The European Space Agency (Esa) is to mount a billion-euro mission to Jupiter and its icy moons.
The probe, called Juice, has just been approved at a meeting of member state delegations in Paris.
It would be built in time for a launch in 2022, although it would be a further eight years before it reached the Jovian system.
The mission has emerged from a five-year-long competition to find the next "large class" space venture in Europe.
Juice stands for JUpiter ICy moon Explorer. The concept proposes an instrument-packed, nearly five-tonne satellite to be sent out to the Solar System's biggest planet, to make a careful investigation of three of its biggest moons.
The spacecraft would use the gravity of Jupiter to initiate a series of close fly-bys around Callisto and Europa, and then finally to put itself in a settled orbit around Ganymede.
Emphasis would be put on "habitability" - in trying to understand whether there is any possibility that these moons could host microbial life.
Callisto, Europa and Ganymede are all suspected to have oceans of water below their icy surfaces. As such, they may have environments conducive to simple biology.
"People probably don't realise that habitable zones don't necessarily need to be close to a star - in our case, close to the Sun," explained Prof Michele Dougherty, a Juice science team member from Imperial College London, UK.
"There are four conditions required for life to form. You need water; you need an energy source - so the ice can become liquid; you need the right chemistry - nitrogen, carbon, hydrogen; and the fourth thing you need is stability - a length of time that allows life to form.
"The great thing about the icy moons in the Jupiter system is that we think those four conditions might exist there; and Juice will tell us if that is the case," she told BBC News.
The mission will cost Esa on the order of 830m euros (£695m; $1.1bn) over its entire life cycle. This includes the cost of manufacturing the spacecraft bus, or chassis, launching the satellite and operating it until 2033.
This sum does not however include Juice's 11 instruments. Funding for these comes from the member states. When this money is taken into account, the final budget for Juice is expected to be just short of 1.1bn euros.
It has not yet been decided which European nations will provide which instruments. An Announcement of Opportunity will be released this summer with a view to identifying the instrument providers by the start of next year.
The final and formal go-ahead for Juice should be given in 2014. In Esa-speak, this stage is referred to as "adoption".
It is the moment when all the elements required to build the satellite are in place and the full costings are established.
It is also the point at which any international participation is recognised.
At the moment, Juice is a Europe-only venture, but there is every possibility that the Americans will get on board.
The US space agency (Nasa) walked away from the idea of producing a companion satellite to Juice - a spacecraft that would orbit Europa rather than Ganymede - due to programmatic differences and budget concerns.
Nonetheless, there is a strong desire among the American scientific community to have some involvement in Juice, especially in those aspects that concern Europa.
Dr Britney Schmidt from the University of Texas at Austin is excited that Europe has chosen to fly Juice, and expects the probe's data to resolve many outstanding questions at the icy moon.
"We know that ice is a really good place [for life] to do business on Earth," she told the BBC.
"There's plenty of microbial and even some macroscopic organisms that use ice to make a living. It's not so hard to imagine that life like that which lives in Antarctica and in the Arctic might be very possible on Europa."
The Esa executive has put down 68m euros as a kind of placeholder, to give some idea of how much Nasa might like to contribute. The sum is roughly the equivalent of two instruments. However, it should be said that no explicit discussions between Esa and Nasa have taken place concerning which specific instruments might come from across the Atlantic.
One further issue needs to be resolved: the name of the mission. The "Juice" label was dreamt up by the science team who devised the mission concept, but the researchers acknowledge there was a touch of humour in its creation.
They would like to use the name Laplace, after the great 18th/19th-Century French mathematician and astronomer Pierre-Simon Laplace. A number of commentators would like to see Esa run a public competition to find a suitable mission name.
The Juice proposal was chosen over two other ideas - Athena, which envisages the biggest X-ray telescope ever built, and NGO, which would place a trio of high-precision satellites in space to detect gravitational waves.
These defeated concepts will probably now be entered into the next competition, due to be announced next year or the year after.
Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter