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Space diamonds formed during giant planetary collisions

Formation of a solar system in planetary collisions

Impression of the artist about the collision of two protoplanets. Credit: NASA / SOFIA / Lynette Cook

An international research team solves the theory of how diamonds form in protoplanets.

Geologists at Goethe University have discovered the largest alien diamonds ever discovered – still a few tenths of a millimeter in size – in meteorites. Together with an international team of researchers, they are now able to prove that these diamonds formed in the early period of our solar system, when small planets collided together or with large asteroids. These new data disprove the theory that they originated deep in the planets – like the diamonds formed on Earth – at least the size of Mercury.

It is estimated that more than 10 million asteroids orbit the Earth in the asteroid belt. They are relics of the early days of our solar system, when our planets were formed by a large cloud of gas and dust orbiting the sun. When asteroids are ejected out of orbit, they sometimes descend to Earth like meteoroids. If they are large enough, they do not burn completely when they enter the atmosphere and can be found as meteorites. The geoscientific study of such meteorites makes it possible to draw conclusions not only about the evolution and development of the planets in the solar system, but also about their disappearance.

Sample from Ureilite Minor Planet Rock

Photo of a rock sample from the small planet of ureilite, discovered as a meteorite in the Sahara. Length of the fragments about 2 cm. Credit: Oliver Christ

A special type of meteorites are ureilites. These are fragments of a larger celestial body – probably a small planet – that has been shattered by strong collisions with other small planets or large asteroids. Ureilites often contain large amounts of carbon, among others in the form of graphite or nanodiamonds. Diamonds currently discovered on a scale greater than 0.1 millimeters or more cannot form when meteoroids hit Earth. The impact of events with such enormous energies would cause meteoroids to evaporate completely. So far, it has been suggested that these larger diamonds – similar to those inside the Earth – must have been formed by constant pressure inside planetary precursors the size of Mars or Mercury.

NWA 7983 Ureylite meteorite

Color-coded Raman spectroscopic map of the studied ureilitis. Diamond (red), Graphite (blue). Credit: Sirena Goodrich

Along with scientists from Italy, the United States, Russia, Saudi Arabia, Switzerland and Sudan, researchers at Goethe University have now discovered the largest diamonds ever found in the ureilites of Morocco and Sudan and analyzed them in detail. In addition to diamonds up to several 100 micrometers in size, many nanometer-only diamond nests were found in ureilites, as well as nanographite. More detailed analyzes have shown that in nanodiamonds there are so-called londdalite layers, a modification of diamonds that occurs only by sudden, very high pressure. In addition, other minerals (silicates) in the studied ureilite rocks show typical signs of impact pressure. Ultimately, the presence of these larger diamonds along with nanodiamonds and nanographite led to the breakthrough.

Professor Frank Brenker of the Department of Geology at Goethe University explains:

“Our extensive new research shows that these unusual alien diamonds were formed by the enormous impact pressure that occurred when a large asteroid or even a small planet crashed into the surface of the parent body of the urethra. In any case, it is possible that this huge impact will eventually lead to the complete destruction of the secondary planet. This means – contrary to previous assumptions – that larger ureylite diamonds are not a sign that protoplanets the size of Mars or Mercury existed in the early period of our solar system, but despite the enormous destructive forces that prevailed at the time.

Reference: “Origin of impact strikes of diamonds in ureilite meteorites” by Fabrizio Nestola, Cyrena A. Goodrich, Marta Morana, Anna Barbaro, Ryan S. Jakubek, Oliver Christ, Frank E. Brenker, M. Chiara Domeneghetti, M. Chiara Dalconi , Matteo Alvaro, Anna M. Fioretti, Konstantin D. Litasov, Marc D. Fries, Matteo Leoni, Nico PM PM Casati, Peter Jenniskens and Muawia H. Shaddad, 28 September 2020,.
DOI: 10.1073 / pnas.1919067117

The international research team consists of scientists from the following institutions:

  • Department of Geosciences, University of Padua, Italy
  • Department of Geology, Goethe University, Frankfurt, Germany
  • Lunar Planetary Institute, USRA, Houston, Texas, USA
  • Department of Earth and Environmental Sciences, University of Pavia, Italy
  • Department of Astronomical Research and Research, Jacobs JETS, Johnson Space Center, NASA, Houston, Texas, USA
  • CNR Institute of Geosciences and Earth Resources, Padua, Italy
  • Vereshchagin Institute of High Pressure Physics RAN, Troitsk, Moscow, Russia
  • NASA Astronomy Acquisition and Curation Service, Johnson Space Center, NASA, Houston, Texas, USA
  • Department of Civil, Environmental and Mechanical Engineering, University of Trento, Italy
  • Aramco Saudi Research and Development Center, Dhahran, Saudi Arabia
  • Swiss Light Source, Paul Scherer Institute, Willigen, Switzerland
  • SETI Institute, Mountain View, California, USA
  • Department of Physics and Astronomy, University of Khartoum, Khartoum, Sudan

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