Festive Fun

It was a bit of a shock last week to find that the Open University had decided to go all festive. Christmas already! Oh no! Not yet, surely? But yes! In the Berrill Cafe the staff are now wearing pixie hats, Santa is in his grotto and the air is filled with the sound of hits from Christmas past. Mind you I never get tired of hearing Chris Rea’s Driving Home For Christmas.

The Open University’s Berrill Cafe in festive mood

And so it was on Friday morning that I met up with Graham Ensor of BIMS amid the tinsel of the Berrill Cafe for one of the lesser known, traditional, yuletide activities: meteorite classification! A couple of weeks earlier Graham had contacted me about some interesting looking specimens he wanted a bit of help with. He suspected they might be HEDs (Howardites, Eucrites, Diogenites); meteorites that are widely believed to be from the asteroid 4 Vesta. If you have a laser fluorination line, as we do, that’s an easy thing to check out, because the oxygen isotope composition of HEDs is highly distinctive. And yes, when we analyzed the samples they were certainly HEDs. But to fully classify a meteorite requires a bit more information than just an oxygen isotope analysis. So we were meeting up to look at the samples using an analytical scanning electron microscope or SEM for short.


Diane Johnson and Open University’s FEI Quanta 3D FIB-SEM instrument

Graham and Diane

Graham and Diane loading our HED sample into the SEM

Although they are generally considered to be routine, workhorse instruments, in fact SEMs are very powerful tools that can provide a wealth of detailed information about your sample. Our HED specimen turned out to be very unusual and complex. The SEM work showed that that it was an impact melt breccia with a very distinctive texture and composition. We decided to concentrate on it for the rest of the session. As the work progressed we also had a few technical hitches with the machine, as one does, but these were quickly resolved by Diane Johnson who runs the facility. Despite having characterized only one specimen, we were really pleased with how things had gone. We were now confident that we dealing with a very interesting specimen that was likely to yield new insights into the geological history of Vesta. We booked another session to look at the second specimen. The nice thing is, that based optical microscope observations, this sample is probably even more interesting than the first. So more fun to come on the SEM! Yes, it does feel like Christmas has come a bit earlier this year!


All images: Richard Greenwood

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