As far as the evidence goes, till date nothing positive about Martian Life has surfaced. Also, no Martian mission or Rover has claimed to have found life, but yes there are hints that Mars may have supported life in the past. Now, some astrobiologists believe that Mars in its earlier days presented an even better and suitable environment than Earth.
According to the statement of Michael Finney, co-founder Genome Partnership, “If Mars ever had life, it may moved and probably gone into hiding, but is probably still present there.” Mars may appear as a wasteland today, but billions of years ago it was wetter, full of rivers, lakes and oceans — just like Earth or even better.
The most satisfying theory that represents the loss of life and turning Mars into a wasteland says that it was caused by the global loss of magnetic field on the planet, which in-turn allowed the harmful charged particles from the Sun to slowly strip away Martian Atmosphere — making it look like it is today.
Even though Mars doesn’t have running water on the surface, various experiments have provided enough evidence regarding the presence of an underground water table on Mars. There are even theories that suggest the possibility of a huge underground lake on the planet’s South Pole.
Other theories regarding Martian Life suggest that life on Earth was brought by falling Martian rocks. Even though it’s a hypothesis, scientists from around the globe have strongly agreed upon this. They say Mars was more conductive cradle for life than Earth in its earlier days.
Nasa’s Curiosity Rover made headlines when it spotted some strange clues regarding the presence of Methane in the Martian air. Methane in Earth’s atmosphere is largely produced by microbes and other microorganisms, so this discovery made scientists claim that there is life on Mars, while there could be other theories such as the reaction of boiling water with some specific material rock.
According to Nasa, the methane detected may have leaked from below the surface, but as there is no evidence such as leak point detections or so, we don’t even know how long ago it was produced or was it actually produced by microorganisms — Everything regarding life on Mars is still a big mystery.