British scientists have finally found a solution to one of the mysteries of the solar system.
Astronomers have been amazed for decades that Mercury has such a huge iron core in proportion to the size of the planet.
This core is 70% of the combined mass of Mercury, a much higher percentage than that of Venus, Earth and Mars.
Scientists have previously explained this by the fact that Mercury lost part of its mantle in collisions with other planets, but that theory does not hold up.
Gravity sucked things in
Measurements by the MESSENGER spacecraft, which was in orbit around Mercury from 2011-2015, showed that Mercury is rich in volatile substances such as potassium, which would have evaporated in the heat of a collision with another planet.
Now astrophysicists at the University of Cambridge in England suggest that Mercury lost part of its mantle in several phases when Mercury and Venus had a very close conjunction.
In the early days of the solar system, the orbits of the planets were not the ones we know today.
The distance between Mercury and Venus may have been much smaller than it is now. Then Mercury has repeatedly come very close to Venus, but without a collision.
When this happened, Venus managed to absorb a large part of Mercury’s mantle, which is why Mercury’s mantle is so thin in proportion to the actual core.
The scientists estimated that Mercury’s iron content was 30% in the beginning, similar to that of the oldest known meteorites in the solar system.
Mercury lost traction
Close transits of the inner planets have transferred much of Mercury’s mantle to Venus.
The theory cannot be proven by observations of Venus, which is ten times more massive than Mercury, and therefore it is difficult to detect traces of these material migrations.
On the other hand, the scientists hope to gain more knowledge when the BepiColombo spacecraft arrives at Mercury in 2025 and makes new measurements of the elemental composition of the planet’s surface.
