There is a sentence that seems to imply that the frozen status implies there is no life. I'm not so sure we can be sure of that. There are microbes on Earth that basically live in virtually frozen environments. (All you need are moments when the water is liquid.)
All you need are moments when the water is liquid.
But you don't get those at such low atmospheric pressure. Mars atmospheric pressure is around 600pa. Below 611pa, the boiling point of water drops to the freezing point; you can have ice or steam, but not liquid water.
An unsealed hole underground would have to be dug to the same depths as that crater. If you're pressurizing it, you'll probably target 1 bar to live in it, instead of 600 KPa.
A glacier that has the pressure to melt ice, would have more than enough pressure to keep it from sublimating. A rough estimate says that a foot or so of ice could provide over 600KPa of pressure, but that doesn't account for any means of keeping the water liquid or the ice solid. However, I wouldn't expect to actually find that on Mars. You might be able to keep water that way for a while until it froze again.
They do have recent satellite images that appear to show signs of water running down ravines at certain times of the Mara year. Don't have a citation handy, though.
You could even just have life that moves more slowly because of the lower available energies. If we ever find some life that does not have an Earth origin perhaps we can finally get some more data points about what environments are really required for life.