"Prisoners of conscience" perhaps?

Some people are accused and convicted of a crime, know they are at fault, and even want to be sentenced for their crime. EG, they knew they were negligent, made a mistake they should not have, etc.

Such types could potentially feel almost relief with such exile, if their personalities aligned with that of an explorer. And if they truly desire censure, punishment, "doing their time" on Mars, instead of rotting in a jail cell, may seem very good to them.

Of course, lots of profiling would need to be done -- but, that is already done for such missions.