3,476 km

12,756 km


0.7 x 1023 kg

59.8 x 1023 kg

Escape velocity

2 km/sec

11 km/sec

Atmospheric pressure at surface

1 x 10—12 torr

760 torr

* Vostok, Antarctica, coldest temperature ever recorded on Earth

* Vostok, Antarctica, coldest temperature ever recorded on Earth

The Moon is tidally locked to the Earth, such that we always see the same side. Thus we refer to the "near side" and the "far side".5 In order for tidal locking to occur, the Moon must rotate on its axis at the same average rate that it revolves around the Earth.

The Moon has a very low albedo, which means that it reflects very little of the light that falls on it. It appears bright in the sky, but that is only because of the contrast between the lunar surface and the deep blackness of the night sky. In reality, the surface of the Moon is about as bright as coal dust.

Temperatures of the regolith at the Moon's equator range from 127°C (261°F) at midday to —173°C (—279°F) shortly before lunar dawn. The extreme temperatures are due to the fact that there is no blanket of air or water to moderate the temperatures. Surface temperatures at the lunar poles are much colder, ranging from —113°C to —258°C due to the very low incidence angle of sunlight. Thus, although it is much colder at the poles than at the equators, there is also less temperature variation, a fact which may prove useful for the operation of machinery and habitats.

The Moon, like the Earth, has mountain ranges and valleys. However, the origin of these features was very different for the Moon than for the Earth.

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