The moon formed a little later than previously thought. When a protoplanet the size of Mars was destroyed in a collision with a young Earth, a new body was created from the debris ejected during this collision, which became the Moon. Scientists used a new numerical model to restore the time at which the event occurred – 4.425 billion years ago. Previous moon formation assumptions were based on the age of 4.51 milliliters. years, that is, 85 million years earlier than the new calculations show. Scientists reported their findings in the journal Science Advances.
Four and a half billion years ago, the solar system was still chaotic. Earth still grew to its current size, collecting matter in the form of planetesimals. They previously formed in a disk of dust and gas orbiting the early Sun. Young Earth consolidated, becoming hotter inside. All large parts of the rocky mantle melted and formed an igneous ocean. It was at this time that the Earth acquired a natural satellite. A massive cosmic collision between the Earth and the protoplanet threw the stone into space from a young Earth. In the end, this debris thickened, forming a new planetary body – the Moon.
In principle, most scientists agree on how the moon was formed, but not about the details of the process, and especially not about the time when it occurred.
The results of the latest planetary geophysicist simulations at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR), led by Maxim Moris, together with researchers from the University of Münster, suggest that protoplanet collided with young-Earth about 140 million years after the birth of the solar system 4.567 billion years ago. According to their calculations, this happened 4.425 billion years ago.
At that time, the Earth had just turned into a planet. During this development, heavy metal components drowned toward the center of the earth and formed a core of iron and nickel, which was surrounded by a thick mantle of silicate rocks. Mantle rocks are getting hotter. This allowed the separation of metals and silicates in the bowels of the Earth for several tens of millions of years.
At this stage, the Earth was hit by Tei, a protoplanet that was the size of Mars. In the early days of the solar system, there would be many such bodies. Some were thrown out of the solar system, while others were destroyed as a result of collisions with other bodies. Thea, however, hit the Earth and ejected so much material from the mantle of the planet that the moon could form from it. During this strong blow, an igneous ocean was formed with a depth of several thousand kilometers. Today, after this clash, there are no traces of Thei left.
The collision of two bodies with its enormous energy also vaporized a large number of stones from the early mantle of the Earth. All this substance was thrown away and collected in a dust ring around the Earth before it gathered again to form into stone. Based on this, the moon formed in a short time, possibly in just a few thousand years.
Scientists largely agree with the history of the formation of the moon. However, they could not establish the exact date, since not one of the lunar rocks delivered to the Earth records the age of the Earth’s natural satellite. Researchers from DLR and the University of Münster determined when the moon formed using a new indirect method. Their calculations show that this most likely happened at the very end of the formation of the Earth.
Not only the Earth had an ocean of magma at an early age. The energy obtained as a result of accretion also led to the formation of an igneous ocean on the moon. The moon almost completely melted and, like the Earth, was covered by an igneous ocean with a depth of more than 1000 kilometers. This magmatic ocean quickly began to solidify and formed a crust of floating light crystals on the surface. But beneath this insulating crust, which slowed down further cooling and solidification of the magmatic ocean, the moon remained molten for a long time. Until now, scientists have not been able to determine how long it took for the igneous ocean to crystallize completely, so they could not conclude when the moon originally formed.