How to search for micrometeorites
Collecting and processing samples as part of the Cosmic Dust in the City project
Equipment you will need
- Dustpan and brush – supplied by you
- Bucket/large bowl – supplied by you
- Sieve – supplied by you, or via the project science kit
- Strong magnet – supplied by you, or via the project science kit
- Sample bags – supplied by you, or via the project science kit
- Picking tray – supplied by you, or via the project science kit
- Picking paintbrush – supplied by you, or via the project science kit
- Sample vial – supplied by you, or via the project science kit
- Microscope – supplied by you, or via a loan request made to the project team
Step 1
Identify a suitable location, either a flat roof with internal or side drainage, or a low angle tilted roof with guttering around the edge. The larger the roof and the dirtier it is, the better.
If the tiles on your roof look damaged, or you suspect they may be made of bound asbestos, then please do not collect samples from the roof.
Step 2
After arranging safe access to either the flat roof or a gutter, sweep any visible sediment up into a pile. Place this sediment in either a labelled sample bag for later processing or into a bucket for immediate processing. It is best to collect samples after a prolonged dry period as it easier to sweep up the fine sediment, which is critical to your search, when it is dry.
If you do not wish to process the roof material yourself, then you can send us the sediment you have collected and we will process it for you. Any micrometeorite finds that are made by us on your behalf will be attributed to you.
Step 3
If you are processing your own sample, then slowly add water to the bucket with the roof sediment in it. Give the water a vigorous stir and wait a few seconds. The organic matter should float on the surface while the heavier material, which will include the micrometeorites, will sink.
Either skim off the floating material using a container or gently tip the bucket to the side to decant it off. Repeat this process multiple times until there is no longer any floating material.
Step 4
Place a sieve with a mesh size of around half a millimetre over another bucket, or large bowl. Slowly pour the contents of the first bucket through the sieve into the second bucket/large bowl. If the sieve gets full at any point, then discard the material in it and keep sieving.
We are interested in the material that passes through the sieve and into the second bucket/large bowl.
Step 5
Once the sieving is complete and the sediment in the second bucket/large bowl has settled out, then slowly decant off the excess water, making sure not to lose any of the sediment at the bottom of the bucket/large bowl. Don't worry if the water you are decanting looks slightly muddy. This is the ultra-fine fraction suspended in the water, and we are not interested in that.
Step 6
Leave the sediment at the bottom of the bucket/large bowl to fully dry out. Once dry, spread it out evenly and thinly on a piece of paper. Place your strong magnet inside a plastic bag and place this plastic bag inside another one. Holding these two bags about a centimetre or two above the sediment, slowly move the magnet over the sediment in a grid-like manner.
After completing a few grid lines, hold the bags over another piece of paper and remove the inner bag with the magnet in it. This should cause the sediment you have collected on the magnet to fall onto the new piece of paper.
Repeat this process until you have moved the magnet over all the original sediment. Once done, bag up the original sediment in a sample bag.
Step 7
Place the magnetic fraction you have collected into another sample bag. From that bag gently sprinkle a little bit of the magnetic fraction onto the picking tray and place it under the microscope. In a grid-like fashion, search through the sediment on the picking tray looking for micrometeorite candidates.
Micrometeorites will be matt black in colour, smoothish and spherical in appearance. Grains that are very rounded, very smooth and metallic looking, are unlikely to be a micrometeorite.
Step 8
Micrometeorite candidates should be picked out using the paint brush provided. To do this, wet the end of the paint brush and then give it a shake or two. While looking down the microscope, move the paint brush slowly towards the candidate sample and gently touch it with the bristles. The sample should stick to the bristles. Place the end of the paint brush into the sample vial and gently tap it against the side. This should dislodge the sample from the paint brush and leave it in the sample vial.
You may want to practice this step on non-micrometeorite samples first until such time as you are confident you can pick material out and place them in the sample vial.
Step 9
Once you have picked through the material on your picking tray then place this picked fraction in another sample bag and repeat the process until you have picked through all the magnetic fraction. At this stage, never throw any material away.
Step 10
Post your picked magnetic sediment and your separated candidate samples in their sample vial to the Cosmic Dust in the City project team, making sure you label everything clearly, including your name.
We will take an initial look at your candidate samples and either invite you to the University of Plymouth to look at them under our scanning electron microscope (SEM), or we will bring a benchtop SEM to you, along with your samples, so you can look at them at your place.
Step 11
All confirmed micrometeorites will be added to a national archive with an accompanying online database which will acknowledge any finds you make as yours. You will be kept informed about any future research involving the micrometeorites you have found.
At the end of the project, you will be invited to an exhibition showcasing images of all the micrometeorites found as part of this project.
Do you have questions?
To register to participate in this project, or to contact the project team with any questions about collecting and processing your micrometeorite samples, visit the project page:
Cosmic Dust in the City
