Hi Guillaume. Very nice talk! I just wanted to confirm something that you said. As far as I understood, nitrogen (N2) is radiatively inactive, so there is no intrinsic opacity of N2 that can explain the overshoot. Rather, the effect of N2 (or presumably any background gas?) is to reduce the volume mixing ratio of H2O in the atmosphere for a certain temperature range, and this changes the atmospheric structure and hence emission temperature. In this regard, does this mean that we should not by default ignore radiatively inactive species in interior/atmosphere models, since even a radiatively inactive species can impact the evolution in the presence of other active species (such as CO2, H2O)?

Thanks Dan ! Yes that's right ! Inactive species can have an impact on the atmospheric structure but also change the broadening of the absorption lines. The effect on the structure is different if the background gas is lighter or heavier than the main gas and the second effect is very strong in my study case and sometimes not really discussed. I don't know well interior models but in atmospheric models neglecting inactive species (N2, H2 etc) can strongly modify simulation results through interactions with active species.

Hi Deniz,

Nice work!
Does this work bear any implication for the magnetic fields of terrestrial-type planets, e.g., in terms of any discrepancy between the MF observations and the dynamo modelling outcome?

Thanks.

Hi Noah,

Thank you for your presentation, this is very interesting!

Could you explain the main reasons why the magma cooling timescale seems to be much shorter that what has been calculated for e.g. Venus? (I am thinking here about the Lebrun et al. 2013 or Hamano et al. 2013 papers). How much does it depend on the initial volatile reservoir size and composition?

Also, do you expect any kind of observations (e.g., from BepiColombo?) to constrain your model results? (i.e. on the true nature of an early Mercury atmosphere)


ps: That was nice to have the subtitles! (what software did you use for that?) But I am wondering ... who are those mysterious "ten Bowers"?

Hi Noah,
Nice talk!Thanks!

Are you planning to use the codes framework you described to study hot exoplanets like TRAPPIST-1 b or 55 Cnc e?

Hi Marit, Thank you for your presentation! I have several questions:

(1) What is the motivation for considering solar metallicity atmosphere for such low mass planets? (and not higher metallicity). Based on the empirical trend (see e.g., https://stellarplanet.org/science/mass-metallicity/ ), don’t you expect higher metallicity atmosphere to be more common around low mass planets?

(2) On your log(ENV)/distance(AU) diagram, wouldn’t you expect (for distance typically larger than 10 AU) that the amount of photons that reach the liquid water ocean is so low (due to both the low insolation and the thickness of the atmosphere that absorb/scatter photons) that phototrophic life would be prevented?

I also have two remarks:

- regarding the possibility to simulate H2-rich atmospheres in 3-D on temperate low-mass planets, I recommend you to read the recent paper: https://www.aanda.org/component/article?access=doi&doi=10.1051/0004-6361/202039525

- regarding moist convection in H2-rich atmospheres, an effect that may be very important to consider (or at least, to think about) is the inhibition of convection by the molecular weight vertical gradient caused by water condensation (see https://ui.adsabs.harvard.edu/abs/2017A%26A...598A..98L/abstract )

Hi Marit, thanks for your talk! (and the memes)
On your long(env)-distance diagram, taking into account the time. Did you consider the luminosity evolution of the host star?

Hi Marit,

Very interesting work!

In my simplistic understanding, the speciation of H2 and H2O in the atmosphere depends on oxygen fugacity or the redox state of the atmosphere among other parameters. Sometimes the redox state is also set by the initial chemistry. Under which conditions do you find the coexistence of H2 and H2O?

Hi Marit,

Very interesting work!

In my simplistic understanding, the speciation of H2 and H2O in the atmosphere depends on oxygen fugacity or the redox state of the atmosphere among other parameters. Sometimes the redox state is also set by the initial chemistry. Under which conditions do you find the coexistence of H2 and H2O?

Hi Martin,

Thank you for the questions and comments!

(1)
Yes I do expect the metallicity of these planets to be/become higher than solar.
The initial motivation was to simulate the greenhouse effect of just hydrogen and see how it behaves alone. Previous work was with a composition of only hydrogen or hydrogen + helium. I did the same first to compare, then added some metals as solar composition, and also ran the same simulations for 10x and 100x solar metallicity.
However, currently increasing the metallicity in my case means just increasing the opacities. This does have some effect on the relation between the duration and the equilibrium temperature + envelope mass, but not a very drastic one. I think in this case it's even more important to improve on how I treat condensibles as their actual role could be more different from my simulations.
For the emperical trend between mass and metallicity, I don't think I would necessarily want to go as far as extrapolate the trend to the masses that I'm using for example. I would argue that the exoplanets that we observe which have a mass of a few earth masses receive a lot more atmosphere loss by radiation that discriminates the lighter hydrogen. Then for the very small, cold object in our solar system (like Pluto, I don't know if this scale is still relevant in the trend) Jeans escape would be much higher than the planets I simulate. What I would like to try in the future is to see if I can simulate atmosphere loss by collisions. Maybe this can lead to cases where the planets are of a few earth masses but have the same metallicity as solar system gas giants. In any case the formation + evolution path needs to be different than any planet that we can currently observe and I hope to work and improve on this during the project.

(2)
Yes that's true. This also has to do with the two theoretical habitable hydrogen planets that were proposed in literature. The first would use the greenhouse effect with radiation from the star and this would create a 'habitable zone' of a few au, with some photon flux from the star reaching the surface albeit not as much as on earth. The second type requires a more massive envelope and the liquid water conditions are entirely due to the heat from the interior. This would not only prevent photosynthesis; there would not be a day-night rhythm, which is also argued as a requisite for life, or seasons. In contrast if there are temporal variations in the heat from the interior this can be crucial to the habitability for these planets. In my simulations I choose parameters that cover both these 'types', so there are also cases in between where sunlight and internal heat are both important.
Since we do have life on earth that doesn't require photosynthesis, I wouldn't call these planets uninhabitable. If on earth we can only find one type of bacteria that can live under these (for us extreme) conditions this would prove life is not impossible and might evolve itself to the circumstances.

Hi Emeline,

We already discussed the question in the zoom but for completeness I'll answer here too. Yes, I used a model of a solar-type star that simulates it's temporal evolution on the main sequence.

Hi Emeline,

Do you know if it is in principle possible to have several states of equilibrium for interior+rotation for a rocky planet? (through feedbacks between interior composition, viscosity, dissipation and tides) Or do you instead always expect to have one single final equilibrium state?

I don't have a question, but clearly we can couple to SPIDER! It would be more optimal to find a shared student/post-doc since I have lots of other projects I'm juggling. But we should try and get something moving. With the publication of my next solubility paper, I hope to clean up the code a little and make it more user friendly. Coupling to orbital evolution would be a good motivator. I think there's low hanging fruit we can tackle!

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