Although they try hard, they have not yet shown that Mars has life. Therefore, it is noteworthy that in the recently held American Astronomical Congress, two geologists show that the living creatures that the Viking probes wanted to find on Mars could have been destroyed.
Specifically, the Viking probes reached their surface in 1976. Samples were collected there and a series of experiments were conducted to find out if there was any kind of life similar to those on Earth. Among other things, the samples threw enriched water in food so that it could be fed if there was life. Samples were also burned to check for organic remains.
According to the two geologists, given the characteristics of Mars, it is possible that in the cells of living beings in the area there is not only water, but a mixture of water and hydrogen peroxide (oxygenated water). On the one hand, this would explain why there is a very oxidizing substance -- presumably hydrogen peroxide -- on the surface of Mars. On the other hand, this type of cells have a low freezing point and require little water. It would, therefore, be ideal for living on Mars.
Well, through the experiments carried out in the Viking mission, the cells proposed by the researchers would be destroyed without leaving any organic trace. However, for most scientists this is not very credible.