How to search for micrometeorites yourself, safely
You do not need to go to Antarctica. With permission, a bucket of sediment from the foot of a downpipe, some water, a magnet, sieves and a microscope, you can search for real space dust at home, without ever climbing a ladder or going onto a roof.
Collect sediment that rain has already brought down to ground level, at the bottom of a downpipe or in a drain gully. Wash away the mud and plant debris, pull out the magnetic grains with a magnet wrapped in plastic, dry them, sieve them by size, and search the 0.2 to 0.4 mm fraction under a microscope. Expect to find thousands of look-alikes for every genuine micrometeorite, and enjoy the hunt.
Key facts
- Where to collect
- At ground level only: downpipe outlets, water butts, drain gullies, the edges of paved yards
- Never
- Climb onto roofs or ladders to collect; work near traffic; enter drains
- Key kit
- Bucket, gloves, sieves, strong magnet in a plastic bag, microscope
- Best size to search
- About 0.2–0.4 mm
Safety and permission first
- Stay on the ground. Do not climb onto roofs, ladders or walls to reach gutters. Falls from height are a leading cause of serious injury at home. Rain does the work of carrying roof sediment down the downpipes for you.
- Ask permission from the owner before collecting on any property, including schools, churches and shops, and leave the place as you found it.
- Wear gloves. Gutter and drain sediment can contain bird droppings, bacteria, sharp fragments, moss treatments and lead or other metals from old roofing. Do not touch your face while working, and wash your hands thoroughly afterwards.
- Keep away from traffic and never lift heavy drain covers or reach into deep drains.
- Children can help with washing, sieving and looking down the microscope, with an adult in charge. They should not handle raw sediment without gloves, and no one should taste samples, heat them or use chemicals on them.
- Work outdoors or on a covered table, and do not pour sediment into household sinks, where it can block pipes.
Where to collect
The best source is sediment from a large, flat or gently sloping roof that has not been cleaned for years, collected where it comes out at ground level. Look for the dark, gritty deposit that builds up at the foot of a downpipe, in a water butt fed from the roof, or in the trap of a drain gully that only takes roof water. Older, larger buildings in quieter areas, away from busy roads, railways, building sites and workshops, have fewer industrial particles.
A few litres of sediment is enough to start. Note where and when each sample was collected and keep samples from different places separate.
The method, step by step
- Remove the big stuff. Pick out leaves, twigs and moss, and pour the sediment through a kitchen sieve or garden riddle with a mesh of a few millimetres, discarding what stays on top.
- Wash away the mud. Put the sediment in a bucket, add water, stir and let it settle for half a minute, then pour off the cloudy water. Repeat until the water stays fairly clear. Micrometeorites are dense and sink quickly; clay and organic matter float away.
- Collect the magnetic grains. Put a strong magnet inside a plastic freezer bag and swish it through the wet sediment. Lift it out over a clean dish, pull the magnet out of the bag, and the grains drop off. Repeat several times. Most cosmic spherules are attracted to a magnet because they contain magnetite or metal.
- Dry the concentrate. Spread it on paper or a saucer and let it dry at room temperature. Do not heat it in an oven or microwave.
- Sieve by size. Use test sieves, for example 0.4 mm, 0.2 mm and 0.1 mm, to split the grains into fractions. Most finds are in the 0.2 to 0.4 mm fraction, which is also the easiest size to handle.
- Search under the microscope. Sprinkle a thin layer of one fraction on a dark or white tray, or in a small dish, and scan it slowly at 20 to 40 times magnification. Look for round, dark, shiny spheres, then examine each one more closely for the features described in recognising a micrometeorite.
- Pick and store candidates. Lift each candidate with a fine, damp paintbrush or a needle tip, and place it on double-sided tape or in a labelled micro box. Record the sample, date and fraction.
What to expect
Most of what you find will be rust flakes, magnetite sand, metal shavings and industrial spheres. Even experienced hunters may examine thousands of spheres before finding one convincing micrometeorite, and some samples contain none at all. Patience is part of the hobby. Keep your best look-alikes too: a labelled collection of industrial spheres is the quickest way to train your eye.
Without a roof
You can also collect fresh dust yourself by setting out a clean, flat collecting surface, such as a large shallow tray, outside in an open place for weeks or months and washing out whatever lands in it. Far fewer particles will gather than on a large roof, so this works best as a long-term project or a class experiment comparing sites.
Getting help
A good photograph is the first step to an expert opinion; see equipment and photography. Astronomy and geology societies, museums and university earth-science departments may be able to advise, and some have electron microscopes. Be patient: specialists are busy, so send clear photos and details of where and how the sample was collected.
Did you know?
A large roof is a better collector than any tray: a flat roof of 1,000 square metres gathers dust from an area the size of four tennis courts.
The magnet-in-a-bag trick is used by geologists everywhere because it lets the grains drop off cleanly when the magnet is removed.
Because the method needs only rain, a magnet and a microscope, it is one of the few ways anyone can collect a genuine space sample at home.