History
The so-called "Second Moon" or "New Moon" was claimed to orbit around the Earth and was invisible from detection, at least by 20th Century detection methods. The aliens who lived there claimed that they needed to take water from the Earth in order to survive it's rotation around the sun. They developed a device that pulled the Earth's entire water supply so they could take the amount they needed then return the rest. If this is to be believed, then the New Moon's orbit must take thousands of years as there are no recorded incidents of Earth's surface water being stolen prior to 1954.[1]
In that year, the Second Moon came into orbit around the Earth, eclipsing the sun. The aliens then pulled Earth's water supply to their planetoid causing a sudden an near complete loss of surface water on Earth, sending the planet into chaos. The Sub-Mariner traveled to the planetoid by riding an exposed underground water supply that was pulled to the planet when exposed. There Namor, who was blamed for the water shortage by the United Nations, attempted to convince the aliens to keep the water. However after getting a telepathic distress message from his mother Princess Fen, Namor realized that Atlantis was doomed if the water was not returned. Namor fought the aliens and returned the water to Earth.[1]
The so-called Second Moon then moved out of Earth's orbit and has not been seen since.