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After reading a couple dozen entries about rogue planets and their implications (for those unaware, a rogue planet is a planetary mass that has been separated from the star by gravitational instability or otherwise forceful means).

If a planet was geologically active underneath the surface, enough so that the surface of the planet was heated above freezing temperature, would it be viable for life to evolve on the planet? The planet would, obviously, be bombarded periodically by meteorites of various sizes, and the surface must be exceedingly cold. But, as theorized with a few moons in our Solar System, wouldn't underlying water be able to be heated to the point where life is possible?

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Yes! The more we discover on life, the more we realize it'll evolve anywhere it can. Europa, moon of Jupiter, could likely support life using heat that's generated from the gravitational interactions of it and Jupiter.

However it is questionable how far this life could make it as you require some stability to have anything beyond basic cells start to evolve. The universe is a messy place and this planet could easily be under constant bombardment by asteroids. But more over, our sun supports what is known as the Heliosphere. Just like Earth, the sun supports a magnetic field as it travels through space that deflects much of what would kill life on Earth...cosmic rays, solar winds, and all sorts that would have a catastrophic effect had it interacted with any life form. Outside of the Heliosphere in intergalactic space, we can see things like protons travelling 99.99999% the speed of light (only way we can detect this is they occasionally shoot neutrons at us). This is an atom with the energy of a baseball going 100mph...if that strikes a cell, it ain't surviving. What exactly is protecting this rogue planet from the harshness of stellar weather?

So the answer to your question ultimately becomes 'define life'. If you are looking for single celled organisms, it's gotten to the point that it's hard to deny that they would be there. Extremophiles thrive on Earth in some of the harshest conditions possible. We can find life on Earth capable of repairing it's own DNA, which would likely be an essential component of life on this rogue planet. So the possibility is there...However if you're talking some relatively advanced life, even creatures like small fish, then this life is going to have to overcome some incredible odds (like surviving space weather) in order to survive.

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  • $\begingroup$ "Rogue planet" mean no star nearby. That means no energy. Thus, no dynamic processes, no evolving life. $\endgroup$ – enkryptor Aug 9 '16 at 17:25
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    $\begingroup$ @enkryptor - just because it lacks a star to orbit, it does not mean it isn't being gravitationally effected by the bodies it passes and interacts with. Even a rogue planet is going to enter a star system and be flung out of it from time to time. $\endgroup$ – Twelfth Aug 9 '16 at 17:43
  • $\begingroup$ @enkryptor There are dynamic processes present. The OP specified the rogue planet is geologically active. $\endgroup$ – a4android Aug 10 '16 at 7:04
  • $\begingroup$ How can it be possible, when the planet only looses energy and not receives it? $\endgroup$ – enkryptor Aug 10 '16 at 9:16
  • $\begingroup$ @enkryptor - what a4android and I just stated is it does and can receive energy. The sun/star is not an end all in receiving energy for a planet...gravity, magnetic, raditation (internally and externally via 'space weather'), etc... are all additional methods a planet can receive energy through $\endgroup$ – Twelfth Aug 10 '16 at 16:26
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The moons in our solar system are around large gas giants and most of their internal heat is being generated by tidal pressures from the gravity of the gas giants they are orbiting. Your rogue could have a similar setup if it is part of a rogue system of moons around a large rogue gas giant.

The other sources of internal heat in planets is the residual energy from formation and the decay of radioactive elements. The formation energy comes from all the kinetic energy of the coalescing asteroids and other bodies that came together to form the planet and could be quite high. Some of the elements in the core are also radioactive and their decay releases energy also providing heat. Your planet could always tweak these parameters to increase your rogue planets heat budget.

https://en.wikipedia.org/wiki/Earth%27s_internal_heat_budget

As the Earth's internal heat has been going for 4+ billion years this should easily provide enough time for life to evolve.

For Earth analogues look at the life present around deep sea thermal vents.

https://en.wikipedia.org/wiki/Hydrothermal_vent#Biological_communities

Also if this planet has left its star and gone rogue it is very unlikely to suffer asteroid impacts. Space is big and empty away from stars.

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This is quite feasible. The key point can be found in the Wikipedia entry on rogue planets

Interstellar planets generate little heat nor are they heated by a star. In 1998, David J. Stevenson theorized that some planet-sized objects adrift in the vast expanses of cold interstellar space could possibly sustain a thick atmosphere that would not freeze out. He proposes that atmospheres are preserved by the pressure-induced far-infrared radiation opacity of a thick hydrogen-containing atmosphere.

If the rogue planet is geologically active, this is something the OP specified, then there is a good chance that a biosphere could develop. Most so in the light of what is known about the extreme conditions where life can survive.

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Theoretically it should be ok so long as heat generated by the planet itself was not escaping at too high a rate.

However

Due to the lack of any kind of inbound energy to substitute for a star, photosynthesis would be impossible, therefore an ecological biosphere would be unsustainable.

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