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SRH
2014-Oct-16, 10:42 PM
If there was a silicon-based bacteria that lived millions of years ago, is it possible that the bacterial-fossils would decompose into the sand we see today?
Is there any evidence for or against this hypothesis? Would it even be possible to prove?

Thanks.

Jens
2014-Oct-16, 10:57 PM
Well, silicon is one of the most common elements in the earth's crust. Hence, many mineral contain silicon. Sand comes from rocks. Hence, sand should contain silicon. Now, whether that silicon was ever used in bacteria is an interesting question, but the presence of the silicon itself is not evidence. Similarly, the fact that there is aluminum in sand makes it possible that people long ago made aluminum tools, but it can't be evidence because the aluminum would be there whether it was used or not.

Swift
2014-Oct-16, 11:07 PM
Sand particles range from 0.06 to 2 mm (http://en.wikipedia.org/wiki/Sand)
Bacteria are typically 0.5–5.0 micrometers (http://en.wikipedia.org/wiki/Bacteria) (0.005 to 0.005 mm).

Those would be very big bacteria.

We also know the mechanisms by which sand forms (it forms constantly). There is no evidence for a mechanism from extinct lifeforms.

SRH
2014-Oct-16, 11:43 PM
More generally, could the rocks themselves be the decomposed remains of ancient non-carbon based life?

Ross 54
2014-Oct-17, 04:17 PM
Silicon-based life could be looked for via silicones, silicon-oxygen chains with methyl radicals (CH3) attached. These are described as synthetic compounds. Their discover under circumstances that ruled out a man-made origin could mean that they had been synthesized by life processes.

FarmMarsNow
2014-Oct-19, 09:36 PM
Sand particles range from 0.06 to 2 mm (http://en.wikipedia.org/wiki/Sand)
Bacteria are typically 0.55.0 micrometers (http://en.wikipedia.org/wiki/Bacteria) (0.005 to 0.005 mm).

Those would be very big bacteria.

We also know the mechanisms by which sand forms (it forms constantly). There is no evidence for a mechanism from extinct lifeforms.
Yes. We already have good reasons to believe that sand comes from rocks, so there is very little reason to look for a biological source for sand. The evidence shouts that sand comes from rocks while biological evidence shouts that the older forms of life in the deep strata were carbon based and are the source of fossil fuel deposits.

If there was a silicon-based bacteria that lived millions of years ago, is it possible that the bacterial-fossils would decompose into the sand we see today?
Is there any evidence for or against this hypothesis? Would it even be possible to prove?

It is possible to investigate sand further, too. It is possible to determine the ratios of isotopes in different kinds of sand, and it may be possible to pick up a grain of sand and study it to try and determine what rock bed it is from. If there aren't already people who specialize in that, you might want to consider it as a potential new branch to study. I could see that as helpful for many things like forensics, geological date methods and locating where animals have been or where things flow. Actually I think there are already people who do have the means to track grains and estimate both where they are from and how old they are, and I believe that they do play a role in both industry and research. If there were a possibility of silicon based lifeforms in ancient Earth history they would be best equipped to detect it.

kzb
2014-Oct-20, 12:15 PM
Then again, chalk comes from calcium carbonate shells of marine life. There's little sign of that once it's been been through the mill and compressed to chalk. The particle size is no clue. Same with coal. Although you do get tree fossils in coal, on casual inspection, it does not look like it used to be a jungle.

One big clue though is that there is no other evidence that there was ever any silicon based life.

Jens
2014-Oct-20, 11:16 PM
Then again, chalk comes from calcium carbonate shells of marine life. There's little sign of that once it's been been through the mill and compressed to chalk. The particle size is no clue. Same with coal. Although you do get tree fossils in coal, on casual inspection, it does not look like it used to be a jungle.


The important thing though is that it's the chalk, not the calcium that matters. Lots of minerals have calcium in them, because carbon is a relatively abundant element in the crust, but you cannot conclude from that that anything that includes calcium is from shells. Same with charcoal. Simply finding carbon in a mineral does not mean it's biogenic. I mean, we find aluminum in sand too but you can't conclude from that that there were aluminum based bacteria...