Do you realize that the terraces picture you have posted looks (from the air) very much like a front end loader being driven by a recumbent alien?
Could this be a signal to Gods from Space that the incas broke or wore out the great machines left by alien visitors and need more of them?
Perhaps this is the reason the culture ultimately failed—the lack of machines necessary for moving huge stones and building terraces.
That's been known for decades.
It sounds like an interesting field of study.