Serpentinization — rock–water reactions, H₂ and abiotic methane

44:48Trench. And you see that like the sort of crescent of the Mariana's Trench, >> the Captain Hook. Yeah, that hook is the Mariana's trench, right? That is one plate subducting under another. Okay. >> And right, not in the trench itself. The trench is like the bottom of that subduction zone, right? Where the the ocean is like a few Mount Everests deep or whatever. It's very very deep. Here, this is a part of the of the subduction zone that's at the top. M. >> Okay. It's only about 3,000 m below the surface, but it's still impossible conditions. Okay, hyper alkaline pH, so you've got 12.6

45:30pH. >> Jesus Christ. >> Okay, water is at 7. And we're going to get into that a little bit. >> Um, it's really cold. 3.5° C, >> right? So that's about maybe what uh 40 30 37° F. Very cold. Very cold still. I mean, I might have surfed in that kind of temperature, but I didn't have a good time. >> Yeah, exactly. But somehow these bacteria are living there. And there's also a nutrient scarcity. There's profound limitation, especially when it comes to phosphate, right? There's not a lot of phosphate there. >> And what's what's really cool is this paper finds life there and then tries to characterize how that life is doing

46:11living right >> down there, which I thought was very very cool. Yes. The geochemical engine is something called serpentinization. Okay. It's a reaction between water and whatever mantle rocks are down there because this is like very close to the earth's earth's crust, right? So, you've got water, you've got some rocks, and what what is output is a mineral called serpentine. >> You've got a lot of molecular hydrogen, >> okay? >> H2. >> Okay. And H2 is a very energetic molecule, right? You can burn H2 and create energy in water and CO2.

46:52So, um, that's what's very interesting here. Okay. And the analogy is like, you know, when when when you've got iron and minerals, that iron splits and reacts with the oxygen and creates creates hydrogen because the water, it's going to strip the the oxygen out of the water and create H2. >> Yep. Something similar is happening down there, right? The minerals are reacting with the oxygen. Yes. In the water and liberating the hydrogen. Yep. >> Okay. And then that hydrogen then goes and then creates methane because there's going to be carbon there too >> cuz there's a free It's free hydrogen floating around. >> Yeah. Free hydrogen floating around. And that fuel is then going to create

47:33abiotic methane. So this is not methane coming from life. This is methane just coming from the chemistry down there. >> Got it. Okay. You know what I mean? >> Yeah. Yeah. No, that makes sense. Yes, that makes sense. >> And and so that's that's what's really interesting. We got to understand sort of the the the tectonic setting here >> in in the Mariana's Trench. So I told you, right? It's a subduction zone. >> Yes. >> Um you've got you've got one plate going under and another plate going over. >> And the fluids in that subduction zone in the mantle itself are what create the serpentinization. You've got like a sort of chemical process that like rejuvenates the ocean floor with with with new chemicals and things like that,

48:15but that resulting chemical is like the the the the water there is like really really messed up. Okay, >> which which makes sense. >> Which makes sense. It's like way deep. >> It's it's near a subduction zone, but the pH is 12.6. Okay. That's like bleach and oven