Field emission scanning electron microscope

Did You Know…

…how the Meteorite In Russia Was Identified?


Since time immemorial, celestial phenomena have provided spectacular viewing material and fuel for doomsday scenarios. Comet Pan-Starrs is currently in the headlines – it recently flew past the earth at a distance of 160 million kilometers and is now at its brightest in its orbit around the sun. Comet Ison is expected to be even more spectacular in November – it will shine as bright as a full moon in daylight according to NASA.

But unfortunately, not all encounters with celestial bodies go as well as in these two cases. For instance, on 15 February 2013 a meteorite measuring approximately 15 meters in diameter and weighing 10,000 tons exploded over the Ural Mountains. Some 1,200 people were injured, mainly by shards of shattered glass. The remains of the meteorite plunged into Cherbakul Lake. Since the lake was frozen over and it was not possible to examine the impact crater right away, scientists gathered dozens of small rock fragments that lay strewn around the lake as a result of the impact. Under the direction of Dr. Victor Grokhovsky, scientists at the “Nanomaterials and Nanotechnologies” Research and Educational Center of the Ural University in Yekaterinburg analyzed these specimens using a ZEISS SIGMA field emission scanning electron microscope.

The researchers were able to establish definitively that the rock fragments were indeed from the meteorite. With an iron content of around ten percent, the meteorite is a classic chondrite, one of the most common types. The evidence was obtained by element analysis using the EDX method (energy dispersive X-ray spectroscopy). When an object is observed in an electron microscope, there are various interactions that occur between the sample and the electron beams. One such interaction involves the emission of weak X-rays by the sample. The energy contained in these X-rays depends on the material being examined. The EDX detector can analyze the X-radiation generated based on its intensity and determine the basic composition of the sample.

The field emission scanning electron microscope is particularly suitable for analyzing materials, such as different types of rock. Thanks to its high-contrast imaging, it is even capable of representing highly topographic specimens with outstanding resolution. Thus the use of this microscope made it possible to identify the rock chips as the remains of the extra-terrestrial visitor.

 

13 March 2013

 

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