In the linked-to article it says:

During the day, one of the features - nicknamed "Annie" - is warmer than surrounding pits and cooler than sunlit areas.
Night time temperatures are warmer than nearly all surrounding areas.

http://news.bbc.co.uk/2/hi/science/nature/6461201.stm

My suspicion is that these temperature differences are caused by water vapour. The atmosphere of Mars does have clouds and the polar regions have ice, so how do the clouds form unless the moisture evaporates somehow.
Perhaps these “pits” are places where the ice is able to melt and evaporate, that of course needs the ground water system to be liquid, at least some of the time, and like on Earth, the water flow would be towards the lower area which will then replenish the moisture in the pits.

At least on Earth, when there is moisture or liquid water there usually is also some type of life associated with it.
Mars seems to have all the ingredients needed for life such as carbon, water, energy etc., so why not life?

Conjecture on my part naturally, but still knock on the door before you enter the pit. ;-)

I’m certain that the puzzles will be solved eventually, and what ever the truth is, it will be accepted by everyone.