[ooc: A series of notes Hojo stole from other scientists summaries of Hojo's findings on JENOVA, the Lifestream, Geostigma, Deepground, and SND, which are floating online and available to those who can hack through Shinra security and download them. It's very much incomplete at the moment, though I will come back and update them as I get more written. This post serves as a way to gather my own thoughts about the very... interesting 'science' present in the games. OOC comments are more than welcome.
Thanks to Shelke for all her help and encouragement. :3
Also note that although I based this on canon, most of it is pure BS pseudoscience I made up for fun, because I am a nerd. So if I say anything about your character that you disagree with, please by all means ignore it.]
(Portion of Gast's earliest notes, with later annotations made by Hojo marked with 'N:')
The alien known as Jenova is an organism unlike anything on earth. It is not a biological specimen - the most apt description is that it is a a form of free energy, not unlike the Lifestream in its properties. Its survival on earth depends on altering the genome of infected cells within a host organism, inducing a type of malignant neoplasm. Unlike the known kinds of cancer, however, the growth and proliferation of affected host cells can be directly controlled and influenced by Jenova. Infected cells within the Central Nervous System, particularly the brain, are responsible for the altered behaviour seen in affected individuals - aka the 'Puppet Effect' [N: refer to notes on Jenova's Will].
Approximately 2000 years ago, the Cetran race encountered the Jenova 'virus' (aka. 'Crisis from the Sky') for the first time. Texts from the time describe a being able to 'shapeshift' into different forms, resembling a victim's relatives or friends, to lower the victim's defenses, though whether this was a result of a real physical manifestation or hallucinations caused by Jenova's infiltration into the brain is unclear [N: both cases now confirmed; refer to notes on Geostigma]. The latter is more likely, at least in the first stages of Jenova's invasion, as the acqiuring of a solid body, able to shapeshift or not, depended first on the successful invasion of host organisms (this will be discussed later). Affected individuals displayed a score of psychological symptoms, including psychopathy, delirium, and thought disorder, as well as the systemic symptoms characterising active cancer. The 'disease' exhibited both high morbidity and high mortality, and those who did not die from contact were more often than not rendered mentally disabled for life.
It is unknown when the biological body of Jenova, found in the Northern Crater, was established. Here, the word 'established' is used because tests have shown Jenova's body to be composed of a myriad of different cells with different genetic make up - ie, its female form is more alike a 'colony' of cells taken from other organisms than an organised, individual being in itself. How it manages to maintain this remarkable form is material for further research [N: refer to notes on Jenova Reunion Theory], but according to Ifalna, the Cetra's efforts to seal the lifeform using the Lifestream were only successful once Jenova became bound to an earthly body. This may be due to the complex and specific interactions between Jenova's so-called 'Will' (aka its initial, metaphysical form), and the Lifestream, which, as previously mentioned, shares with the alien certain crucial characteristics.
Description and analysis of the properties of the Lifestream and its various states belongs more to the field of physics, though a very brief summary will be given here for the sake of completeness. The Lifestream exists in three distinct phases - the 'Life' phase, unique to the Lifestream, exhibited as an emerald haze (NOT gaseous, as previously thought); the liquid phase, a form inducible and maintainable only under stringent conditions (aka 'Mako'); and the solid phase, a supercondensed form which is able to interact with and manipulate the Life phase in its immediate vicinity to create certain effects (aka 'Materia' and 'Magic'). The Life phase, being singular, has always been the most fascinating and also the most difficult to study.