This depends on a lot of factors, mostly rainfall density, the size of your roof, the age of your roof (or when it was last swept), and type of roof. The best search site would be flat, made of a smooth material (such as vinyl), have a large area, and be in an area of low rainfall. Being away from construction sites would also mitigate the amount of industrial metal spherules collected. For reference, 6 micrometeorites on average fall on every square metre of the Earth’s surface per year.

The average size of modern cosmic spherules is around 200 microns in size (roughly the width of human hair). Although we can see these particles with the naked eye, we do not have the ability to resolve its fine textures, meaning it would be very difficult to distinguish a black terrestrial grain from a cosmic spherule. This problem worsens when dealing with fossil micrometeorites with a much smaller size (~50 microns). Using a microscope with at least x50 magnification is thus essential in identifying spherules.

The most essential equipment needed to separate spherules are:

(1) Magnets
(2) Reflected light microscopes
(3) Picking tools (such as artists’ brushes)
(4) Containers for the collected sediment and suspected spherules, and
(5) Sieves.

The most expensive item on this list would be a reflected light microscope. You can purchase these on Amazon starting from ~£100, or you can buy them second hand. This cost increases if you want to buy a microscope with a camera attachment, but this is not necessary. It may also be possible to ask your local academic institution to borrow one of theirs.

A lot of collection methods require some physically demanding rolls, but these can be mitigated. For example, instead of sweeping dust from your roof, you can use a bucket with a magnet inside placed under your rain catchers to collect micrometeorites. If you struggle to micro-manipulate particles due to low dexterity, you can still search for spherules under a microscope, take a photo of them and note their position in the searching dish. Then, you can ask a friend to pick it for you if you wish, but you will still have a photo of your own micrometeorite! Check out Collection Methods for more info.

Not necessarily. There are three broad types of rocks:
(1) Igneous - these form when magma/lava cool and crystallise. Igneous rocks that form from lava on the surface such as basalts cool quickly so they are unlikely to incorporate many cosmic spherules. Coarser grained igneous rocks such as granites form underground, so similarly any fossil micrometeorites are unexpected.
(2) Metamorphic - when rocks undergo prolonged change due to high temperatures and/or pressures, they “metamorphose”. Any spherules contained in the initial rock will experience extreme chemical and physical changes and can become unrecognisable.
(3) Sedimentary - accumulated sediments such as sand, mud, calcites, and salts can compact during diagenesis to form sedimentary rocks. During this assemblage, cosmic spherules can become incorporated in the sediment, thus this is the most probably rock type to contain fossil micrometeorites.

The best rock to search through, however, is a chalk due to it’s soft and easily crushable nature, semi-consistent deposition rates, white contrasting colour, and near-pure calcite composition. Check out Collection Methods for more info.

Congratulate yourself! Even though they fall everywhere across the Earth, these tiny particles can be hard to find! When you see a spherical, dark, shiny grain you suspect could be a cosmic spherule, take a photo incase it’s lost during the picking process. Then, use a micromanipulator (a fine tipped artists paint brush will do) to transfer the spherule into a container. If you want to keep it in place, stick some double sided sticky tape on the container and place the spherule on top.

If you think you have quite the collection and want to look at them in more detail, you can take them to your local academic institution and ask if they can image and analyse them using a scanning electron microscope (SEM). You can also take detailed photos using an optical microscope with a camera attachment if this is not an option. When you give the samples to a researcher, they will likely want to embed them in resin and polish the surface which allows them to see the spherule interior and get more accurate chemical compositions. This is the final step in scientifically identifying a cosmic spherule! Collection Methods for more info.

All spherules published on this website will have descriptions that detail the collections they are from. Any particles from the “ICL (Imperial College London) group” are free to use if credited accordingly to the website, original paper, or research group. For all other samples, please enquire the described origins before using the photos/data. For more information, please contact us on the above form.