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Stromatolites

12volcS.jpg There's another line of evidence that go along with the microfossils and this really doesn't look like much to the person who doesn't study them, but this is my bread and brother. These are laminated sedimentary deposits. These laminated sedimentary deposits are what are called stromatolites. Stromatolites are produced by sediment trapping and binding and sediment precipitation by photosynthetic microbes. Read between the lines: Cyanobacteria. These microbial mats today are found in a variety of environments, from thermal springs, lakes, intertidal regions in the marine environment, so under ten or twenty or thirty meters of water in the marine environment. They're found below ice covered lakes in Antarctica.

So today we have examples and we can use that kind of information to postulate maybe what these things are. To a person who studies stromatolites, like myself, there's very little problem interpreting this as a stromatolite. However, we don't have the preserved microorganisms within this rock but we have it six kilometers down the road in another kind of rock here. Actually, these rocks in which the microfossils were found, although they don't have little domes and things like that, they are laminated, organic rich, organic poor flares. And they appear to be sort of planar laminated stromatolites.

13marsS.jpg So, there's a variety of information to suggest that by 3.5 billion years, we had a very, very complex world. A lot of volcanic activity, springs probably harboring life, marine environment harboring life. It was probably really a wonderful microbial world. But now we have some interesting evidence that even goes back further and this is chemical evidence that life was around 3.8 billion years ago. In a recent paper in Science, some geologists studied some minerals preserved in a rock 3.8 billion years, from Greenland. The mineral apatite contains carbon. They did isotopic analysis on the carbon in that apatite and the found it was enriched with the lighter isotope of carbon just like those 3.5 billion year old rocks that I talked about, just like billion year old rocks, just like if you dig in some soil today what you would find as a result of photosynthetic activity. The conclusion then is that 3.8 billion years ago, there was carbon fractionation and there might have been photosynthesis around. Now you juxtapose that with the impacting going on and maybe the early evolution of life occurred very, very rapidly, maybe within a 100 million years and it might even exceed the rates of evolution for the creation of phyla in the Metazoa. Speculation, but nevertheless, it's an interesting feature.

14meteoriteS.jpg Now we go back to Mars. 3.8 billion years ago, Mars was probably a much more clement place than it is today for life. There's evidence on Mars that there was running water. There are deposits that appear to have maybe been laid down by lakes. Indeed, the missions to Mars will help clarify some of this stuff.

15microS.jpg So, Mars underwent a history very similar to Earth's. It probably had an atmosphere very similar to Earth, it was impacted at the same time that early Earth was and therefore, the microfossils or the alleged microfossils found in the Martian meteorite in Antarctica that I mentioned earlier-- 16ecostratoS.jpg and here's a picture of one of these scanning electron micrographs of a septated tubular structure preserved in the Martian meteorite, the age of the meteorite is about 3.6 billion years in age--it would be permissible within that model. It would post-impact. One problem is that these tubular structures and small coccoidal structures found in the meteorite, not in this picture, are extremely small. They're on the order of 40 or 50 nanometers in diameter. And at least based on what we understand from Earth in terms of genetic systems, it's not sure if a cell that small occupying one of these little cellular units there, could contain enough genetic material to exist. But that again is based on Earth standards.

So where does that leave us? We go back to astrobiology. No longer really can we look at the origin of life within a very, very narrow perspective. There's a cosmological perspective. Life may have originated on other planets. It may have originated on Mars. Right now studies with regard to the origin of life are moving in very, very new and exciting dimensions that are going to affect the fabric of science and how we teach it in the classrooms. Thank you very much.


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