When I was working at the Natural History Museum, a while ago now it has to be said, one of my jobs involved the study of micrometeorites. These are tiny particles that almost certainly form the largest fraction of extraterrestrial material swept up by Earth each year. Estimates of just how much they represent vary enormously, from 60,000 tons to only about 1,000 tons per year. This uncertainty is not surprising. A lot of these particles are destroyed on atmospheric entry and only a small fraction makes it to the ground. Of course, the ones that burn up are still adding new material to the Earth. But let’s not worry about that for the moment. It is more important to mention that micrometeorites are, well, micro! The have diameters of 0.5 mm or less. Their small size makes them tough to collect, but not impossible.

So, anyway, one day I was working in the lab on some stuff called cryoconite. It is a fancy name for a dark sediment with a high content of organic material that can build up locally on the surface of glaciers, for example the giant Greenland ice sheet. It is known that cryoconite can contain a high concentration of micrometeorites, which was why I was working on the stuff. But I was having problems, big problems. The samples I was studying had a very high content of filamentous blue-green algae. Lovely if you are a biologist, but not if you want to study the cosmic particles trapped in all that organic material. I was in a bad mood. The cryoconite consisted of a dense mass of tiny fibers that was almost impossible to tease apart. As a result, there was little to no chance of recovering those miniscule space particles. Very frustrating!

The lab I was using for this needle in a haystack job was located in the electron microscope suite in the basement of the Natural History Museum. People working at the museum look at all sorts of tiny things in addition to cosmic particles; bugs, seeds, minerals, fossils etc. So, not surprisingly, they have an amazing array of sophisticated instruments, which for the moment I couldn’t use. Sue, the lady in charge of all those microscopes, came by to see how I was getting on. “It’s not going well” I probably said, or perhaps something a bit stronger. I explained the problem. With a knowing look on her face, well she was a biologist, Sue had a suggestion to make. “You need bleach”. I was a bit surprised by this advice. To me bleach was for cleaning toilets and generally something used in the home, not for the sort of high-value space research that I was engaged in. Well, in fact I wasn’t doing any such research thanks to all that organic stuff. But of course, as advertised on the bottle, bleach “kills 99.9% of all viruses and bacteria” and probably wasn’t so nice to filamentous blue-green algae either. Sue’s advice was, leave the cryoconite in bleach overnight and have another look in the morning. It was certainly worth a try.

The next day I was excited to see what the bleach had done to those pesky algal filaments. I hurried down to the microscope suite. I had a look at my beaker of cryoconite. But it was gone! Not sort of gone, or a bit gone, but completely and utterly and totally not there anymore. It had apparently just vanished into thin air. I was astonished and a little bit worried. I looked at the contents of the beaker using an optical microscope. There was a little bit of fluid at the bottom and a small amount of sediment. But the algae had vanished. I zoomed in on the sediment and that’s when I got the shock of my life. There, amongst the mineral grains, were these perfectly round particles. They are known as cosmic spherules and form when extraterrestrial dust is heated and melts as it descends at high velocity through the Earth’s atmosphere. Now I could see them clearly and recover them with just a pair of tweezers. Tiny, tiny grains from outer space liberated by something as ordinary and everyday as bleach. It was an experience I have never forgotten.