Mercury will become a poorer puzzle «DiePresse.com

The smallest planet in our solar system, Mercury, is also one of the poorest studied. The many puzzles must now be solved with the Euro-Japanese space mission Bepi-Colombo. Hopefully, an Ariane 5 rocket with the two mission satellites on board was launched today at 3:45 am from the Kourou spaceport. In seven years, the 4100-kilogram probes reach the Mercury and measure it for a year after all the rules of the art. The mercury has a diameter of 4878 kilometers, its distance to the sun is 58 million kilometers, or nearly 40% of the corresponding values ​​of the Earth.

Ten times more radiation

So few things on the planet know it, it's because of its proximity to the sun. From the earth, it can only be seen in a narrow radius of the sun, so it is often overshadowed by it. Satellites, on the other hand, fight against the extremely powerful solar radiation, which is ten times more powerful in Mercury than on Earth. The planet gets hot at 450 degrees on the sunny side, but it is minus 170 degrees in the shade. Until now, only two NASA satellites have been sent into this inhospitable area: Mariner 10 flew three times in 1974 and 1975 on Mercury, Messenger stirred in 2011 in a Mercury orbit (and was controlled in 2015).

Mercury is a planet similar to the Earth: it consists of a metal core with a silicon crust. However, it is too small and too light to maintain a significant atmosphere. There is therefore only an extremely fine gas envelope (exosphere) containing hydrogen and helium from the sun and oxygen and sodium, which are released from the surface of the planet. This surface is dotted with craters that have not been eroded by wind or water, but have been overshadowed by volcanic events.

Questions about the magnetic field

In the permanent shadows of the polar craters, water ice is suspected, as well as organic carbon and nitrogen compounds – the origin of which is perplexing. The same thing applies to the question of why Mercury (like the Earth but unlike the Moon or Mars) has a magnetic field and how it interacts with solar winds.

The mission of Bepi-Colombo is quite possible, due to its namesake, the Italian mathematician and engineer Giuseppe (Bepi) Colombo (1920-1984), who conceived in the 1960s trajectories in which the attractions of the planets skillfully used during flyover. The Bepi-Colombo probes will perform a total of nine "tilting" maneuvers – one around the Earth, two around Venus and six around Mercury – before pivoting into stable orbits. They will gravitate around the sun 18 times over a total distance of about nine billion kilometers.

The biggest problem with this is that satellites have to be slowed down constantly because they are more and more attracted to the sun, the closer they get. Braking is performed by alternating maneuvers and by special solar and ion electric motors. This requires more energy than a mission to Pluto.

Hightech of Austria

Aboard Bepi-Colombo, Austrian advanced technologies are also available: thermal insulation (ceramic fiber) and control elements come from the largest space technology company in the country, Ruag Space. The Graz Institute for Space Research (IWF) of the Academy of Sciences plays a key role in three measuring devices: two magnetometers and an ion camera, which are used to analyze by particle mass spectrometry which are projected out of the surface of Mercury.

These instruments complement the wide range of 16 scientific mission instruments, ranging from cameras and spectrometers to plasma detectors and laser altimeters. IMF participation is funded by the FFG research funding agency.

The data from 2026 are not only important for the exploration of Mercury and our solar system, they should also provide more knowledge about the formation of solar cells near exoplanets and serve to design innovative tests of the theory of general relativity of Einstein.

("Die Presse", printed edition, 20.10.2018)