A solar eclipse – on the planet Mars

Phobos crosses the sun.


The apparent diameter of Phobos is about a third that of Earth’s moon, so no full solar eclipse is possible from that configuration, despite the fact that the sun itself appears smaller from Mars. It’s still mighty spooky, because Phobos is not very close to spherical.


It’s one of the great marvels of our existence on this planet that our moon and our sun are so similar in size when viewed from Earth, thus creating solar eclipses of dramatic beauty (and, to the ancients, impenetrable mystery).

One thought on “A solar eclipse – on the planet Mars

  1. It’s probably less of a coincidence that the moon is about the same size as the sun than you think. The big moon stabilizes the Earth’s axis of rotation and this was pretty important to the development of complex life since an unstable axis means unstable seasons and unstable biomes. It was also critical for the much larger tides in the Paleozoic era that helped the first Tetrapods make the jump to an amphibious lifestyle. There’s also more iron and heavy metals in the core because of the collision that created the moon, which is important for the magnetic field and the persistence of the atmosphere.

    For most of Earth’s history, the moon was closer and consequently larger in the sky. So the coincidence isn’t that the moon is big enough to cause total eclipses, the coincidence is that we happened to evolve at one of the last periods when total eclipses could happen.

    Even this may be less random then it looks, because the proximate cause of our evolution seems to have been the emergence of the ice age causing Milankovich Cycles. I know the orbit of the moon plays a big part in these, but whether its exact apihelion and perihelion were critical in this is above my pay grade.

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