Raining Diamonds

According to scientists at the University of California at Berkley the hot, crushing atmospheres of Neptune and Uranus may be transforming methane gas into diamonds.  

  It is believed that just like ice in the earth's atmosphere, carbon could coalesce to produce diamond hail that would pelt the surface of the planets.  It's speculated the diamond could range in size from dust to pebbles as big as hailstones.