or moon of our own solar system. Eventually, however, the species Homo Sapiens could have developed on Earth. After a possible great natural catastrophe mankind was reduced to the stone age. The survivors of that time (assuming that this theory is right), were perhaps working in Earth orbit, in large space stations. Who knows? Perhaps, when the Palenque tombstone was chiseled, this flying object had not existed for centuries. Since photos bleach very quickly, these may not have existed anymore. The author assume, however, that technical plans on thick paper still existed and were still in the orbital stations. Unfortunately the Catholic clergy destroyed just about everything they found. Thus the last evidence was also eliminated.