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BepiColombo
Investigating Mercury's mysteries
Launch

20 October 2018

status

En route to Mercury

destination

Mercury, arriving November 2026

type

Planetary explorer

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Close to the Sun and more difficult for an orbiter to reach than Saturn, small, barren Mercury is the least explored planet of the inner Solar System. Its surface and interior hold vital clues to the formation of all the inner planets. BepiColombo will be only the second mission to orbit Mercury. With two spacecraft, it will study the composition, geophysics, atmosphere, magnetosphere and history of the planet, providing key clues to help us understand the history of the Solar System.
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a unique mission
What makes **BepiColombo** unique?

BepiColombo is unique in comprising two science orbiters: the Mercury Planetary Orbiter (MPO) to study both the planet itself and its surroundings, and Japan's Mercury Magnetospheric Orbiter (MMO or Mio) which will primarily study Mercury’s magnetic and plasma environment. They are travelling together to Mercury, attached to the Mercury Transfer Module, and will separate into complementary orbits. The spacecraft are designed to endure extreme heating by the Sun and reflected heat from the planet itself.

Timelapse of BepiColombo's fourth Mercury flyby (September 2024). Credit: ESA/BepiColombo/MTM.

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science questions
What questions are we addressing?

We want to uncover the secrets of the closest planet to the Sun:

Investigate Mercury's origins:
Where did Mercury form?

Examine the presence of water on the planet:
Is there really water on Mercury?

Compare historical with current activity:
Is Mercury dead or alive?

Understand the magnetic activity:
Why does Mercury have a magnetic field?

Explain the planet's brightness:
Why is Mercury so dark?

method & instruments
How are we conducting the science?

BepiColombo uses in-situ measurements and remote sensing to study all aspects of Mercury, from the structure and dynamics of its magnetosphere and how it interacts with the solar wind, to its internal structure with its large iron core, and the origin of the planet’s magnetic field. It will make global maps of the surface’s elemental and chemical composition and capture detailed images to help scientists understand geological processes. This includes how the surface has been shaped over time by impact craters, tectonic activity, volcanism, and polar ice deposits.

The spacecraft is equipped with five science instruments and one experiment:
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MOSIF (Mercury Magnetospheric Orbiter’s Sunshield and Interface Structure)
Shields MMO from extreme temperatures and provides the necessary connections between MMO and Mio.
MOSIF was built by ESA.
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MPO (Mercury Planetary Orbiter)
Will study Mercury's surface and internal structure upon arrival at Mercury.
MPO is provided and operated by ESA.
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MTM (Mercury Transfer Module)
Is carrying both orbiters (MPO and Mio) to Mercury using solar-electric propulsion.
MTM was built by ESA.
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MMO or Mio (Mercury Magnetospheric Orbiter)
Will investigate Mercury’s magnetosphere upon arrival at Mercury.
Mio is provided and operated by JAXA.
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Probing of Hermean Exosphere by Ultraviolet Spectroscopy (PHEBUS)
Will use UV emission from Mercury's exosphere to characterise its composition, structure and dynamics, as well as investigate surface-exosphere connections.
Principal Investigator: Eric Quémerais, LATMOS-IPSL, Guyancourt, France
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Mercury Radiometer and Thermal Imaging Spectrometer (MERTIS)
Will measure spectral emittance of different locations with high spectral resolution to provide detailed information about the mineralogical composition of Mercury's surface layer.
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Mercury Gamma-Ray and Neutron Spectrometer (MGNS)
Will determine the elemental compositions of the surface and subsurface of Mercury, and identify the regional distribution of volatiles in permanently shadowed polar regions.
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Italian Spring Accelerometer (ISA)
Will support the study of the planet Mercury and also the test of Einstein's theory of General Relativity to an unprecedented level of accuracy.
Principal Investigator: Francesco Santoli, INAF-IAPS (Istituto di Astrofisica e Planetologia Spaziali), Rome, Italy
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Solar Intensity X-ray and particle Spectrometer (SIXS)
Will perform measurements of X-rays and particles of solar origin to study its surface.
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Mercury Radiometer and Thermal Imaging Spectrometer (MERTIS)
Will measure spectral emittance of different locations with high spectral resolution to provide detailed information about the mineralogical composition of Mercury's surface layer.
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BepiColombo Laser Altimeter (BELA)
Will characterise and measure the figure, topography, and surface morphology of Mercury to create a digital terrain model for exploring the planet.
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Magnetic Field Investigation (MPO-MAG)
Will measure Mercury’s magnetic filed, the interaction of the solar wind, and the formation and dynamics of the magnetosphere, and understanding of the origin, evolution and current state of the planet’s interior.
Principal Investigator: Daniel Heyner, Technische Universität Braunschweig, Institut für Geophysik und extraterrestrische Physik (IGeP), Braunschweig, Germany
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Mercury Orbiter Radio science Experiment (MORE)
Will provide information on the whole surface-exosphere-magnetosphere connected system and the processes involved, plus the interactions between energetic particles, the solar wind, micrometeorites and the interplanetary medium.
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Mercury Imaging X-ray Spectrometer (MIXS)
Will take several types of measurements to understand surface modifications (e.g. cratering, volcanism), and the structure and variation of Mercury’s magnetosphere.
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Spectrometers and Imagers for MPO BepiColombo Integrated Observatory (SIMBIO-SYS)
Will examine the surface geology, volcanism, global tectonics, surface age, surface composition, and geophysics of Mercury to investigate its surface.
Principal Investigator: Gabriele Cremonese, INAF-Osservatorio Astronomico di Padova, Italy
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Mercury Dust Monitor (MDM)
Will detect impact momentum, direction and the number density of the dust with a field of view covering almost a half-sphere to explore the dust environment at Mercury's region of the solar system.
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Mercury Sodium Atmospheric Spectral Imager (MSASI)
Will measure a narrow sodium D2 emission line against the bright surface of Mercury.
Principal Investigator: Ichiro Yoshikawa, The University of Tokyo, Japan
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Mercury Magnetometer (MMO-MGF)
Will observe and measure Mercury’s magnetic field.
Principal Investigator: Wolfgang Baumjohann, Austrian Space Science, Graz, Austria
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Mercury Plasma Particle Experiment (MPPE)
Will take measurements of the plasma, high-energy particles and energetic neutral atoms.
Principal Investigator: Yoshifumi Saito, Institute of Space and Astronautical Science (ISAS), JAXA, Kanagawa Japan
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Mercury Plasma Wave Instrument (PWI)
Will observe both waveforms and frequency spectra in the frequency range from DC to 10 MHz for the electric field and from 0.1 Hz to 640 kHz for the magnetic field.

Credit: ESA. Instruments list: MPO – BepiColombo Laser Altimeter (BELA), Italian Spring Accelerometer (ISA, Magnetic Field Investigation (MPO-MAG), Mercury Radiometer and Thermal Imaging Spectrometer (MERTIS), Mercury Gamma-Ray and Neutron Spectrometer (MGNS), Mercury Imaging X-ray Spectrometer (MIXS), Mercury Orbiter Radio science Experiment (MORE), Probing of Hermean Exosphere by Ultraviolet Spectroscopy (PHEBUS), Search for Exosphere Refilling and Emitted Neutral Abundances (SERENA), Spectrometers and Imagers for MPO BepiColombo Integrated Observatory (SIMBIO - SYS), Solar Intensity X-ray and particle Spectrometer (SIXS). MMO/Mio – Mercury Magnetometer (MMO-MGF), Mercury Plasma Particle Experiment (MPPE), Mercury Plasma Wave Instrument (PWI), Mercury Sodium Atmospheric Spectral Imager (MSASI), Mercury Dust Monitor (MDM).

Where is BepiColombo? Track ESA’s Mercury explorer:
scientific context

BepiColombo is the first ESA mission to Mercury, in collaboration with JAXA (Japan) and building on the legacy of NASA's Mariner 10 and Messenger. Mariner 10 provided the first-ever close-up images of Mercury, and Messenger collected new data whilst orbiting the planet. BepiColombo will go a step further with its two complementary orbiters, en route to reveal information on the composition and history of Mercury, and the formation and history of the inner planets in general.

science highlights
What have we discovered so far?
Since its launch, BepiColombo has yielded significant findings:​

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NEW IMAGES
BepiColombo releases 3 images from its sixth Mercury flyby
The spacecraft flew just a few hundred kilometres above the planet's north pole, collecting close-up images which possibly expose icy craters whose floors are in permanent shadow, and the vast sunlit northern plains.
9 January 2025
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new insights
BepiColombo reveals Mercury in a new light
During this flyby, BepiColombo became the first spacecraft ever to observe Mercury in mid-infrared light. The new images reveal variations in temperature and composition across the planet's cratered surface.
9 December 2024
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new insights
Mercury’s magnetic landscape mapped in 30 minutes
As BepiColombo sped past Mercury during its June 2023 flyby, it encountered a variety of features in the tiny planet’s magnetic field.
3 October 2024
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flyby
BepiColombo flies by Venus en route to Mercury
The mission completed the first of two Venus flybys needed to set it on course with the Solar System’s innermost planet, Mercury.
3 October 2024
building the mission

BepiColombo is a joint mission between ESA and the Japan Aerospace Exploration Agency (JAXA). ESA provides the Mercury Planet Orbiter (MPO) and JAXA provides the Mercury Magnetospheric Orbiter (MMO or Mio). ESA selected Airbus as prime contractor to design and build MPO and the Mercury Transfer Module.

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Sounds of the BepiColombo spacecraft passing by Mercury. Credit: ESA/BepiColombo/ISA & MTM

sounds of bepicolombo
What does BepiColombo sound like?

Listen to the ESA/JAXA BepiColombo spacecraft as it flew past Mercury on 8 January 2025. This sixth and final flyby used the little planet's gravity to steer the spacecraft on course for entering orbit around Mercury in 2026.

What you can hear in the sonification soundtrack of this video are real spacecraft vibrations measured by the Italian Spring Accelerometer (ISA) instrument. The accelerometer data have been shifted in frequency to make them audible to human ears – one hour of measurements have been sped up to one minute of sound.

more about bepicolombo
Keep exploring the mission's science
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more about space science
Discover our science missions

Explore a subset of the ESA Science Programme missions here. Additional mission pages are in progress.
The currently available mission pages are ESA's flagship missions launched from 2013 and to be launched (L-class), and the ones in development (M- and F-class).

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