There must have been a moment at the beginning, where we could have said no. Somehow we missed it. Well, we'll know better next time.
Place one astronaut on a spaceship and replace another player's astronaut on a spaceship (in the air or on the ground) or a zone of Mars with another one of your astronauts. My question is does it need to be existing astronaut before i take the turn? It sounds like I can not use the newly placed astronaut to use this conversion ability.
You can use the newly placed one.
The another is another from your supply that you swap out with the one from your opponent.