LJK asked:

"The question is, could life survive under the Martian surface away from the cold temperatures and unfiltered ultraviolet rays?"

I think we're agreed that nothing could live on the Martian surface today. However the $64,000 question is whether something could ever live deep underground on Mars? MER-B seems to indicate that condtions at Meridiani a zillion years ago might have allowed an archaea bacteria-like organism to survive. However this raises a whole bunch of questions: How long ago was a "zillion years"? Was the Meridiani aqeous area on the Martian surface or deep underground? Are there areas underground on Mars today with conditions like Meridiani a zillion years ago? Meridiani may have briefly provided conditions hospitable to archaea. However did Meridiani or anywhere else on Mars ever provide conditions enablying biogenesis? My semi-educated engineers hunch tells me that a planet needs an ocean for biogenesis. Evidence indicating that Mars once had an ocean has been refuted (Oceanus Borealis). The best permanent surface water condition that the Meridiani evidence indicates is moist surface sand.

Gary