In the search for micrometeorites we must be prepared for the unexpected. I had already found 827 micrometeorites, and thought I had an idea about what they look like. Then I found this barely melted one!

Measuring 0.5 mm, NMM 828 is considered to be a giant micrometeorite and is completely different from any other particle I’ve found before. It looks like slag and is not aerodynamic; The elongated sub-spheric shape indicates that the surface tension barely managed to pull it together.

What could this be?

An analysis of the scanning electron microscope (SEM) image produced by yours truly, Jon Larsen, and Siri Simonsen at the University of Oslo reveals chondritic chemistry. This is how we know the little rock is indeed extraterrestrial.

This was my first barely melted micrometeorite!

The small chunks of nickel, iron, and sulfide distributed all over the particle create a fascinating surface that is decorated with both silver and gold tones. There are also dark “chimneys” surrounding the openings, which were made during the degassing of volatile elements. Together, these two characteristics indicate the little space rock suffered a relatively low temperature during its entry into the Earth’s atmosphere.

In its barely melted state, this micrometeorite is much closer to what cosmic dust looks like out in space. What a catch!

Do you prefer rare micrometeorites like this one, or the flashy crystalline spherules I normally find?

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Yours truly,

Jon Larsen