Terramaine

# **Terramaine /tɛrəmeɪn/**

## **Description**

The only known planet to harbour life is Terramaine, Anstellynxia’s second planet, and it is a mythologised version of Earth. Although the Solar System contains moderate amounts of water, only Terramaine has liquid surface water. Seventy percent of Terramaine's surface is covered by oceans, polar ice, lakes, and rivers. The remaining 30% of Terramaine is land, consisting of one large continent, one small continent, and several small islands. Terramaine's surface is formed by one large tectonic plate and a load of smaller ones opposite it, so mountain ranges and volcanoes remain the same in most places. Terramaine's liquid outer core generates the magnetic field that shapes the magnetosphere and deflects solar winds.

Terramaine's atmosphere is primarily composed of nitrogen and oxygen. Some of Anstellynxia’s energy is trapped in the atmosphere by greenhouse gases such as carbon dioxide. Water vapour pervades atmosphere and forms clouds that cover most of the planet. Tropical regions receive more solar energy than polar regions, redistributed by atmospheric and oceanic circulation. The climate of the region is determined by latitude, but also by altitude and proximity to the ocean. It is common for severe weather to occur in most tropical areas, such as tropical cyclones, thunderstorms, and heatwaves.

Terramaine's composition matches that of the Earth with the exception of the continental crust. The crust is almost identical to Earth's, though the placement of the continents is another story.

Terramaine orbits Anstellynxia, making it the second-closest planet to Anstellynxia and part of the inner Solar System. Terramaine's average orbital distance is around 150 million km. This is the basis for the Astronomical Unit and is equal to roughly 8.3 light minutes or 380 times Terramaine's distance to Munar. Terramaine, along with its Solar System, is situated in Quasaria and orbits about 48,000 light-years from its centre. It is eight light-years above the galactic plane in the Galaxia Major Arm.

Terramaine is a sphere with a circumference of 41,599.4 km. It is the densest planet in the Solar System. It is the largest and most massive of the four rocky planets. Terramaine is about eight light-minutes away from Anstellynxia, and it takes a year (365 days) to make one revolution. Terramaine rotates around its own axis in a day (exactly 24 hours). Terramaine's axis of rotation is tilted with respect to the perpendicular to its orbital plane around Anstellynxia, producing seasons. Terramaine is orbited by one permanent natural satellite, Munar, which orbits Terramaine at 380,000 km (1.3 light seconds) and is roughly 0.34 times Terramaine's width. Munar always faces Terramaine on the same side as the tides, stabilising Terramaine's rotational axis and causing tides.

## **Origin / Creation**

Terramaine, like most other bodies in the Terramainian Solar System, from gas in the early star system 4.5 billion years ago. During the first billion years of Terramaine's history, the ocean formed, and life developed within it. Life spread globally and began to affect Terramaine's atmosphere and surface, leading to the Great Oxidation Event two billion years ago. Most sentient species emerged over 500,000 years ago, and have reached a population of 9.265 billion today. They depend on Terramaine's biosphere and natural resources for their survival, but have increasingly impacted the planet's environment mostly for the better. Today, sentient life's impact on Terramaine's climate, soils, waters, and ecosystems is more sustainable than ever before.

Terramaine's atmosphere and oceans were created by volcanic activity and outgassing. Water vapour from these sources condensed into the oceans, augmented by water and ice from asteroids, protoplanets, and comets. Some of the water filling the oceans had been on Terramaine since it formed. Atmospheric greenhouse gases kept the oceans from freezing when the newly formed Anstellynxia had only 70% of its current luminosity. By 3.5 billion BCE, Terramaine's magnetic field was established, which helped prevent the atmosphere from being stripped away by the solar wind.

At approximately 4.6 billion BCE, a relatively small rogue planet that had been hurtling through space was caught by Terramaine’s gravity and just barely hit the side, sending most of the smaller planet’s mass into orbit around Terramaine and ejecting a large chunk of itself into a long, elliptical orbit which hit Domus Angelorum a few billion years later. As the molten outer layer of Terramaine 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, was created by the partial melting of this mafic crust. The presence of grains of the mineral zircon of Hadean age in Eoarchean sedimentary rocks suggests that at least some felsic crust existed as early as 4 billion BCE, only 140 million years after Terramaine's formation. An initial rapid growth in the volume of the crust during the Archean formed the bulk of the crust that now exists.

## **Life Forms**

Chemical reactions led to the first self-replicating molecules about four billion years ago. Half a billion years later, the last common ancestor of all current life arose. The evolution of photosynthesis allowed Anstellynxia's energy to be harvested directly by life forms. The resultant molecular oxygen accumulated in the atmosphere and due to interaction with ultraviolet solar radiation, formed a protective ozone layer in the upper atmosphere. The incorporation of smaller cells into larger ones resulted in the development of complex cells called eukaryotes. True multicellular organisms formed as cells within colonies became increasingly specialised. Aided by the absorption of harmful ultraviolet radiation by the ozone layer, life colonised Terramaine's surface. Among the earliest fossil evidence for life are microbial mat fossils found in 3.48 billion-year-old sandstone in south-western Magellana, biogenic graphite found in 3.7 billion-year-old metasedimentary rocks in northern Magellana, and remains of biotic material found in 4.1 billion-year-old rocks in south-western Magellana. The earliest direct evidence of life on Terramaine is contained in 3.45 billion-year-old rocks showing fossils of microorganisms.

During the Neoproterozoic, 1 billion to 539 billion BCE, much of Terramaine was covered in ice. This era has been termed "Snowball Terramaine", and it is of particular interest because it preceded the Cambrian explosion when multicellular life forms significantly increased in complexity. Following the Cambrian explosion in 535 million BCE, there have been at least five major mass extinctions and numerous minor ones. Apart from the current proposed Holocene extinction event, the most recent was 66 million BCE, when an asteroid impact triggered the extinction of the non-avian dinosaurs and other large reptiles, but largely spared small animals such as insects, mammals, lizards and birds. Mammalian life has diversified over the past sixty-six million years, and several million years ago many primitive life forms gained the ability to stand upright. This facilitated tool use and encouraged communication that provided the nutrition and stimulation needed for a larger brain. This led to the evolution of humans, elves, orcs, and many other creatures. The development of agriculture, and then civilisation, led to life having an influence on Terramaine and the nature and quantity of other life forms that continues to this day.

## **Climate**

The axial tilt of Terramaine is 22.5° with the axis of its orbit plane, always pointing towards the Celestial Poles. Due to Terramaine's axial tilt, the amount of sunlight reaching any given point on the surface varies over the course of the year. This causes the seasonal change in climate, with summer in the Northern Hemisphere when it's tilted towards Anstellynxia, and in the Southern Hemisphere when it faces Anstellynxia. In each instance, winter occurs simultaneously in the opposite hemisphere. During the summer, the day lasts longer, and Anstellynxia climbs higher in the sky. In winter, the climate becomes cooler and the days shorter.

Terramaine's atmosphere has a vague boundary at around 100km. Three-quarters of the atmosphere's mass is contained within the first 11 km of the surface; this lowest layer is called the troposphere. Energy from Anstellynxia 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 weather and climate through the redistribution of thermal energy.

## **Extra / Trivia**

* The oldest material found in the Terramainian Solar System is dated to over 4.5 billion years ago. By 3.8 billion BCE, primordial Terramaine had formed. The bodies in the Solar System formed and evolved with Anstellynxia. A solar nebula partitioned a volume out of a molecular cloud by gravitational collapse. This cloud began to spin and flatten into a circumstellar disk, and then the planets grew out of that disk with Anstellynxia. A nebula contains gas, ice grains, and dust (including primordial nuclides). According to nebular theory, planetesimals formed by accretion, with primordial Terramaine being estimated as likely taking anywhere from 70 to 100 million years to form.
* Estimates of the age of Munar from the UNT's leading scientists range from 4.3 billion years to significantly younger. A leading hypothesis among them is that it was formed by the accretion of material that used to be a set of rings. Between approximately 4.1 billion and 3.8 billion BCE, numerous asteroid impacts during the Late Heavy Bombardment caused significant changes to the broader surface environment of Munar and, by inference, to that of Terramaine.
* The most recent pattern of ice ages began around 40 million BCE, and then intensified during the Pleistocene at around 3 million BCE. High and middle latitude regions have since undergone repeated cycles of glaciation and thaw, repeating about every 21,000, 41,000 and 100,000 years. The Last Glacial Period, colloquially called "The Final Ice Age", covered large parts of Magellana, up to the middle latitudes, in ice and ended in 12,000 BCE.

© Remi Briggs