A spacecraft carrying European and Japanese probes will complete an eight-year journey to arrive at Mercury on Thursday, while still facing high-risk manoeuvres to study the Sun-scorched planet. From April, ESA's Mercury Planetary Orbiter (MPO) will begin studying the planet closest to the Sun with unprecedented precision, passing just 480 km from its surface, while the Japanese Mercury Magnetospheric Orbiter (Mio) will focus on its space environment and magnetic field, following an elliptical orbit that will carry it as far as 11,000 km away.