Long time ago, Gehenna meant something to a lot of folks in fancy suits. The Company used it as a testing ground for tech too dangerous for more civilized corners of the galaxies, chewed it up and spat it out. Now the Company's gone, and all that's left is a rock. Whatever they were testing for, it seems they didn't like the answer.
— In-game description
Gehenna is a rocky planet that once was utilized by the Company as a testing ground for powerful technology deemed too dangerous to be tested elsewhere.