I am well aware of the quote and its use in stopping analysis for a further reason, because it is the reason. I don't see why there is a threshold between moon

I am well aware of the quote and its use in stopping analysis for a further reason, because it is the reason. I don't see why there is a threshold between moonshot and mars colonization, it seems arbitrary to me. Could you explain to me the method for determining the threshold of validity in the reasoning behind "Because it's there"?