Deciphering the story of the solar system

Research reveals meteorites found in Sudan in 2008 are remnants of lost planet

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Almahata Sitta Meteorite
In December 2008 a first meteorite fragment was discovered close to a train station called Almahata Sitta – “Station Six” in Arabic – and thus the meteorite was named.

Scientists have long theorized that many more fledgling planets once circled the sun – some of which were likely little more than a mass of molten magma. One of these lost planets – dubbed Theia – is believed to have crashed into our young planet, ejecting a large amount of wreckage that later formed the moon.

A meteorite called Almahata Sitta crashed in Sudan’s Nubian Desert in October 2008. 480 pieces of battered material weighing 4 kg were found. In 2015, researchers argued that the diamonds found inside the meteorite were much larger than could be formed in collisions with other asteroids.  Early inspections revealed it to be a ureilite, an unusual composition that does not match other space rocks known to have come from the moon or Mars. The finding led some scientists to speculate that it may have had a more exotic origin, yet evidence was still missing.

New research confirms assumptions

Writing in the journal Nature Communications, a team of Swiss, French and German scientists have now examined these diamonds of a few dozen to a few hundred microns large. ZEISS focused ion beam scanning electron microscopy (FIB-SEM) revealed that these diamonds contain crystalline particles made of iron and sulfur that would have required sustained high pressures that only exist inside a planet.

“We have used ZEISS Crossbeam 550 for the investigation of the composition at larger scale and the preparation of the lamellae for transmission electron microscopy. The focused ion beam technique is the only method to achieve a well targeted sample extraction and preparation of these tiny inclusions”, evaluates Dr. Marco Cantoni, researcher at EPFL in Lausanne and one of the authors of the paper.

Calculating a pressure of 2.9 million pounds per square inch would be required to form such diamonds, the research team concluded the planet was as least as big as Mercury, or even Mars. It may have been one of the first planets to circle the sun at least 4.55 billion years ago, before they collided with each other to create the planets we have today.

SEM analysis of meteorite
a) The SEM image shows a carefully selected region with a diamond phase (already covered with a carbon protection layer b) Some material has been removed with the aid of the gallium ion beam so that a free standing lamellae is formed c) A Piezo-controlled micro-manipulator needle is attached in order to extract the lamella for the transfer to a grid for the transmission electron microscop (TEM) analysis d) Lamella containing the diamond phase and its inclusions attached to a TEM grid and polished down to a uniform thickness of about 80-100 nm, ready for the investigation in the TEM

More information on ZEISS FIB-SEM

Tags: Electron and Ion Microscopy

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