New insights into the origin of diamonds in meteorites

New insights into the origin of diamonds in meteorites

NWA 7983 Photomicrograph of a carbon field in ureilite meteorites. Raman spectroscopy depicting the distribution of diamonds (red) and graphite (blue) depicts the image of reflected light with a false color map. Credit: Ryan Jacbek and Siren Goodrich

Scientists have offered new insights into the origins of diamonds in urelites (a group of stony meteorites). These diamonds most likely result from acute shock changes from graphite (the normal low-pressure form of pure carbon) during one or more major impacts in the solar power system.

Earlier, researchers have proposed that diamonds in Euralite are formed like those on Earth – deep in the mantle of the planet, where the high pressure (a very dense, hard form of pure carbon) needed to make diamonds. , Is formed by the weight of the occupation. Rock. If diamonds formed in the urethra in this way, then the original original body on which they were formed would have been a large protoplanet – at least the size of Mars or Mercury.

However, Prof. Fabrizio Nestola (University of Padova, Italy), Drs. New research conducted by Sirena Goodrich (University Space Research Association at the Lunar and Planetary Institute) and her colleagues suggests that the state of high static pressure and long rise time of the deep interior of a planet.

The team examined diamonds in three ureteral samples using electron microscopy, micro X-ray diffraction and Raman (laser) spectroscopy. Their investigation revealed both large (100 micrometers in size) and small (diamond nanometer in size) metal iron and graphite as well as carbon-rich areas in carbon-rich areas located between silicate mineral grains in these samples. .

New insights into the origin of diamonds in meteorites

NWA 7983 microphotographs show areas of diamonds and graphite surrounded by Mg-Fe-Ca silicate minerals. Credit: Fabrizio Nestola and Oliver Christ.

“We discover the largest single-crystal diamond ever seen in an urelite,” Dr. Siren Goodrich says. “Crucially, all of the ureters we examined, based on evidence of silicate minerals, have suffered a great setback, strongly suggesting that both large and small diamond rocks in these rocks are formed through shock processes. Made of graphite. ”

The origins of diamonds in urilites have important implications for models of planetary formation in the early solar system. Currently asteroids from which most meteorites originate are much smaller than planets. However, models of planetary formation predict that planets are formed as planet-shaped embryos (protoplanets) as a result of the Moon’s accumulation. Advocates of the high static pressure hypothesis for the origin of ureteral diamonds argue that the ureteral root body was one of these embryos. However, Nestola and co-authors demonstrate that the presence of diamonds in the ureter does not require the original Mars-shaped body.

It was previously thought that micrometer-sized diamonds were formed in a very short period of time (eg, microseconds) during which peak pressure is maintained in impact events. However, Nestola et al. It was calculated that the peak shock pressure could remain for 4-5 seconds during a major impact such as was estimated for the diuretic parent body. It is sufficient to manufacture diamonds of the size of 100 micrometers when catalyzed by the presence of metal, a process commonly used in the production of diamonds in industry. Since the metal is ubiquitously linked with carbon phases in the urethra, catalytic formation of diamonds larger than the original graphite under shock compression is very likely.

Dr. Goodrich further notes, “Our findings are important because they not only indicate the origin of a shock to the diamond in the urethra, as discussed by many previous researchers, they also refute the arguments that larger The basic body has been made for the hypothesis. Thus scientific debate and hypothesis testing is an essential part of progress in science. ”

New insights into Earth’s carbon cycle

more information:
Fabrizio Nestola et al. Effect of diamonds in uralite meteorites Proceedings of the National Academy of Science (2020). DOI: 10.1073 / pnas.1919067117

University provided by the Space Research Association

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