Paleobiologist J. William Schopf and colleagues have produced 3-D images of ancient fossils -- 650 million to 850 million years old -- preserved in rocks, an achievement that has never been done before.
If a future space mission to Mars brings rocks back to Earth, Schopf said the techniques he has used, called confocal laser scanning microscopy and Raman spectroscopy, could enable scientists to look at microscopic fossils inside the rocks to search for signs of life, such as organic cell walls. These techniques would not destroy the rocks.
Confocal microscopy uses a focused laser beam to make the organic walls of the fossils fluoresce, allowing them to be viewed in three dimensions. The technique, first used by biologists to study the inner workings of living cells, is new to geology.
Raman spectroscopy allows you to see the molecular and chemical structure of ancient microorganisms in three dimensions, revealing what the fossils are made of without destroying the samples. This technique involves a laser from a microscope focused on a sample; most of the laser light is scattered, but a small part gets absorbed by the fossil.
"It's very difficult to get any insight about the biochemistry of organisms that lived nearly a billion years ago, and this gives it to you. You see the cells in the confocal microscopy, and the Raman spectroscopy gives you the chemistry”, said Schopf.
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His research is published in the January issue of the journal Astrobiology, in which he reports confocal microscopy results of the ancient fossils. (He published ancient Raman spectroscopy 3-D images of ancient fossils in 2005 in the journal Geobiology.)
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