After 8 Years In Transit, BepiColombo Reaches Mercury For Epic Close-Up
The joint European and Japanese BepiColombo Mercury mission that left Earth some eight years ago has finally entered its arrival phase, shedding its propulsion module to begin a months-long orbital insertion of its two science orbiters.
The jettisoning of the Mercury Transfer Module comes as a relief for this joint endeavor between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA). Launched in October 2018, the mothership has logged over six billion miles, and to prevent being pulled into the Sun's gravitational draw, ground controllers executed nine gravitational assist flybys, utilizing Earth, Venus, and Mercury itself, alongside solar-electric propulsion to continuously slow the probe. Flight operators at ESA’s control center in Darmstadt, Germany confirmed normal operations after acquiring the post-separation signal, leaving the remaining spacecraft stack on course for capture by Mercury's gravity.
BepiColombo’s capture sequence relies on a technique known as weak stability boundary capture to maximize safety, and will culminate in orbital entry on November 21. Once in Mercury's grasp, the remaining payload will separate into two science orbiters in December. ESA’s Mercury Planetary Orbiter (MPO) will descend into a low polar orbit to map the planet’s surface topography, elemental composition, and internal structure. Simultaneously, JAXA’s Mercury Magnetospheric Orbiter (dubbed "Mio") will swing into an elongated orbit to analyze the planet's magnetic field and surrounding plasma environment.
Only two prior missions have ever visited our system's innermost planet: NASA’s Mariner 10, which performed rapid flybys in the mid-1970s, and NASA’s MESSENGER probe, which orbited from 2011 to 2015. BepiColombo’s dual-orbiter strategy is designed to resolve mysteries left behind by its predecessors, including the origins of "hollows," i.e. the strange, shallow depressions peppering the surface, plus why Mercury possesses an unexpectedly high density and an active magnetic field despite its small size.
The two orbiters are expected to begin full scientific operations in April 2027.
