Europe's Rosetta mission has launched successfully and is now heading into space on its daring journey to chase and land on a comet.
Lift off of the Ariane rocket went as planned
The £600m probe lifted off at 0717 GMT from its launchpad in Kourou, French Guiana, on an Ariane 5 rocket after being delayed twice.
Rosetta is primed for a 7bn-km journey to Comet 67P/Churyumov-Gerasimenko.
The probe has separated from the upper stage of its Ariane rocket and left Earth orbit for the outer Solar System.
"Rosetta is part of our quest for knowledge and our dreams. A huge scientific community has dedicated years of work to this day today," said Jean-Jacques Dordain, director-general of the European Space Agency (Esa).
Speaking to scientists assembled at mission control in Kourou, Professor David Southwood, Esa's director of science, said: "We now have yet another mission in space. We've got 10 years ahead of us and everyone who has contributed to get us to this point feels very proud."
Once in orbit around the 4km-wide ball of ice and dust in 2014, the craft will despatch a small lander to the comet's surface to study its chemistry.
This mission used a very specific launch instant rather than the typical launch window used to put most satellites into Earth orbit.
After lift-off, booster separation and burn-out of the central core stage of the Ariane 5 rocket, the upper stage entered a prolonged ballistic phase. This was followed by a delayed ignition of almost 17 minutes.
After this burn, Rosetta separated from the upper stage and set off on an Earth-escape trajectory.
This set the spacecraft on its long Solar System journey that will take around the Sun four times, around Mars once (2007), the Earth three times (2005, 2007, 2009), and into the asteroid belt twice.
The rendezvous with Comet Churyumov-Gerasimenko is set for early 2014.
At this time, the comet will be cold and inactive, and Rosetta will be able to release a washing-machine-sized lander, called Philae, on to the object's surface.
As the comet moves into the inner Solar System, radiation from the Sun will cause its ices to sublime - they will turn straight from solid to gas. Material will be ejected at supersonic speeds.
Gas and dust will be thrown out around the comet to form a coma, and away from the comet to form tails.
The comet is currently 600 million km from Earth. Pictured here by the La Silla Observatory in Chile
The Rosetta orbiter and lander will watch and record these events as the comet hurtles along at speeds up to 135,000km/h.
Scientists are keen to study comets close up because they are thought to contain materials that have remained largely unchanged since the formation of the Solar System 4.6bn years ago.
They may give clues as to why the Solar System evolved the way it did. Some researchers think comet impacts may even have seeded the early Earth with the chemistry needed for life to develop.