Super-enhanced copy of the the face of Mars. Even in the old original pictures of it I always thought it looked like a collapsed building, & still do. Really, what advanced civilization is gonna build a face on Mars hundreds of yards long? You'd think they'd have better things to spend their time & resources on than building giant faces for no good reason.
That's why crop circles are made by people. They're pranksters with nothing better to do in rural areas but cow-watch. Aliens wouldn't bother with such cryptic nonsense -- Really, Aliens carving pretty pictures or random circles in wheat?