So, lets see what Mars can do in 1st house without any conjunction or aspect from any other planet. 1st lets see what these 2 things represent --
Mars represents our will power, courage, ability to take actions, aggressive nature, anger, our fighting ability, brother, male friends, a boy friend for a girl, a soldier, an athlete and real estate etc.
1st house/Ascendant is your self, personality, overall health, life path and head in human body etc.
So, when this action oriented planet comes into the 1st house of personality, this person is very active by nature. They are natural athletes and sports-persons. They want to remain fit and active. They go through hard regimes to keep their body fit. As Mars also represents anger and aggressive nature and 1st house represents Head in human body, these people can be hot headed at times. As Mars also represents Brothers and Male Friends and 1st house is house of Personality, it shows that your Brothers and Male Friends had a big impact in making your personality.
Now, Mars is represented by a Soldier in Astrology. What is Soldier's job? It is to protect his land and people.So, from 1st house, Mars aspects the 4th house of home, home environment and mother etc, hence these people become very protective of their home and family. Mars then aspects 7th house of Marriage and they become protective of their spouse and marital happiness. Last aspect of Mars is on 8th house of occult and mysticism, and Soldier (Mars) here wants to dig deep into the secrets of mysticism.
Hope this helps.
Tomorrow - Mars in 2nd house.
Vishal S Saxena - Astrologer