What type of life is considered most likely to thrive in the dark, geothermally heated subsurface environments of rogue planets?

Answer

Extremophile microbes relying on chemosynthesis.

Due to the incredibly low energy flux compared to stellar input, the most probable life forms would be hardy microbes utilizing chemical energy sources (chemosynthesis) found deep within.

What type of life is considered most likely to thrive in the dark, geothermally heated subsurface environments of rogue planets?
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