British scientists are to play a key role in a one billion euro (£812 million) space mission to explore the icy moons of Jupiter.
The Juice (Jupiter Icy Moons Explorer) mission will investigate the possibility of "waterworlds" that may harbour life.
Its primary target is Ganymede, the Solar System's biggest moon, which is 8% larger than the planet Mercury.
Ganymede is thought to conceal a deep ocean of salty water beneath a thick crust of ice.
It also has its own magnetic field, offering protection against Jupiter's powerful radiation belts, and an ancient surface littered with many types of crater.
The plan is to send a probe into orbit around Ganymede to study its sub-surface ocean and assess whether life could exist there.
The Juice spacecraft will also make fly-bys of two other moons, Callisto and Europa, which are also believed to have ice-covered oceans.
Juice is scheduled to launch in 2022 and will take eight years to make the long journey to Jupiter.
After its arrival in 2030 the spacecraft will spend three years collecting data to be transmitted back to Earth.
The mission was approved by the European Space Agency (ESA) at a meeting in Paris today.
It will be the first European-led space mission to the outer Solar System.
British scientists make up four of the 15 members of the ESA Science Study Team for Juice and are bidding to design instruments for the probe.
Universities involved include Imperial College, Leicester and University College London.
Dr Leigh Fletcher, from Oxford University, said: "Scientists have had a lot of success detecting the giant planets orbiting distant stars, but the really exciting prospect may be the existence of potentially habitable 'waterworlds' that could be a lot like Ganymede or Europa.
"One of the main aims of the mission is to try to understand whether a 'waterworld' such as Ganymede might be the sort of environment that could harbour life."
As well as orbiting Ganymede, the spacecraft will extensively study Jupiter's dynamic atmosphere and swirling storm systems.
It will also look at the magnetic and charged particle environment of Jupiter and how it affects the planet's moons.
Dr Emma Bunce, from the University of Leicester, said: "We need to place the possible habitability of these 'waterworlds' into some broader context, and Juice will do that by also studying the surrounding environment.
"Ganymede is strongly coupled to its parent Jupiter through gravitational and electromagnetic forces. Studying this interaction gives us further insight into its unique place in the Solar System."
Professor Andrew Coates, from University College London, a member of the ESA Science Study Team, said: "Studying these watery worlds is the next vital step beyond Mars in the search for the conditions for life in our Solar System.
"Ganymede's unique magnetic shield helps protect it somewhat from Jupiter's harsh radiation belts and rapidly rotating magnetosphere, and we want to understand its effectiveness. Europa and Callisto provide key comparisons as we search for the Solar System's 'sweet spots' for habitability."