Mercury rules 1st and 4th house is in 9th house in Aquarius

Mercury in the 9th house in Aquarius sign is generally considered to be a favorable placement for native's ability to understand and communicate complex ideas. This placement promotes a strong interest in higher knowledge and opens up opportunities for higher education, philosophical ideas, spirituality and spiritual practices. The individual with this placement is likely to have good analytical and research skills and has a natural inclination to scientific and technical fields.

This placement suggests that the individual will be a quick learner and absorb information easily, particularly about different cultures and their belief systems. They may have a natural talent for teaching, espousing ideas and theories to others. Furthermore, those with Mercury in 9th house generally exhibit a good sense of humor, ironic wit and enjoy playful banter.

However, the Aquarius sign of Mercury can sometimes make the individual prone to being over-critical, skeptical and even detached in their analysis of certain ideas, hindering their open-mindedness. Therefore, they should work towards adopting a more receptive and empathetic outlook towards other people's opinions and views.

Overall, this placement highlights a need for the individual to focus on developing their intellect and broadening their horizons. They will likely benefit from enriching themselves through travel, educational pursuits and exploring different cultures.