A fascinating thing about complex life in the deep crust lies how said life allows the earth to regenerate ecosystems even under the most extreme hypothetical conditions, and has probably done so in the past:
For example, if a super-asteroid the size of a minor planet were to hit the Earth, it's believed that it would essentially boil away all the oceans and cook the whole of the planet's atmosphere. Studies have also shown that it would likely super-heat the crust down to a depth of hundreds of meters, even in parts far from the immense and totally liquefied impact site itself.
But, in those more distant parts of the crust, far down in the dark beyond the reach of post-impact heating, below a depth of several hundred meters, microbes of all kinds would continue to live, hidden in so many tiny, watery cracks. As thousands of years pass after such a colossal impact, as the atmosphere reforms, as the earth's water re-condenses, and falls back to the surface in gigantic ocean-filling torrential rain storms, those hidden microbes, which had found their refuge in the deep rocks, would eventually creep upwards.
They'd slowly find their way back into these reformed oceans, lakes and rivers, back into the again cooled atmosphere, back into the sunlight, and the evolutionary process would kick into gear all over again.
It's speculated that our planet has survived at as many as several completely surface destroying impacts by minor planets or asteroids several hundred kilometers across, impacts that make the dinosaur impactor seem like a children's party firecracker in comparison, and this is how life regenerated from these cataclysms.
This reminded me of a Kurzgesagt video from a few months ago on the same topic [0]. I see that the author, Karen Lloyd, was one of the experts they consulted when making that video.
I got sucked into spending quite a while reading about that stuff after seeing a link to Gold on HN. He was an interesting guy. Since he died in 2004 some of his ideas, like a lot of life in the crust seem to have proven correct. Others - that most oil and gas has a primordial origin, not from life seem mostly wrong. There are definitely primordial hydrocarbons - Titan has seas of methane. However on the inner planets a lot evaporated and the majority of our fossil fuels seem of biological origin.
There's a maybe better (very good) article on life in the crust from the NYT june 2024 here https://www.nytimes.com/2024/06/24/magazine/earth-geomicrobi... . Top comment "This article is one of the most powerful articles I have ever read in the NYT. I am so grateful that the author wrote it. It cemented my belief that that all life is deeply connected from the beginning to the present day and beyond..."
> The major categories of visible life on Earth have been pretty much settled for centuries. But it wasn’t until the 1980s that scientists found “intraterrestrials” — microscopic organisms living in what the biogeochemist David Valentine calls a “microbial purgatory deep below the Earth’s surface."
Does anyone know the paper(s) from the 1980s where the discovery was published?
I think there are two strands: petroleum companies have long been interested in any connection between deep biology and oil; and I think around that time people found microbes in a few sterile-seeming aquifers.
There are areas on Mars where we strongly believe brine is right below the surface, so there could be life underground but it may not all be that deep.
Perhaps. If it does, it probably couldn't be past a certain depth. The deepest man-made hole was about 12km, and reached roughly 180C at that depth. That's well beyond what even the most durable hyperthermophile organisms can withstand, to speak nothing of what the pressure would be like at greater depths.
Every time we assume a limitation like this we've been wrong. If tardigrades can survive floating through space, I think it's reasonable to guess that there might be life that survives at the other extreme.
Where do you draw the line for the other "extreme"?
Assuming carbon based life as we know it, 300-400C is the probably a hard limit at which point single carbon bonds begin to break down.
Assuming life on earth as we know it, with ATP universally conserved across the entire evolutionary tree, the limit is really 150C. We've seen incredible survival adaptations like cryptobiosis but no organism exists that doesn't use ATP as its most basic unit of energy storage. That's the theoretical limit, but realistically other highly conserved critical pathways start to break down well before that temperature.
While it’s true and impressive that tardigrades can survive all that, that doesn’t mean they can thrive there. They survive it by entering a stasis, but that’s about as far from living as one can get temporarily.
There's loads of life down there but there seems a top limit to all known life around 130C. "The current record growth temperature is 122 °C, for Methanopyrus kandleri".That allows you to go ~10km down.
Hmm, but speculation is so easy and sampling is anything but. Some of Einstein's speculations were pretty damn productive. The later experiments aka samplings (Einstein proved right again!) were in my view not particularly productive.
From what i read, this post doesnt announce we’ve found some crazy extremophile unicellular microbe. Just that there is evidence to suggest they are there (due to the chemical makeup of soil/boreholes).
Readit News
For example, if a super-asteroid the size of a minor planet were to hit the Earth, it's believed that it would essentially boil away all the oceans and cook the whole of the planet's atmosphere. Studies have also shown that it would likely super-heat the crust down to a depth of hundreds of meters, even in parts far from the immense and totally liquefied impact site itself.
But, in those more distant parts of the crust, far down in the dark beyond the reach of post-impact heating, below a depth of several hundred meters, microbes of all kinds would continue to live, hidden in so many tiny, watery cracks. As thousands of years pass after such a colossal impact, as the atmosphere reforms, as the earth's water re-condenses, and falls back to the surface in gigantic ocean-filling torrential rain storms, those hidden microbes, which had found their refuge in the deep rocks, would eventually creep upwards.
They'd slowly find their way back into these reformed oceans, lakes and rivers, back into the again cooled atmosphere, back into the sunlight, and the evolutionary process would kick into gear all over again.
It's speculated that our planet has survived at as many as several completely surface destroying impacts by minor planets or asteroids several hundred kilometers across, impacts that make the dinosaur impactor seem like a children's party firecracker in comparison, and this is how life regenerated from these cataclysms.
[0] https://www.youtube.com/watch?v=VD6xJq8NguY
https://www.reddit.com/r/kurzgesagt/comments/10jlyyk/kurzges...
There's a maybe better (very good) article on life in the crust from the NYT june 2024 here https://www.nytimes.com/2024/06/24/magazine/earth-geomicrobi... . Top comment "This article is one of the most powerful articles I have ever read in the NYT. I am so grateful that the author wrote it. It cemented my belief that that all life is deeply connected from the beginning to the present day and beyond..."
Does anyone know the paper(s) from the 1980s where the discovery was published?
Ghiorse & Wilson, https://doi.org/10.1016/S0065-2164(08)70206-5
I think there are two strands: petroleum companies have long been interested in any connection between deep biology and oil; and I think around that time people found microbes in a few sterile-seeming aquifers.
Do we know anything about the occasional Methane emissions I heard about on Mars?
Edit: found it:
https://www.jpl.nasa.gov/images/pia10911-ice-on-mars-now-its...
There have been cases where we believe we've seen ice form in rover tracks, hinting at water just below the surface.
Update: It’s so hard to believe that this was captured in 2008!
Assuming carbon based life as we know it, 300-400C is the probably a hard limit at which point single carbon bonds begin to break down.
Assuming life on earth as we know it, with ATP universally conserved across the entire evolutionary tree, the limit is really 150C. We've seen incredible survival adaptations like cryptobiosis but no organism exists that doesn't use ATP as its most basic unit of energy storage. That's the theoretical limit, but realistically other highly conserved critical pathways start to break down well before that temperature.
How about the organisms living in or around the hydrothermal vents in the mid-ocean ridges?