Thalassia

Thalassia is the second planet in the Acumense system. Slightly smaller than Sol's Jupiter, apparently made mostly or entirely out of high-salinity, nearly anoxic water. No geologic crust is detectable, and dive teams have yet to reach any kind of ocean floor. Very thin atmosphere of mostly hydrogen and oxygen gas, but abnormally low winds. The air pressure remains more or less uniform across the entire surface. Many species cannot breathe properly due to the thinness of the gasses, and will quickly expire of hypoxia if unprotected. There are no polar ice caps, a physical impossibility considering the planet's composition, overall temperature, and rotation. Thalassia has a 31-hour day cycle, but despite lengthy exposure to the sun's rays, water does not evaporate at expected rates while within the planet's local gravity well, nor is heat absorbed or transferred normally, with temperatures remaining more or less constant throughout the ocean and atmosphere, close to 41°F.

It is theorized that Thalassia appeared in the Acumense system approximately 32,000 years ago, and that the introduction of the planet into the system is the cause of Petriva's gradually decaying orbit. Thalassia currently maintains a perfectly circular orbit around Acumense, with no signs of deviation.

Thalassid

The Thalassid is the unofficial name given to a titanic entity of unknown physical description located at or near the planet's core. Popular theories posit that the Thalassid itself makes up the core of the planet, with no geologic surface of any kind present, but evidence for this theory is insubstantial.