Some astronomers suspect that in the past of Mars there could be favorable conditions for there to be living beings. In fact, evidence has been found of the presence of liquid water, which at least on Earth allows the creation of living beings. However, according to recent studies, the water of Mars seems too salty to create and receive living beings.
In the plain of Meridiani, for example, the remains of the presence of water appear evident at some point, and the geochemicals of Harvard University have analyzed the samples collected by the vehicle Opportunity. Samples collected elsewhere and from meteorites fallen from Mars to Earth have also been investigated. Hence it is deduced that the microorganism that lives in the most brackish zone of the Earth could not survive in the waters that, apparently, existed on Mars 4 million years ago.
In fact, it has been calculated that the water of Mars was between 10 and 100 times more salty than that of the sea and that the medium was acid and oxidizing. Therefore, they consider that there was little chance of creating life, which in any case would have been in a short space of time.