These blobs of green gel are colonies of nostoc, bacteria that get their energy through photosynthesis. When on the ground, nostoc is ordinarily not seen, but after a rain it swells up into a jelly-like mass. Once thought to have fallen from the sky it has the common names - star jelly and troll’s butter. It dries to a black crust but comes back to green life when there is sufficient moisture. To discourage its growth, improve drainage and eliminate synthetic fertilizer use. Vinegar and fatty acid herbicides can be used to kill it in lawns if it bothers you.