This is an SEM image in SEI mode of a nanofossil collected from marine sediment. Some marine algae form structures of calcium carbonate called coccoliths. These structures are unique signatures of the species of microorganism. After the death of the organism, these calcium carbonate structures sink through the water column and become part of the marine sediment.
This image is of a coccosphere, a spherical arrangement of coccoliths. The complicated shapes are the result of cellular processes within the microorganism. The biological function is unclear and hypotheses suggest that they might aid in photosynthesis and/or assist in the bouyancy of the organism. Despite the underlying biology, these coccoliths are of profound interest to earth scientists as they give clues to oceanic conditions.
The bottom image is also a coccosphere. In this case the sphere consists of umbrella like structures packed into a spherical arrangement. Some of the coccoliths have come apart and can be seen to the bottom left of the image.
Thanks to Dr. Woody Wise, FSU Department of Earth, Ocean and Atmospheric Science.