I was going to say deranged elves. Then I did a search and found "fairy rings."

Here is a link that might be useful: Fairy Rings

Maybe teh alienz have landed and are planning to haxzor your lawn? Seriously, I have no idea, first time I've seen that before.

There is definately something making more nitrogen available there. It could be those fairy rings already mentioned or even something as simple as a mole/vole digging around bringing up nutrient rich soil to the surface. I like going with the comment that link had about a good fertilizer added to the area to mask them.

there I said it without out a single comment about crop circles and alien invasions and.... oops

They're Baaaack! Those are most definitely the circles left by a minature space craft full of tiny space aliens. I'm assuming that once they landed they wrecked havoc elsewhere in your yard/garden which you'll probably stumble upon later. I bet they're hiding in those trees somewhere. Run for the hills.

thank you all for the information and hilarious posts!

i'm just gonna leave them be, so that if people see them and ask, i can say "oh, we've got fairy rings"

as far as crop circles and aliens...well, that would be okay, since alien spacecraft couldn't possibly do any more damage than the deer.

oh jeez, this is just too funny...last year's mystery was fairy lights out back (glow worms in the lawn).

fairy lights in the back yard, fairy rings in the front.
well, it all makes sense now LOL! oh, i can't stop laughing.

fairy rings AND fairy lights!
I would say you live in a magical place!
Any fairy dust!???

Nice front yard, naturenut! Looks very quiet and serene, and I like the wooded area across the street.

According to this site, once your rings hit each other they'll kill each other. You should lose at least two. Don't know about the third.

Here is a link that might be useful: From Superstition to Science