In terms of chronology, Theia, as a planet today, was the first planet to form in its current shape, mostly due to its small size, allowing for a faster cooling process, and was the first to allow life, the event of which caused perhaps the largest impact on the planets history.
Incipentic Eon
The Incipetic Eon was perhaps the most violent of all eons in Theian history; taking place over a 540 million year portion of the planets history. This time period took place 4.54 to 4 billion years ago (Gya) and encompassed much of the planets early history.
Early History
A young solar system 4.5 Gya
The standard model for the formation of the Solar System (including Theia) is the solar nebula hypothesis. In this model, the Solar system formed from a large, rotating cloud of interstellar dust and gas called the solar nebula. It was composed of hydrogen and helium created shortly after the Big Bang 13.8 Gya and heavier elements ejected by supernovae. About 4.5 Ga, the nebula began a contraction that may have been triggered by the shock wave of a nearby supernova. A shock wave would have also made the nebula rotate. As the cloud began to accelerate, its angular momentum, gravity and inertia flattened it into a protoplanetary disk perpendicular to its axis of rotation.
Small perturbations due to collisions and the angular momentum of other large debris created the means by which kilometre-sized protoplanets began to form, orbiting the nebular center. The center of the nebula, not having much angular momentum, collapsed rapidly, the compression heating it until nuclear fusion of hydrogen into helium began. After more contraction, a T Tauri star ignited and evolved into the Sun. Meanwhile, in the outer part of the nebula gravity caused matter to condense around density perturbations and dust particles, and the rest of the protoplanetary disk began separating into rings.
One of these young planets was Theia, one of many "Mars-sized" protoplanets formed shortly after the Solar System. Following a build up of materials via accretion, Theia's heavier metals (iron, sulphur, ect) sank to the centre of gravity, building up over millions of years. This process, which took tens of millions of years allowed a future Theia, with a solid iron core, to grow and maintain its magnetosphere. However, a large collision early on in its history saw the planet lose its stable orbit, and instead, it began to fall towards the Sun. Over the next 100 thousand years, Theia drifted listlessly towards the inner Solar system. However, 4.48 Gya, Theia's falling orbit was interrupted by a far larger planet, Earth, which caused a "slingshot" effect to occur; when Theia was picked up by the Earth, it couldn't begin a fall into a stable orbit around the planet, but it did begin to fall back out of the Earth's own orbit around the Sun. This effect caused the planet to arrive at a distance from the sun it is today, and, like fate, its seemed to "stop" within the habitable zone, an area of a planetary system that would allow life to proliferate, just like Earth and Theia would go onto do.
Formation of Oceans
Oceans on Theia began to form 4 Gya
Gradual cooling prior to 4 Gya allowed for the formation of an outer crust, a portion of the lithosphere that encompasses the outer layer of Theia's physical structure, and the coolest part thereof. Composed of many different layers of chemical elements, it allowed for the formation of the planet's oceans. These large bodies of water, comprised mainly of liquid water, was formed following a long period called the late heavy bombardment in which the last of the large, non planet structures struck planets. During this period, comets, carrying frozen ice water, fell towards Theia (as well as Earth) and began to form small lakes. This continuing process went on for millions of years, during which time, Theia's early atmosphere and magnetosphere allowed for this to continue unabated by the Sun's solar storms.
Primavian Eon
The Primavian Eon took place over a 1.2 billion year period, 4 billion to 2.8 billion years ago and encompassed much of early life and the evolution of basic bio-molecules to almost modern prokaryotic cells.
Origins of Life
DNA and its basic chemical components
Around 4 Gya, history on Theia would take a drastic turn in which it would not recover; the formation of life. Formed from nucleobases and simple amino acids, the first "bio-molecule", chemicals that act like life, formed. This even was furthered by RNA, a structure that would one day send signals to other DNA strands to give instructions to said DNA strands. Their formation would finally be followed by the formation of DNA, the chemical structure of all life, on Theia as well as Earth, that codes, and holds, genetic information for a molecule, or in this case bio-molecule. RNA's "transformation" into DNA would be perhaps the first of untold genetic changes that would permeate history; it was the first case of evolution.
These microscopic DNA and RNA strands would survive through the final period of the Late Heavy Bombardment, and would allow for another major innovation within the genetic structure of DNA, self replication, or perhaps more specifically, the first form of reproduction. Allowing itself to constantly be split and reformed, in a constant pattern, DNA had begun to reproduce itself. However, changes within the genetic structure would continue to further this early form of "evolution", and allow for life to adapt at an ever increasing rate.
The last ancestor
Around 3.9 billion years ago, around 100 million years after the formation of life, the lineage of proto-cells came to one species. This cell, whatever it was, was to be the ancestor to all life that has lived, is currently living, and will live on the surface and in the oceans of Theia, and would be the last of its kind. The cell itself was a prokaryote, a cell without a membrane around the nucleus. This species however, was far more archaic; it had no nucleus to begin with, nor any membrane surrounding its organelles. However, like life on Earth, and the future of its own planet, it used DNA for holding genetic data, as well as RNA for the transport of said data.
Untillian Eon
The Untillian Eon took place 2.8 billion to 780 million years ago (mya), a 2 billion year period, and the longest of all geologic Eons (bar the Novisimonic Eon). It encompassed the formation of the planet's Ozone layer, the oxygenation of the atmosphere, the Theian Oxygenation Catastrophe (TOC) and the extreme beginnings of "advanced", multi-cellular life.
Oxygenation of the Atmosphere
Around 2.9 Gya, 100 million year prior to the beginning of the Untillian, an evolutionary event occured that would changed the planets history forever; the appearance of Carbon reducing bacteria. These small cells would proliferate during the first years of the Eon, and eventually cause a major extinction event, the largest in the planets history (per percentage of the overall population). This was brought about by a simple chemical expelled by the cells as a by-product; oxygen. Carbon was a major source of energy, and when the cells drew in the Carbon dioxide from the air, it converted inside the cells leaving a waste product behind that would eventually be dispelled into the air; oxygen. This began a major change within the planet's chemical make-up, first within the ocean, then the atmosphere.
The early oceans of the Unitllian were filled with oxygenated iron
So many of these cells appeared during the first 100 million years, oxygen began to build up within the ocean itself, at that time filled with iron molecules. When the oxygen mixed with the iron, it reacted. Over the next hundred thousand years, chemical reactions similar to this were seen, with the oceans turning from its average blue-green colour, to a red, iron rust colour.
Without iron to keep reproducing the chemical elements needed to provide energy for anaerobic, or non-oxygen breathing life, those that couldn't stand the oxygen rich ocean died out, in spectacular fashion. 98% of said life went extinct, and only the oxygen breathers, and the anaerobic cells that could reach the safety of the deep sea vents, rich in sulphur, survived.
Formation of the Ozone
Much like the event that occured on Earth, over the next billion years or so, the oxygen within the ocean escaped, flowing into the atmosphere. When the Carbon reducing life became one of the only survivors of the TOC, more and more oxygen began to pump into, and proliferate the air. This allowed for the immediate growth and abundance of oxygen reducing life. Once small in size and in number, the TOC allowed for their growth in both side and number due to the fact that there was far more of the chemical in the atmosphere than there was before or ever was again. Around 2.5 Gya, the oxygen percentage within the atmosphere itself was upwards of 50%.
This dramatic chemical transformation caused another major event to occur, the formation of the Ozone layer, or O³. The amalgamation of oxygen molecules within the atmosphere resulted in the Ozone forming, which in turn allowed for life on land to actually be a possibility. This is because the dangerous UV radiation which the Sun emits can causes vicious mutations within a life form, and genetic deform or kill it. The Ozone changed this, as the chemical itself can absorb the harmful radiation, allow life to live on the land relatively uninhibited.
Appearance of Eukaryotes
The first Eukaryote cells didn't look dissimilar from this one
Around 2.5 Gya, life had been on Theia for around 1.51 billion years, and life had evolved from bio-molecular structures with only a simple membrane protecting the DNA followed by the emergence of Prokaryotes using proteins and cell walls to protect the nucleus. However, during the entire history of life on Theia, one of the biggest evolutionary leaps was to be the appearance of Eukaryotic cells.
These cells, with a membrane covering the nucleus, as well as reproducing via mitosis, rather than binary fission. These two simple changes within the genetic make-up of life, cells could adapt to change far quicker than ever before, and would allow for one of the most spectacular events to begin to occur; multicellular life.
Whilst Prokaryotes can sometimes form a larger organism by becoming multicellular, Eukaryotes managed to become far more able in forming colonies with other cells. This process gave the cells two advantages over single celled lifeforms;
- They could be more easily defended against future invasive bacteria and/or viruses, and;
- They could more easily identify and capture nutrients, allowing them to live longer than any life before them.
The capture of Lares
Lares orbiting above Theia
2.3 Gya, perhaps the most historically important event occured to Theia; the capturing of the asteroid Lares. The asteroid itself was as old, or perhaps older than, Theia, however, it was not captured by its planet for another 2 billion years. During this time, it spent years orbiting the area of space between Mars and Jupiter known as the asteroid belt. However, an uncommon event occured 2.6 Gya; a collision between space rocks. Lares was hit by a fast moving comet, and sent falling towards the inner planets. A descending orbit held it in place for around 300 million years, but by 2.3 Gya, it was moving towards Theia's orbit.
However, Theia's orbit was strong enough to capture the asteroid during one particular orbit, and the following thousand years would be dominated by an elliptical orbit. Steadying occured over hundreds of years, and when Lares' orbit finally managed to be stabilised, it caused massive tidal waves on Theia. Hundreds of meters tall, all across the planet, Theia's oceans were being pulled and stretched by the planet's satellite, causing massive tsunamis to coarse across the surface. This finally managed to calm after one million years, but the stabilisation of the planets rotation speeds, as well as the axis tilt, coupled with a constant, repeating seasonal structure, would allow for life to adapt far easier, and allow for life to colonise the land.
The First Animals
Around 1 Gya, life began to diversify at a rate unseen before; basic, visible organisms began to appear. These first groups of multicellular life could be considered the first forms of animal on the planet Theia, but were far off from those of today. They were often incredibly small, with the largest of them being no longer than 3 cm in length. They had no rigid skeleton, external or otherwise, were comprised mostly of water and they left absolutely no fossils. Around 800 million years ago (mya), all of these animals died out, going extinct leaving no markings or fossil evidence. However, the tracks that they laid in the dirt would soon be moved upon by organisms featuring in perhaps the largest diversifications of life ever to occur, on Earth, Theia, or Mars.
Formeszoic Eon
The Formsezoic Eon was a geologic eon that spanned Theia's history 780 - 155 mya, and saw the rise, evolution and proliferation of complex, multicellular life. These came in the form of eukaryotic oxygen reducing animals, either being soft or hard bodied, and the Solimarium, Carbon reducing animals that are mostly soft bodied, and often times undertook photosynthesis to synthesise Carbon into energy.
Florentine Explosion
One of the earliest "large" creatures, the soft bodied Molloribus was one of the first classes of life on Theia to adapt to the process of sexual reproduction to pass on its genes
Whilst the first multicellular lifeforms evolved over a course of billions of years, it would be only a short, 100-200 million year period over which they began to proliferate and diversify at a rate never before seen. One of the major reasons behind the mass expansion of life, as well as its extensive evolutionary pattern seen during the Florentine era was the "sexual revolution"; the expansion of the use of sex cells to produce offspring.
For billions of years, mitosis (the process of an individual cell replicating through the separating of its chromosomes) was the primary method used by life to replicate, survive, and pass on its genes, and it would not be until the appearance of the first multicellular "animals" in which sexual reproduction would mutate into something that resembles its modern-day counterpart. One of the first species to adopt this process of passing on its genes was the class Molloribus (meaning "soft bodied floater"); perhaps the most advanced species of the early Florentine.
A latter Nitronea species with its "tooth" protruding from beneath its head (note that Nitronea lacked sight receptors for millions of years into the Formeszoic)
Appearance of Predators
Spurred on by the new genetic diversity brought about through the process of reproduction, many soft bodied animals began to evolve the first mouths, guts, and anus' during the first years of the Formeszoic eon, and as such, the first predators appeared. With a new need for energy to process their fully mobile actions, many species began to eat and absorb other living creatures for nutrients and sustenance, one of the first being those within the Nitronea class. Using a large, mineralized "tooth", it first grabbed at its prey with its "antennae", then impaled them on its incisor, consuming it's insides through a small hole in its tooth leading to the gut.
 | |||||
|---|---|---|---|---|---|
|
Theia | Theian History • Theian Timescale • Future of Theia • Theian Biomes | |||
| Earth | Terran History • Terran Timescale • Future of Earth • Terran Biomes | ||||
| Lares | Laretian History | ||||
 |
Theian Life | Theian Species • Theian Energy Sources • Evolution • Theian Biosphere • Extinctions | |||
| Terran Life | Terran Species • Terran Energy Sources • Evolution • Terran Biosphere • Extinctions | ||||
 |
Theian Geography | Continents • Plate Tectonics • Atmosphere • Structure | |||
| Terran Geography | Islands • Plate Tectonics • Atmosphere • Structure | ||||