On 25 Jan 2019 at 18:02, Tim wrote:

> On Thu, Jan 24, 2019 at 09:40:31PM -0800, shadow at shadowgard.com
> (via tml list) wrote: > Short of buildiong a "planet buster", I don't
> think humanity is > *capable* of affecting the deep rock bacteria
> ecosystem.
>
> If the surface rose to 100 C or so and stayed there, the deep rock
> temperature would rise enough that no known life form could survive.
> Granted such a high temperature seems unlikely, especially around the
> poles.

Take some time to heat the rock a mile or two down hotter than it
already is. Remember, there are organisms that live in mineral
springs that run 100 C or more.

> > We'd have trouble doing much to the deep thermal vents ecosystems in
> > the oceans too.
>
> Yes, we'd pretty much have to poison the oceans to wipe out
> chemosynthetic extremophiles there.

And the more "normal" critters that live off the extremophiles.

> Even a surface temperature of 100 C wouldn't kill some of them, since
> almost all of the ocean would remain liquid and keep the deep water
> temperature not very much greater than the surface.  Sustained surface
> temperatures of 140 C would likely do it, but about all I can think of
> to achieve that would be a runaway greenhouse effect.  Such an effect
> could possibly happen, but is thought to be very unlikely while oceans
> remain.

Don't forget that the base of those ecosystems is single-celled
organisms that live in fluid coming out of the black smokers. Which
is can be as hot as 464 C!!!

Interesting bit in the wikipedia article on hydrothermal vents.

Seems that the giant tube worms found there use hemoglobin...

They use it to transport hydrogen sulfide to the bacteria that live
in their bodies. The bacteria use the H2S to produce ebnergy and the
compounds they excrete are what the tube worms live on.

Now *that* is a use for hemoglobin  I'd never have expected!

> > Even our worst pollution/climate change/extinction scanarios don't
> > hold a candle to what the discovery of photosynthesis did to life on
> > earth.
>
> Yes, poisoning the entire planet with oxygen and glaciating the Earth
> almost certainly drove most of the previously living species to
> extinction.

But a number survived. Which is where the various anaerobic organisms
come from.

--
Leonard Erickson (aka shadow)
shadow at shadowgard dot com