Containment Class:
euclid
Special Containment Procedures: Joint Project Nammu compartmentalization protocols remain in effect. Apzu 2 is en route to Jupiter, and will arrive in 2023. Apzu 3 and Apzu 4 are each in the construction phase for followup expeditions.
Description: SCP-XXXX is a subaquatic megastructure of alien origin, located on the seafloor of the Nerean Ocean on Europa, the second moon of Jupiter.
An isolated SCP-XXXX cell, in a typical state of disrepair.
Cartographic efforts are ongoing, but preliminary surveys indicate that SCP-XXXX primarily consists of a network of hexagonal cells, ranging from several meters in height and width to roughly 2 kilometers in height and dozens of meters in width, in areas of especially dense concentration. These cells are primarily composed of concrete derived from the available rock and sediment in the seafloor, but also contain various as yet unidentified and potentially anomalous materials. Also present are a minority of simpler circular structures, which tend to be substantially smaller and more isolated from the denser hexagonal structures. In total, at least 20% of the Nerean seafloor analyzed thus far by Nereus is occupied by SCP-XXXX.
At least 36% of SCP-XXXX structures in excess of 600 cubic meters and a much greater proportion of its smaller structures are compromised by water. Many of the structures, regardless of size, display signs of serious damage, appearing incomplete, warped, or highly eroded. Despite the level of disrepair, non-invasive scans have yet to penetrate the interior of any the structures.
Also of note is that, as yet, no evidence of any kind of bacterial, fungal, plant, animal, or other known biological life form has been located anywhere within the Nerean Ocean (or on the surface), other than the presence of SCP-XXXX.
Addendum XXXX-1: Apzu 1 Expedition
Since Nereus had been constructed merely as a test craft, it was not designed to function long term in the conditions of the Nerean Ocean. Over six months, it mapped the seafloor from the underside of the Europaen ice crust before shutting down entirely.
To continue its mission, Joint Project Nammu commissioned a new series of spacecraft specifically designed for missions to the Europaen subsurface, designated the Apzu series. The first Apzu was launched in March of 2013, and arrived at the Jupiter system in January of 2019.
Date: 1/29/2019 - 2/5/2019
Foreword: In order to avoid the logistical and ethical issues with human deep space flight, Apzu 1 was crewed only by a .aic unit designated Enki.aic, incorporated especially for this mission. Enki.aic was programmed to come online and assume mission control functions upon achieving Jupiter orbit.
Irrelevant data omitted.
Enki.aic: Jovian orbit achieved. Command and control packages online. T minus 10 hours, 12 minutes, 7 seconds to descent.
Apzu 1 descends to the surface of Europa.
Enki.aic: Landing achieved. Initiating ectoentropic drill.
Apzu 1 drills into the surface ice for 3 hours, penetrating to the Nerean Ocean.
Enki.aic: Subsurface penetration achieved. Deploying to UUV.
Enki.aic installs itself onto Apzu 1's exploration submersible and disengages itself from the landing craft, descending into the water at approximately 10kph. Within 3 hours and 10 minutes, it obtains a visual of an isolated SCP-XXXX structure.
Enki.aic: Visual contact with SCP-XXXX instance established. Navigation reference established. Proceeding to phase four.
After 7 hours of travel, Enki.aic approaches a denser concentration of SCP-XXXX structures. Close examination indicates that virtually all SCP-XXXX structures display evidence of substantial erosion to their outermost layers. However, all structures appear seamless and watertight, and Enki.aic's limited instrument package is unable to discern anything about their interiors. No apparent meaning can be discerned from the relative sizes and positions of the structures mapped by Enki.aic. Furthermore, no evidence of any sort of inter-structural vehicles or any other kind of external technology is identifiable.
Several days of exploration pass in this manner, before Enki.aic enters a structure constructed of several hundred cells that have in various places fused together, as though affected by lava flows. This structure incompletely covers a large depression in the ocean floor, believed to lead to an as yet unknown artificial subterranean structure or group of structures. Before it can progress more than several dozen meters inside, Enki.aic is immobilized by unknown means.
Enki.aic: System failure. Propellers nonresponsive.
Unidentified object, approaching Enki.aic.
Enki.aic attempts various diagnostics and workarounds, but is unable to solve or diagnose the problem. After approximately 30 minutes, it is approached by an unidentified, slightly luminous ovoid object. The object closes to very near proximity to Enki.aic and extends some form of limb or limbs, pulling it deeper into the structure. As this occurs, Enki.aic's field of view is obscured by the object reforming itself around it, and it abruptly shuts down.
Afterword: Given Enki.aic's confirmation of currently active, apparently extraterrestrial living or technological forms of unknown capability, SCP-XXXX was upgraded to Euclid. Existing assets in the Jupiter system are to be considered available for reconfiguration should SCP-XXXX become a greater security concern.
Per 
