When comets pass close to the sun, they give off a residue of particles that make their way through the Earth's atmosphere. This dust, scientists have reported, might be older than the sun itself.
Scientists discovered grains called GEMS (glass with embedded metal and sulfides), which are believed to originate from comets, might be a dusty relic from before the formation of our solar system. The researchers reported their findings Monday in the journal Proceedings of the National Academy of Sciences.
Scientists believe particles of amorphous silicate, carbon and different kinds of ice were the basic ingredients of our solar system. Over long periods of time and intense formation processes, this dust morphed into the planets we recognize today.
Surviving pre-solar dust, the research team thought, might linger in some form in the icy bodies of comets that emerged on the edges of something called the "solar nebular."
The sun formed billions of years ago in the heart of a molecular cloud of interstellar dust and gas that contracted under its own immense gravity. Any matter that wasn't sucked into this hot, dense "solar nebula" span around the infant sun in a disk.
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The researchers discovered their glassy grains were made up of smaller "subgrains" that collected together before their host comets formed. They are bound together by a layer of carbon that acts like glue. This adhesive, the scientists reported, couldn't possibly have survived the hot, violent solar nebula.
Instead, these tiny particles must have formed somewhere cooler, like the molecular cloud that would eventually birth the sun, or the outskirts of a protoplanetary disk. GEMS, the authors suggested, "are consistent with surviving interstellar dust, condensed in situ, and cycled through multiple molecular clouds."
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There's good reason to think this unimaginably well-traveled dust is an example of "the original building materials of planetary systems," the authors added in the paper.
"Our observations suggest that these exotic grains represent surviving pre-solar interstellar dust that formed the very building blocks of planets and stars," researcher Hope Ishii, who is based at the University of Hawaii at Manoa, 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."
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