It's thought that the Moon stabilizes Earth's axial tilt, and so without it, seasons as we know them could not exist i.e. there could be extremes during periods where the tilt approaches 90 degrees. This has implications for potentially habitable exoplanets as it may be unlikely that an otherwise habitable exoplanet would have a large moon like Earth does. Uranus has been cited as an example of a planet developing an extreme axial tilt in the absence of a stabilizing moon, but it has also been theorized that Uranus developed its tilt because of an impact. No other planet in the solar system shows such an extreme tilt, so it seems to raise the question of whether a large moon really is a requirement for a planet to maintain its rotational axis in a relatively stable orientation.

What is the foundation on which the theory is based that Earth's rotational axis is stabilized by the Moon? If it's based on simulation, could there be errors, omissions, limitations in fidelity?

  • $\begingroup$ Mars has a tilt similar to Earth's, 25 deg versus 23.5 deg, but the two Martian moons are almost insignificant compared to Earth's moon. How would the concept you are proposing apply to Mars & would this have a bearing on your question? $\endgroup$
    – Fred
    Jan 17, 2022 at 0:34
  • $\begingroup$ "No other planet in the solar system shows such an extreme tilt." Venus has entered the chat. :) $\endgroup$
    – notovny
    Jan 17, 2022 at 15:21


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