The object was first noticed by a US early warning system designed to detect intercontinental ballistic missiles; it was flagged as an error as the trajectory, speed, and destination were well outside the parameters for a nuclear strike. What possible use would there be in firing a missile at remote Bouvet Island in the South Atlantic, especially if the telemetry that indicated the object came from a lunar orbit was to be believed.
But remembering the Vela Incident of 1979, which may or may not have been a covert nuclear test, the US government duly warned Norway, which administered the remote and glacial rock in question. Bouvet Island was uninhabited but did feature an advanced weather station complete with a satellite link and video feed; the Norwegian government made this data available to the US as the object approached. It recorded impossible atmospheric conditions, a surge of radiation, and what appeared to be infrared or ultraviolet lights in the sky before the transmission was abruptly terminated. The object disappeared from scopes immediately afterward.
Unable to image the site due to heavy cloud cover, the light vessel USS Eldridge was dispatched to investigate with a hastily assembled American-Norwegian survey team aboard. Upon reaching a distance of approximately 6.2832km from Bouvet, contact with the Eldridge was lost after a few badly distorted final transmissions. A few pieces of debris traceable to the ship washed up on the coast of South Africa some months later. A second ship, the frigate HMAS Darwin, sought to investigate at the request of the American and Norwegian governments after the Eldridge vanished. It too vanished on reaching a position 6.2832km from shore.
With over 300 people now missing near Bouvet, any further attempts at investigation were suspended. Instead, several spy satellites equipped with radar and other advanced telemetry were moved to orbits above the island. In each case, the satellites malfunctioned shortly after arriving on station, as if they had been affected by a powerful electromagnetic pulse. Intense analysis of the fragmentary data seemed to indicate some kind of new construction on Bouvet and a series of bizarre trenches in the glaciers there. The designs and patterns of the structures and glacial trenches, such as they could be discerned, matched no known architecture.
Since that time, despite rampant speculation, no satellites, ships, or aircraft have approached Bouvet by order of the International Maritime Organization. Private vessels have attempted landings, often at the behest of fringe groups, but all have disappeared with only the occasional bit of scattered wreckage to attest their fate.
Whoever or whatever landed on Bouvet has not sought to interfere, but will brook no interference itself.