Interior dynamics talks
Please find below the talks of people who work mainly on the interior dynamics and the link to the atmosphere of planets.
You can leave questions below the video of each speaker! These questions will then be asked to the speaker the day of the workshop.
Dan Bower: Retention of H2O in a magma ocean
Paolo Sossi: Experimental constraints on melt--gas equilibria
Kaustubh Hakim: A Lithology-based Silicate Weathering Model for Earth-like Planets
Tobias Meier: Hemispheric tectonics on LHS 3844b
Retention of H2O in a magma ocean
Ask your questions to Dan!
Thank you for the interesting talk!
(1) In your numerical model for the outgassing of a magma ocean, how is the core cooling computed?
(2) Would it be possible to have additional radial sources of heat in your code? To see if that could lengthen the duration of the magma phase or create interior magma oceans? Somehow related to that, I guess you account for radiogenic heating, how exactly do you do that?
(3) How much time do your simulation run typically? For the Lichtenberg, Bower et al. 2021 paper for instance. How long is it to do a 10 Myr simulation?
(2) Certainly straightforward to add additional heating into the model. Modelling interior magma oceans would be very interesting, although depends on the form of the melting curve (basically, a monotonically increasing melting curve is unlikely to produce interior magma oceans, but a melting curve with an overturn might -see Stixrude et al., 2009)
(3) In real time, the models are fast (minutes to hours) if you use the built in grey body model for the atmosphere. In Tim's recent paper, we have a coupler that sits between the interior and radiative model to allow him to use his own atmosphere model (SOCRATES) which is obviously more sophisticated.in terms of the treatment of opacity and radiative transfer. Incidentally, in the same way we could flip between an orbital model and the interior model! I hope to think more about this once my current work on solubilities is somewhat wrapped up.
Leave a Reply
Experimental constraints on melt--gas equilibria
Ask your questions to Paolo!
Thanks for the nice talk!
I have maybe a naive question, but can the calibrated dependence of Fe2+/Fe3+ on oxygen fugacity be used for other planets than the Earth? Or is it very specific for the Earth?
Leave a Reply
A Lithology-based Silicate Weathering Model for Earth-like Planets
Ask your questions to Kaustubh!
Thank you for your very educational presentation!
I have a question regarding the positive feedback you mention between temperature and weathering in the thermodynamic weathering regime. How would you place this feedback in the context of the Hadean Earth (hot temperature and thick CO2-dominated atmosphere?) and the progressive drop in CO2 atmospheric concentration and temperature.
This is a very interesting question!
In the thermodynamic regime, there is a tug-of-war between the effects of T and P_CO2 on the intensity of weathering (Fig. 5 of the paper). In the late Hadean and early Archean, T was higher than today by several tens of Kelvin but P_Co2 was orders of magnitude higher. This results in the domination of the effect of P_CO2 on weathering and thus the effect of T does not kick in (Fig. 9b of the paper).
Here is the preprint: https://arxiv.org/pdf/2008.11620.pdf
Leave a Reply
Hemispheric tectonics on LHS 3844b
Ask your questions to Tobias!
Thank your for your presentation! Your results are really cool!
I have several questions for you:
(1) What is the motivation for fixing the CMB at 4500K? Did you explore the impact of varying this parameter?
(2) If I understood correctly the Kreidberg et al. 2019, it seems the LHS3844b phase curve is in principle still compatible with a 'thin' (lower than 10 bar) atmosphere, which could in principle redistribute heat from the dayside to the nightside, and warm the nightside up to 800-900K. How would that affect the results of your simulations? Do you expect the dayside/nightside convective pattern dichotomy to be reduced or even to disappear?
(3) What is the typical range of outgassing (in the atmosphere) rates in your simulations? How does that compare to the typical range of (e.g., energy-limited) escape rates?
Nice talk! I have a couple of questions for you:
1) can you please elaborate a bit more how and why the strength of lithophile affects the heat exchange between stellar flux and interior outflow heat flux? I am a bit unclear with the 3rd scenario particularly for the downwelling on the night side.
2) In the mix heating scenario, how did you constrain the radiogenic heating budget? what's its fraction over the total heating.
1) We adopted a rather conservative estimate for the CMB temperature to ensure that the base of the mantle does not melt to have solid convection only as we wanted to see the general pattern of of convection without the complexity of melt (although this is definitely something interesting and worth to look into in the future). We haven’t run models with higher CMB temperatures. A higher CMB temperature would facilitate the formation of plumes. However, in order to change the convection behaviour in the mantle, the temperature at the CMB would have to be increased significantly, as the Rayleigh number depends linearly on the temperature drop between the surface and the CMB. But to change the style of convection, it would probably have to be at least an order of magnitude higher. By increasing the temperature at the CMB, there would also be strong effect on viscosity. But numerically, we are limited by the viscosity contrast, so viscosity would probably be truncated.
2) Yes, from Kreidberg et al. 2019, the temperature on the nightside could be 0-710 K. We have run models with nightside temperatures of 710 K and 355 K (not shown in the presentation) and we found that hemispheric tectonics persist for these cases (although for 710 K, hemispheric tectonics tends to become less stable) . We haven’t run models with higher temperatures. But yes, it’s very likely that the dichotomy becomes weaker and eventually will disappear. It would be interesting to follow up on this and see at which nightside temperature the dichotomy disappears.
3) Our models don’t include outgassing. But that is definitely something we would like to look into in the future and where interior-atmosphere collaborations would become very useful.
1) We haven’t investigated in depth what the exact mechanism is that causes downwellings to appear either on the nightside or the dayside (which is difficult to analyse because of the highly-coupled system). For the strong lithosphere case, we think that it’s the temperature dependance of viscosity that allows the near-surface on that side to be weaker and therefore downwellings to appear on that side. The nightside is too stiff to subduct for this strength of the lithosphere.
If the lithosphere is weak, there are downwellings on both sides, but they are stronger on the nightside because of the stronger temperature contrast (between the surface and CMB). When we add internal heating to these models (with a weak lithosphere), the downwellings persist (but weaker) on the nightside, but not anymore on the dayside.
However, I’m not sure if this answers your question in terms of stellar and interior outflow heat flux?
2) As of today, the planet’s radiogenic heat budget is unknown. We therefore assume it to be Earth-like. In our models it is 5.2e-12 W/kg (constant over time). For the models with mixed heating, the ratio between internal heating and basal heating is between 0.7-0.8. We have also run models (not shown in the presentation) where we reduced the internal heating budget by half. We found that hemispheric tectonics persist for these models.
Leave a Reply