Exploration of Mercury with
the BepiColombo Mission
Mattia Gregory, Jill Irving, Deanna Morrison, Kate Stensrud, Lidya Tesfalem Abadi and Allan Yaskowich
Astronomers throughout history have strived to discover as much as possible about our solar system and its planets. Recently, the focus has been placed on one of the least studied, and therefore least understood, planets: Mercury. A mission to investigate Mercury has been undertaken by the European and Japanese Space Agencies with a space probe called BepiColombo. The mission objective of BepiColombo is to collect data about Mercury’s magnetic field, geological makeup, and other features. As BepiColombo enters Mercury’s atmosphere, it will split into two separate space crafts. The Mercury Planetary Orbiter (MPO), which was designed by the ESA (European Space Agency), and the Mercury Magnetosphere Orbiter (MMO), designed by JAXA (Japanese Space Agency). Both of these crafts have been designed to conduct specific experiments. As can be deduced by their names, the Planetary Orbiter has many instruments on board to take observations of Mercury’s physical characteristics. While the Magnetosphere Orbiter is focused on studying the upper atmosphere, or magnetosphere, of Mercury. The hope for the BepiColombo mission is to allow scientists to take a more in-depth look into the planet of Mercury and give better details on the poorly researched planet. This project will highlight our current knowledge of Mercury while illustrating what we hope to learn from the BepiColombo mission and how this mission will later impact scientific findings.
Mercury is the smallest planet within our solar system, as well as the closest to the sun. The name Mercury came from the swiftest of the ancient Roman gods.1 Due to Mercury’s proximity to the sun, it has no moons or rings because of the effects of the sun’s gravity. Mercury’s rotation is unique compared to the other planets within our solar system, as it rotates on its axis very slowly compared to its orbital period.2
- Rotation period – the time that it takes an object to complete a single rotation around an axis, relative to the background stars.3
- Orbital period – the given time an astronomical object takes to complete one orbit around another object.4
One rotation of Mercury takes 56.85 days on Earth, while one orbital period takes 88 days.5
Past research shows us that Mercury has a hostile environment that could not sustain human life. Because of the proximity to the sun, the planet is hot, reaching temperatures as high as 430 degrees Celsius during the daytime and as low as -180 degrees Celsius at night.6 In addition to the extreme temperature changes, the thin atmosphere makes it tremendously hard to breathe. The air is made up of Oxygen, Sodium, Hydrogen, Helium, and Potassium.7 These physical features would not have been possible to discover without various space missions orbiting the planet and sending information back to Earth for astronomers to examine. The first spacecraft that was sent to Mercury was the Mariner 10, launched by NASA (National Aeronautics and Space Administration) on November 3, 1973. The goal of the mission was to examine Mercury’s environment, atmosphere, and capture images of its surface.8 During the time of this mission, the spacecraft was able to view 45% of the surface. This informed astronomers that the surface of the planet is rocky, solid, and cratered, much like Earth’s moon, but ice was found on Mercury’s poles. The second mission that was sent to Mercury by NASA was the MESSENGER, which launched on August 3, 2004. The goal of this mission was to study the planet’s geology, magnetic field, and chemical composition.9 In April of 2015, NASA announced that the spacecraft would impact the surface of Mercury because it had run out of propellant, ending the mission entirely.10 Past missions have given more profound insight into Mercury and its orbit. As discoveries are made about the solar system, astronomers and physicists know there is much more information to be gathered. The newest mission to Mercury was developed by the European Space Agency (EPA) and the Japan Aerospace Exploration Agency (JAXA).11 This mission will assist astronomers in finding new information about Mercury that will allow individuals to enhance their knowledge on the planet closest to the sun.
BepiColombo Mission Objectives
The BepiColombo Space mission, launched in October 2018, is the first European mission to Mercury. Since Mercury is one of the least explored planets in our Solar System, the BepiColombo mission will increase our understanding of the composition, geophysics, atmosphere, magnetosphere and the history of the planet.12
There are twelve main scientific objectives to this mission:
- What can we learn from Mercury about the composition of the solar nebula and the formation of the planetary system?
- Why is Mercury’s normalized density markedly higher than that of all other terrestrial planets?
- Is the core of Mercury liquid or solid?
- Is Mercury tectonically active?
- Why does such a small planet possess an intrinsic magnetic field?
- Why do spectroscopic observations not reveal the presence of any iron?
- Do the permanently shadowed crated of the polar regions contain sulphur or water ice?
- Is the unseen hemisphere of Mercury different from that imaged by Mariner 10?
- What are the production mechanisms of the exosphere?
- In the absence of any ionosphere, how does the magnetic field interact with the solar wind?
- Is Mercury’s magnetized environment characterized by features reminiscent of the aurorae, radiation belts or the magnetospheric substorms observed at Earth?
- Can we take advantage of the proximity to the Sun to test general relativity with improved accuracy?13
All of these questions focus on increasing our knowledge of Mercury and testing the planet with modern scientific equipment. BepiColombo will also map the entire surface of the planet, looking at key features and deposits to learn more about what elements are present on the planet and in their quantities.14 Other mission objectives look at Mercury as an example to learn more about the formation of our solar system.15 Studying Mercury can give us more knowledge about the composition of the solar nebula that created our planetary system. It shows another variation of how planets in our solar system can be formed, and it will help us to understand which elements were a part of our solar nebula. Lastly, BepiColombo will study the orbit of Mercury and how it is affected by the extreme gravity, radiation, and heat of the sun.16
BepiColombo is a joint space exploration mission between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) that launched in October of 2018, is set to arrive in Mercury’s orbit in 2025 and will orbit the planet for one year. The mission is currently 20% complete. The mission received its name
from Professor Giuseppe (Bepi) Columbo, who suggested to NASA (when they were planning their Mariner 10 Mission to Mercury) to use a gravity-assisted swing-by of Venus to allow the craft to enter the orbit of Mercury.17
The craft is composed of two separate spacecrafts that will split apart once they arrive in Mercury’s orbit. The Mercury Planetary Orbiter (MPO), which was designed by the ESA and will be operated by them once it has arrived in Mercury’s orbit, and the Mercury Magnetosphere Orbiter (MMO), designed by JAXA, is currently under the control of the ESA during transport. JAXA will operate it during its one year orbit of Mercury.18 Both of these crafts have been designed to conduct specific experiments that will ultimately lead to answering the central questions of the mission. The ESA was also responsible for the design and creation of the Mercury Transfer Module (MTM), which will carry the two orbiters to Mercury, and the MMO Sunshield and Interface Structure (MOSIF), which will provide thermal protection for the MMO and house the mechanical and electrical interfaces for the MMO. The MTM will be ejected from the craft shortly before they arrive in Mercury’s orbit, at which point the MPO will provide the necessary power to propel the craft into orbit.19
The journey to Mercury will take seven years, including flying by Earth once, Venus twice, and Mercury six times before it will be able to be captured by the orbit of Mercury. The fly-bys of Earth and Venus are to use their gravity to help propel the craft on its journey to Mercury, and the six fly-bys of Mercury are to slow the craft down enough so that it can be captured by Mercury’s orbit.20
→To keep up to date on the mission, you can go to the ESA’s twitter page, where they post live updates about the mission: BepiColombo Twitter Feed
Mercury Planetary Orbiter (MPO)
The MPO is a three-axis spacecraft designed and created by the ESA. Its purpose is to carry the necessary instruments to perform eleven experiments while orbiting Mercury. These instruments include a laser altimeter, magnetometer, Mercury radiometer, thermal infrared spectrometer and several other kinds of spectrometers. Additionally, there is a particle and neutron spectrometer, particle analyzers, Mercury gamma ray, Ka-band transponder, and accelerometers and imagers for the MPO integrated observatory system.21 All the instruments are designed to provide a special advantage in the Bepicolombo mission. Without instruments like BELA (BepiColombo Laser Altimeter), ISA (Italian Spring Accelerometer), MAG (Magnetic Field Investigation), MIXS (Mercury Imaging X-Ray Spectrometer), and SERENA (Search for Exosphere Refilling and Emitting Neutral Abundances), the mission would not be possible. The BepiColombo laser altimeter, which is the first planetary system for providing an accurate digital terrain model, examines the volcanism and tectonics of the planet. SERENA is an instrument that provides information on the surface-exosphere-magnetosphere system and handles some of the main objectives of the BepiColombo mission, including the study of composition, origin, structure, dynamics and Mercury’s exosphere (an outer layer of the atmosphere). Instruments such as spectrometers and imagers measure fluorescent X-ray emissions from the surface and have been selected for the payload of the ESA MPO of BepiColombo mission. The equipment on the MPO will study the surface and internal composition of the planet during its one-year orbit.22 The experiments that the MPO will conduct focus primarily on the planet itself, mapping the surface of the planet, which elements are present and in what quantities, and looking at the core of the planet. This information also helps to give us more information about the solar nebula that created our solar system because we can learn more about which elements were present in that nebula, and how they were dispersed throughout the solar system. The MPO also has the main communication equipment that will connect the entire craft to the mission control during its journey to Mercury.23
Mercury Magnetospheric Orbiter (MMO)
The MMO is one of the two satellites that is designed and developed by JAXA. It carries the necessary scientific instruments for five experiments to observe Mercury’s atmosphere. The tools include MDM (Mercury Dust Monitor), MMO-MAG (Magnetometer), MPPE (Mercury Plasma Particle Experiment Instrument), MSASI (Mercury Sodium Atmosphere Spectral Imager), and PWI (Plasma Wave Investigation).24 Each of those instruments mentioned has their objectivity and are crucially vital to the mission with MDM being one the most important since it can detect impact momentum, crude direction, and examine the dust particles around Mercury. While the MDM is essential for studying the dust particles created by comets and asteroids, the magnetometer is also one of the vital advanced devices used to map the surface of Mercury and detect the changes in its magnetic field. Thirdly, The Mercury Plasma Particle experiment instrument is a large particle sensor instrument that consists of seven sensors. MPPE’s primary purpose is to measure plasma and high energy particles around the Mercury, while the primary purpose of MSASI is to measure the temporal variation of the Sodium release in the atmosphere. Lastly, the Plasma Wave Investigation allows us to measure the electric fields, electromagnetic waves, and radio waves around Mercury. The MMO is one of the satellites equipped with a communication system so that when it is in orbit and under the control of JAXA, they can control and receive information from it.25 These experiments focus more on researching the atmosphere and magnetic field of the planet. They will help us to learn more about how both the Earth and Mercury were created. Also how Mercury functions with a minimal atmosphere and an extremely thin exosphere. The MMO will also help to understand the magnetic field of the planet that has currently only been witnessed in more massive planets.26
The BepiColombo mission will answer several questions about our solar system because Mercury is one of the least explored planets. By examining the chemical composition of Mercury, scientists hope to learn more about the elements present in the solar nebula and how these materials were spread amongst planets in the solar system. Hopefully, the mission can explain why Mercury’s density is much greater than the other bodies in our solar system. Mercury has a strong magnetic field compared to other small bodies in our solar system. The mission will help us better understand this and other anomalies in the solar system. Lastly, scientists wonder if frozen water is present at Mercury’s poles. This has been found on many other bodies in the solar system.27 Before BepiColombo is has been impossible to answer many of these questions because it is only the third satellite sent to Mercury, and only the second to orbit. The fact that Mercury has not been studied in detail is the reason why this mission stands to reveal so much information about our solar system. BepiColombo has incredible potential for discovering new knowledge and furthering the study of astronomy. This space mission, though not widely spoken about currently, may very well become one of the most influential of the modern age. A deeper understanding of our Solar System could start at the beginning, Mercury.
1 NASA. Mercury: In Depth. https://solarsystem.nasa.gov/planets/mercury/in-depth/ (Accessed 6 November 2019)
2 Jerry Coffey. Rotation of Mercury. https://www.universetoday.com/14008/rotation-of-mercury/ (Accessed on 6 November 2019)
3 European Southern Observatory. Night and Day on Mercury. https://www.eso.org/public/outreach/eduoff/vt-2004/mt-2003/mt-mercury-rotation.html (Accessed 6 November 2019)
4 European Southern Observatory. Night and Day on Mercury. https://www.eso.org/public/outreach/eduoff/vt-2004/mt-2003/mt-mercury-rotation.html (Accessed 6 November 2019)
5 Jerry Coffey. Rotation of Mercury. https://www.universetoday.com/14008/rotation-of-mercury/ (Accessed on 6 November 2019)
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7 NASA. Solar System Exploration. https://solarsystem.nasa.gov/planets/mercury/overview/ (Accessed 6 November 2019)
8 NASA. Mercury: Exploration. https://solarsystem.nasa.gov/planets/mercury/exploration/?page=0&per_page=10&order=launch_date+desc%2Ctitle+asc&search=&tags=Mercury&category=33 (Accessed 6 November 2019)
9 NASA. MESSENGER: In-depth. https://solarsystem.nasa.gov/missions/messenger/in-depth/ (Accessed 6 November 2019)
10 NASA. MESSENGER: In-depth. https://solarsystem.nasa.gov/missions/messenger/in-depth/ (Accessed 6 November 2019)
11 Fraser Cain. Missions to Mercury. https://www.universetoday.com/14012/missions-to-mercury/ (Accessed 6 November 2019)
12 ESA. BepiColombo Overview. https://www.esa.int/Science_Exploration/Space_Science/BepiColombo_overview2 (Accessed November 7, 2019)
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26 NASA. BepiColombo. https://solarsystem.nasa.gov/missions/bepicolombo/in-depth/ (Accessed November 7, 2019)
27 ESA. BepiColombo, Objectives. https://sci.esa.int/web/bepicolombo/-/31350-objectives (Accessed November 7, 2019)