A micrometeorite (MM) is a microscopic object from space that falls to Earth and survives the trip through the atmosphere.
About 60-100 tons per day of micrometeorites hit our Earth, much more than all other meteorites and space debris put together. (see graphic below). Despite that, very few have been found outside of Antarctica, a few deserts and the deep ocean… until 2015, when Jon Larsen from Norway discovered the first “urban” micrometeorite.
Since they are tiny (only a few times the width of a hair!), they are difficult to find. (see image below).
Micrometeorites enter the atmosphere at 25,000 to 150,000 mph or more and usually heat up due to Friction and Ram Pressure (compression) and become spheroidal (not usually spheres but close).
The textures seen are formed from the heating they receive from passing through the atmosphere.
Depending on how micrometeorites ‘hit’ the atmosphere, they can produce heat from about 400-2800 degrees C (~750-5000 degrees F).
In order to identify your micrometeorite, you must take an image since microscopes at high power only show ‘slices’ of objects in focus. By taking 100’s of images and Focus Stacking (using a program to take ‘in-focus’ parts of images and put them all together into one totally in-focus image) you can get an image to use for identification. (see image series below).
Distribution of objects from space by size in mm and mass. As you can see, most space debris is tiny - micrometeorites
Searching for micrometeorites on rooftops and gutters can put you at risk. If you decide to try this, you bear full responsibility for your actions!
· Find a flat roof or gutters
· Use a strong magnet to search for magnetic particles
· Double bag the magnet to prevent particles from sticking to it
· Collect material - wash thoroughly with laundry soap and ‘latex’ gloves
· Let water settle and pour off/repeat until water is clear
· Dry material
· Sieve or screen material (window screen would work in a pinch)
· Collect smaller material and examine it under 20-60x microscope/lens
· Examine any spheroids found under 100-500x microscope
· Take Focus-Stacked images of any possible micrometeorites
· Remember that MANY objects look like micrometeorites but are human-made!
Strong magnet in double plastic bags.
Micrometeorites fall into three very broad classification categories:
The four S-type micrometeorites we can identify are based on texture and mineralogy. They are:
The S-Type micrometeorites we find have compositions similar to some meteorites (Chondrites) and this is reflected in their analysis. Almost all micrometeorites have a 'chondritic' composition. The SEM ( Scanning electron microscopy) images show the micrometeorites in fine detail. The EDS (Energy Dispersive X-ray Spectroscopy) charts show the chemistry of the micrometeorites. As with the 'Chondrites', the chart shows high Oxygen (O), Magnesium (Mg) and Silicon (Si) as well as much lower amounts of Iron (Fe) and Nickel (Ni). Thanks to Al Falster at the Maine Mineral and Gem Museum And Dr. Tasha Dunn at Colby for help with the SEM and EDS analyses below!
SEM of MM 040, a Barred Olivine micrometeorite showing parallel Olivine crystals
1.To gain a better understanding of our solar system – micrometeorites were formed from the material that formed our solar system and can tell us more about that time in our solar system and Earth’s history.
2.They are beautiful and interesting – micrometeorites have amazing flight patterns ‘grown’ onto their surface and yet, many retain their structure and compositions within. Each is like a snowflake with no two alike.
3.There are a lot of things we don’t know about micrometeorites – they have been around for billions of years, and since they are by far the most abundant extraterrestrial material on Earth, we should endeavor to learn more about them and perhaps ourselves.
•Delivery to Earth:
–Meteorites are blasted off asteroids and float around in space in a random process that may eventually lead to crossing Earth’s orbit.
–Micrometeorites are either blasted off or stream off the surface and the light from the Sun affects their motion – called Poynting-Robertson Light Drag. This slows the object down and makes it move inward, in slow spiral orbits, toward the Sun. This provides a reliable method to deliver material to the Earth within 10,000 years. Thus we get a better sampling of asteroids and other objects in our solar system than with meteorites.
•Micrometeorites deliver organic molecules and elements to Earth and may be an important source of nutrients for organisms in the deep ocean.
•When micrometeorites pass through Earth’s atmosphere, they react with oxygen and give us a record of the oxygen in the upper atmosphere.