Terran Planet

A Terran Planet is a planet template that mimics Earth. Terran Planets will follow Earth's history in how they are first formed, the first few geological events they face, and how life evolves on them. It is the template we will use to initially generate planets and design our game, until we have enough content in the game and enough knowledge on the team to start simulating more exotic and alien planet templates.

Overview

Terran Planets always share the following characteristics:

• Planet Composition: The planet is formed with a nitrogenous atmosphere, and mostly solid and molten silicate rocks, and an iron/nickel based core which creates a magnetic field around the planet.
• One Moon: The planet forms an orbiting moon early in its history
• Liquid Water Oceans: Liquid water oceans form early in the history of the planet, as the planet cools and as the densifying atmosphere condenses the water vapour to precipitate into rain
• Creation of Biomolecules: Lightning and radiation constantly generate and destroy biomolecules (glucose, ammonia, phosphate) near the ocean surface, but water currents carry some of these to the deep ocean where they accumulate. By the time life develops, there will be large reserves of these biomolecules accumulated.
• Origin of Life: Life first develops near Hydrothermal Vents, facilitated by their heat and the accumulation of biomolecules around them.
• Chemistry of Life: Life evolves to be carbon-based, using Glucose, Ammonia, and Phosphate to grow and reproduce
• Evolution of Niches: Life quickly proliferates and starts consuming the biomolecules faster than natural processes can replace them. Eventually, the surplus biomolecules in the environment will run out, and there will be life's first extinction event on this planet. Species that adapted new reliable ways to acquire energy will survive, and the rest will die out.
• Oxygen: Life eventually evolves Oxygenic Photosynthesis, a biological process that begins to produce oxygen in the planet.
• Great Oxygenation Event: The accumulation of oxygen eventually leads to a Great Oxygenation Event (GOE), where much of the chemical composition of the planet is radically changed by the introduction of oxygen. Oxygen is a highly reactive element that reacts with many of the formerly present chemicals to produce new substances. There is also a massive extinction as many species die from oxygen toxicity. The remaining species adapt to use oxygen, or retreat to anoxic environments (deep oceans and caves).
• Ozone: The release of oxygen into the atmosphere leads to the creation of an ozone layer. The ozone drastically reduces radiation levels on the surface, making it more tolerable for life to survive. However, it also reduces the natural production of glucose, ammonia, and phosphate from radiation hitting surface water.
• Snowball Planet: The onset of a GOE event leads to a Snowball Planet event later on. This is because the oxygen reacts with the methane in the air to produce carbon dioxide and water. This leads to a largely methane filled atmosphere being replaced with a largely carbon dioxide and oxygen filled atmosphere. Methane is a much stronger greenhouse gas than oxygen and carbon dioxide, and so a rapid cooling of the planet begins. This Snowball Planet event acts as another extinction event, killing all of the species that do not adapt in time.
• From the end of the Snowball Planet event onwards, the rest of the planet's history is essentially random.
• To be filled out with the rest of the characteristics...

Timeline

The following is a timeline of major natural events that are likely or guaranteed to occur on Terran planets.

Hadean Eon

The Hadeon Eon is the first geological eon in a Terran planet's history. It begins with the original genesis of the planet, and ends with the origin of life.

Conditions

• Atmosphere
  • Compounds: Mostly CO2, some Hydrogen and Water Vapour.
  • Surface Temperature: 230 degrees Celsius.
  • Pressure: 27 atm.
• Hydrosphere
  • Oceanic Temperature: Around 50-85 degrees Celsius.

Atmosphere

The atmosphere at this time would be largely comprised of carbon dioxide, water vapour, methane, and sulfate (1)(Need a reference for sulfate). As time goes by and the planet cools, the subduction of tectonic plates draws carbon dioxide out of the atmosphere and into the lithosphere. The oceans as well slowly dissolve carbon dioxide out of the atmosphere and into the hydrosphere. This gradually reduced the pressure and temperature of the atmosphere.

Hydrosphere

The starting planet would have a lot of water vapour, and the intense pressure of the early atmosphere would condense this water into the planet's first oceans despite the fact that surface temperatures exceed 200 degrees Celsius (1).

Lithosphere

Many parts of the planetary surface are molten at this time, but the formation of oceans rapidly cools some of these regions. Additionally, the planet itself is cooling as the energy of its initial formation dissipates. Lastly, the gradual decrease of carbon dioxide from the atmosphere (as it gets drawn into the lithosphere and hydrosphere) cools the surface temperature on the planet by reducing the greenhouse effect, helping the molten rocks solidify.

Moon Formation

Placeholder.

Archaean Eon

The Archaean Eon is the second geological eon in a Terran planet's history. It begins with the origin of life on the planet, and ends with the accumulation of oxygen in the atmosphere.

Conditions

• Atmosphere
  • Compounds:
  • Surface Temperature:
  • Pressure: 10-100 atm. (4)
• Hydrosphere
  • Oceanic Temperature:

Proterozoic Eon

The Proterozoic Eon is the third geological eon in a Terran planet's history. It begins with the accumulation of oxygen in the atmosphere, and ends with the origin of multicellular life.

Snowball Planet

The accumulation of oxygen in the atmosphere from the GOE triggers a cascade of many effects. One of these is the depletion of much of the methane in the atmosphere. This is because oxygen reacts with methane in the atmosphere to form carbon dioxide and water. The reduction of methane reduces the greenhouse effect of the atmosphere, and leads to a rapid cooling of the planet. (3)

Phanerozoic Eon

The Phanerozoic Eon is the fourth and final geological eon in a Terran planet's history. It begins with the origin of multicellular life, and ends with the death of the planet.

Sources

1. https://en.wikipedia.org/wiki/Hadean
2. https://en.wikipedia.org/wiki/Mesoarchean
3. https://en.wikipedia.org/wiki/Huronian_glaciation
4. https://en.wikipedia.org/wiki/Eoarchean