How to Make a Moon Out of Gas

The sun gobbles up a lot of gas and dust. Once it starts fusing it blows away all remaining gas and dust like the solar wind blew away the earth's atmosphere in the early formation of the solar system. Any hydrogen in the inner solar system either fell into the sun or got blown out by the sun's radiation which is why we end up with only the heavier stuff making planets in the outer solar system. In principle you can make a moon out of gas but you probably can't keep a Moon out of Gas because in order to hold onto gas you have to have enough mass Like the earth holds onto its thin layer of atmosphere because of its mass The gravity of the earth is holding