For a complex world-building scenario I want a habitable moon orbiting a habitable earth-like planet. The habitable moon should allow for flora, fauna and landscape as similar to earth as possible. The same goes for the habitable earth-like planet it is orbiting.
I have checked the various topics concerned with habitable moons:
- What would a habitable moon most probably look like?
- Habitable moon of a gas giant: working out the sizes and distances
- Naturally making a gas giant moon habitable
- How would an earth-like planet with a habitable moon work and how to get there?
- mass: 0.33 of earth’s mass (around 3 times the mass of mars)
- density: 1.3 of earth's density (because I want a higher surface gravity)
- radius: 0.6332 of earth’s mass (calculated by the application using mass and density as a given)
This is all calculated by the program:
- Diameter = 8070 km
- Density = 7.176 g/cm³
- Surface Area = 204.5 million square km
- Roche Limit = 1000 km (nearest possible natural satelite)
- Surface Gravity = 0.83 Gs
- Geosynchronous orbital distance = 24820 km, or miles (from surface of planet)
- Geosynchronous orbital velocity = 2.13 km/s , or miles per second
Maximum surface* temperature to hold onto an atmospheric component for billions of years, for each type of gas:
- Carbon Dioxide? 2972 °C
- Oxygen? 2087 °C
- Helium? 22 °C
- Hydrogen? -126 °C
Could such a moon possibly exist? And if not what changes would be needed to make this moon around an earth-like planet possible?
Please consider the following points particularly:
- Density of the moon: I need it as high as possible to have the surface gravity of the moon approximate 1 g. Playing around with the calculator I have settled on 1.3 times the density of earth, which gives a surface gravity of 0.83 Gs. This means a density of 7.176 g/cm³. Is this density achievable by still keeping a similar elemental composition to earth's? If not, could that be achieved by replacing some of the iron with a denser element? What properties would such an element have to have?
- Atmosphere: Could this moon sustain the necessary atmosphere considering the surface temperatures?
- Earth-like planet the moon is orbiting: This planet has the roughly same mass and radius as earth. If a larger mass and/or surface is necessary to have such a moon, that would be ok, as long as the density of the earth-like planet could be lower to keep the surface gravity of said planet at 1 G.
- Distances between planet and moon: No specific requirements. Can be anything to make this planet-moon relationship work.
- Size relations between planet and moon: Apparently accretion disk formations would make such a large moon compared to the planet unlikely, but would it be impossible? Could there be any other scientifically explanation for a planet having such a large moon, for instance a "rogue moon" captured by the planet (Theia captured instead of a collision), the moon being debris from the planet itself or something else? This alternate explanation can be unlikely, as long as it is scientifically sound and possible at all.