Plumes of water vapor.
Apparently they were first sighted in 2013. Attempts to reacquire them and to replicate that sighting failed. But it was announced today that since then, the Hubble space telescope has been watching Europa and has seen plumes of water vapor three more times. They weren't coming from the same spot on the moon that the first plume came from, so the thinking is that they are intermittent.
The outgassing appears to be coming from fractures in the icy surface of the moon, presumably directly from liquid into vacuum since I don't believe that Europa has an atmosphere. The amount of water vapor involved has to be pretty substantial, to be visible against the Jovian surface.
http://www.nature.com/news/europa-s-peek...ed-1.20685
I hear there's alot of outgassing from Uranus.
![[Image: x8fjmojborrepyzuaca1.jpg]](http://i.kinja-img.com/gawker-media/image/upload/x8fjmojborrepyzuaca1.jpg)