If our moon had an atmosphere, could it have seasons?
Because our moon is tidally locked with Earth, then the same half always faces the Earth regardless of where the Moon is in its orbit. As such, would a tidally locked satellite such as our moon (assuming it meets the criteria for an atmosphere) be able to have seasons?
I can see that if a satellite has a tilt like the Earth's and it orbits a planet orbiting a star then it would have seasons similar to how Earth does. But a moon that is tidally locked cannot do this as far as I can conceptualize. I'd love some clarification on this, thank you!
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The reason why Earth has seasons in the way it does is Earth's axial tilt relative to the Sun combined with its atmosphere.
Earth's moon has a much smaller (about 1.5°) axial tilt relative to the ecliptic than does the Earth (23°). Thus its seasonal variations are much smaller. Note that this is irrespective of the fact that Earth's moon is tidally locked to Earth! The contribution of Earth to the Moon's heating is negligible.
In order to actually notice seasonal variations, there has to be something to smooth out variations on a shorter time scale. Earth's moon essentially (but not completely!) lacks an atmosphere, so there is nothing to even out the differences even between sunlight and shadow, let alone over time. If Earth lacked an atmosphere, the temperature swings would be equally brutal here despite Earth's 23° axial tilt.
So what you need for a natural satellite to have some kind of seasons is a difference of insolation across its surface, which is usually caused by having a significant axial tilt relative to the sun, and a significant atmosphere to even out the extremes and thus make the seasons noticable against the noise of local temperature variations.
Compare Are there seasons on Luna? on Space Exploration.
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