Mercury, messenger of the gods.
The first planet out from the sun is more of a moon than a planet.
In fact, it''s not much bigger than our moon, and only about half the size of Mars, which is about half the size of Earth.
Because it between us and the Sun, Mercury is never far from the Sun, in the sky (from our perspective)
- thus, is always either a morning or evening star, one of the brightest.
Hence, was it noticed by the ancients, who gave it a name, and then made up stories about it.
Mercury has no moons, but resembles ours up close.
Mind you, if you were up close to Mercury, you wouldn't be able to see our moon
- at best it would be a very tiny gray dot, next to an only slightly bigger blue dot, and sometimes behind it.
But if you were to hold up pictures of the two, you would see by comparison
that they are equally, more or less, pockmarked with craters from countless collisions
- giving the impression one gets from something which has spent billions of years
within close proximity to the Sun, or some other large gravitational attractor.