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Parametrised mass loss from giant impacts #407
Description
https://arxiv.org/abs/2505.04343
...we present a scaling law that precisely approximates loss from 0.35 to 5.0 Earth mass planets with 5% mass fraction H-He atmospheres for any combination of impactor mass, impact velocity, and angle.
Such a scaling law could be included in PROTEUS. It would potentially account for the stochasticity of such events.
... while individual impacts rarely cause significant loss (10%) from roughly Earth-mass planets with such massive primary atmospheres, the cumulative effect of multiple impacts can be substantial (40-70% loss).
Activity
nichollsh commentedon Dec 13, 2025
See also https://iopscience.iop.org/article/10.3847/2041-8213/adf282
timlichtenberg commentedon Dec 13, 2025
The mistake is to assume that the water iceline is static at a certain distance and non-moving, that planetesimals form also in the dry part, that planets do not substantially migrate in the disk, and that planetesimals dehydrate the same way as in the Solar System from Al-26 (even they don't even realise they do this). Planets nucleate at the water iceline and grow from there, and then move inwards, populating the inner disk with volatile-rich planets. What you put in is what you get out. My humble opinion. 🫠
nichollsh commentedon Dec 13, 2025
Good to know. On the iceline point: they do an extra set of simulations where they move it outwards at earlier stages because of the increased luminosity in the pre-main sequence. Apparently makes a difference? I wonder how this could be parametrised in our modelling, since the PROTEUS simulations are maybe too expensive to treat migrations/mergers/impacts on a statistical basis.
timlichtenberg commentedon Dec 13, 2025
That's not what I mean; it should start much further inwards, which then makes the seed planetesimals much more water-rich. With some colleagues we currently prepare a paper for this, since no one in the M-dwarf disk modelling community has picked this idea up so far. Will share once it's available. The overall technical framework from then Chen paper is useful though, the next step to do first will be to work in re-melting by giant impacts.
My criticism there at the top was their derived water budgets, which simply result from how they set up their simulations.
nichollsh commentedon Dec 13, 2025
Ahh - I see - so good news for volatile retention. Looking forward to seeing this paper when it is ready.
Integrating re-melting by giant impact events into PROTEUS would be nice. We will need to think about how to treat this with SPIDER/Aragog. E.g. how is this energy distributed in the mantle?
timlichtenberg commentedon Dec 13, 2025
The first thing I can of is https://www.sciencedirect.com/science/article/pii/S0012821X21002429.
timlichtenberg commentedon Jan 22, 2026
Another scaling law; strongly enhancing impact atmospheric loss from re-accretion of debris: https://academic.oup.com/mnras/article/544/2/2120/8300801
timlichtenberg commentedon Feb 4, 2026
Anna Grace Ulses, PhD student in Josh KT's group will visit us this summer and work with Tadahiro Kimura and me on this project, starting with allowing remelting of the mantle and timing of GIs.
nichollsh commentedon Feb 4, 2026
Sounds awesome! Looking forward to hearing more.
timlichtenberg commentedon Oct 6, 2026
New scaling law that includes the atmospheric mass: https://arxiv.org/abs/2610.06077 (Roche et al.). SPH impacts onto planets with 1-20% mass fraction atmospheres show that lower-mass atmospheres are much easier to remove, and roughly Earth-mass bodies lose 30-100% of their atmospheres through multiple impacts.
We want to implement this law so it is available in Morrigan, PROTEUS and ZEPHYRUS. The implementation should go into ZEPHYRUS next to the current impact mass-loss law (FormingWorlds/ZEPHYRUS#29), which is the function the coupled PROTEUS runs call.
Add the Roche et al. (2026) impact-loss law as the default (#975)
Merge main and keep the mole columns in step with the trapped masses (#…