[azeemba]

The funny thing is that an oxygen-rich environment is a hell-hole! Oxygen is insanely reactive and will corrode anything. Even early life on earth found oxygen toxic. It was released as a waste product by early life and they were so successful that all that oxygen accumulated resulting in the Great Oxidation Event (https://en.wikipedia.org/wiki/Great_Oxidation_Event).

That likely resulted in many species going extinct!

[eru]

Yes, first everything rusted, and then the excess oxygen collected in the atmosphere.

Many of our iron ore deposits we still mine today are from that rusting. (That iron used to be mostly dissolved in the oceans.)

[dredmorbius]

And the concentration into BIFs, banded iron formations, was all but certainly the result of biological activity.

Our present technology based on iron and steel owes itself to early life on Earth, from 1.6 to as much as 4 billion years ago. As with petroleum and coal-bed formation, a process unlikely to repeat in Earth's future. Iron ores are abundant, but still a finite resource.

<https://en.wikipedia.org/wiki/Banded_iron_formation>

[jrussino]

Human civilization feels so much more fragile to me since I realized how much we owe our technological progress to the accumulated effects of biological processes over geological timescales. Fossil fuels seem like the most obvious part of this story. If we had to start over "from scratch", would it even be possible? Or have we already so thoroughly exhausted the low-hanging energy stores that a second "industrial revolution" would be effectively impossible if our present civilization collapsed deeply enough?

I wasn't aware that concentrated stores of iron are also an important part of this story!

[eru]

> Or have we already so thoroughly exhausted the low-hanging energy stores that a second "industrial revolution" would be effectively impossible if our present civilization collapsed deeply enough?

There's plenty of coal left, and we will likely never exploit it, because solar is getting so cheap.

Also, despite long prophecies, peak oil never arrived either. So it doesn't look like we are running out of that stuff.

[meindnoch]

>Iron ores are abundant, but still a finite resource.

The iron doesn't go anywhere (ok, except for the iron making up our space probes). It is infinitely recyclable.

[dredmorbius]

It doesn't concentrate itself, at scale.

That's what ores are. Ores are useful because they are concentrated, the result of some ore-formation or ore genesis process.

The "not going anywhere", after it's been dispersed throughout the lithosphere, is precisely the problem.

<https://en.wikipedia.org/wiki/Ore_genesis>

[meindnoch]

But scrap metal is still purer than any ore.

[dredmorbius]

And ferrous mineral recycling accounts for roughly 33% of present production (2018 data, most current available):

<https://www.epa.gov/facts-and-figures-about-materials-waste-...>

That's a loss of 2/3 of production to non-scrap effluvia on an annual basis. I'll let you work out the ultimate resource depletion cycle from that. Recycling is useful, but it's no magic bullet, and there are always losses.

The most heavily recycled metal in the US is lead, per USGS data and prior comments of mine, with recovery rates of about 75%, accounting for 40% of net production.

<https://news.ycombinator.com/item?id=20164506>

<https://news.ycombinator.com/item?id=26412585>

Source citation: "USGS 2020 Minerals Yearbook: Recycling — Metals"

<https://www.usgs.gov/centers/nmic/recycling-statistics-and-i...>

[gorgoiler]

I once heard a similar point and it has fascinated me ever since: an alien observing human culture would be appalled at how dangerous our lives are.

Everything around us is bathed in warm oxygen, just waiting to catch fire! Our homes, our clothes, our fields, our possessions, …our hair. Ready oxidation brings vitality to Earth but it’s also ridiculously dangerous.

[brazzy]

It's very unlikely the aliens would not have something very similar going on in their own biosphere. Life needs energy to operate, after all.

[Terr_]

It might be a lot more sedate, imagine crystalline creatures from deep below the surface of an ice-ball that rely on indirect chemical gradients or geothermal.

"Your planet is how close to that star!? H20 would be liquid! How do you protect yourselves from the polar solvent leaking down into the rock?"

[wahern]

Conversely, a slower rate of reactivity suggests intelligent life might not yet have arisen in such environments, or ever arise before the opportunity passes.

[meindnoch]

They need a sufficiently dense energy source, sure. But it may not involve their atmosphere at all. Their plants could store solar energy in self-contained chemical batteries, and the aliens could be using those batteries to power their bodies. Instead of having to constantly breathe, they would instead need a daily battery swap.

[Terr_]

I often like to quip that the [21%] corrosive gas is pretty nice today, and I think I'll go consume a big container of industrial solvent to help counteract the radiation from the uncontrolled nuclear [fusion] explosion in the sky.

[acron0]

Industrial solvent? Does this mean "inside air"?

[psini]

I'm thinking water

[dredmorbius]

An oxygen-rich environment is so thermodynamically unstable (it would lead to oxidation and rusting of virtually every other prevalent element) that it would be exceedingly short-lived without the presence of oxygen-liberating biological metabolism. To that extent, a high-oxygen atmosphere is one of the very clear and detectable indicators of probable life which we are capable of detecting even on extra-solar planets (via spectroscopic analysis of reflected or filtered light).

Far more an Eden, then.

[freedomben]

Definitely true, but oxygen is also immensely useful for life evolved to benefit from it, enabling much more complexity. I'm fascinated by the giant insects that got huge back when the oxygen level was much higher.

Related: highly recommend Robert M. Hazen Great Courses and book

[cactusfrog]

I hope humans are like Cyanobacteria in that in destroying the environment we create the substrate for something grander.

[sl-1]

I fear that