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Still working on that world with with a 93% ocean covering. My star Xat is 1.71 LSol, and my planet Jasmi orbits at 2.14 AU. I've been warned that the resulting apparent brightness of about 37% Sol from Earth may halt my world's evolution at the dirty snowball stage; is this necessary?

If so, is there a way to bring my planet to Earth-like or slightly colder temperatures without brightening my star?

I'm hoping to bring my world to a point where it has a band of persistent hurricanes around the equator/tropics/subtropics, or at the least, Nor-easters.

I'm told that Nor-easters would be very difficult to sustain, because I don't have enough land mass to dry out my air columns and mix cool dry air with hot humid air. The only way to change that would be to dramatically change my world map, which I don't want to do. So that leaves me with just a way of heating up my world a bit more.

Based on the answers to a prior question, I can generate heat on and in my planet in a few ways: radiation from Jasmi's core, solar radiation from Xat compounded by a greenhouse effect, frictional heating from incoming meteoroids, and tidal flexing from Jasmi's large moon. As mentioned, the distance from Xat means that it gives Jasmi about 30% of the radiation that Sol gives Earth.

The atmosphere I'm working with is 1.33 Earth atmospheres at the surface--by mass: 67% N2, 16% CO2, 15% O2, 1% CH4, and the remains made up of NH3, H2, Ne, O3, and He. Obviously if I keep this atmospheric composition I'm going to have problems with ocean acidity. I just threw this together and I'm expecting it to change; I just wanted to induce a high greenhouse effect. I could tinker with it by decreasing the CO2 and increasing the N2 and/or CH4.

Tidal flexing would maybe generate some more geological activity, but it wouldn't be incredibly significant.

I could hand-wave away the temperature problem by increasing the amount of radiation from the planet's core, but the distance from the star sets a limit on just how much radioactive material I could put in there without looking too implausible.

I'm concerned about putting an asteroid belt too close to my planet's orbit, because

  1. shouldn't my planet have cleared its orbit?
  2. I want my civilization to have as few barriers to space exploration as possible. But the amount of frictional heating I'd need to make up for my lack of solar radiation would be...significant.

Thanks for your help!

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Perhaps scale your planet up to a somewhat super terrestrial planet. It may then have increased volcanic activity, heating the atmosphere which would also be heavier due to the increased gravity which would warm things up still a bit more with the increased pressure.

To have a 93% ocean covering means it got hit by a lot of ice during formation, which suggests perhaps the planet formed beyond the ice line and was pushed in by the Grand Tack of a Gas Giant. This kind of activity is likely what stirs up circumstellar debris and created the Asteroid Belt nearby.

You could also explain a nearby asteroid belt as the result of a rogue moon torn asunder. Perhaps the star system has a long period binary companion which occasionally flies in and stirs things up. Or a massive Brown Dwarf could be doing the same.

A saltier ocean would stay liquid at lower temperatures. Perhaps the ocean is shallow so the salt is highly concentrated. If it is mixed with some other things like ammonia maybe that would act as antifreeze.

Another option could be an eccentric orbit to your planet which makes close swings every summer which heats up the world enough to keep it warm during the long winters. A binary star companion or a trinary companion could keep it in a permanent state of eccentricity. Or at least for a long long time.

Axial tilt as mentioned would help with those storms.

At 67% atmospheric nitrogen, would it be possible to sustain a fire on your planet's surface? Would that negate combustion engines? I'm not a chemist but I think increased nitrogen and low oxygen makes combustion more difficult. Not sure what the exact concentrations in your atmosphere would do.

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    $\begingroup$ I hope you are aware that what matters for combustion is the amount of Oxygen... $\endgroup$ – L.Dutch Feb 18 '18 at 9:53
  • $\begingroup$ @L.Dutch Not exclusively. Even if there is enough oxygen, additional gasses that raise the heat capacity of the air without participating in combustion themselves will inhibit combustion, by increasing the power required of a reaction to keep the temperature high enough for that reaction to remain self-sustaining. $\endgroup$ – Logan R. Kearsley Feb 19 '18 at 5:24
  • $\begingroup$ grasys.com/products/gas/fire $\endgroup$ – Catonfire Feb 20 '18 at 22:10
  • $\begingroup$ Sorry, above link is to Nitrogen fire fighting systems. Only a small increase in nitrogen will snuff out a fire without damaging equipment or killing people instantly. Nitrogen partial pressure is a factor in combustion reduction. However too much Nitrogen will kill oxygen breathers and unlike CO2, we wouldn't have a clue, we'd just pass out & die. Supposedly. thenakedscientists.com/forum/index.php?topic=46526.0 $\endgroup$ – Catonfire Feb 20 '18 at 22:16
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Axial tilt

The planet Uranus is so far from the sun that it shouldn't have much weather. The planet has an axial tilt of 98 degrees. So in the equivalent of summer, its north pole always faces the sun. Solar energy is absorbed by the sun facing side and fuels a weather system with 400 mph winds.

This does not provide for planet wide heating, but it can give you concentrated heating which will drive strong winds.

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    $\begingroup$ "its north pole always faces the sun" That's not the case $\endgroup$ – Alexander Feb 18 '18 at 8:53
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    $\begingroup$ Unfortunately, planets with high axial tilt such as Uranus probably could never develop such squishy life as Earth's, even in the habitable zone, according to the works cited in this video $\endgroup$ – Rúnatál Davino Feb 18 '18 at 11:21
  • $\begingroup$ Thorn's world orbits at 2 AU, so it shouldn't need a full 90 degrees of tilt to melt the ice and get the weather raging. $\endgroup$ – Jim Wolford Feb 18 '18 at 18:02
  • $\begingroup$ @Alexander "in the equivalent of summer", it is. $\endgroup$ – Logan R. Kearsley Feb 19 '18 at 5:25

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