Geological evidences of previous habitability on the surface of Mars

Zbog svoje blizine i sličnosti Zemlji, Mars je jedan od najboljih kandidata za istraživanje mogućnosti života izvan Zemlje i potencijalne planetarne nastanjivosti. Moderna istraživanja Marsa započela su 1971. godine. U posljednjih 15 godina sonde Opportunity, Spirit, Phoenix i druge donijele su mnoštvo informacija o biogeokemijskom sastavu i fizikalnim karakteristikama Marsa temeljnih za postanak života. U narednim godinama nove misije nastavit će istraživati prijašnje i trenutne okoliše. Najveći broj dokaza o nastanjivim okolišima doprinijela je misija znanstvenog laboratorija Marsa s roverom Curiosity. Opremljen s različitim instrumentima, otkrili smo mineraloške i petrološke pokazatelje okoliša sposobnog za razvoj života poput sekundarnih minerala nastalih alteracijama uzrokovanih vodom te sedimentoloških tekstura. Najvažnije su pukotine ispunjene kalcijev sulfatom jer daju mnogo informacija o vodenom okolišu tijekom njihovog nastanka. Po omjeru vodikovih izotopa, shvatilo se da je došlo do velikog gubitka atmosfere i vodene mase na Marsu. Raspravlja se o potencijalnom biogenom izvoru pronađenih organskih spojeva klorbenzena, nitrata i metana. Nadalje, privremeni vodeni tokovi bogati perkloratnim solima, zabilježeni samo u specifičnim uvjetima, nagovještavaju nam nekadašnju nastanjivost okoliša na Marsu. Doduše, ovakve slane otopine ne mogu podržati život pri današnjim uvjetima. U konačnici, najvažniji kriterij je vrijeme – uvjeti su mogli biti bolji nego na prvobitnoj Zemlji, ali ako nisu ustrajali dovoljno dugo život se nije mogao razviti.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