Origin of life on a waterworld

Question

Take a planet like Gliese 1214 B, which has no land, an ocean 100s of kilometres deep and a seabed of Ice VII. For the purposes of the question, let's assume that the pressure and/or temperature near the bottom makes it simply impossible for any form of life to survive. Maybe it does.

Of all the plausible posited models for abiogenesis, excluding panspermia, could any occur in these conditions? If the deep truly is uninhabitable, then abiogenesis will have to happen without any solid seabed, and therefore without hydrothermal vents, clay etc.

Answer 1

Organic molecules delivered by comets.

https://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_s_comet_contains_ingredients_for_life

Ingredients regarded as crucial for the origin of life on Earth have been discovered at the comet that ESA’s Rosetta spacecraft has been probing for almost two years.

They include the amino acid glycine, which is commonly found in proteins, and phosphorus, a key component of DNA and cell membranes.

Scientists have long debated the important possibility that water and organic molecules were brought by asteroids and comets to the young Earth after it cooled following its formation, providing some of the key building blocks for the emergence of life.

Your water world suffers a constant and generous rain of greasy organic space shmutz. The long chain hydrocarbons all float, entrapping other hydrophobic molecules. Rafts of this waxy filth accumulate on the gentle oceans of your world. These serve as a substrate for tholins and other organics from space to combine and recombine under the gentle radiant proddings of your star. I envision certain molecule might avoid sinking into the deep by virtue of their ability to accumulate their own buoyant collection of hydrocarbons. Just as with earth, selective pressure will favor molecules of this sort which can replicate themselves and their ability to stay at the resource-rich surface. These go on to be your waterworld's life forms.