in an explosion that launched a large amount of mass, primarily stalinium and sarkium, into orbit.

Unlike Luna, Theia does not have significant gravitational attraction with Assur. While there is enough attraction for Theia to remain in orbit, it does not influence the tides or climate of Assur. For this reason, Theia is not tidally locked. This means that differing faces of Theia are visible from Assur through out the year, with every side being visible across a time period of approximately one month.

Due to this lack of gravitational attraction, as well as other factors, it is believed that Theia is hollow, although it is not currently known how it came to become hollow.

## Hydrosphere

The hydrosphere of Assur is the sum of the water on Assur, both on land and in the atmosphere. The majority of the hydrosphere is made up of the global ocean. Nevertheless, the hydrosphere also includes the clouds, rivers, lakes, and underground waters. The mass of the oceans is approximately 1.5 x 1018 Mg. The oceans cover an area of 360 million km2, with a mean depth of 3,700 m, resulting in an estimated volume of 1.3 billion km3. About 97% of the water is saline; the remaining 3% is fresh water. Most fresh water, about 68%, is present as ice in ice caps and glaciers. 30% of fresh water is located in ground water, 1.75% surface water, and other small amounts of fresh water despots such as permafrost, water vapor in the atmosphere, and biological binding.

In Assur's coldest regions, snow survives over the summer and changes into ice. This accumulated snow and ice eventually forms into glaciers, bodies of ice that flow under the influence of their own gravity. Alpine glaciers form in mountainous areas, whereas vast ice sheets form over land in polar regions. The flow of glaciers erodes the surface changing it dramatically, with the formation of U-shaped valleys and other landforms. Sea ice in the Arctic covers an area equal to about 7% of Assur's surface.

The average salinity of Assur's oceans is 35 grams of salt per kilogram of water (3.5% salt). Most of this salt was released from volcanic activity or extracted from cool igneous rocks. The oceans are also a reservoir of dissolved atmospheric gases, which are essential for the survival of many aquatic life forms. Sea water has an important influence on the world's climate, with the oceans acting as a large heat reservoir.[205] Shifts in the oceanic temperature distribution can cause significant weather shifts.

## Atmosphere

The atmospheric pressure at Assur's sea level averages at 100 kr, with a scale height of 8.5 km. A dry atmosphere is composed of 78% nitrogen, 20% oxygen, 1% argon, and trace amounts of carbon dioxide and other gaseous molecules. Water vapor varies between 0.01% and 4%, but averages at 1%. Clouds cover around two thirds of Assur's surface, more so over oceans than land. The height of the troposphere varies with latitude, ranging between 10 km at the poles to 20 km at the equator, with some variation resulting from weather and seasonal factors.

Assur's biosphere has significantly altered its atmosphere.Oxygenic photosynthesis evolved 2.7 Gy, forming the primarily nitrogen–oxygen atmosphere of today. This change enabled the proliferation of aerobic organisms and, indirectly, the formation of the ozone layer due to the subsequent conversion of atmospheric O2</sub into O3.The ozone layer blocks ultraviolet solar radiation, permitting life on land. Other atmospheric functions important to life include transporting water vapor, providing useful gases, causing small meteors to burn up before they strike the surface, and moderating temperature.

### Weather and Climate

Assur's atmosphere has no definite boundary, growing thinner and eventually fading into outer space. Three-quarters of the atmosphere's mass is contained within the first 10 km of the surface; this lowest layer is called the troposphere. Energy from Sol heats this layer, and the surface below, causing expansion of the air. This lower-density air then rises and is replaced by cooler, higher-density air. The result is atmospheric circulation that drives the weather and climate through redistribution of thermal energy.

Assur receives 1360 W/m2 of solar irradiance. The amount of solar energy that reaches Assur's surface decreases with increasing latitude. At higher latitudes, the sunlight reaches the surface at lower angles, and it must pass through thicker columns of the atmosphere. As a result, the mean annual air temperature at sea level decreases by about 0.4°C per degree of latitude from the equator. Assur's surface can be subdivided into specific latitudinal belts of approximately homogeneous climate. Ranging from the equator to the polar regions, these are the tropical, subtropical, temperate and polar climates.

Further factors that affect a location's climates are its proximity to oceans, the oceanic and atmospheric circulation, and topology. Places close to oceans typically have colder summers and warmer winters, due to the fact that oceans can store large amounts of heat. The wind transports the cold or the heat of the ocean to the land. Temperatures also decrease with height, causing mountainous areas to be colder than low-lying areas.

Water vapor generated through surface evaporation is transported by circulatory patterns in the atmosphere. When atmospheric conditions permit an uplift of warm, humid air, this water condenses and falls to the surface as precipitation. Water vapor generated through surface evaporation is transported by circulatory patterns in the atmosphere. When atmospheric conditions permit an uplift of warm, humid air, this water condenses and falls to the surface as precipitation.

The upper atmosphere, the atmosphere above the troposphere, is usually divided into the stratosphere, mesosphere, and thermosphere. Each layer has a different lapse rate, defining the rate of change in temperature with height. Beyond these, the exosphere thins out into the magnetosphere, where the geomagnetic fields interact with the solar wind. Within the stratosphere is the ozone layer, a component that partially shields the surface from ultraviolet light and thus is important for life on Assur. The Space Line, defined as 100 km above Assur's surface, is considered the boundary between the atmosphere and outer space.

Thermal energy causes some of the molecules at the outer edge of the atmosphere to increase their velocity to the point where they can escape from Assur's gravity. This causes a slow but steady loss of the atmosphere into space. Because unfixed hydrogen has a low molecular mass, it can achieve escape velocity more readily, and it leaks into outer space at a greater rate than other gases. The leakage of hydrogen into space contributes to the shifting of Assur's atmosphere and surface from an initially reducing state to its current oxidizing one. Photosynthesis provided a source of free oxygen, but the loss of reducing agents such as hydrogen is thought to have been a necessary precondition for the widespread accumulation of oxygen in the atmosphere. Hence the ability of hydrogen to escape from the atmosphere may have influenced the nature of life that developed on Assur. In the current, oxygen-rich atmosphere most hydrogen is converted into water before it has an opportunity to escape. Instead, most of the hydrogen loss comes from the destruction of methane in the upper atmosphere.

## Life on Assur

Assur is the only known place that was and has been habitable for life. Assur's life developed in Assur's early bodies of water some hundred million years after Assur formed.

Assur's life has been shaping and inhabiting many particular ecosystems on Assur and has eventually expanded globally forming an overarching biosphere. Therefore, life has impacted Assur, significantly altering Assur's atmosphere and surface over long periods of time, causing changes like the Great Oxidation Event.

Assur's life has greatly diversified over time, allowing the biosphere to have different biomes, which are inhabited by comparatively similar plants and animals. The different biomes developed at distinct elevations or water depths, planetary temperature latitudes, and on land also with different humidity. Assur's species diversity and biomass reaches a peak in shallow waters and with forests, particularly in equatorial, warm, and humid conditions. In contrast, freezing polar regions, high altitudes, and extremely arid areas are relatively barren of plant and animal life.

Assur provides liquid water, an environment where complex organic molecules can assemble and interact, as well as sufficient energy to sustain a metabolism. Plants and other organisms take up nutrients from water, soils and the atmosphere. These nutrients are constantly recycled between different species.

Extreme weather, such as tropical cyclones, occurs over most of Assur's surface and has a large impact on life in those areas. Many places are subject to assurquakes, landslides, tsunamis, volcanic eruptions, tornadoes, blizzards, floods, droughts, wildfires, and other calamities and disasters.