Abiogenesis of chemosynthetic life

[EdEarl]

On the origins of cells: a hypothesis for the evolutionary transitions from abiotic geochemistry to chemoautotrophic prokaryotes, and from prokaryotes to nucleated cells by William Martin and Michael J Russell proposes that

The first free-living cells are suggested to have been eubacterial and archaebacterial chemoautotrophs that emerged more than 3.8 Gyr ago from their inorganic confines.

 

Chemosynthesis makes oxygen.

Hydrogen sulfide chemosynthesis:[2]
12H2S + 6CO2 → C6H12O6 (=carbohydrate) + 6H2O + 12S

From: http://en.wikipedia.org/wiki/Chemosynthesis

 

Oxygen combines with iron to make iron oxide (in prehistoric oceans), that we mine today to make iron and steel. The source of that oxygen is attributed to photosynthesis by microorganisms that made stromatoliths that are now fossils from about 3.5 Gyr ago.

The banded iron formations were laid down in the time between 3,700 million years ago and 1,800 million years ago

From: http://en.wikipedia.org/wiki/Iron#Occurrence

 

Fossil stromatoliths and iron ore deposits are evidence of earliest life AFAIK. However, if Martin and Russell are right, the deep ocean may hide additional evidence, perhaps earlier evidence.

 

What is the chance of earlier evidence? Is there already earlier evidence. Is there more evidence of earliest life than fossil stromatoliths and iron ore deposits?

[EdEarl]

The oldest rocks found so far are about 3.5 GYr old. We will not find older fossils unless we find older rocks. The only places older rocks may be found is places unknown, which probably means under the ocean or under ice.

 

Does anyone know whether there are places on earth where older rocks may be found?

[krash661]

hmm, interesting,

i have not read this or the links yet

but i will.

[EdEarl]

A facebook post discusses manganese being precipitated in early oceans as evidence of early life on earth.

 

The rocks you see here being sampled by Caltech grad student Jena Johnson look rather ordinary; somewhat weathered and covered by dirt, but they sit in a key spot for the development of life as we know it. These rocks, found across large portions of South Africa, are just over 2.4 billion years old. That age means these rocks come from the time just before the rise of oxygen, when the mechanism that would allow for photosynthesis was evolving.

https://www.facebook.com/photo.php?fbid=532455516815497&set=a.352867368107647.80532.352857924775258&type=1&theater

 

The facebook post links to these two sources:

 

http://www.caltech.edu/content/stepping-stone-oxygen-earth

http://www.pnas.org/content/early/2013/06/20/1305530110.full.pdf+html

[__Ben__]

It's either an awesome fluke we had abiogenesis here, or being ~10 billion years into this universe was the right time for life to get here.

 

If life could have started here in less than a billion years. How many times could abiogenesis have happened and already be a part of our solar system when it was forming?

 

Ok, life as we know it, account for iron.

Edited July 21, 2013 by __Ben__

[EdEarl]

Ben, This thread is about chemosynthetic life, and evidence of it on Earth. Your questions are not related to this thread, or at most remotely related.

Edited July 21, 2013 by EdEarl

[Ophiolite]

Here are two observations that may aid the dicussion:

 

1. Oceanic crust is continually recycled via plate tectonics. No oceanic crust has yet been found that is older tna about 200 million years. Of course we have relic crust in the - wait for it - ophiolite complexes, so they could be worth examining further.

2. The oldest rocks are slightly older than the 3.5G yr you mention. Deabte surrounds many of the determinations, but 3.6G yr is certain, 3.8 probable and 4.0 possible. (And I exclude the Jack Hills zircons, which are minerals, not rocks.)

[EdEarl]

 

The oldest rocks are slightly older than the 3.5G yr you mention. Deabte surrounds many of the determinations, but 3.6G yr is certain, 3.8 probable and 4.0 possible. (And I exclude the Jack Hills zircons, which are minerals, not rocks.)

 

From reading wiki, the ophiolites are mainly igneous with a top layer of "sediments: muds (black shale) and cherts deposited since the crust formed." Are the dates you give (above) for the lower level igneous rocks or the sediments?