|Mass:||0.96 Earth Masses|
Though not suitable for life and inhospitable to most machinery, Tetanion X is a major point of interest to scientists, because its very existence defies logic, and everything known, or at least thought to be understood, concerning planet formation. It has only a tiny core, surrounded completely by ice, yet has a form of volcanic activity, which keeps its cold atmosphere from completely freezing. It is believed that the "volcanoes" on it surface are the result of pockets of unfrozen water under pressure and heat from the tiny, but active core.
Ghost, its lonely moon, is believed to be the former core of a hypothetical sister planet, Tetanion Z, which was probably stripped of its atmosphere and most of its liquid water by none other than its big sister, Tetanion X. Though it has no atmosphere, Ghost has a weathered surface, with most of its numerous craters showing signs of being filled in or worn down by some kind of weathering. Bands of ice also lend to its ghostly, and eerily undead appearance.