Scientists have uncovered samples of interplanetary particles collected from Earth's upper atmosphere which are said to originate from comets and contain dust leftover from the initial formation of the solar system.
The experiments which aided the discovery of the particles were conducted at the Department of Energy's Lawrence Berkeley National Laboratory by an international team, led by Hope Ishii, a researcher at the University of Hawaii, at Manoa.
They studied the particles' chemical composition using infrared light as well as exploring their nanoscale chemical makeup using electron microscopes.
Published in the journal Proceedings of the National Academy of Sciences, the research found that the initial solids from which the solar system formed consisted almost entirely of carbon, ices, and disordered (amorphous) silicate.
This dust was mostly destroyed and reworked by processes that led to the formation of planets, the researchers said, and surviving samples of pre-solar dust are most likely to be preserved in comets - small, cold bodies that formed in the outer solar nebula.
Staff scientist at the Molecular Foundry, Jim Ciston, explained that the particle-mapping process of the microscopy techniques provided key clues to their origins.
"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," he said.
"Therefore, these interplanetary dust particles survived from the time before formation of the planetary bodies in the solar system, and provide insight into the chemistry of those ancient building blocks."
He also noted that the "sticky" organics that covered the particles may be a clue to how these nanoscale particles could gather into larger bodies without the need for extreme heat and melting.
Ishii added: "Our observations suggest that these exotic grains represent surviving pre-solar interstellar dust that formed the very building blocks of planets and stars.
"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."
In the future, the scientists are planning to search the interiors of additional comet dust particles, especially those that were well-protected during their passage through the Earth's atmosphere.
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