In the early solar system, a "protoplanetary disk" of dust and gas rotated around the Sun and eventually coalesced into the planets we know today, according to a new analysis of ancient meteorites by scientists at Massachusetts Institute of Technology (MIT).
The results, appearing in the journal Science Advances, showed that a mysterious gap existed within this disk around 4.567 billion years ago, near the location where the asteroid belt resides today.
"Over the last decade, observations have shown that cavities, gaps and rings are common in disks around other young stars," said Benjamin Weiss, professor of planetary sciences in MIT's Department of Earth, Atmospheric, and Planetary Sciences (EAPS).
"These are important but poorly understood signatures of the physical processes by which gas and dust transform into the young Sun and planets," he said.
The cause of such a gap in our own solar system remains a mystery. One possibility is that Jupiter may have been an influence. As the gas giant took shape, its immense gravitational pull could have pushed gas and dust toward the outskirts, leaving behind a gap in the developing disk.
Another explanation may have to do with winds emerging from the surface of the disk. Early planetary systems are governed by strong magnetic fields. When these fields interact with a rotating disk of gas and dust, they can produce winds powerful enough to blow material out, leaving behind a gap in the disk.
"It's pretty hard to cross this gap, and a planet would need a lot of external torque and momentum," said lead author and EAPS graduate student Caue Borlina.
"So, this provides evidence that the formation of our planets was restricted to specific regions in the early solar system," Borlina said.
Using models to simulate various scenarios, the team concluded that the most likely explanation for the mismatch in accretion rates is the existence of a gap between the inner and outer regions, which could have reduced the amount of gas and dust flowing toward the Sun from the outer regions.
"Gaps are common in protoplanetary systems and we now show that we had one in our own solar system," Borlina said and added, "This gives the answer to this weird dichotomy we see in meteorites, and provides evidence that gaps affect the composition of planets."