“couldn't this sort of thing have happened before”
Seems to me that it definitely could -- although, given that this life would've needed to develop in an ecosphere utterly different to our own (e.g., no free oxygen), we would be talking about lifeforms that might as well have developed on other planets. Utterly unlike anything we know.
But quite possible. This is an extremely spiffy idea.
But if I recall correctly, said plants woulda needed to develop under much hotter conditions than now, so chances are they were still biochemically very different? (Or do I not recall correctly? Been a long time since I read up on any geology...)
I don't think we know -- we think the oceans were liquid and that the Earth rapidly cooled after coalescing, and the Sun was supposed to be yielding a lot less energy then than now.
Obviously if Snowball Earth scenarios happened multiple times, though, there were radical variations in temp across time.
(One thing you can be sure of is that any earlier civilization that used Celsius to measure that temp wouldn't have lasted long.)
The next question is: If you posit the existence of any such civilization, where -- despite everything -- would you look for evidence of it?
It would be the first stop for any advanced civilization, it has no atmosphere nor has ever had one, it is not subject to plate tectonics, objects left there would not be subject to chemical decay. So, despite being repeatedly hit by bolides, it would still preserve traces for 700 million+ years far better than the Earth.
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branchandroot
no subject
Date: 2012-07-04 02:04 pm (UTC)Seems to me that it definitely could -- although, given that this life would've needed to develop in an ecosphere utterly different to our own (e.g., no free oxygen), we would be talking about lifeforms that might as well have developed on other planets. Utterly unlike anything we know.
But quite possible. This is an extremely spiffy idea.
no subject
Date: 2012-07-04 02:15 pm (UTC)http://en.wikipedia.org/wiki/Oxygen_catastrophe
Subsequently, not much life would have survived circumstances like this:
http://en.wikipedia.org/wiki/Snowball_earth
Throw in plate tectonics and there's not a lot of trace-leaving going on in this cyclical scenario.
no subject
Date: 2012-07-04 02:25 pm (UTC)But if I recall correctly, said plants woulda needed to develop under much hotter conditions than now, so chances are they were still biochemically very different? (Or do I not recall correctly? Been a long time since I read up on any geology...)
no subject
Date: 2012-07-04 02:41 pm (UTC)Obviously if Snowball Earth scenarios happened multiple times, though, there were radical variations in temp across time.
(One thing you can be sure of is that any earlier civilization that used Celsius to measure that temp wouldn't have lasted long.)
The next question is: If you posit the existence of any such civilization, where -- despite everything -- would you look for evidence of it?
no subject
Date: 2012-07-04 04:09 pm (UTC)no subject
Date: 2012-07-04 04:26 pm (UTC)It would be the first stop for any advanced civilization, it has no atmosphere nor has ever had one, it is not subject to plate tectonics, objects left there would not be subject to chemical decay. So, despite being repeatedly hit by bolides, it would still preserve traces for 700 million+ years far better than the Earth.