Tuesday, 1 November 2016

The Planet Cain

Approximately Earth-sized;
just over one astronomical unit from its G-nine star;
15 % denser atmosphere;
more greenhouse effect;
20 hour day;
no moons;
32 degree axial tilt;
therefore, complicated seasons.

Is "no moons" possible? I have heard of several ways in which Earth's comparatively large Moon might have made our planet habitable, e.g., here, but I am not a scientist.


  1. Kaor, Paul!

    It was long ago, but I read an article by Isaac Asimov discussing the Moon--and I recall him saying our Earth SHOULDN'T have a moon as large and massive as it is. In fact, I read somewhere of astronomers calling the Earth/Moon system a double planet.


  2. Paul and Sean:
    I've seen it written many times that nowhere else in the Solar System is there a moon so close in size to the planet it orbits (at least not until we took a good look at Pluto and Charon).

    One of Asimov's articles about the Moon was titled "The Tragedy of the Moon" (it can be found collected in the book of the same title). He followed up with a companion piece, "The Triumph of the Moon" (in the same book). Part of what he considered the Moon's "triumph" is that life on land might never have got a start without lunar tides.

  3. David,
    The Earth-Moon system is unique in the Solar System but I have heard that such double planets have been detected elsewhere.
    It was suggested that lunar gravity thinned out the Terrestrial atmosphere, preventing Earth from being another Venus. And lunar gravity fluidizes the Earth's core, thus maintaining the magnetic field.

    1. Kaor, DAVID!

      I might very well have read either or both of the Asimov articles you cited. And I agree it HELPS for a planet to have a moon. But I don't think it will always be the case that life bearing worlds with free oxygen will have moons. Poul Anderson gave us some speculations along those lines in "The Troubletwisters, featuring Ikrananka, a tidally locked planet orbiting a red dwarf with one side permanently facing the sun.