Natal house is the sign where a planet was originally placed during your time of birth.
If Jupiter was placed in Aries in your personal horoscope, then during transit, Mercury forming conjunction (in Aries), sextile (aspect of 60° which are Aquarius and Gemini in this case), square (aspect of 90° which are Cancer and Capricorn here), trine (aspect of 120° which are Leo and Sagittarius here), opposition (aspect of 180° which is Libra here) are discussed in this article.
Conjunction is transiting through same sign as in birth chart, sextile is transiting 3rd or 11th house, trine is transiting 5th or 9th house, opposition is transiting 7th house from natal sign.
Transit Mercury conjunct Natal Jupiter : Optimism, educational and work planning related to long range goals etc. characterize this transit. A favourable transit for commercial communications and transactions and gains through investments. The native is intellectually interested in religion, foreign cultures, philosophy, travel and higher education. The native may get into the right field of his future employment. A good period for advertising, publicity and signing agreements. The native has hormonious and amicable relations with coborns and neighbours. The native takes interest in social welfare and charity, reconcillation with opponents and in group activities. The native should not get carried away in over enthusiasm and over confidence if the transit is under afflictions.
Transit Mercury Sextile Natal Jupiter : Positive mental outlook and a zeal to make social contacts characterize this transit. A good time for individuals employed in literary pursuits like news communication media, lecturing and teaching. The native is engaged in journeys to understand foreign cultures and remote things. The individual sometimes has prophetic insights into future trends and development. The native is able to get proper medical advice and diagnosis for lingering illness.
Transit Mercury Square Natal Jupiter : Lack of attention, laziness, unrealistic thinking characterize this transit. The native tries to achieve his goals very early without a discipline. The native lacks clear focus in intellectual efforts. There is misplaced sympathy and hypocrisy in the native’s ideas. This is not a favourable period for any kind of change. Under this transit the native is always troubled by his ideas of grandiose without practical and objective view of reality.
Transit Mercury Trine Natal Jupiter : Optimistic mental outlook and harmony in ideas and practicality characterize this transit. This is the period of growth and expansion through one’s contacts, relations, friends and one’s life experiences. This is an excellent time for study, intellectual pursuits, business communications, travels and for trade with foreign countries. The individual is promoted in his professional field. Advertising and communication bring healthy response. There is good balance between attention to practical details and a comprehensive view of the things. Optimism improves health due to the relaxation of the nervous and glandular system and emotional happiness helps in personal growth.
Transit Mercury opposite Natal Jupiter : Over optimism, selfishness, unrealistic goals and promises characterize this transit. This transit requires a little care in social and business interactions. One is likely to lose clarity and precision about details and may indulge in mean selfish motives which may harm one’s long range goals. On the bad side hypocrisy is sometimes present in communications with co-borns, neighbours, friends and group associates and it is likely to be exposed if this transit is under afflictions. Over eating and improper diet may also cause health problems.