15,000-year-old viruses discovered in Tibetan glacier ice
Another interesting article from Science Daily  
Scientists who study glacier ice have found viruses nearly 15,000 years old in two ice samples taken from the Tibetan Plateau in China. Most of those viruses, which survived because they had remained frozen, are unlike any viruses that have been cataloged to date.
So if life can exist in these extreme environments on Earth, could life also exist on other planets, moons in the solar system or Exoplanets and or Exomoons around other stars that have similar conditions.
“These are viruses that would have thrived in extreme environments,” said Matthew Sullivan, co-author of the study, professor of microbiology at Ohio State and director of Ohio State’s Center of Microbiome Science
So while the question of life out side of Earth is not the subject of this paper it does, for me at least, prompts the question could those conditions support life (even viruses) under any frozen surfaces.
I have created a discourse discussion for this . The article is under Biology.
There is also a link here and on discourse to an explanation of 'habitable zone' means.  so this states “neither too hot nor too cold”
1 Science Daily
2 Article Link
3 Discourse Link
4 Habitable zome