Life in Jupiter-like conditions?

Question

In a neighboring star system to my Conworld, there is a jupiter-sized planet that many of the species believe to harbor life.

The star it is orbiting is a red dwarf, and the aforementioned "Re-Jove" has about 90% the mass of our Jupiter, and within the star's habitable zone.

Its chemical composition is extremely similar to Jupiter, but with ammonia compounds in excess.

In these high-pressure, high-temperature conditions, could life evolve, and even thrive? If so, where? keep in mind, I am not asking for the creature's biology, only if life is plausible.

Answer 1

Jupiter has no surface to speak of - the hydrogen atmosphere just thickens more and more until it becomes it becomes liquid and later turns into metallic hydrogen (yes, there is such a thing). Physically, there is no clear boundary — the gas smoothly becomes hotter and denser as one descends. Hence, you are going to need to have life evolve in the atmosphere (unless you invent some extremely exotic life forms living in metallic hydrogen).

There are layers in Jupiter's atmosphere where both pressure and temperature are earthlike (10^6 pascal, 300 kelvin) - see graph. This layer has clouds of water, also similar to Earth, and layers above have clouds of various nitrogen compunds. This would be a good place to imagine life. In fact, Arthur C. Clarke did exactly that in his novella A Meeting with Medusa. The protagonist discovers that Jupiter's atmosphere supports at least two large forms of life, as well as microscopic and bioluminescent air plankton, producing atmospheric sea-fire. One form is a giant jellyfish-like creature (the Medusa of the title) about one mile across, and the others are manta ray-like creatures about a hundred yards wide that apparently prey on the Medusa.

Such life would have to float in the atmosphere (or live on larger lifeforms that float). They would have to be very light, possibly using bags of heated hydrogen to stay afloat.