Formation of Mercury
Mercury and the rest of the planets formed with the Solar System 4.5 billion years ago. A nebula of gas and dust collapsed down from mutual gravity, forming the Sun, and then a disk of material around it. These particles of dust collected together into larger and larger grains of sand, rocks, boulders and eventually planetesimals.
Mercury formed inside a region of the nebula that was rich in iron and heavier elements, which is why the planet is so dense. The surface of Mercury was pounded by comets and asteroids during a period of Solar System history known as the late heavy bombardment, that came to an end 3.8 billion years ago.
Some planetary geologists think that a large planetesimal, 1/6th the mass of Mercury might have collided with the planet early in its history, blasting much of its lighter crust into space. This could explain why Mercury has such a thick core, mostly made of iron.
As Mercury cooled, its outer crust cooled down first, and then the inner portions of the mantle. The outer crust then collapsed down as the inside of the planet contracted as it cooled. This created numerous narrow ridges.
Another theory is that Mercury formed from the solar nebula before the Sun's energy output has stabilized. It would have had twice its current mass, and blasted huge amounts of radiation at the surface of Mercury. This would have raised the temperatures on the surface of Mercury above the boiling point of the rock. This rock vapor would have been carried away by the solar wind, leaving the iron core.
Filed under: Astronomy
Leave a Reply