Micrometeorites

SEM Atlas of Micrometeorites

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Micrometeorites are small (<2mm) extraterrestrial particles that have survived atmospheric entry. They range from unmelted and partially melted particles that retain much of their original mineralogy to totally melted cosmic spherules some of which have lost a significant fraction of their mass by vaporization. Micrometeorites are thought to contribute most of the extraterrestrial matter accreted by the Earth on ten million-year time scales (Peucker-Ehrenbrink 1997, Love and Brownlee 1993, Kyte & Wasson, 1986). Their small size and large number (~ 10^15) suggest that collections of micrometeorites should contain particles from all dust producing objects in the solar system including asteroids, comets, and fragments from our Moon and Mars. Two hundred and thirty four micrometeorites collected from the bottom of the South Pole water well were photographed by a Scanning Electron Microscope. This web-based atlas consisting of SEM images of all of these particles along with the chemical element composition of some of the particles will serve as a guide to other researchers wishing to compare and classify micrometeorites collected at different locations throughout the world.

Types of Micrometeorites:

There is no standard system of classification for micrometeorites. They can, however, be grouped based on their composition and their texture. Most of these particles we analyzed have chondritic compositions (bulk solar). There are only a few minerals found in micrometeorites and these are determined both by the composition of the particle and by the degree of heating each particle sustained entering the earth’s atmosphere.

We hope that by displaying these images on the web, other researchers will have the opportunity to comment on their own interpretations of how these particles should be classified. For several particles, the exact classification type is not readily apparent. It is therefore important that we begin a dialog so that a universal system of classification for micrometeorites can be someday developed.

View Entire Atlas:

View Particles according to our classification system:

Chondritic Particles: listed in order from highest heating to lowest

CAT

Glass

Cryptocrystalline

Barred Olivine

Porphyritic

Porphyritic with interstitial FeS

Equant Olivine/ Relict Grain

Scoriaceous

Partially Melted to Unmelted

Nonchondritic:

Iron Type

G Type

Single Mineral

Different types of Contaminants:

It is important to look at some of the terrestrial contaminants we found in order to note the differences between these particles and the micrometeorites. Three types of contaminants are found in the South Pole water well samples: copper spheres (from welding), plastic spheres (from a fire in one of the water hoses) and iron oxide grains (from a pump failure). The electron microscope can easily distinguish these contaminants from extraterrestrial particles. However, the iron oxide grains make it difficult to find irregular, unmelted micrometeorites when one has sorted through the 'sediment' vacuumed from the bottom of the well.

Images of Contaminants:

 

 

Please note: This page is still under construction - EMILY SCHALLER

 

Links:

Dartmouth College