Super Earths With Hydrogen Atmospheres!

[Moontanman]

This paper suggests some very interesting possibilities about life on other planets. Dense hydrogen atmospheres might support life on super Earth type planets! 

 

http://www.ncbi.nlm....les/PMC4284464/

 

Quote

 

 

Abstract

The diversity of extrasolar planets discovered in the last decade shows that we should not be constrained to look for life in environments similar to early or present-day Earth. Super-Earth exoplanets are being discovered with increasing frequency, and some will be able to retain a stable, hydrogen-dominated atmosphere. We explore the possibilities for photosynthesis on a rocky planet with a thin H2-dominated atmosphere. If a rocky, H2-dominated planet harbors life, then that life is likely to convert atmospheric carbon into methane. Outgassing may also build an atmosphere in which methane is the principal carbon species. We describe the possible chemical routes for photosynthesis starting from methane and show that less energy and lower energy photons could drive CH4-based photosynthesis as compared with CO2-based photosynthesis. We find that a by-product biosignature gas is likely to be H2, which is not distinct from the hydrogen already present in the environment. Ammonia is a potential biosignature gas of hydrogenic photosynthesis that is unlikely to be generated abiologically. We suggest that the evolution of methane-based photosynthesis is at least as likely as the evolution of anoxygenic photosynthesis on Earth and may support the evolution of complex life.

 

 

Does this suggest that fire could take place? 

 

Quote

 

 

Secondly, oxidative metabolism yields so much energy because of the food it has to oxidize. Carbohydrates and fats are the storage materials that plants and animals chose to use exactly because they are the most efficient ways of storing energy in an oxidizing environment. However, they are not the only storage option. Predatory plankton preying on phytoplankton gain substantial energy from the metabolism of dimethylsulfonium proprionate (DMSP), releasing dimethyl sulfide (DMS) in large amounts [103,104]. DMSP is accumulated for reasons other than energetics (no one has convincingly argued what those reasons are [104,105,106]). Its energy of hydrolysis would be the same in oxidizing or reducing environments. In a reducing environment, highly oxidized compounds could be stored as energy storage materials, having the highest energy density when reduced with hydrogen, or other compounds with roles comparable to DMSP could be accumulated and be used as high-energy food. The absence of oxygen does not therefore preclude the possibility that other biomass components could be metabolized to yield lots of energy per gram.

 

Would this indicate that hydrogen breathing life forms on super earths dominated by hydrogen might be more common than oxygen dominated terrestrial planets? If so what could this indicate for exo life  and our search for such life? 

 

The main problem with such worlds was their supposed scarcity, now it would seem that they may out number oxygen worlds  and fire might be possible and by extension technological civilization!  

 

Our first contact or lack there of could be because hydrogen breathers wouldn't see oxygen worlds as hospitable for life... 

[Moontanman]

I can see it now, a planet 20,000 miles in diameter, vast oceans with maybe 10% of the surface exposed land the rest shallow or deep seas, 2 x the surface gravity of the Earth. Most of the land would be islands or archipelagos like new zealand, madagascar, or maybe the British Isles. Surface pressure of 10 to 20 bar, huge flying creature.

 

edit: Paper says 30 bar as an upper limit for surface photosynthesis 

Edited August 5, 2016 by Moontanman

[Moontanman]

Does no one else see how exciting this is? It expands the possible habitable worlds by orders of magnitude! around a sun like star the goldilocks zone is expanded to 10 AU! 

[Super Polymath]

Does no one else see how exciting this is? It expands the possible habitable worlds by orders of magnitude! around a sun like star the goldilocks zone is expanded to 10 AU!

I do.

 

You know I'm anti-athropecentric and the idea that the evolution of life on earth shows the cause for a natural selection of intelligent life doesn't sit well with me. I'd like to see how intelligent life develops elsewhere just to see how it really happens through selection. It would probably be quite bizarre to us and would require a very different, bizarre, alien, somehow intellectually-competitive hostile environment that unlike earth would be inducive to the selection of linguistically limitless organics.

Edited August 3, 2016 by Super Polymath

[Moontanman]

I do.

 

You know I'm anti-athropecentric and the idea that the evolution of life on earth shows the cause for a natural selection of intelligent life doesn't sit well with me. I'd like to see how intelligent life develops elsewhere just to see how it really happens through selection. It would probably be quite bizarre to us and would require a very different, bizarre, alien, somehow intellectually-competitive hostile environment that unlike earth would be inducive to the selection of linguistically limitless organics.

 

 

I've had similar thoughts about human evolution, but so far I have not been able to amass any evidence to support that particular conjecture seeing how we only have one data point...

 

If indeed I had managed to get a conversation going about this one I would have had to say that such worlds would almost certainly be dominated by water worlds, how ever the very same can be said for the Earth, there is some idea that the giant impact that formed the moon also depleted the Earth of most of it's primordial water resulting in a planet with oceans and continents instead of a world wide ocean, of course some computer models suggest that terrestrial planets almost always are the result of massive late development impacts and both Venus and Mercury show some signs of being formed this way, Mars however is not as well defined.

 

This could result in super Terrestrials with large moons but not a world wide ocean, or more likely if we take our own solar system into consideration, still very few data points I would have to point out, it still bodes well for a super terrestrial with oceans and land.. 

[Super Polymath]

I've had similar thoughts about human evolution,

 

If indeed I had managed to get a conversation going about this one I would have had to say that such worlds would almost certainly be dominated by water

You mean competitive dolphin-like species capable of grabbing and lifting material to form technologies? Like then where do they invent writing, books, fire, electricity?

 

Don't go into speculation, there can be extremely exotic conditions - no rocky crust but gas giants in which rock-like psuedo-terrestrial continents are organic or something earth-sized Godzilla-caliber sendentary creatures evolving from strange methane-breathing microbes that adapted from goldilock worlds colliding with the gas giant. These solid continental organisms on floating gas clouds housing their own forest-thing and minerals to be used in tool making, agriculture, and industry by competitive species with better innate neumonic devices for learning language and applying math than humans had....lol

 

Not really but when every star out there has its own planetary systems, evolution because a maddening numbers game. Until we've evolved beyond organic forms of life we will only have one real concrete data-point, earth. As far as I'm concerned politics, science, religion all come secondary to the miniaturization of computer tech.

 

What the evolution of organic life might look like out there, we can't even fathom. Have you seen interstellar? Remember the water-world with slightly higher gravity orbiting around the black hole sun, where the astronauts were in a state of slowed-time where a minute was a year?

 

I liked your hydrogen breathing theory expanding to 10 AU.

 

But again we don't need to waste brain-power on speculative string-theory and finding other life. We need to transcend. Transhumanism was actually posed as a solution to the theory of everything. Meaning that to humans the theory of everything can't be grasped due to our limitations.

Edited August 4, 2016 by Super Polymath

[exchemist]

 

This paper suggests some very interesting possibilities about life on other planets. Dense hydrogen atmospheres might support life on super Earth type planets! 

 

http://www.ncbi.nlm....les/PMC4284464/

 

Quote

 

 

Does this suggest that fire could take place? 

 

Quote

 

Would this indicate that hydrogen breathing life forms on super earths dominated by hydrogen might be more common than oxygen dominated terrestrial planets? If so what could this indicate for exo life  and our search for such life? 

 

The main problem with such worlds was their supposed scarcity, now it would seem that they may out number oxygen worlds  and fire might be possible and by extension technological civilization!  

 

Our first contact or lack there of could be because hydrogen breathers wouldn't see oxygen worlds as hospitable for life... 

 

I don't think this paper says anything about either fire or hydrogen-breathing creatures. It seems to be solely concerned with potential photosynthesis routes for carbohydrate from methane and water, in an atmosphere containing >70% hydrogen.

 

In fact it makes the point that making carbohydrate from methane and water requires only one fifth the energy of doing so from CO2 and water. That implies the reverse reaction, reduction (by hydrogen) of carbohydrate to methane, with production of water, would only be one fifth as energetic as the oxidation of carbohydrate (e.g. cellulose) involved in fire on Earth. So it seems to me that "fires" of carbohydrate reacting with hydrogen on such a planet are not likely. 

 

Disappointingly perhaps, it concludes that there are no reliable signature gases produced by these photosynthesis scenarios. So we would have no ready means of inferring extraterrestrial life from the spectrum of the atmospheric gases on such a planet.

 

But I found it a very interesting exercise in exploring some aspects of alternative life chemistry in a reducing environment. Many thanks for drawing it to my attention.

[Moontanman]

I don't think this paper says anything about either fire or hydrogen-breathing creatures. It seems to be solely concerned with potential photosynthesis routes for carbohydrate from methane and water, in an atmosphere containing >70% hydrogen.

 

In fact it makes the point that making carbohydrate from methane and water requires only one fifth the energy of doing so from CO2 and water. That implies the reverse reaction, reduction (by hydrogen) of carbohydrate to methane, with production of water, would only be one fifth as energetic as the oxidation of carbohydrate (e.g. cellulose) involved in fire on Earth. So it seems to me that "fires" of carbohydrate reacting with hydrogen on such a planet are not likely. 

 

Disappointingly perhaps, it concludes that there are no reliable signature gases produced by these photosynthesis scenarios. So we would have no ready means of inferring extraterrestrial life from the spectrum of the atmospheric gases on such a planet.

 

But I found it a very interesting exercise in exploring some aspects of alternative life chemistry in a reducing environment. Many thanks for drawing it to my attention.

 

 

No one was suggesting anything or anyone breath fire... The suggestion was that in a hydrogen dominated atmosphere energy could be stored by plants as oxidizers instead of carbohydrates as is used on earth. 

 

Secondly, oxidative metabolism yields so much energy because of the food it has to oxidize. Carbohydrates and fats are the storage materials that plants and animals chose to use exactly because they are the most efficient ways of storing energy in an oxidizing environment. However, they are not the only storage option. Predatory plankton preying on phytoplankton gain substantial energy from the metabolism of dimethylsulfonium proprionate (DMSP), releasing dimethyl sulfide (DMS) in large amounts [103,104]. DMSP is accumulated for reasons other than energetics (no one has convincingly argued what those reasons are [104,105,106]). Its energy of hydrolysis would be the same in oxidizing or reducing environments. In a reducing environment, highly oxidized compounds could be stored as energy storage materials, having the highest energy density when reduced with hydrogen, or other compounds with roles comparable to DMSP could be accumulated and be used as high-energy food. The absence of oxygen does not therefore preclude the possibility that other biomass components could be metabolized to yield lots of energy per gram.

 

[exchemist]

No one was suggesting anything or anyone breath fire... The suggestion was that in a hydrogen dominated atmosphere energy could be stored by plants as oxidizers instead of carbohydrates as is used on earth. 

OK you have misconstrued my reply a bit. I didn't mean to refer to fire-breathing, obviously, that would be ridiculous. What I meant was there is no suggestion there could be fire, which was one of your earlier speculations.

 

As to hydrogen breathing, yes I see now what you mean. The reduction of carbohydrate to methane and water by hydrogen would yield energy, though, as they say, only about a fifth as much as oxidation to CO2 and water does. 

 

I think though it is important to realise that these authors have not come forward with any plausible biochemistry that would achieve these results. All they are doing is reviewing the energetic potential of these overall reaction schemes.

 

But its an intriguing concept, certainly. I recall reading Hal Clement's "Mission of Gravity", in which there are hydrogen-breathing intelligent creatures. 

[Moontanman]

OK you have misconstrued my reply a bit. I didn't mean to refer to fire-breathing, obviously, that would be ridiculous. What I meant was there is no suggestion there could be fire, which was one of your earlier speculations.

 

As to hydrogen breathing, yes I see now what you mean. The reduction of carbohydrate to methane and water by hydrogen would yield energy, though, as they say, only about a fifth as much as oxidation to CO2 and water does. 

 

I think though it is important to realise that these authors have not come forward with any plausible biochemistry that would achieve these results. All they are doing is reviewing the energetic potential of these overall reaction schemes.

 

But its an intriguing concept, certainly. I recall reading Hal Clement's "Mission of Gravity", in which there are hydrogen-breathing intelligent creatures. 

 

 

No plausible biochemistry? We already have organisms on earth that use these chemical pathways, they are dominated by oxygen as a environmental poison! In an anoxic environment they can and did dominate the planet. The metabolic pathways of hydrogen metabolism already exist. We already have complex life forms living in anoxic environments, it's not difficult to justify extrapolation to larger more complex life forms. 

 

On a super terrestrial planet with a dense hydrogen atmosphere oxygen would never be able to accumulate to a level that would allow it to become an environmental poison paving the way for these organisms to evolve into a complex biosphere.

 

As for the oxidizers being used to store energy as they explained such metabolic pathways are already in use by earth organisms.

 

Secondly, oxidative metabolism yields so much energy because of the food it has to oxidize. Carbohydrates and fats are the storage materials that plants and animals chose to use exactly because they are the most efficient ways of storing energy in an oxidizing environment. However, they are not the only storage option. Predatory plankton preying on phytoplankton gain substantial energy from the metabolism of dimethylsulfonium proprionate (DMSP), releasing dimethyl sulfide (DMS) in large amounts [103,104]. DMSP is accumulated for reasons other than energetics (no one has convincingly argued what those reasons are [104,105,106]). Its energy of hydrolysis would be the same in oxidizing or reducing environments.

 

  

 

[exchemist]

No plausible biochemistry? We already have organisms on earth that use these chemical pathways, they are dominated by oxygen as a environmental poison! In an anoxic environment they can and did dominate the planet. The metabolic pathways of hydrogen metabolism already exist. We already have complex life forms living in anoxic environments, it's not difficult to justify extrapolation to larger more complex life forms. 

 

On a super terrestrial planet with a dense hydrogen atmosphere oxygen would never be able to accumulate to a level that would allow it to become an environmental poison paving the way for these organisms to evolve into a complex biosphere.

 

As for the oxidizers being used to store energy as they explained such metabolic pathways are already in use by earth organisms.

Do we have hydrogen breathing organisms? I did not know that. Where do they find the hydrogen?

[Moontanman]

Do we have hydrogen breathing organisms? I did not know that. Where do they find the hydrogen?

 

They exist in anoxic environments, other bacteria produce hydrogen, others metabolise that hydrogen. A tiny multicellular creature has been found that lives in an anoxic environment and it has replaced it's mitochondria with hydrogenosomes that allow it to metabolise with out oxygen.   

 

I don't think I mentioned it here but Issac Asimov suggested that since we would expect a hydrogen world to have very high pressures, 10 bar is reasonable I think, but anyway, due to the size of the hydrogen molecule and the pressure a lung full of such "air" would contain orders of magnitude more hydrogen molecules than a ling full of "air" on earth contains oxygen molecules. 

 

Also we would expect evolution of various catalysts and other chemical pathways to pull energy out of the system the same way they are used to by earth life to pull more energy out of oxygen metabolism..  

Edited August 7, 2016 by Moontanman

[exchemist]

They exist in anoxic environments, other bacteria produce hydrogen, others metabolise that hydrogen. A tiny multicellular creature has been found that lives in an anoxic environment and it has replaced it's mitochondria with hydrogenosomes that allow it to metabolise with out oxygen.   

 

I don't think I mentioned it here but Issac Asimov suggested that since we would expect a hydrogen world to have very high pressures, 10 bar is reasonable I think, but anyway, due to the size of the hydrogen molecule and the pressure a lung full of such "air" would contain orders of magnitude more hydrogen molecules than a ling full of "air" on earth contains oxygen molecules. 

 

Also we would expect evolution of various catalysts and other chemical pathways to pull energy out of the system the same way they are used to by earth life to pull more energy out of oxygen metabolism..  

I am aware of various anaerobic respiration processes, certainly, but I was not aware of any in which energy is obtained by reacting carbohydrate with hydrogen. Can you give an example, to help my understanding?  

 

P.S. Having googled "hydrogenosome" it appears to me that these produce hydrogen rather than consuming it.

Edited August 7, 2016 by exchemist

[Moontanman]

I am aware of various anaerobic respiration processes, certainly, but I was not aware of any in which energy is obtained by reacting carbohydrate with hydrogen. Can you give an example, to help my understanding?  

 

http://www.phschool.com/science/science_news/articles/hungry_for_hydrogen.html

 

To find out what kinds of microbes inhabit these extreme environments, where water temperatures can surpass 70°C, researchers at the University of Colorado at Boulder collected bacteria-bearing sediment samples from Yellowstone's geothermal system. Then, the team sequenced some of the microbes' genes. Much to the researchers' surprise, the sequences in most of the microbes closely resembled those of hydrogen-metabolizing bacteria that had been characterized elsewhere.

With extensive measurements, the researchers also determined that molecular hydrogen is abundant throughout the geothermal system. "These are the first systematic measurements of hydrogen in Yellowstone's springs," says lead investigator Norman Pace.

His computer model suggests why, even in the presence of sulfur, bacteria favor hydrogen. It's because sulfur-metabolizing organisms require oxygen, which serves as the depot for electrons that the microbes strip from sulfur. At temperatures greater than 70° C, however, oxygen is poorly soluble. So, most of the microbes living in the geothermal springs turn to hydrogen instead.

 

 

http://phys.org/news/2010-04-scientists-multicellular-life-doesnt-oxygen.html

[Moontanman]

There is also the possibility that such planets might have frozen ice mantles like Titan but much bigger. Hydrogen atmospheres and methane seas! Life on Titan:

 

http://phys.org/news/2015-10-kind-life-titan.html

[exchemist]

http://www.phschool.com/science/science_news/articles/hungry_for_hydrogen.html

 

 

http://phys.org/news/2010-04-scientists-multicellular-life-doesnt-oxygen.html

Thanks, the first reference indeed seems to refer to use of hydrogen for energy. The second I'm not sure.

 

But I'm still struggling to find evidence that the reaction scheme put forward in the paper (hydrogen + carbohydrate -> methane + water) is actually used by these organisms.  

[Moontanman]

Thanks, the first reference indeed seems to refer to use of hydrogen for energy. The second I'm not sure.

 

But I'm still struggling to find evidence that the reaction scheme put forward in the paper (hydrogen + carbohydrate -> methane + water) is actually used by these organisms.  

 

 

That is a good point, wasn't CO2 involved in that reaction in the paper?