As the earth endlessly circles round the Sun, it’s orbit takes it through clouds of dust in apparently empty space and approximately 100 metric tonnes of cosmic dust collides with Earth every day, mostly in the form of stony sand and metal fragments. The International Space Station actually collides with some of these tiny particles and the astronauts have to be ready for any leaks caused should a larger particle penetrate its metal walls.

Micrometeorites are any of these tiny dusty particles that survive their fiery journey through Earth's atmosphere and land on the surface. Cosmic dust is defined as being smaller than ~2 millimetres in diameter. Micrometeorites originate from asteroids and comets. Analysing them provides valuable insights into the composition of the early solar system and the processes that occurred on their parent bodies. They can even shed light on the composition of Earth's ancient atmosphere.

Rosemarket Local History Society (RLHS) committee member and micrometeorites enthusiast, Robin Pearce, has been exploring possible evidence of micrometeorites in Rosemarket and documents his findings below:

“I was fascinated to read about them a year or two ago and decided I would like to try and find some. It seemed unlikely if not odd to hope to find something like that here in Rosemarket. However, I had read that the ideal hunting ground would be in dusty deposits that come down in rain – every raindrop is formed around a tiny particle of dust. While micrometeorites were initially studied primarily in pristine environments like Antarctica and deep ocean sediments, it was realised in 2016 that in fact this dust can be found anywhere on the earth’s surface, particularly in areas such as flat rooftops and gutters.

A recent study has shown on every square metre of the earth’s surface probably one micrometeorite lands every year. Therefore, if you look in a gutter that hasn’t been cleaned thoroughly since Victorian times there should be hundreds! The most crucial tool for collecting them is a strong magnet, as most micrometeorites have a high iron and nickel content. They are often found among other magnetic particles and require washing and careful examination under a microscope for certain identification.

Several members of RLHS had volunteered to clean the gutters of St Ismaels Church in the village, to get rid of the weeds growing there and I thought ‘Here’s my chance! I’ll help do that but with an ulterior motive of collecting some of the ancient mud from the bottoms of the guttering!’ Sneaky I know, and I did mention it to some of my fellow helpers who thought I was mad, but they decided I could get on with it as I didn’t mind climbing wobbly ladders and pulling out all the weeds. And so we did.

All weeds were removed and at the same time I collected a plastic box of ancient mud. I took it home and put it in a safe place until I could get round to checking it. Time passed, there was always something more pressing to do, mainly trying to make my house more habitable. Anyway, in the last few months I thought again of my box of mud and set to gather what I needed. I purchased a digital microscope ready to examine my finds and a really strong neodymium magnet.

My dust was really mud, so first I had to clean away the sediment and leave the possible fragments from space clean and visible. Endless washing started, filling my box full of soapy water, carefully stirring the mud so all the bits of dead leaf and goodness knows what floated up and I could drain away time after time.

Eventually I was left with a tea plate sized heap of sandy, gritty possible space dust. I spread it out to dry in a low heat in the oven on a dinner plate and then put my magnet in a sturdy plastic bag and began to draw the magnet over the surface. It collected quite a lot of fragments, more than I expected, which I kept carefully brushing off the plastic bag and keeping. Further reading had told me that every magnetic bit of dust was not necessarily space dust as all around us there are industrial processes sending often metallic dust into the air, which is called fly ash, and not what I was looking for. And in the vicinity of Rosemarket, we have a lot of refineries which certainly are endlessly working and at night you can see the flames as they burn off surplus gas.

Then at last the exciting bit started. I spread a couple of square inches of my rough dust on a piece of white card, fired up my digital microscope with about 100 times magnification and started to look for my micrometeorites. Poking through the debris with a sharp cocktail stick which looked enormous on the viewing screen, I could barely keep my hand steady as I was so excited. A couple of hours later as backache set in, I realised it wasn’t as easy to find the right thing as I had hoped! There are two main sorts of micrometeorite. A metallic one which looks like a tiny blob of melted metal, with often a shiny surface with patterns caused by the metal setting as it fell to earth after being melted by the heat of the friction of hitting the atmosphere, and glassy ones which often have an almost teardrop shape after setting again as they fall to earth, sometimes with a little tail.

The glassy ones also have some metallic content which is why the magnet picks them up. The fly ash is much more jagged and rough looking. And then I saw it! A beautiful tiny glass sphere with a bit of a tail. I excitedly pushed it with my cocktail stick, but too hard and it shot off the card and was lost on my floor. ‘Bother!’ I said, and possibly ‘Fiddlesticks!’ After a cup of tea, I started to look again. And found another glass one which I managed not to lose! This one is about 0.75mm long. Tiny, really! And then, soon after, a metallic one – about 0.5mm”.

 

Left: Metallic meteorite / Right: Glass sepherule