I am confusal about something from the Saturday briefing. the panel first explained the rationale for the choice of site: The ice is likely to have preserved a record of ancient climate/life when/if Mars had a warmer past. And that Phoenix will detect. But the last question from the press about the origin of this tundra surface was explained as a refreeze of meltwater from an impact.

They didn't quite finish the train of thought. Is there a contradiction between these two things. In other words, would the impact erase the the historical evidence of life in the meltwater?