If you had some way of injecting large masses of gas into a small planets gravitational field, would it form an atmosphere?

You would have to pump it at an extreme rate but would it still work if the planet was small enough and we could achieve these conditions?

After creating an atmosphere you could inject an air mixture inside it to allow it to sustain life. But would it?

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    $\begingroup$ Small enough to achieve what conditions? $\endgroup$ – GdD Nov 1 '19 at 13:13
  • $\begingroup$ I think the lesson of the solar system is that if a body can have an atmosphere, it does have one. Take Titan for example: it has the same gravity as the Moon, but is so distant from the Sun that it has a thick nitrogen atmosphere. If it was closer to the sun, say in Jupiter's orbit, it would have no atmosphere. $\endgroup$ – Ags1 Nov 1 '19 at 15:52
  • $\begingroup$ This Wikipedia article on Atmospheric Escape is relevant. The graph of escape velocity versus surface temperature, shows which gases will be retained in the atmospheres of the planets & larger moons of the solar system. $\endgroup$ – Fred Nov 1 '19 at 17:30

A small planet may hold gas only if it is a very cold planet far away from its sun. But the gas would be a liquid or frozen, too cold to sustain life. But an atmosphere should be gaseous, not liquid or solid.

The thermal movement of the gas atoms should be so slow that they could not escape the planet's gravity.

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    $\begingroup$ A liquid or frozen atmosphere is an oxymoron. It's either gas or it's not an atmosphere. $\endgroup$ – Ags1 Nov 1 '19 at 15:53

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