Funny you should say that, i've had a screencap from Total Recall as my desktop pic for a while now. That movie had some really beautiful scenery in it.
Meh well, even if that rover came across a full blown alien city they'd still only show us pics of rocks and sand.
The ramifications of showing actual developed alien life would be beyond comprehension, , the word would erupt in panic and turn to religion. Prolly would be like entering a new stone age.
I don't think intelligent life was ever possible on Mars (climate, atmosphere). They are more likely just looking for signs for the possibility of bacteria and tiny cell organisms to have existed there, somewhen.
I wouldn't be thinking about local martian life in that context,more like an alien species far mor advanced than our own who have established a colony on Mars.
That seems entirely possible, if they have the tech to travel across those vast distances they sure as fuck can manage to survive on the surface.
If they have the tech to colonize Mars we'd not stand a chance versus them if they were hostile. They probably wouldn't even bother to talk to us and just annihilate us if they felt provoked in some way.