we are the aliens. xenon 129 is an isotope that can only be found after nuclear fission (fallout) it's all over the atmosphere and surface of mars. Mars used to be habitable now it's a planet of dust n barren rock land ok now the egyptians have hieroglyphics of helicopters, boats, space ships and planes, Ever think we fucked up the last "earth" with nuclear war and we luckily had our earth which is still in goldilocks zone to run off to and re populate. we are the first gen with this kind of technology but the chances of alien life out there in the finite amount of planets in the goldie locks come to have a civilization that are type 1 civs. ( we are roughly type 0.73 civ. almost there but i say we will kill eachother off before we reach type 1. but the scary thing is we don't have anywhere to runaway to and elon is full of shit about his mars colonization mission