Cosmic diamonds formed during gigantic planetary collisions
International research team solves theory of how diamonds formed inside protoplanets

Date:
September 29, 2020
Source:
Goethe University Frankfurt
Summary:
Geoscientists have found the largest extraterrestrial diamonds ever
discovered - a few tenths of a millimeter in size nevertheless
- inside meteorites. Together with an international team of
researchers, they have now been able to prove that these diamonds
formed in the early period of our solar system when minor planets
collided together or with large asteroids. These new data disprove
the theory that they originated deep inside planets - similar to
diamonds formed on Earth - at least the size of Mercury.



FULL STORY ==========================================================================
It is estimated that over 10 million asteroids are circling the Earth
in the asteroid belt. They are relics from the early days of our solar
system, when our planets formed out of a large cloud of gas and dust
rotating around the sun. When asteroids are cast out of orbit, they
sometimes plummet towards Earth as meteoroids. If they are big enough,
they do not burn up completely when entering 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 planets in the solar system but also their extinction.


==========================================================================
A special type of meteorites are ureilites. These are fragments of a
larger celestial body -- probably a minor planet -- which was smashed
to pieces through violent collisions with other minor planets or large asteroids.

Ureilites often contain large quantities of carbon, among others in the
form of graphite or nanodiamonds. The diamonds on the scale of over
0.1 and more millimetres now discovered cannot have formed when the
meteoroids hit the Earth. Impact events with such vast energies would
make the meteoroids evaporate completely. That is why it was so far
assumed that these larger diamonds -- similar to those in the Earth's
interior -- must have been formed by continuous pressure in the interior
of planetary precursors the size of Mars or Mercury.

Together with scientists from Italy, the USA, Russia, Saudi Arabia,
Switzerland and the Sudan, researchers from Goethe University have now
found the largest diamonds ever discovered in ureilites from Morocco
and the Sudan and analysed them in detail. Apart from the diamonds
of up to several 100 micrometres in size, numerous nests of diamonds
on just nanometre scale as well as nanographite were found in the
ureilites. Closer analyses showed that what are known as londsdalite
layers exist in the nanodiamonds, a modification of diamonds that only
occurs through sudden, very high pressure. Moreover, other minerals
(silicates) in the ureilite rocks under examination displayed typical
signs of shock pressure. In the end, it was the presence of these larger diamonds together with nanodiamonds and nanographite that led to the breakthrough.

Professor Frank Brenker from the Department of Geosciences at Goethe
University explains: "Our extensive new studies show that these unusual extraterrestrial diamonds formed through the immense shock pressure
that occurred when a large asteroid or even minor planet smashed into
the surface of the ureilite parent body. It's by all means possible
that it was precisely this enormous impact that ultimately led to the
complete destruction of the minor planet. This means - - contrary to
prior assumptions -- that the larger ureilite diamonds are not a sign
that protoplanets the size of Mars or Mercury existed in the early period
of our solar system, but nonetheless of the immense, destructive forces
that prevailed at that time."

========================================================================== Story Source: Materials provided by Goethe_University_Frankfurt. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. 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, Nicola P. M. Casati, Peter
Jenniskens, Muawia H. Shaddad. Impact shock origin of diamonds
in ureilite meteorites. Proceedings of the National Academy of
Sciences, 2020; 201919067 DOI: 10.1073/pnas.1919067117 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200929123418.htm

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