Earthlike-Planet Simulator

[lpetrich]

Design your Earth, with parameters land fraction, volcanism, and habitable-zone position.

Design your Earth - advanced has land fraction, volcanism, star type, and distance in AU.

All of these parameters have Earth values as their defaults. Land fraction = 0.29, volcanism = 1, habitable-zone position = 0.19 (0 = closest, 1 = farthest), star type = Sun (TRAPPIST-1, Proxima Centauri, Alpha Centauri B, Sun, and Tabby's Star), and distance = 1. It does a respectable job of simulating our planet, with an average surface temperature of 15.1 C instead of 14.9 C. Its temperature and carbon quantities barely change.

The model simulates the geochemical carbon cycle. Carbon is present in a planet's atmosphere is carbon dioxide, and it causes a greenhouse effect, warming the planet. CO2 is removed from the atmosphere by weathering, and is removed faster when there is more land and when the atmosphere is warmer. It becomes carbonates in the oceans, and then in sediments. From there, it gets returned to the atmosphere by volcanic activity.

The planet's influx of light from its star, or insolation, also affects its surface temperature, and when less than the present-day Earth's, more CO2 is necessary to keep the surface warm, and when more, less CO2.

The amount of carbon is given in gigatons, and the mass of our atmosphere is 5.3*10^(18) kg or 5.3*10^6 gigatons (Mass of the Atmosphere - The Physics Factbook). If it was all CO2, then the carbon in it would have a mass of 1.4*10^6 gigatons.

 

[lpetrich]

I took the model and adjusted the parameters in various ways.

Decreasing the land area makes more atmospheric CO2 and a warmer planet. At 3% land area, the temperature becomes 30 C and the CO2 becomes enough to cause noticeable hypercapnia in the form of stronger breathing.

Increasing the land area makes less atmospheric CO2 and a cooler planet. At 95% land area, the temperature becomes 12 C and the atmospheric carbon level drops to a few parts per million, making it hard for plants to grow.

Increasing the volcanism also makes more atmospheric CO2 and a warmer planet. Decreasing it also makes less atmospheric CO2 and a cooler planet.

Moving the planet inward makes a warmer planet and less atmospheric CO2. Moving it outward makes a cooler planet and more atmospheric CO2. Using a habitable-zone factor of 0.49 (outward) gives first a snowball state, but CO2 builds up in the atmosphere and causes a greenhouse effect that melts the oceans again. The CO2 settles down to hypercapnia levels and the planet's temperature to 6 C. Going further outward to 0.81 gives a CO2 atmosphere thicker than ours and temperature barely above freezing of water.

To simulate the early Earth, I used sunlight input of 75% present, or a distance of 1.15 AU, a land fraction of 0.03, and volcanism 3. After going through a snowball phase, the planet settles down to a temperature of 36 C and atmospheric carbon dioxide almost entirely equal to the entire present-day atmosphere. Thus demonstrating a solution to the "faint young Sun" problem.

For a late Earth, I used a distance of 0.85 AU, giving 138% present sunlight, a land fraction of 0.5 from more plate tectonics, and volcanism 0.5 from declining radioactive decay. The temperature becomes 53 C, and most of the atmosphere's CO2 is removed by weathering.