If aliens visited the Earth, their traces would be unusual, preternatural and having no scientific explanation. There have been plenty of such artifacts.
In 1959 joint Soviet-Chinese paleontologist expedition led by Dr Chzhou Minchen found a weird footprint in the Gobi desert. This footprint appeared in Gobi millions of years ago when dinosaurs were among the living species. Paleontologists are unable to give other explanations except for extraterrestrial visitor's version, to this footprint.
In Libyan desert mysterious glassy formations – tektites – were found. Radioactive isotopes were detected in the tektites. They prove that the tektites came into being as a result of strong radioactive emanation not earlier than one million years ago. The Earth was formed not millions, but billions of years ago, and tektites appeared on the formed planet. There were many attempts to give the explanation to these mysterious formations. There was a version that they appeared after comet collided with the Earth, but no version was able to explain many peculiar features of tektites, such as their concentration on some areas of the surface of the Earth.
Recently during aerial photography in the Andes in Naska plateau weird sings made of light stones has been found. There was a version that it was some solar calendar. Some of its lines were allegedly supposed to sparkle under sunrays in the days of equinox. However, the signs configuration could be could be seen from very big altitude. They looked like indicators for landing. Could they be put for those whose visit Incas were expecting?
Scientists saw unusual phenomena in Odessa catacombs. They found bones of fossilized ostriches, camels and hyenas in the burrow which was a cave in ancient times. The bones were processed one million year ago with some metal tools.
There was no contemporary human being one million years ago, the Stone Age had not even started at that time. What kind of metal tools could it be? There are round and square holes and grooves in the bones, some of the bones are polished.
Steel rectangle 67х67х47 millimeters in size and 785 grams in weight was found in by Austrian physician Mr. Gurlt in the layer of coal the tertiary period. This item was made by human beings.
High in the Andes, in the kingdom of ancient Inks, there is Titikaka lake. There are remains of the seashore around this lake – algae remains, shells and ruins of the sea-port.
How could a bay be raised to the mountains to become a lake?
Geologists have no common opinion on this. Some of them think this happened several hundred thousands years ago. There hardly were creatures capable of constructing sea-port at that time. Interestingly, ruins of giant constructions and well-preserved Sun Gates covered with hieroglyphs were found near the sea-port remains.
Scientists became interested in the hieroglyphs and managed to decode them. They were an astronomic calendar of high precision, however the year in this calendar had 290 days – ten months of 24 days and two months of 25 days. Obviously, there was extraterrestrial calendar on the Sun Gates.
Many mysteries are connected with the legendary state of ancient Incas. Spanish conquerors were amazed with the principles of Incas' society: no private property, contempt to wealth, mandatory work for everybody. Could aliens from some planet plant these features to Incas?
Balls of perfect geometry curved from granite were found in South America. The balls were located at the tops of correct polygons. It is hard to imagine that people knew Geometry several thousand years ago.