E2015: The Moons of Enderra

Back when I first designed Enderra, I decided that it had three moons and a (thin) ring system. I did this mostly for the imagery, not really thinking about the consequences much. Multiple large moons can have severe effects on the planetary environment. Universe Today has a summary of some of the effects of adding a second, Moon-sized, moon to Earth.

White Moon, Meet Red Moon

The scenario they describe is extreme, and I am not quite sure where they get some of their numbers (tides “thousands of feet” in height seem off) but I am sure they know more about this stuff than I do. Anyway, even with lessened effects, I have come to think of three moons as excessive.

At the same time, I do like the “exotic” visuals. Let’s ditch one moon and the ring system.

Enderran Moons . Size Comparison
Enderran Moons . Size Comparison

I’ve done some math to make sure the moons don’t cause huge problems. I mostly used GURPS Space for this, since I couldn’t find formulas easily, and ran the numbers for the Moon (of Earth) through the same process – for verification. Even when the two moons align, their effect on tides should be at most twice that of Earth’s Moon. The actual tidal levels, though, depend a lot on geography and local conditions. Yes, we will have some tides that are more extreme than on Earth, but it won’t mess with the fundamental state of affairs. Nights will be a bit brighter, and there will be a little bit more volcanism on Enderra than on Earth.

Both moons are tidally locked to Enderra – that is, they always show the same face to Enderra. The White Moon’s synodic month is 30.33 days, the Red Moon’s is 43.22.

What’s in a Name?

The two moons are simply named “the Red Moon” and “the White Moon”, similar to how Earth’s moon is just called “the Moon”. I might give them name later (the three original moons had names) but I think I like the simplicity of “Red Moon” and “White Moon”.

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