Question: why cant we use gravity of an object in space and create an artificial atmosphere. how could that be done?

Jose Eliel Camargo Molina answered on 14 Mar 2019:

Cool question. In principle it is possible, but you have to be able to bring all the gas there too. If you want to make an earth-like atmosphere it means you have to take nitrogen, oxygen and many other gases in huge quantities somehow.

Very difficult but not impossible. Provided the planet has enough gravity you could make it self-sustained, in the sense that you don’t have to “pump” new gas all the time, just like on Earth.

An option would be to generate the gases on the planet by chemical reactions, perhaps even using some of the elements in the planet itself. However, because of the conservation of energy, you will need to bring a lot of mass (fuel for the reactions) anyway, so it is a very hard problem.

But again, not impossible!