Pebbles as evidence – Earth formed earlier than assumed?

Previous estimates of the formation of the earth said that our planet was formed in 100 million years. A research team in the The journal Nature published a study last week, which points to a different era. The theory is now the subject of controversy.

According to this, the earth is said to have formed much more quickly – within three million years. The team of experts attributes this forecast to so-called pebble accretion.

According to this theory, planets form in a disk of dust and gas. Pebbles are then attracted from a certain size of the planet.

The research group led by Isaac Onyett, the study’s lead author, describes that parts of these pebbles are icy and could have supplied water to the earth. This phenomenon is referred to in the publication as a kind of pebble snow.

From this effect an earlier version of the earth was created – the proto-earth. This is what science describes as the forerunner of a planet that is currently in its second stage of development.

According to the experts, the earth was only half the size of today during this phase. Such protoplanets already have a relatively well-formed spherical shape and can reach the size of a dwarf planet.

The team’s theory is that about 100 million years later, there was a major collision involving another protoplanet and early Earth, which is also thought to have formed the Moon. However, this view is not unambiguous.

Disregarding various theories, the scientists in the published study created a time scale of the formation of the earth. For this, more than 60 meteorites and planetary bodies near Earth were examined.

Because the samples were of different ages, the team was able to use an analysis of the silicon composition to compile a chronological sequence of the processes in the dust disk before the earth was formed. The result: the composition of the asteroids changes with increasing age of the samples in the direction of the composition of the cosmic dust collected from Earth.

“This is strong evidence that this dust was also entrained as it drifted towards the sun. It was swept along by the earth as it grew by accretion,” explains Onyett in the Washington Post.

Large parts of the scientific community agree that the formation of gas giant planets such as Jupiter and Saturn can be explained by the accretion of pebbles. Some continue to argue that rocky planets like Earth were instead formed by increasingly large asteroid collisions.

Onyett and his team see it differently. The scientists are sure that they could also find other galaxies containing water worlds, since they would have to have been formed by the same mechanism – so the necessary components for life would also be present in other systems.