Thanks, Dilyn, for clearing that up. I was hoping my assumption about Daniel was correct but no such luck. That does leave us with the possibility that Daniel is inoperative, or the more paranoid notion that the mission was compromised from the start and Daniel has been subverted.
Is there any way differentiate the source of a signal? What I mean is can we be certain that a response is coming from a particular probe just because it identifies itself in a way we expect for a particular unit? I am wondering how we can be certain of which probe is reporting in when? Could one be impersonating another? More than one?
What if Daniel is not inoperative? What if he was reprogrammed before the mission was sent and is now an "agent" of one of the hostile forces on its way to Mars? That would explain his silence and could also go a long way to explaining why the other probes are not aware even of some wreckage that could have once been Daniel.
One last point... Was I essentially correct that the transmission system does include the authentication codes with anything we send? Obviously, we the casual users do not know them, but they must be sent along with our messages. If not we must then lean why the probes are responding at all.
Thanks for answering my WSU-like meanderings.
Space Turtel
(WSU = Wild Speculation Unit. I'd give credit where it is due for that one, but I have to apologize for not knowing to whom it belongs.)