You may think of them as huge rocks hurtling through the sky, but the asteroids that helped create our planet may have started life as balls of mud, according to a new study.
Infographic: Mining asteroids
Asteroids containing carbon, also known as carbonaceous or C-type asteroids, are the most common type in our solar system. They are believed to be the precursors to the terrestrial planets, but exactly how they formed is not fully understood.
Now, a paper has been published offering a completely new take on these space rocks.
Philip Bland, from Curtin University of Technology in Perth, developed his model of the early solar system by thinking about the formation process in a new way.
To form an asteroid, water and rock have to interact. Previous studies had assumed when this happens the resulting object is always lithified - which means sediments become compact under pressure.
The main ingredients of a carbonaceous asteroid are fine dust, ice and round mineral grains called chondrules. The new study says that when these ingredients came together, they would not have been lithified at all. Instead, when the ice melted, the minerals would have become part of a sludgy mud.
Bland and his team are calling this, the ‘mudball model’.
“The real innovation is relaxing the requirement that the body becomes ‘rocky’, like the meteorites we see in the collections,” Daniel Britt, from the University of Central Florida, who was not involved in the study, told WIRED.
“The real problem for planetary scientists is to think through alien processes in very alien environments,” says Britt.
These alien environments, which were present at the start of the solar system, are low gravity, odd mixtures of materials, and lots of radioactive decay heat.
“I think the mudball model is very much a step in the right direction,” Britt told WIRED, “since they integrate the model with the ideas about how this type of material accreted in the first place”.
The model also helps explain some strange features found in meteorites. However, more work is needed before it becomes a widely accepted theory.
The paper is published in the journal Science Advances.