I was sitting in a mall food court of all places a couple days ago and this thinking is there a proper grace for atheists to say over a meal. This is what came to me:
We give thanks to the sun and the ashes of stars. The sunlight for growing the food the nourishes us or that fed the animals that nourished us. The ashes of stars that provided the matter of the solar system and ultimately us. In the act of eating we reconnect with the universe and billions of years of history. We also give thanks for a brain that is conscious of this connection. Perhaps one of the rarest things in the universe.
From the stars we come and the stars we return from now until the end of time.