Rhea Base was established by the Earth Space Defense under the jurisdiction of Russia sometime after June 2013. It was designed to be the outermost point in the ESD's defense network. Rhea Base was under the command of Commander Piotr Belyaev. The base was built along the lip of a giant crater.
By 2016, Rhea Base was currently under construction and experiencing power shortages, and a total communication blackout. On July 2, 2016, a gravitational anomaly appeared above Rhea (caused by the Harvester Mothership) which forced Rhea Base's personnel to evacuate. Unfortunately, the anomaly turned into a wormhole which consumed and obliterated Rhea and the ESD crew, thus becoming the first casualties of the War of 2016.
The ESD on Earth first became aware of Rhea Base's loss after they were unable to receive contact from the base. After repeated attempts to contact Rhea Base, the ESD used the Hubble Space Telescope to examine Rhea in which they find it gone.