Cap on Mercury to unravel the mystery of the rocky planets

Cap sur Mercure pour percer le mystère des planètes rocheuses

Cap sur Mercure pour percer le mystère des planètes rocheuses

The planet Mercury photographed by Nasa in may 9, 2016.

Cape on the planet Mercury, “missing link” to try to unravel the mystery of the formation of rocky planets : Ariane 5 is to launch in the night of Friday 19 October to Saturday 20 October from Kourou, in French Guyana, with its edge the two probes of the mission BepiColombo.

“BepiColombo will come as a white knight, with better data, more accurate,” says Alain Doressoundiram, astronomer of the Observatory of Paris – PSL.

But before they reach the orbit of Mercury, the two probes will have to travel seven years and to travel 9 billion miles. “In order to understand the formation of the Earth, says the specialist, it is necessary to understand the formation of rocky planets (Mercury, Venus, Earth and Mars, editor’s NOTE) in its entirety.

Gold Mercury stands out from her sisters,” but we do not understand why. To unravel these mysteries, sixteen instruments, will be divided on two probes, one from the european space Agency (ESA), the other Agency japanese aerospace exploration (Jaxa). The liftoff is scheduled for Friday at 22: 45 Kourou ( 03: 45 Paris time on Saturday morning).

A planet “abnormally” small

With a diameter of 4 879 km (the Earth is 12 756 km), Mercury is the smallest rocky planet in the solar system. According to Pierre Bousquet, project leader of the contributions by French BepiColombo at CNES, it would even be “abnormally” small.

This feature suggests that, in his youth, Mercury had to be struck by a large object. “A huge crater visible on its surface could be the scar of this disaster,” notes the engineer.

Has support to BepiColombo to go study it. Such a scenario would explain the size abnormally large core of Mercury (55% of the total mass of the planet compared to 30% for the Earth).

A magnetic field “surprising”

With the exception of the Earth, Mercury is the only other terrestrial planet to have a magnetic field. A magnetic field is generated by a liquid core. However, given the size of Mercury, its nucleus would have had to cool with time and become solid, like Mars.

Several trails are in the study in order to understand this possible anomaly, as the presence of an element in the kernel which prevent it to cool down. The two probes, in studying the gravity field of Mercury, will allow researchers to define the composition and structure of the planet.

Will then remain to understand why the core of the planet is different from those of her sisters, so that they formed roughly at the same place.

Ice at 400 °C

On Mercury, it is extremely hot during the day (430°C) and very cold at night (- 180°C), knowing that the one does not pass from one to the other that all three terrestrial months. However, previous missions have highlighted the presence of ice at the bottom of craters near the poles.

The researchers presume that ice would have accumulated there as the bombardment of comets and have since escaped to the Sun’s UV rays. “It is suspected but no direct evidence. BepiColombo will try to check this with its infrared cameras,” notes Alain Doressoundiram.

“If the presence of ice is confirmed, it would then have a sample of water in which some pieces are thought to date from almost the beginning of the solar system”, marvels at Pierre Bousquet.

A lab study of solar winds and their effects

Mercury is the planet closest to the Sun, only 58 million km (the Earth is 149,6 million km). “She experienced the full force of the solar winds”, the constant flow of ionized particles that travel at over 500 kilometres per second, ” says Pierre Bousquet.

The researchers will be able to study the impact of this wind (10 times more important than that which is on Earth) on the magnetic field of the planet, and also see how its surface is affected in the long term. Scientists fear that a severe solar storm could affect the power grid land for months or even years in some areas.

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