Like asteroids, our own planet Earth was formed by a cosmic ocean of millimetre-sized particles that orbited the young sun, said a new study led by Lund University in Sweden.
Scientists said fragments of asteroids which land on Earth as meteorites regularly comprise millimetre-sized round stones called chondrules, believed to be the original building blocks of the solar system. The new study shows that asteroids were formed by capturing chondrules with the help of gravitational force and is our Earth.
“The chondrules are of exactly the right size to be slowed down by the gas that orbited the young sun, and they could then be captured by the asteroids’ gravity”, says Dr Anders Johansen of Lund University. This causes them to fall down and accumulate like sand piling up in a sandstorm, explained researchers.
In collaboration with Mordecai-Mark Mac Low from the American Museum of Natural History, researchers from Lun University developed a computer simulation for what the process may have looked like. They assumed that the asteroids were formed in a kind of cosmic ocean of chondrules and that the asteroids started out much smaller than they are today.
In computer simulations, the asteroids grew quickly to a diameter of up to 1 000 km, the same size as those found today in the asteroid belt between Mars and Jupiter, where NASA spacecraft Dawn is exploring the Ceres dwarf planet. The largest asteroids continued to grow to the same mass as the planet Mars, which has ten per cent of the mass of Earth.
“We suddenly realised that this rapid process could say something about the formation of the Earth as well”, explains Anders Johansen.
The new study also sets aside previously believed notion that the Earth was formed through collisions between protoplanets over a period of 100 million years but they never understood how these protoplanets themselves formed.
“Our study shows that protoplanets may have formed very quickly from asteroids, by capturing chondrules in the same way as the asteroids did”, says Martin Bizzarro, an expert on chondrules from Copenhagen University and a co-researcher.
The study gets more authenticity in view of the studies of meteorites from Mars which have shown that Mars was formed about 1–3 million light years ago, which is within the same time span as the researchers have obtained in the computer simulation.
“Traces of this process remain in asteroids that still contain intact chondrules. The terrestrial planets, however, have all melted after their birth and therefore do not show any direct traces of their original building blocks”, says Johansen and their findings have been published in the journal Science Advances.