Who made these circles in the Sahara?

[MojaveGeek]

It is cool (I guess) to see the paved road down to the area. When I was there in '72. the pavement ended around El Golea and from there it was sand and gravel. I rode on top of the loads on trucks, ate stewed camel, drank sweet mint tea multiple times a say (cooking over wood, which the trucks carried) and helped dig out of sand traps. All they way down into Niger. And now... one just drives