Because of its proximity and similarity to Earth, Mars is one of the best candidates for exploration of extraterrestrial life and potential planetary habitability. Modern exploration of Mars began in 1971. In the last 15 years probes Opportunity, Spirit, Phoenix and others have brought a wealth of information on the biogeochemical composition and physical characteristics of Mars fundamental for the genesis of life. In the coming years the new mission will continue to investigate former and current environments. The mission Mars Science Laboratory with its Curiosity rover contributed the most evidences for habitable environments. Equipped with a variety of instruments, it found mineralogical and petrological indicators for environment capable of developing life like secondary minerals formed by hydrous alterations and sedimentological textures. The most important evidence are fractures filled with calcium sulphate because they give a lot of information on the aquatic environment during their genesis. By the ratio of hydrogen isotopes it was realized that there was a large loss of atmosphere and body of water on Mars. We discuss the potential source of biogenic organic compounds found like chlorobenzene, nitrates and methane. Finally, a transient water flows rich in perchlorate salts, observed only under specific conditions, suggest a former habitable environment on Mars. Although, these liquid brines cannot support life in today’s conditions. In the end, the most important criterion is time – conditions could have been better than on primordial Earth but if they hadn't persisted long enough life couldn't have developed.