Even if we could, any event catastrophic enough to require us to do so would likely kill us all off way before we can figure out yet alone practically do so. A

Even if we could, any event catastrophic enough to require us to do so would likely kill us all off way before we can figure out yet alone practically do so. As long as there is an atmosphere you are probably better off at moisture farming than trying to extract oxygen and hydrogen out of minerals to make water. This is what would happen if the sun disappeared tomorrow style of events. Yes we have an active core and the planet would likely be warm enough at its depths that we can survive of that heat but we will all be deader than dead well before we will be able to do that.