Our Solar System began 4.6 billion years ago with the formation of our Sun inside a giant cloud called the solar nebula. Ultimately, this nebula gave rise to the planets and other objects that also inhabit our Solar System today.
In an intriguing study, scientists say they have found remnants of that initial nebula in Earth’s upper atmosphere. They suggest that some interstellar dust from that nebula was stored on comets, which later transported the material to Earth. The findings were published in the journal Proceedings of the National Academy of Sciences.
The team, led by the University of Hawaii at Manoa (UH Manoa), studied the chemical composition of dust samples using a particle accelerator and an electron microscope at the Lawrence Berkeley National Lab (LBNL) in California. The samples were collected by a NASA aircraft at an altitude of 12 miles (20 kilometers).
In the study, the team examined glassy grains known as GEMS (glass embedded with metal and sulfides), which are less than a hundredth the width of human hair. The researchers found that the grains were made of subgrains that had stuck together, before the comet’s formation.
"Our observations suggest that these exotic grains represent surviving pre-solar interstellar dust that formed the very building blocks of planets and stars,” Dr Hope Ishii, lead author on the study, said in a statement. “If we have at our fingertips the starting materials of planet formation from 4.6 billion years ago, that is thrilling and makes possible a deeper understanding of the processes that formed and have since altered them.”
Based on this research, it’s thought our Solar System formed mostly from carbon, ices, and silicate. Most dust was likely destroyed and reworked to form planets, but some dust from before the birth of the Sun survived on comets, which formed in the outer solar nebula.
What’s more, the GEMS were found to contain a type of carbon that decomposes with weak heating, suggesting they would not have survived being formed nearer the Sun. This points to the idea that they formed in the outer solar nebula of the early Solar System.
"The presence of specific types of organic carbon in both the inner and outer regions of the particles suggests the formation process occurred entirely at low temperatures," said Jim Ciston, a staff scientist from the Molecular Foundry at LBNL, which looked at the particles under an electron microscope to work out their chemical makeup.
The exciting discovery means that we can use interplanetary dust in our own atmosphere to peer back into the dawn of the Solar System. This could reveal interesting details about the formation of the planets and more, and give us an insight never before possible.
“This is an example of research that seeks to satisfy the human urge to understand our world's origins,” said Ishii.