A significant assertion of the publication by Joseph et al. (2019) (%93Evidence for Life on Mars%94) is the claim that lichens and their symbionts may have colonized Mars. This commentary critically reviews this assertion with evidence for and against. Evidence for the claim includes first, that lichens are %91extremophiles%92, have an ability to adapt and thrive in some of the most extreme environments on Earth, and in experiments at the International Space Station (ISS) under space and simulated Martian environments exhibit considerable resistance to the extreme conditions Second, detailed examination of images of the Martian surface has led to claims of the presence of %91lichen-like%92 structures and third, observations in extreme environments on Earth have suggested that lichens could live within rocks on Mars (%91endolithic lichens%92). Evidence against includes first, in experiments at the ISS, desiccation-induced breakdown of lichen cell integrity, which is more severe under space than Martian conditions. Second, it is doubtful lichens could survive on rock surfaces where they could be subjected to the scouring effects of Martian dust storms Third, the majority of Earth lichens contain eukaryotic green alga as the photobiont and there is little evidence for such alga on Mars. Fourth, putative fungi resembling %91puff-balls%92 have been observed on Mars but the interpretation of these structures has been controversial and very few species on Earth incorporate members of the basidiomycota. LICHEN EXTREMOPHILES, MARS, SURVIVAL, INTERNATIONAL SPACE STATION, ENDOLITHIC LICHENS