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In this scenario we have a brown dwarf with a powerful magnetic dynamo from metallic hydrogen. The magnetic field is modeled after Jupiter’s but just three orders of magnitude more powerful.

Orbiting the brown dwarf are two exact copies of Earth in a close horseshoe orbit. These planets are stripped of, and feed charged particles of atmosphere into a plasma torus, which is in all respects similar to Io’s.

Discounting the improbability of the setup, what are ways that the Atmosphere of these planets can be sustained with breathable compositions?

So far my research has led me to a few different processes that could help feed the atmosphere, but I’m doubtful of their ability to maintain breathability for humans. .

  1. Erosion: Both Earth-like planets are tidally locked to the brown dwarf. If their sub-solar points have continental structures then the erosion from near constant precipitation could release large quantities of CO2. In addition, powerful tidal forces between horseshoe orbits will erode many coastal areas.

  2. Volcanic Activity: Though the two planets have 0 eccentricity, they switch their orbits every 120 days. This change produces tides of 70m on the closer planet. My rough estimations based on period and tidal forces says that my planets should be two to three orders of magnitude less geologically active than Io. However, during “change events” volcanoes and Earthquakes should be common. These volcanoes will spit out water vapour, CO2, sulfur dioxide and other unpleasant vapours.

  3. Plant life: Plants will do their thing and convert CO2 and H2O to oxygen. This could help keep our atmosphere breathable.

Are there any other ways that I’ve overlooked to plausibly sustain my atmosphere? The answers don’t have to be perfect, but I want some science base to them. No magic allowed. Natural processes are preferred, even if they are unlikely or rare effects. I will also accept “derelict/self sustaining technology” Perhaps in the form of abandoned terraforming equipment. Still:Natural processes are preferred

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The torus alternately feeds and is fed by the planets.

A horseshoe orbit implies that the planets take one pass close to their sun and then the return trip farther away. The difference in distance means a difference in the forces stripping atmosphere from the planets. The planets can reclaim gas they have given up.

On the near pass, the more intense interaction with the star means atmosphere is stripped from the planets. Possibly enough to produce a "low-atmosphere" hot season on the ground. On the far pass, however, the distance and lower intensity energies means atmosphere can be recaptured. The planet sweeps through the outer edge of the torus and collects back gas that it (and its twin) donated. The high atmosphere cool season ensues.

This uses the same setup you already have. Occam!

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Natural: The planets would have to have a very strong magnetosphere themselves. This could be maybe caused by the massive molten iron core that interacts with the other planet and the star itself. (Disclaimer: My knowledge of the subject is nowhere near where I would like it to be, but this makes sense to me.)

Plants: It doesn't matter that plants do their thing if there is no atmosphere at all, which is exactly what would happen if there is no way of maintaining the atmosphere.

Tidal lock: I assume that your planets are fully in the habitable zone, if there even is such a thing with the brown dwarf, therefore they could be expected to be tidally locked to the star since it would be even closer to it than habitable zone planets orbiting red dwarves.

Tech: Magnetosphere could be created artificially using an array of satellites. These could be powered by some variation of solar panels. If left behind by some advanced ancient civilization you could expect them to be fairly robust and almost maintenance-free or maintained by similarly robust robots.

Hope my thoughts help at least a little

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  • $\begingroup$ Your answers are informative. However, the magnetospheres of our planets isn’t in question. It exists, but cannot stop atmosphere loss due to the amount of energy we’re dealing with. Each of these planets will end up forming a flux tube conmecting them to the brown dwarf. The flux tube will be sending ionized particles into the poles of our planets causing atmosphere loss among other things. Ive resigned myself to having atmosphere loss. What Im more interested in is: What natural or artificial ways can I continue to feed my atmosphere? $\endgroup$ – Hippeus_Lancer Dec 14 '18 at 12:06

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