Gravity has to do with the amount of mass an object has; not an atmosphere. The bigger the object, the stronger the gravitational pull. That's why people feel lighter on the moon than they do on Earth.
The Moon has almost no atmosphere, so that is unable to influence lunar gravity - which is about one sixth of Earth's gravity.
The moon's gravity is too weak to hold on to an atmosphere.
That is related to the fact that the Moon has less gravity - its escape velocity is less. This allows any atmosphere to evaporate into space within a reasonable time.
The Moon's gravity causes the lack of atmosphere (any possible atmosphere evaporates out into space in a fairly short time); and the lack of atmosphere causes the extreme temperatures.
There certainly is gravity outside the atmosphere. For example, it is gravity that keeps the Moon in orbit around the Earth, and the Earth in orbit around the Sun.
The Moon has almost no atmosphere, so that is unable to influence lunar gravity - which is about one sixth of Earth's gravity.
There is no atmosphere on the Moon because it does not have sufficient gravity to hold an atmosphere to it's surface.
The moon has gravity because it has mass, which creates a gravitational pull. However, the moon has no atmosphere because its gravity is too weak to hold on to gases like air. As a result, the moon has a vacuum environment with no air or atmosphere.
The moon's gravity is too weak to hold on to an atmosphere.
The moon is too small to created the gravity necessary to retain an atmosphere.
There is no atmosphere on the moon. There is insufficient gravity to keep an atmosphere there.
That is related to the fact that the Moon has less gravity - its escape velocity is less. This allows any atmosphere to evaporate into space within a reasonable time.
The moon's gravity is not strong enough to support an atmosphere.
The Moon does not have enough gravity to retain an atmosphere.
Where a planet or moon has an atmosphere, it is the gravity of the moon or planet that holds the atmosphere on the planet or moon.
The atmosphere we breath is held round the earth's surface due to earth's gravity. Without this gravity, earth's atmosphere would disperse into space. Because our moon's gravity is weak, so there is no atmosphere on the moon.
The Moon does have gravity! It is weak (just 1/6th of the Earth's) so the Moon has very little atmosphere.