Enigmatic Europa

Discovered in 1610 by Galileo, Europa is the smallest of the four 'Galilean Moons' of Jupiter. Through a small telescope its easy to spot as the second one out from the planet. It is named after a Phoenician noblewoman in Greek mythology, Europa, who was courted by Zeus, the father of Gods, and became the queen of Crete. Europa is slightly smaller than our own moon and orbits Jupiter in just over three and-a-half days. Its density suggests that it is similar in composition to the terrestrial planets, such as Earth and Mars, and is mainly composed of silicate rock. It has long been thought that Europa has an outer layer of water around 60 miles thick, some of this frozen as an ice upper crust, some as a liquid ocean underneath that ice. Europa has also featured high in science fiction, most notably in Arthur C Clarke's '2001' where it was home to a primitive life form, seeded there by aliens and set into evolutionary overdrive when Jupiter is transformed into the Star Lucifer.

It was long thought that it would be difficult for any water to travel up though Europa's thick icy crust, but researchers at the The University of Texas found the best evidence yet for water just beneath the surface of Europa. An analysis of the surface suggests that plumes of warmer water well up beneath the icy shell, melting and fracturing the outer layers. They also suggest that small lakes exist just a couple of miles below the crust.

The researchers studied the surface of Europa trying to work out what formed its scarred and fractured surface. They suggest say up-welling of warmer water causes melting of surface ice, forming cracks. Freezing water then flows in the cracks and so you get existing ice cemented in with new ice. The underside then freezes again, which causes more uplifting. These shallow lakes mean that surface waters are probably vigorously mixing with deeper water. It is also possible that icy eddies could transfer nutrients between the surface water and the deeper ocean below. All this is another boost to those who think Europa is a place which may well harbor life.