It’s one of the most challenging space flight missions ever.

The BepiColombo spacecraft has launched to explore the solar system’s smallest planet, Mercury.

It took off from the Kourou spaceport in French Guiana on Saturday morning.

It’s going to take BepiColombo seven years to reach Mercury, the planet closest to the sun – and it won’t be easy.

But the spacecraft is specially designed to withstand the sun’s high temperatures, as well as its gravitational pull.

BepiColombo has to circle the Earth once, Venus twice and Mercury itself six times during its journey.

“In the first hours, the spacecraft has to become autonomous,” said Andrea Accomazzo, the European Space Agency flight director. “It means it has to deploy its solar panels, get energy from the sun and live on its own without the batteries. Then we take over control, and we slowly configure it for the very long cruise phase that we have to reach Mercury.”

The joint venture between the European and Japanese space agencies doesn’t come cheap – the mission costs $1.8 billion.

Because Mercury is one of the solar system’s least explored planets, Accomazzo said the knowledge scientists hope to gain by exploring it is priceless.

“By understanding this environment, and this planet as well, our scientists hope they can actually interpret better how our own solar system has formed and also other planets have evolved,” he said.

When BepiColombo finally arrives in the year 2025, it will place two probes around the planet.

Those probes will roam Mercury for a year before sending their findings back to Earth.

Only two previous missions, carried out by NASA, have ever even reached the planet.

Scientists hope that in the years to come, some of the mysteries of Mercury will finally be solved.