Rose then says "so, are we in the future then?".
The Doctor sits examining some of the ice, he sees water below the ice and says "what makes you think that?".
Rose points at the ice and says "well, I know there's no ice on Mars now?".
The Doctor then points to the sky and he says "look up there" Rose looks up and nods "what am I looking at? There's nothing".
The Doctor nods at her "exactly, Earth hasn't even formed yet, Mars is only in it's early days, a lot changes over the years and centuries".
Rose then says "so, is there any life?" The Doctor then says "well-".
Suddenly, an Ice Warrior then shouts "do not move, you are prisoners of the Ice Warriors!".