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Home > Research > Space Plasmas > Space missions > Bepi Colombo (2018) > Description of the mission

Description of the mission

Our knowledge about Mercury

The environment of Mercury has been the object of only two exploratory in situ missions. All we know of the ionized environment of the planet comes from the results collected during these missions. The first one was Mariner 10. It was launched in the early 70s and made three flybys of Mercury. The second mission, MESSENGER is still ongoing. The MESSENGER probe made three flybys of the planet and was put into orbit in March 2011.

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Mercure seen by MESSENGER (NASA)

Mariner 10 led to the discovery of the intrinsic magnetic field of Mercury. Observations have shown that it is strong enough to repel the plasma from the Sun (solar wind) at some distance from the planet. The area around Mercury, dominated by its internal magnetic field (magnetosphere) has also been explored. According to these observations, the spatial and temporal scales of Mercury’s magnetosphere are small compared to those of the Earth’s magnetosphere. Mariner 10 has also made possible the first observations of the thin atmosphere of the planet (exosphere). Finally, it has provided many images of the surface of the planet.

The MESSENGER mission has confirmed many of the observations made by Mariner 10. It provided a significant number of additional information on the Mercury environment. The characteristics of the intrinsic magnetic field have been refined through the measurements made during overflights of the planet. Furthermore, magnetospheric ions were detected for the first time.

These in situ observations combine with those of the surface and the exosphere made from Earth. This combination provides a better understanding of processes linking the magnetosphere and exosphere of Mercury’s surface. However, Mariner 10 and MESSENGER leave many questions open.

Deepen our knowledge with Bepi Colombo

The Bepi Colombo mission is the result of a close collaboration between ESA (European Space Agency) and JAXA (Japan Aerospace Exploration Agency). It offers a more complete instrumentation than MESSENGER and an innovative flight plan. Both will offer the scientific community many elements to improve the understanding of the planet and its environment. The investigations concern in particular the interaction between Mercury and the solar wind.

The main objectives of the mission Bepi Colombo are the following:

  • Understanding the origin and evolution of a planet very close to its star.
  • Understanding of the origin and structure of the intrinsic magnetic field of Mercury.
  • Study of the shape of the interior structure, geology and composition of the planet.
  • Study of the composition and dynamics of the exosphere of Mercury.
  • Study of the structure and dynamics of the magnetosphere of Mercury.
  • Determination of the composition and origin of the deposits observed at the poles.
  • Tests of Einstein’s theory of relativity.
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Orbits of the two Bepi Colombo orbiters around Mercury (ESA )

A double mission

The mission consists in two separate probes. The MPO probe (Mercury Planetary Orbiter) is carried out by ESA. The MMO probe (Mercury Magnetospheric Orbiter) is performed by JAXA. Both spacecraft will not have the same functions but complementary goals. The main role of MPO is to study the solid planet. MMO is dedicated to studies of the magnetosphere of Mercury and of its interplanetary environment.

These two probes will be launched in 2018 by a single launcher. They will be separated at the time of their polar orbit in 2024. MPO will have an elliptical orbit with a periapsis 400km and 1500km apoastre to the surface (radius of Mercury: 2440km). MMO will have a more elliptical orbit with a periapsis also located 400km and apoastre to 12,000 km altitude.


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