The following answer currently has five up votes, and was written by a moderator of the site.
I'd like to know if this answer, without any supporting statements at all, qualifies as a good answer here in Space Exploration stackexchange, considering the number of unsupported answers from other low-rep users which we downvote, or which sometimes receive special moderator annotation with warnings about unsupported statement, or are even deleted.
Why is this a good quality stackexchange answer, and an appropriate example for a moderator to demonstrate to new users?
Yes, in fact it can happen. It happens on Earth to some extent. The term is a "Gas Pocket", and is most commonly associated with oil and natural gas deposits. There are other times of gasses that are sometimes stored as well under the Earth.
If there is a connection with the outside world in the form of a small hole, then the likelihood of there still being any gas in it is much lower. The only way this would work is if the gas was very heavy. Again, this happens to some extend on Earth, most notably in Radon being concentrated in some basements.
The only way that it could sustain long term an atmosphere is if it was completely sealed up, or if there was a source generating the atmosphere on a regular basis.
I've left the following comment:
The question states there are small holes, so gas pockets are not an answer. Can you add some science to explain why "heavy" gas makes it work if there are holes? If there were holes, wouldn't you need to propose a source to replenish the gas in order to make your answer more than unsupported speculation? The science is already available at the links I've left under the question. This is a very low quality stackexchange answer, and is indistinguishable from an opinion. It's just a series of unsupported statements, some of which would in fact be difficult to support with science.