Ice Volcano on Titan
Titan is a fascinating world, it is about as large as the planet mercury, it orbits Saturn and so the weak sunlight that reaches it means that it's surface temperature is about -189C. Despite this it has an active weather system with lakes and rivers, not of water but of liquid ethane and methane. The ground, pebbles etc is not made of rock but of water ice.
This strangely complete low temperature analogy to earth has now been taken a bit further, because Randy Kirk and colleagues seem to have found a volcano a kilometre high on Titan. They have called it Sotra, and it is of course made of ice. It appears to have a different composition to the surrounding ice, and looks like it has spewed water based lava to form a volcano to one side. Right next to the volcano there is a hole about 1600m deep and nearby there appears to be a string of smaller volcanoes, like a volcanic region on earth.
This of course makes Titan an even more interesting place to study, but also raises the possibly of molten water on titan and the interesting chemistry and possibly even life which could be associated with it.