So, lets see what Mercury can do in 9th house without any conjunction or aspect from any other planet. 1st lets see what these 2 things represent --
Mercury represents communication skills, marketing, calculative ability, younger siblings, hobbies, skills with hands, intelligence, quick decision making, logical thinking, youthfulness etc.
9th house represents Religion, Law, Faith, Fortune, Gurus, Teachings of Father (as father is 1st Guru we get) etc.
So, Mercury comes in to 9th house. This is natural house of Jupiter. Jupiter and Mercury are not too good friends with each other due to various mythological stories. Now, as Mercury represents collecting of information and 9th house is house of higher knowledge, Mercury here starts collecting all the information of higher knowledge and religion. When he is exhausted of collecting all the information, then the other side of Mercury comes up, which is Communication.
Now, this person wants to make communicate or spread the information he has learnt. This is where this position shows a teacher, professor, Guru or Guide or Counselor.
Apart from this, this person is highly intelligent as he is able to grasp all the higher knowledge provided by Jupiter from 9th house. They are highly interested in learning religious texts.
From 9th house, it aspects the 3rd house of communications, so they love to tell people around them about their higher learnings and sometimes due to youthfulness of Mercury, it is immature communication.
Hope this helps. Tomorrow Mercury in 10th house.
Vishal S Saxena - Astrologer