Tharsis Major was a small Atlantean outpost located several hundred miles off the coast off the state of Maryland, United States of America. Much of the outpost was nearly destroyed when the US Navy submarine the U.S.S. Dauntless collided with one of its towers, raining rubble onto the rest of the outpost. When Navy SEALs attempted to rescue members of the damaged submarines, they were attacked by Atlanteans from the outpost. Namor arrived to intervene and defend the outpost and was then attacked by the arriving War Machine. Their fight was broken up when a female Navy captain encouraged them to focus on a joint rescue effort. The submarine and its crew were saved. It is unknown if the outpost was repaired.