Where Passion Meets Exploration

Micrometeorites fall into three very broad classification categories:

• · S-type spherules – made primarily of silicate minerals like olivine and pyroxene – these are the types we can identify and are the most common (97%).
• · I-type spherules – made primarily of iron oxides and iron/nickel metal – rare.
• · G-type spherules – Made of glass with magnetite, usually crystallized – very rare!

The four S-type micrometeorites we can identify are based on texture and mineralogy. They are:

• · Barred Olivine spherules (BO) – made primarily of parallel growth of olivine filled in with glass.
• · Cryptocrystalline spherules (CC) – made primarily of branching clusters of fine olivine crystals in glass. They sometimes form raised plates resembling turtle shells called ‘Turtlebacks’.
• · Porphyritic Olivine spherules (PO) – made primarily of ‘large’ crystals of olivine within a finer-grained matrix.
• · Vitreous spherules (V) – completely melted glass – occasionally with metal beads which allow easier identification.

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!

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. 

From: micro-meteorites.com/

•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.

Material from: www.quantamagazine.org/matt-genge-uses-dust-from-space-to-tell-the-story-of-the-solar-system-20210204/