Moon

Earth has a notable natural satellite, which is our iconic Moon. The Moon is actually fairly large as it is larger than every dwarf planet in the Solar System. It has a significant gravitational presence on the Earth as it causes the tides on Earth's surface.

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Properties:

Mass: 7.342 * 10²² kg

Equatorial Radius: 1,738.1 km

Semi-major Axis: 384,399 km(0.00257 AU)

Orbital Period: 27.321 days

Rotational Period: 29.530 days

Surface Gravity: 1.62 m/(s²)

Etymology: Old English(mōna) <-- Proto-Germanic(mēnōn) <-- Proto-Indo-European(mēnsis) <-- related to "measure"

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The Moon has an extremely thin atmosphere that weighs about 10 tonnes in its entirety. It is riddled with basins and craters potentially due in part to the Late Heavy Bombardment which ravaged the surfaces of many of the terrestrial planets. The near side of the Moon has many dark volcanic seas known as maria, nudged between impact craters and lunar highlands.

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Lastly, the Moon is tidally locked with Earth because its rotational period and orbital period are very similar in length. This means that the same side of the Moon, roughly speaking, is always facing our planet. Of course, this isn't perfect due to the slight differences between the rotational and orbital periods of the Moon but the effect isn't extremely significant.