Scientists have released microscopic images of fragments of the meteorite that hit central Russia in February. The fragments represent just a small portion of the remains of the 17m-diameter body that struck the Earth’s atmosphere in a spectacular trail of light over the city of Chelyabinsk.
The team, led by Urals Federal University’s Viktor Grokhovsky, determined right away that the overall chemistry of the meteorite was a familiar “chondrite”. “The fragments contain a standard number of minerals, including olivine, pyroxene, troilite and kamacite. These minerals that can be discovered only in outer space confirm the fragments’ extraterrestrial nature,” he told the Voice of Russia at the time.
However, far more information was in the offing. The team was using a scanning electron microscope, which fires a beam of electrons focused onto a tiny part of a sample, scanning around to see how the electrons are deflected and thereby building up a detailed picture of the sample’s nanometre-scale bumps and valleys.
But that process causes the emission of a small amount of X-ray radiation - with the exact energy of the X-rays corresponding to the chemical element present in the focus of the electron beam.
This is where a silicon drift detector comes in - harvesting these X-rays and determining their energy. The result is a series of what are called X-ray maps [pictured above, coloured images] - pictures of the same sample showing the presence and quantity of different elements.