Note that this world is based off of the Apollo 13 conspiracy theory.
The Apollo 13 mission, originally intended to land in the Frau Mauro Highlands, was redirected to [insert location here] in order to investigate an anomalous formation (it also never had those problems thank to the government making NASA actually bother). The landing went as planned, with the vehicle touching down close to the anomaly. It was a large cube of fused silica, much larger than the moon lander. At first it appeared to be just a cube that had been damaged by meteorites and sandblasting, but closer inspection found that the cube was actually covered in inscriptions, confirming its artificial nature. Seismic data also revealed that it was not actually a cube, but a 1x1x2 with half of its mass below the lunar surface. The region around the landing site was found to be a former crater, filled with compacted rubble from deconstructed terrain nearby, which had been filled around the anomaly.
I have currently constructed an idea for some former inhabitants of the solar system :
PRECAMBRIAN : Possible precursors?
~510 MYA : the gateway builders arrive, along with their wormhole network. They were a race of machine intelligences with clarketech abilities.
PALEOZOIC : It is possible that there were others in this gap. It seems like the lunar cave anomalies [see below] were built between the Cambrian and Triassic, most likely in the Devonian.
201.3 MYA : Saturn Group (origin and biology unclear). Primarily active in the Saturnian system. Their homeworld was a former moon, the size of Mars, that orbited below Titan. It was destroyed in a warp drive experiment 201.3 million years ago, which caused the T-J Event and the complete collapse of their civilisation. It also killed almost all of Titan's surface ecology, disrupted the wormhole terminus around Sol and caused the Saturn system as we know it to form. It is believed that Iapetus, apparently a former centaur, was in the process of being towed into orbit around Saturn when the Event happened, but the programming of whatever they were using to do so continued to operate afterwards.
~150 MYA : Terran landsquid civilisation with spacefaring capabilities. Presumed to have had its space capabilities wiped out by revived Saturn Group technology.
~2 MYA : The Neptune Group was (is?) a slow silicon-nitrogen civilisation. It is known to have set up some space infrastructure in the far outer regions of the solar system, most notably in the Sun-Neptune L4 and L5. It may still be active.
<1 MYA : The Alpha Centauri Group (possibly the same as above) : [SEE BELOW]
Known anomalies [partial list] :
LUNA :
MONUMENT 13 : see above (appears to be of landsquid construction)
RdM anomaly : Actually a modification of the name of the first moonbase associated with the anomaly, now associated with the anomaly itself because of an incompetent reporter. This, at first, appears to be a lava tube with a gate on it, actually the first of a series of airlocks that lead to a deeper part of the lava tube, which contains a large cave with its own biosphere. Other than the gates and some broken-down fusion power generators, there is nothing else of note here. Other similar caves have been found on Luna, all but 3 on the far side, including some broken ones, but this one was the first investigated and the most well-known. Their ages are unclear, but are known to be more than 201.3 million years old.
THE LUNAR NODES : Large spherical crystals of what appears to be something akin to diamond. 3 have been found so far, all on Luna. Imperfections in the spheres appear to indicate that they are some sort of atomic data storage device, but so far all that has happened is that they look pretty (at least, that is what the government says). The three lunar nodes were all encapsulated in corundum cylinders with lead plating. They were discovered with 2 near each of Luna's poles and another near the sub-Earth point. However, one of the polar nodes was not located where it was stated to have been found. In reality, it was first ran across while it was located on a spire in the centre of a permanently shadowed crater by a nuclear-powered rover. An astronaut attached a rope to the top of the spire and moved over in suspension, returning with the node. However, while returning to the rover, the nuclear reactor aboard the rover detonated, causing the complete destruction of it and the other astronaut and destabilising the spire enough to cause it to collapse. The node, having been behind an object at the time, was not damaged, although the astronaut died. Later, another mission, ostensibly surveying the site of the previous disaster on its way to another anomaly, picked up this node. The actual anomaly turned out to be a piece of human space junk, so it was claimed that the node actually came from there and the space junk was the result of an earlier attempt to get to it and that the nuclear explosion had no relation to this. The sites all were disturbed by the Neptune Group, who likely built the spires, but it is believed that the nodes are oder.
EARTH :
Alien technology will probably be concentrated in desert regions and ancient cratons
The katabatic deposits in Antarctica are also important locations. The remains of a spaceship were found there.
A million-year-old alien computer, almost certainly of the Neptune Group, was found in a katabatic deposit in Antarctica.
MARS :
The face on Mars is still not real, sorry
BURIED CONTRAPTION : There is a partially buried contraption that appears to be similar to a rover. It is less than 2 million years old.
WHITE PYRAMID : There is also a symmetric hill made out of an unknown nearly 100% reflective material which is effectively frictionless, underneath which there is some sort of neutrino source. It was almost certainly build by the gateway builders
PHOBOS : You thought it was natural, didn't you? Sucker. Whatever it is, anything coming close enough to it blows up.
A large number of landsquid corpses have been found on Deimos.
GANYMEDE :
There is at least one cave similar to the ones on the Moon, except with an ammonious biosphere rather than a hydrous one.
EUROPA :
EUROPA MAGNETIC ANOMALY : There is a magnetic bubble that protects a region near one of Europa's poles. A structure close to the centre may be the reason for this. Its time of construction is unclear
TITAN :
TITAN CITY : Underneath a lake on one of Titan's poles is a massive complex of spires. They are deliberately not investigated, as with all other anomalies in the Saturn system, for obvious reasons, along with the fact that the Neptune Group appears to have avoided the Saturn system like the plague. However, this has not prevented humans from sending probes to orbit Saturn and even landing one on Titan.
OTHER :
THE WARNING SIGNS : On Ganymede and Iapetus, there are large "paintings" engraved into the surfaces that depict the activation of the Saturn Group relics and the resulting collapse of the landsquid civilisation.
AKKOROKAMUI :
Former codename of a large complex object discovered near Saturn left behind by the landsquid, hence the name. It probably was originally a Saturn Group artifact. It is not Hyperion. Also, its name is IAU-valid for an ungrouped moon of Saturn.
KAPTEYN : How the hell is the concentration of boron compounds in the atmospheres of those planets so high?
The Network :
Wormholes have to be located far away from stars ( >100 AU for the Sun). They fail if they come closer, and it is believed that all gates leading to the builders' home system were destroyed in this way. Unlike most alien technology, the gateway builders future-proofed the wormholes, and a large fraction of the network is still operational. Most stars in the network have multiple wormholes in orbit around them. Some wormholes are located in interstellar space (it is believed that they were formerly around stars but got ejected). Most of the stars in the gateway builders' network are believed to have been close to each other ~510 million years ago, but they have been scattered widely since then. For the others, see below. Wormhole termini will collapse if moved at higher than 0.5 of lightspeed, or if they are moved into a configuration that would allow retrocausality. Most of the stars that are wormhole termini whose systems show signs of habitation are the locations of dyson swarms much older than the currently occupying civilisation(s). The galaxy has a lot of dyson swarms, of which the nearest is located around Sirius. The gateway builders' network is the only confirmed wormhole network, but there are rumours of others connected to it.
LS/NG/AC :
It is unclear when the wormhole network around Earth was repaired after it was disrupted in the T-J Event. The three main hypotheses are that it was repaired by either the land-squid, the Neptune Group or the ALF CEN group, although the former is considered the most likely ; the reason why the others were proposed is that there is little evidence of aliens in the solar system between the landsquid and the Neptune Group. (There is also a fourth hypothesis, which is that the gates self-repaired). It is also unclear whether the Neptune Group or the ALF CEN group are the same. It is considered possible that the signal emitter at ALF CEN sent the Neptune Group to the solar system, possibly for the purpose of taking one of our wormholes to ALF CEN to serve their system. Similar thefts of wormhole gates are the most likely reason for the stars that were not in similar locations during the Cambrian.
