What Mangal Dosha is
In classical Jyotish, Mars (Mangala or Kuja) is the planet of energy, courage, assertiveness and heat. Mangal Dosha is said to arise when Mars occupies the 1st, 2nd, 4th, 7th, 8th or 12th house counted from the ascendant. These houses relate to the self, family, home, partnership, longevity and expenses, which is why the condition is associated with friction in married life.
The idea is rooted in the texts on marriage compatibility and later commentarial tradition, including the writings that follow Brihat Parashara Hora Shastra. Schools differ on the exact list of houses, and some regional traditions leave out the 2nd house, or add or remove houses depending on the sign Mars occupies.
