Thermo Spheres are leaping balls of lava that appear on Bion during M20: Insurrection in Metroid Prime: Federation Force. They are first encountered during the mission in a maze shortly after the Federation Force lose their Mechs. They will roll around the maze and cause damage to the suitless Marines, so care must be taken in navigating the maze to avoid them. Thermo Spheres are next encountered, in fewer quantities in a corridor suspended above lava. They leap out of this lava and damage any Marines that may come into contact with them. However, these ones are avoidable. Thermo Spheres cannot be destroyed with most weapons, except with one shot of ice or with the Charge Beam, and are similar to Squeepts and Puromi in terms of appearance and behavior.