Complex sentence: The cobalt is of a state that does not occur on Earth, and is the only evidence of a close encounter with its makers; only Snowy, who cannot speak, remembers the hijacking and alien abduction.
Split into simpler sentences: The cobalt is of a state that does not occur on Earth, and is the only evidence of a close encounter with its makers. Only Snowy, who cannot speak, remembers the hijacking and alien abduction.