This is a fiddly topic, as there are issues with things like people throwing walls of glass up (there are trolls out there than think it a good use of 7$ to greif until they get banned) or the terrain on Ion spontaneously loading mountains in to the same space you are currently flying through as you try to land.
Sanctuary and Alioth should retain ownership for a large period as these are the starting areas for new players, perhaps two weeks, as it easily permits time to recover, but allows salvage on things when people crash and then quit or for some other reason dont come to re-collect it. Thadies and Madis probably need the same as it provides time for new players doing their first interplanetary run in the safe zone time to get back to their stuff after probably slamming in to a planet at top speed with their only interplanetary ship.
Other planets in the system should give you a few hours so you have time to contact an admin to deal with griefers, with the caveats that this grace-period be removed when the safe-zones are taken from those planets as it will officially be open pvp, and that there be a universal 24hr grace-period after any patch deployment to deal with bugs.
Taelessael got a reaction from merihim in Salvaging - Nerfed as a casualty or by intention?