The mission is a joint project by the European Space Agency and Japanese Aerospace Exploration Agency involving two separate orbiters that will build on the findings of the only two previous Mercury missions, both by NASA.
The BepiColombo spacecraft is due to be launched from the European space port at Kourou in French Guiana, at around 2.45am tomorrow morning.
Bepicolombo has a long journey ahead.
"After months of practice, teams here at mission control are eager to see BepiColombo depart from our planet, and they're ready to guide it carefully every day for seven years until it arrives at Mercury". Mercury's extreme temperatures, the intense gravity pull of the sun and blistering solar radiation make for hellish conditions.
A complex series of fly-bys past the Earth, Venus, and Mercury will also help to reduce BepiColombo's velocity by 7km/s.
"Mercury doesn't really fit with our theories for how the Solar System formed, and we can't understand our planet fully unless we're able to explain Mercury as well", said Prof Dave Rothery, a Bepi scientist from the UK's Open University.
BepiColombo, named after renowned Italian scientist Giuseppe "Bepi" Colombo, is taking a convoluted route to Mercury, flying past the Earth once, Venus twice and Mercury six times before releasing its orbiters to study the latter planet in more detail.
The journey: Although Mercury is relatively close to Earth, the craft will take seven years to get there, so that it can slow down and actually enter orbit. More than 30 years later, NASA's Messenger did the same, before settling into orbit around Mercury in 2011. Mercury's almost non-existent atmosphere also means that the planet itself will be giving off extremely hot temperatures, pinning the obiters in a "heat sandwich" for most of their lifespan. ESA's Mercury Planetary Orbiter has instruments created to study the planet's interior, composition and magnetic field. It is the first European mission to Mercury, the smallest and least explored planet in the inner Solar System, and the first to send two spacecraft to make complementary measurements of the planet and its dynamic environment at the same time. It will spend a year in orbit exploring the planet's magnetic field and atmosphere. The mission of BepiColombo is simple, to figure out Mercury's history. All those close encounters are carefully created to slow down BepiColombo's speed enough to put it into a stable orbit around Mercury in 2025. At its closest approach, Mercury is just 77 million kilometers from Earth, or not all that much further than the closest that Earth comes to Mars.
Mark McCaughrean of the European Space Agency says that "no one country can build these missions" on its own and that "critical" collaborations are being broken up by Brexit.
This interplanetary mission comes hot on the heels of Ariane 5's 100th flight, placing two telecommunications satellites into orbit in the process - which are the bread and butter missions for this launch vehicle.
The last spacecraft to visit Mercury was NASA's Messenger probe, which ended its mission in 2015.
BepiColombo's scientists seek to dig into all of these points with 16 instruments divided between the two spacecraft.
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