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Moontanman
Post  Post subject: Hydrogen Dominated Terrestrial Planets  |  Posted: Fri Aug 05, 2016 11:02 pm
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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/

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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?

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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?



I looked at this a bit deeper, it suggests that about 30 bar is the limit for light to penetrate to the surface, but we can hypothesize a planet, maybe 20,000 miles in diameter. 10 - 20 bar atmosphere of mostly hydrogen. 12 times earths mass, less dense but 2 gravities at the surface, 15.6 times earths volume, 6.25 times the surface area. It would be difficult to escape using chemical rockets but nuclear should do it... day length could be anything, but longer days seems likely to me 36 hours, just arbitrary on that, a couple Titan sized moons... Is this planet more likely than Earth?


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iNow
Post  Post subject: Re: Hydrogen Dominated Terrestrial Planets  |  Posted: Sat Aug 13, 2016 10:24 pm
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That's fascinating, but what's the relevance of your fire question? Also, hydrogen is massively corrosive. Can only imagine what side effects that may have. Could be fun to speculate about how life may have evolved to cope!

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Moontanman
Post  Post subject: Re: Hydrogen Dominated Terrestrial Planets  |  Posted: Mon Aug 15, 2016 5:30 pm
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iNow wrote:
That's fascinating, but what's the relevance of your fire question? Also, hydrogen is massively corrosive. Can only imagine what side effects that may have. Could be fun to speculate about how life may have evolved to cope!


The authors suggest that on a hydrogen world energy could be stored in the form of oxidizers in stead of carbohydrates like on an oxidizing world. If you were in a hydrogen atmosphere and plants contained oxidizers then fire might be possible...

Hydrogen is corrosive? New one on me, can you elaborate? Is it more corrosive than oxygen?


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iNow
Post  Post subject: Re: Hydrogen Dominated Terrestrial Planets  |  Posted: Mon Aug 15, 2016 7:40 pm
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Hydrogen is extremely corrosive, yes. Unsure how it ranks against oxygen, though.

http://corrosion.ksc.nasa.gov/hydrodam.htm
https://en.wikipedia.org/wiki/Hydrogen_damage

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Moontanman
Post  Post subject: Re: Hydrogen Dominated Terrestrial Planets  |  Posted: Mon Aug 15, 2016 11:24 pm
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iNow wrote:
Hydrogen is extremely corrosive, yes. Unsure how it ranks against oxygen, though.

http://corrosion.ksc.nasa.gov/hydrodam.htm
https://en.wikipedia.org/wiki/Hydrogen_damage



The main point of this post is the idea that hydrogen atmospheres could occur on rocky planets, hydrogen being so common in the universe could mean that such planets being able to maintain water oceans at up to 10 AU from a sun like star increases the possible number of habitable planets. Maybe even by orders of magnitude!

This of course begs the question are hydrogen breathers more common than oxygen breathers?

Quote:
I looked at this a bit deeper, it suggests that about 30 bar is the limit for light to penetrate to the surface, but we can hypothesize a planet, maybe 20,000 miles in diameter. 10 - 20 bar atmosphere of mostly hydrogen. 12 times earths mass, less dense but 2 gravities at the surface, 15.6 times earths volume, 6.25 times the surface area. It would be difficult to escape using chemical rockets but nuclear should do it... day length could be anything, but longer days seems likely to me, 36 hours?, just arbitrary on that, a couple Titan sized moons... Is this planet more likely than Earth?


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iNow
Post  Post subject: Re: Hydrogen Dominated Terrestrial Planets  |  Posted: Tue Aug 16, 2016 1:35 am
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Does anyone know if we've managed to replicate hydrogen based life in a lab? Maybe a Michelson-Morley type setup, or even if it is feasible/practical to try?

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Moontanman
Post  Post subject: Re: Hydrogen Dominated Terrestrial Planets  |  Posted: Tue Aug 16, 2016 2:00 am
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iNow wrote:
Does anyone know if we've managed to replicate hydrogen based life in a lab? Maybe a Michelson-Morley type setup, or even if it is feasible/practical to try?



There are already life forms on Earth that metabolise hydrogen, no need to go to a lab at all, http://www.phschool.com/science/science ... rogen.html


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iNow
Post  Post subject: Re: Hydrogen Dominated Terrestrial Planets  |  Posted: Tue Aug 16, 2016 3:24 am
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Holy monkey testicles, batman! That makes the study in the OP even more awesome.

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Moontanman
Post  Post subject: Re: Hydrogen Dominated Terrestrial Planets  |  Posted: Mon Sep 05, 2016 2:33 am
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iNow wrote:
Holy monkey testicles, batman! That makes the study in the OP even more awesome.



Finally out of the hospital! I am surprised more people don't see the potential in this!


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iNow
Post  Post subject: Re: Hydrogen Dominated Terrestrial Planets  |  Posted: Mon Sep 05, 2016 3:14 am
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Don't take it personally. We have like three active members.

Glad you're back out. Hope the situation has been minimally impactful to you and Nancy and the bassetts and that you're once again on the mend with those zen aquariums.

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Moontanman
Post  Post subject: Re: Hydrogen Dominated Terrestrial Planets  |  Posted: Fri Sep 16, 2016 1:52 am
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iNow wrote:
Don't take it personally. We have like three active members.

Glad you're back out. Hope the situation has been minimally impactful to you and Nancy and the bassetts and that you're once again on the mend with those zen aquariums.



Not doing well, fell down again last night, nothing broken but I am back using the walker...

I think the hydrogen dominated rocky worlds has quite a bit to say about the Drake equation. Hydrogen being the most common molecule in the universe could change the very idea of what life bearing planets are.

A hydrogen world with a surface area of up to 25% rocky ground but with the rest vast oceans, Imagine a word with a similar amount of dry land as the earth but with more than 6 times the surface area. Even Earths large landmasses would be lost in such huge oceans. a dense 10 bar atmosphere, significant amounts of gasses that cannot exist in an oxygen atmosphere, H2S, N3h, the possibilities are mind boggling and significantly more likely than oxygen worlds...


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iNow
Post  Post subject: Re: Hydrogen Dominated Terrestrial Planets  |  Posted: Fri Sep 16, 2016 3:21 am
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Sorry about the balance and stability issues. That's a whole lotta suck.

So, you're thinking these findings could shift the Drake equation an order or magnitude or two further along the "life is very likely" dimension? Seems legit to me, but I'm a bit biased. I'm already convinced that life of various sorts is not only out there, but common.

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