Final preparations are underway for the launch of a joint mission by European and Japanese space agencies to send twin probes to Mercury, reports the AP. An Ariane 5 rocket is scheduled to lift the uncrewed spacecraft into orbit from French Guiana shortly before midnight Friday, the start of a seven-year journey to the solar system's innermost planet, which is only slightly larger than Earth's moon and has a massive iron core about which little is known. The European Space Agency says the $1.5 billion mission is one of the most challenging in its history. Mercury's extreme temperatures, the intense gravity pull of the sun, and blistering solar radiation make for hellish conditions.
The BepiColombo spacecraft will have to follow an elliptical path that involves a fly-by of Earth, two of Venus, and six of Mercury itself so it can slow down sufficiently before arriving at its destination in December 2025. Newly developed electrical ion thrusters will help nudge the spacecraft, named after Italian scientist Giuseppe "Bepi" Colombo, into the right orbit. When it arrives, BepiColombo will release two probes—Bepi and Mio—that will independently investigate the surface and magnetic field of Mercury for clues about the formation of the solar system. The probes are designed to cope with temperatures varying from 806 degrees Fahrenheit on the side facing the sun to -292 degrees in Mercury's shadow. (Earth's last visitor to Mercury crashed.)