extra-terrestrial
*extraterrestrial
unknown, attempted
*unknown, and attempted
and contradictory result.
This is kind of an awkward way of putting it — I'd personally say ", and sometimes contradictory, results."
██ and ██ × 10██ years
Scientific notation seems a little odd here, as ages aren't usually written in that fashion. I'd recommend saying "millennia", and adjusting the ██s to match.
SCP-XXXX exhibits different effects when touched … SCP-XXXX seems to detail the extinction of humanity
This entire section seems, well, kind of cluttered and informal. There are numerous SPAG issues, and it reads almost like a ramble. I'd recommend a complete restructuring, with emphasis on a precise description.
This is the point where I stopped reading for specifics. Here're my general thoughts:
Essentially, this SCP doesn't quite…work. It's supposed to detail the history of the human race before they came to Earth, which itself doesn't really work. The cube itself isn't particularly interesting, so you have to make the backstory the focus of the SCP.
Unfortunately, as I said, the backstory isn't that engaging. It's using humanity, which doesn't add anything, it's about a well-traveled and disproved sci-fi concept, which detracts from the general effect, and it's nothing even remotely new, which is, ah, damning.
However, there is a rather simple solution:
Make it the story of the end of the Martians, not the humans. Have the Martians be the civilization which ended, have the discoverers not be the Russians, but that one branch of Prometheus Labs which was apparently on Mars (in fact, you could have this entire thing not be an SCP but be written in Prometheus Labs format or a tale involving Prometheus Labs). If that, then have Prometheus Labs be trying to replicate the tech seen through the cube, which could have interesting results.
