Scientists say the mysterious diamond came from outer space

Scientists say the mysterious diamond came from outer space

Professor Andy Tomkins (left) of Monash University with RMIT PhD scientist Alan Salk and a urilite meteorite sample. Credit: RMIT University

Scientists said that strange diamonds from an ancient dwarf planet in our solar system may have formed shortly after the dwarf planet collided with a large asteroid about 4.5 billion years ago.

The research team says they have confirmed the presence of lonsdaleite, a rare hexagonal form of diamond, in urilite meteorites from the dwarf planet’s mantle.

Lonsdaleite is named after the famous British crystallologist Dame Kathleen Lonsdale, who was the first woman to be elected a Fellow of the Royal Society.

The team — with scientists from Monash University, RMIT University, CSIRO, Australian Synchrotron and Plymouth University — found evidence for how lonsdaleite formed in urelite meteorites and published their findings in Proceedings of the National Academy of Sciences (PNAS). The study was led by geologist Professor Andy Tomkins of Monash University.

Dougal McCulloch, one of the senior researchers involved, said the team predicted that the hexagonal structure of Lonsdalite atoms makes it harder than regular diamond, which has a cubic structure.

“This study conclusively proves that Lonsdalite exists in nature,” said McCulloch, director of the Microscopy and Microanalysis Facility at RMIT.

“We also discovered the largest lonsdalite crystals known to date, which are down to a micron in size – much thinner than a human hair.”

The team says that lonsdaleite’s unusual structure could help inform new fabrication techniques for superhard materials in mining applications.

Scientists say the mysterious diamond came from outer space

Professor Dougal McCulloch (left) and PhD researcher Alan Salk of RMIT with Professor Andy Tomkins of Monash University (right) at RMIT Microscopy and Microanalysis. Credit: RMIT University

What is the origin of these mysterious diamonds?

McCulloch and his RMIT team, Ph.D. Researcher Alan Salk and Dr. Matthew Field used advanced electron microscopy techniques to capture solid, intact slices of meteorites to create snapshots of how common diamonds and diamonds formed.

“There is strong evidence for a newly discovered formation process for lonceddalite and ordinary diamonds, which is similar to chemical vapor deposition The process that occurred in these space rocks, probably in dwarf planet McCulloch said shortly after the catastrophic collision.

“Chemicals vapor deposition It’s one way people make diamonds in a lab, mainly by growing them in a specialized room.”

Tomkins said the team suggested that the lonsdaleite in meteorites formed from a supercritical fluid at high temperatures and moderate pressures, almost perfectly preserving the shape and texture of pre-existing graphite.

“Later, diamonds were partially replaced by lonsdaleite as the environment cooled and the pressure decreased,” said Tomkins, a future fellow at ARC in Monash University’s School of Earth, Atmosphere and Environment.

“Nature has provided us with a process to try to replicate in industry. We believe lonsdaleite can be used to make extremely tough machine parts if we can develop industrial processes encourages the replacement of preformed graphite parts by lonsdaleite.”

Tomkins said the study’s findings helped address a long-standing puzzle regarding the composition of the carbon phases in urelite.

“Lonsdaleite sequential diamond formation in urelite meteorites via in situ chemical fluid/vapor deposition” was published in Proceedings of the National Academy of Sciences (PNAS).


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more information:
Lonsdaleite sequential diamond formation in urelite meteorites via chemical fluid/vapor deposition, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2208814119

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