BepiColombo Mission Nears Mercury Orbit After Eight-Year Journey

The BepiColombo mission, led by the European Space Agency with contributions from Japan and the United States, has been gradually tightening its trajectory around the Sun since launch in 2018. Using a combination of plasma propulsion and carefully timed flybys of Earth, Venus, and Mercury, the spacecraft has slowed itself down to match the velocity needed for orbital insertion around the scorching iron world, the hardest planet in the solar system to reach.

Scientists working on interplanetary missions are accustomed to long waits for scientific payoffs. It took nearly ten years for NASA's New Horizons spacecraft to travel from Earth to Pluto. However, reaching Mercury and entering orbit requires more energy—or delta-v—than sending a probe to fly by Pluto, because any spacecraft must shed the momentum of Earth's orbit around the Sun to fall inward toward the solar system's innermost frontier.

Next time BepiColombo reaches Mercury, its speed will be just right for the planet's gravity to capture the spacecraft into a stable orbit. The mission, which carries a price tag of nearly $2 billion, is expected to begin its primary science phase once in orbit, studying Mercury's composition, magnetic field, and geological history.

Why This Matters

Mercury offers a unique window into the early formation of the solar system and the evolution of rocky planets.
The mission demonstrates the feasibility of complex multi-flyby trajectories and electric propulsion for deep-space exploration.
International collaboration (ESA, JAXA, NASA) pools expertise and resources for high-cost planetary science.

Background

BepiColombo consists of two science orbiters—one from ESA and one from Japan—that will separate once in Mercury orbit. The journey required nine planetary flybys in total to gradually reduce the spacecraft's orbital energy. Mercury is notoriously difficult to reach because of the Sun's deep gravity well; any probe must lose tremendous velocity to avoid being pulled into the Sun. The mission aims to study Mercury's thin exosphere, its unusual large iron core, and its magnetic field, which resembles Earth's but is much weaker.

Key Perspectives

Planetary scientists: The long-awaited arrival of BepiColombo will finally provide high-resolution data from two different instruments simultaneously, potentially resolving mysteries about Mercury's composition and geologic activity. ESA and JAXA mission teams: Successful orbital insertion would mark the culmination of years of painstaking navigation and a major win for European and Japanese deep-space capabilities. Critics and budget watchers: The nearly $2 billion cost and eight-year timespan may be questioned against other scientific priorities, though planetary scientists argue Mercury's unique characteristics make it a high-value target that no other current mission will visit.

What to Watch

The exact orbital insertion date—likely in late 2026—when BepiColombo fires its thrusters to be captured.
The health of the spacecraft's ion propulsion system after years of continuous operation.
The first science data returns, expected within weeks of orbit insertion, particularly from the Japanese magnetometer and the ESA imaging spectrometer.

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