By the way, we owe young HeathrowAirport a response to his/her idea that the module memoire might float.
I don't think it can float. Part of the thermal protection system involves a significant mass of metal which acts as thermal inertia for the memory modules. This is inside of the shielding layer of insulation. Then the whole thing is wrapped in a steel canister to protect it against the crash environment. With all that metal, the memory modules should sink like a stone.