Mystery over ‘great divide’ in the solar system might finally have been solved, scientists say

Our cosmic neighbourhood is split – and astronomers have been unable to explain why

The planet Venus appears close to the crescent Moon as Jupiter (R) appears nearby during a rare planetary alignment on December 1, 2008 in Brighton, England (Mike Hewitt/Getty Images)

Astronomers have finally solved the biggest split in our solar system: the "great divide" that separates its two halves.

The discovery sheds light on how our cosmic neighbourhood was born, and even offers hints about how life was able to flourish on Earth.

The great divide is a name for the strange split that runs down our solar system. On one side of it are the "terrestrial" planets, like Earth and Mars, and on the other are the distant "jovians", like Jupiter and Saturn – the two groups made of different materials and looking fundamentally separate.

The divide is not immediately obvious if you were to look at the solar system, and is located in an empty piece of space, near Jupiter. But the differences between the worlds either side of it can be immense.

On the side nearest the sun, the planets and asteroids have relatively little amounts of organic molecules, for instance, but on the other side alost everything is made up of materials rich in carbon.

Astronomers have long known that the divide separates the two parts of our solar system. But the question of how that came to be, and why the materials from the inner and outer parts of the solar system did not mix, has continued to perplex scientists.

Now scientists have proposed an answer, in a new paper published in the journal Nature Astronomy.

They say the solution might lie in the very beginnings of the solar system, and our young sun, when all that surrounds us today existed as a disc around the star. The differences between the planets began even before they had been formed, scientists said.

"The most likely explanation for that compositional difference is that it emerged from an intrinsic structure of this disk of gas and dust," said Stephen Mojzsis, on of the authors of the paper.

Such discs have been found around other distant, young stars. And so the scientists suggest that if we had one of our own, it could have created the great divide.

It served as a barrier that pulled the materials into different parts of the early solar system – and which would go on to form its planets.

But the barrier did let some materials through, and on Earth those would be the ones that would go on to help form life.

"Those materials that might go to the Earth would be those volatile, carbon-rich materials," Mojzsis said. "And that gives you water. It gives you organics."

Previously, researchers have suggested that Jupiter was the cause of the divide. But by conducting computer simulations of what it would have done in the early solar system, the researchers found that it was not big enough to get in the way of the flow of rocky material on its own.