Abstract Details
(2020) Can Volcanism Build Hydrogen-Rich Early Atmospheres?
Liggins P, Shorttle O & Rimmer P
https://doi.org/10.46427/gold2020.1555
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01c: Room 1, Tuesday 23rd June 00:33 - 00:36
Philippa Liggins
View abstracts at 4 conferences in series
Oliver Shorttle View all 7 abstracts at Goldschmidt2020 View abstracts at 13 conferences in series
Paul Rimmer View abstracts at 2 conferences in series
Oliver Shorttle View all 7 abstracts at Goldschmidt2020 View abstracts at 13 conferences in series
Paul Rimmer View abstracts at 2 conferences in series
Listed below are questions that have been submitted by the community that the author will try and cover in their presentation. To submit a question, ensure you are signed in to the website. Authors or session conveners approve questions before they are displayed here.
Submitted by My Riebe on Sunday 21st June 07:04
Could you explain a bit more why the high H2 episodes on Earth and Mars ended?
Thank you. In the case of Mars, the window of sustained volcanism was probably relatively short; once the volcanic flux dropped below ~20% of the modern Earth's rate, a H2-rich atmosphere would be unsustainable. On Earth, any H2-rich episode would have ended with the GOE as the photochemistry assumptions we use assume an anoxic atmosphere; in the presence of oxygen the H2 fractions produced by Earth's volcanism are quickly removed via photochemical reactions.
Could you explain a bit more why the high H2 episodes on Earth and Mars ended?
Thank you. In the case of Mars, the window of sustained volcanism was probably relatively short; once the volcanic flux dropped below ~20% of the modern Earth's rate, a H2-rich atmosphere would be unsustainable. On Earth, any H2-rich episode would have ended with the GOE as the photochemistry assumptions we use assume an anoxic atmosphere; in the presence of oxygen the H2 fractions produced by Earth's volcanism are quickly removed via photochemical reactions.
Submitted by Tomohiro Usui on Monday 22nd June 22:42
How can you produce a warm Mars condition in the high-H2 atmosphere and what exactly green-house effect do you think of ? Do you assume CO2-H2 collision-induced absorption?
Thank you for your question. Yes, we assume CO2-H2 collision-induced absorption to produce warm Martian conditions. Work by Wordsworth et al., 2017 and Hayworth et al., 2020 (and several others) suggests that H2 fractions on the order of 5% in a CO2 atmosphere is sufficient to generate a warm early Mars, given certain pressure constraints, using CO2-H2 CIA heating.
How can you produce a warm Mars condition in the high-H2 atmosphere and what exactly green-house effect do you think of ? Do you assume CO2-H2 collision-induced absorption?
Thank you for your question. Yes, we assume CO2-H2 collision-induced absorption to produce warm Martian conditions. Work by Wordsworth et al., 2017 and Hayworth et al., 2020 (and several others) suggests that H2 fractions on the order of 5% in a CO2 atmosphere is sufficient to generate a warm early Mars, given certain pressure constraints, using CO2-H2 CIA heating.
Submitted by Tomohiro Usui on Monday 22nd June 22:44
How can you produce a warm Mars condition in the high-H2 atmosphere and what exactly green-house effect do you think of ? Do you assume CO2-H2 collision-induced absorption?
How can you produce a warm Mars condition in the high-H2 atmosphere and what exactly green-house effect do you think of ? Do you assume CO2-H2 collision-induced absorption?
Submitted by Viacheslav Zgonnik on Tuesday 23rd June 07:42
Have you considered that early H2-rich atmosphere could be also the result of degassing of deep-seated (or primordial) hydrogen, which is being trapped during the Earth formation? (for examples and references I invite you to see the section 3.1 of my recent review).
It is certainly possible that other long-term sources of H2 could contribute to forming H2-rich atmospheres. In our paper (in review), we compare the scales of some of these H2 fluxes (e.g., from serpentinisation & metamorphism) to those generated through volcanism (though not nearly as thoroughly as in your review!), and find that volcanism is likely to be the largest H2 input to a prebiotic atmosphere. Deep-seated H2 could certainly be another of these sources, but until more research is done as to how large a flux of H2 this source contributes to the atmosphere, it's importance compared to volcanism cannot be determined.
Have you considered that early H2-rich atmosphere could be also the result of degassing of deep-seated (or primordial) hydrogen, which is being trapped during the Earth formation? (for examples and references I invite you to see the section 3.1 of my recent review).
It is certainly possible that other long-term sources of H2 could contribute to forming H2-rich atmospheres. In our paper (in review), we compare the scales of some of these H2 fluxes (e.g., from serpentinisation & metamorphism) to those generated through volcanism (though not nearly as thoroughly as in your review!), and find that volcanism is likely to be the largest H2 input to a prebiotic atmosphere. Deep-seated H2 could certainly be another of these sources, but until more research is done as to how large a flux of H2 this source contributes to the atmosphere, it's importance compared to volcanism cannot be determined.
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