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 curve around the sun. The spectacle of Comet Ison in November is predicted to be even more amazing – it will shine as bright as a full moon in daylight, according to NASA.
But unfortunately not all encounters with celestial bodies go as smoothly as both of these instances. On 15 February 2013, a meteorite measuring 15 meters in diameter and weighing 10,000 tons exploded over the Urals. Approximately 1,200 people were injured, mainly by flying glass fragments. The remains of the meteorite plunged into the Cherbakul Lake. Because the lake was frozen and it was not possible to examine the impact crater, scientists gathered dozens of small rock fragments that were left on the lakeshore as a result of the impact. Under the leadership of Prof. Dr. Victor Grokhovsky, the scientists analyzed these at the "Nanomaterials and Nanotechnologies" Research and Educational Center at the Ural University in Jekaterinenburg, using a ZEISS SIGMA field emission scanning electron microscope.
The researchers were able to clearly establish that the rocks were indeed from the meteorite. With an iron content of around 10 percent, they are from a classic chondrite, one of the most common types of meteorite. The evidence was obtained using element analysis with the EDX method. EDX stands for energy dispersive X-ray spectroscopy. During the observation of an object in an electron microscope, various interactions occur between the sample and the electron beams. One interaction consists of the sample emitting weak X-rays. The energy the X-rays contain depends on the material under examination. The EDX detector can analyze the X-radiation based on its intensity and determine the basic composition of the sample.
The field emission scanning electron microscope is particularly suitable for materials analysis, e.g. different types of rock. Thanks to its contrast imaging, it can display specimens featuring significant topographical features with outstanding resolution. Using this microscope, the rock chips were identified as the remains of the extra-terrestrial visitor.
March 13, 2013