All WHAT way? They're not necessarily extra-terrestrial. They could be extra-dimensional.Then take into account that our solar system resides in a far off lonely arm of our galexy. Why come al that way, leave a message and leave?
And time and time again, there have been circles found that have NOT been man-made (at least that could be proven). Actually, very few of the crop circles can be proven to have been man made.Crop circles ahve been PROVEN time and time again to be man made.
Again, to believe that there are only either/or solutions to these mysteries displays, I think, a poverty of imagination.