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Can capillary networks be a biomarker in rocks?

 
 
Reply Sat 17 Dec, 2011 02:50 am
For recognizing extraterrestrial past life, there are quite a few biosignatures (biomarkers) in astrobiology (ref.1 http://en.wikipedia.org/wiki/Biosignature#In_astrobiology). But few of them are generally accepted and easily verifiable. The author hereby proposes a new and simple biosignature for astrobiology—structure of capillary network for extraterrestrial past life. The proposed biosignature can be easily verified by comparing living animal's capillary network with similar structures in Earth rocks, meteorites, moon rocks, Mars rocks, etc.

Capillaries are the smallest blood vessels, measuring 3-15 micrometers in diameter in humans. Capillaries form network to supply tissues with blood and exchange gases/nutrients with tissues (ref.2 http://www.sciencephoto.com/media/303632/enlarge).

The structure of capillary network can be a biomarker for the followng reasons:
Their morphologies are unique in their branching into networks (ref. 3 http://www.visualphotos.com/image/1x3744372/
micrograph_of_capillary_vessels_micrograph_of ,
ref. 4 Edit [Moderator]: Link removed.

Non-biological veins of rocks 3-15 microns across are improbable to form the kind of branching structures found in capillary networks, as the crystal habits of minerals are quite regular in their patterns. Some natural minerals and non-life material do form dendrites, but their dendrites are too big or too regular or too symmetric to be capillary network. Two examples:
http://en.wikipedia.org/wiki/Pseudofossil,
http://www.sciencephoto.com/media/216423/enlarge

Fractures (cracks) and fracture fills can mimick capillary networks. But branching cracks of 3-15 microns across never appear in a large number in a thin section of rock. If they do, the rock would break at the cracks and the cracks would not be included in the thin section. An example of a large number of look-alikes: Edit [Moderator]: Link removed.

Scientists have found that dinosaur blood vessels can be well preserved (ref. 5 http://www.smithsonianmag.com/science-nature/dinosaur.html ). But no one expects most of the capillary networks to be preserved intact in rocks. So, it is reasonable to find irregular and unpredictable patterns of capillaries that survive billions of years. Such branching, irregular and unpredictable structures are found in meteorites and moon rocks. Examples: Edit [Moderator]: Link removed

Edit [Moderator]: Link removed

Edit [Moderator]: Link removed

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