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> If a super-Earth is ejected from its star system and has a dense atmosphere and watery surface, it could sustain life for tens of billions of years, far longe

> If a super-Earth is ejected from its star system and has a dense atmosphere and watery surface, it could sustain life for tens of billions of years, far longer than life on Earth could persist before the sun dies. What would be the energy source to sustain life on an ejected super-Earth? Radioactivity? Tidal forces from orbiting moons?

mr_toad 4y ago
I don’t think we’re exactly sure how much of the Earth’s heat is due to radioactive materials in the core or just left-over heat from its formation, but either way a super Earth should have more of both.
- hinkley 4y ago
  One of the early pieces of evidence for the existence of radioactivity had to do with the fact that the Earth’s core is way too hot to be billions of years old. Even if there were coal veins down there just burning slowly forever.
tambourine_man 4y ago
Yeah, I wondered about that as well. It must be radioactive and residual heat from the core. I can’t imagine geothermal supporting as vibrant an ecosystem as photons pouring in everyday allow photosynthesis to do.
njarboe 4y ago
This seemed off the me also. Reading through the paper quoted in this sentence makes it clear that the sentence is just wrong. From [1]: "The team found that planets 10 times the mass of the Earth, with an atmosphere 100 to 1000 times thicker than Earth’s, may be the most favorable for storing life for billions of years. But to do this, they must orbit the star at a distance that the orbit of Mars occupies in the Solar System. At such a potentially safe distance, the original atmospheres can act as greenhouse gases, absorbing infrared radiation, providing the necessary heat and pressure that can support life in oceans of liquid water." So the planet is not ejected from the system, just pushed out so that instead of an orbit of days it is as far away as Mars is to our sun (1.5 AU). Gell-Mann Amnesia comes into play here. [1] https://universemagazine.com/en/life-on-super-earths-can-exist-for-84-billion-years/ https://universemagazine.com/en/life-on-super-earths-can-exi...
- ReptileMan 4y ago
  Just to point that water is almost exactly 1000 times thicker than air Edit: 800 times if we have to be precise
- divbzero 4y ago
  Thanks for spotting that link. Digging one link farther reveals the original article [2] which is more detailed and descriptive than the others. The original article explores super-Earths where the primordial H–He atmosphere is retained and traps enough heat to sustain liquid water, and includes simulations of “unbound” super-Earths that are ejected from their star systems. The mathematical model [3] incorporates the initial heat from planet formation and radiogenic heat but does not mention tidal forces. [2]: https://www.nature.com/articles/s41550-022-01699-8 https://www.nature.com/articles/s41550-022-01699-8 [3]: https://github.com/mollous/Data_Liquid_Water_Conditions https://github.com/mollous/Data_Liquid_Water_Conditions --- The original article also includes this discussion of habitability: Life on the type of planet described in this work would live under considerably different conditions than most life on Earth. The surface pressures in our results are on the order of 100–1,000bar, the pressure range of oceanic floors and trenches. There is no theoretical pressure limit on life, and some of the most extreme examples in Earth’s biosphere thrive at ~500bar. These habitats also receive a negligible amount of direct sunlight, and therefore photosynthesis would not be an optional mechanism to provide for metabolism. Chemoautotrophic life on Earth would be a more likely analogue to possible life on this type of planet.
  - deleted 4y ago
    [deleted]

mr_toad 4y ago

I don’t think we’re exactly sure how much of the Earth’s heat is due to radioactive materials in the core or just left-over heat from its formation, but either way a super Earth should have more of both.

hinkley 4y ago
One of the early pieces of evidence for the existence of radioactivity had to do with the fact that the Earth’s core is way too hot to be billions of years old. Even if there were coal veins down there just burning slowly forever.

tambourine_man 4y ago

Yeah, I wondered about that as well. It must be radioactive and residual heat from the core. I can’t imagine geothermal supporting as vibrant an ecosystem as photons pouring in everyday allow photosynthesis to do.

njarboe 4y ago

This seemed off the me also. Reading through the paper quoted in this sentence makes it clear that the sentence is just wrong. From [1]: "The team found that planets 10 times the mass of the Earth, with an atmosphere 100 to 1000 times thicker than Earth’s, may be the most favorable for storing life for billions of years. But to do this, they must orbit the star at a distance that the orbit of Mars occupies in the Solar System. At such a potentially safe distance, the original atmospheres can act as greenhouse gases, absorbing infrared radiation, providing the necessary heat and pressure that can support life in oceans of liquid water." So the planet is not ejected from the system, just pushed out so that instead of an orbit of days it is as far away as Mars is to our sun (1.5 AU). Gell-Mann Amnesia comes into play here. [1] https://universemagazine.com/en/life-on-super-earths-can-exist-for-84-billion-years/ https://universemagazine.com/en/life-on-super-earths-can-exi...

ReptileMan 4y ago
Just to point that water is almost exactly 1000 times thicker than air Edit: 800 times if we have to be precise
divbzero 4y ago
Thanks for spotting that link. Digging one link farther reveals the original article [2] which is more detailed and descriptive than the others. The original article explores super-Earths where the primordial H–He atmosphere is retained and traps enough heat to sustain liquid water, and includes simulations of “unbound” super-Earths that are ejected from their star systems. The mathematical model [3] incorporates the initial heat from planet formation and radiogenic heat but does not mention tidal forces. [2]: https://www.nature.com/articles/s41550-022-01699-8 https://www.nature.com/articles/s41550-022-01699-8 [3]: https://github.com/mollous/Data_Liquid_Water_Conditions https://github.com/mollous/Data_Liquid_Water_Conditions --- The original article also includes this discussion of habitability: Life on the type of planet described in this work would live under considerably different conditions than most life on Earth. The surface pressures in our results are on the order of 100–1,000bar, the pressure range of oceanic floors and trenches. There is no theoretical pressure limit on life, and some of the most extreme examples in Earth’s biosphere thrive at ~500bar. These habitats also receive a negligible amount of direct sunlight, and therefore photosynthesis would not be an optional mechanism to provide for metabolism. Chemoautotrophic life on Earth would be a more likely analogue to possible life on this type of planet.
- deleted 4y ago
  [deleted]