No not created by aliens, but it is a hard work of the OSU Linux Users Group in Oregon. They created a 45,000+ square foot crop circle of Firefox.
From project home page/wiki, "The Firefox Crop Circle project shows that we have so much passion for Firefox that we want it to be visible from space! Planned in under two weeks and completed in under 24 hours, the crop circle had a final diameter of 220 feet. We constructed the circle in an oat field near Amity, Oregon, where it was completely invisible from the road but unmistakable from the sky."
Awesome Job Guys! :D