A SUMMER OF STARDUST: MICROMETEORITES AND WHERE TO FIND THEM

Micrometeorites offer a look into our solar system’s past, Earth’s past, our past. They can tell us all about the space we live in before we were even part of it. These particles ]are coming to rest all over Earth’s surface. Their presence offers a scientific opportunity for anyone with a few rudimentary tools and the will to look. They also provide a unique opportunity to involve the public in primary scientific research.

Because they are often undisturbed by humans, rooftops are prime candidates for collection. We collected samples from multiple locations in the Granville (Ohio) area to look for micrometeorites. The accumulated sediment was gathered with brushes and a vacuum from 2 rooftops in the area, taken to the lab, cleaned, divided into magnetic and nonmagnetic material, and sifted down into the optimal grain of most micrometeorites (200µm-400µm). Aerodynamic particles were then identified using an optical microscope.

After 125 candidates were isolated, they were imaged using a JEOL JSM-IT500HR scanning electron microscope (SEM) using secondary electron (SE) imaging and backscattered electron imaging (BSE). The SE was used primarily to observe and image surface features while the BSE was used to observe and image differences in composition. Overall, 4-10 barred and porphyritic olivine micrometeorites were found alongside many industrial and terrestrial spherules.

There is no single guide for identifying micrometeorites. Through this study and other research, we have developed a proposed rubric for recognizing micrometeorites. The criteria include morphology, aerodynamic form, composition, and magnetism. The rubric grades candidates A-E, A being the highest likelihood of a micrometeorite and E being the least likelihood of a micrometeorite.

Samples were collected from the roof of Mitchell Center at Denison University and the roof of Granville Middle School. Many more grade A-C micrometeorites were found at Mitchell Center versus Granville Middle School based on our rubric.