That means we may have to refine our search strategy. If the surface of Mars is toxic, we might expect any indigenous life to thrive in the subsurface, where UV radiation does not reach. The new experiments may motivate us to look a bit deeper below the surface than we had planned to, or focus more on possible niche habitats such as within salt rocks.

200-yard-wide pit on Mars
This 200-yard-wide pit on Mars, likely a cave entrance, was photographed by the HiRISE camera on NASA’s Mars Reconnaissance Orbiter. 
(NASA/JPL/University of Arizona)

We also have to keep in mind that Mars is a big planet with different types of soils, rock layers, and environmental conditions. Past rover and lander missions have given us a glimpse of this variety. The so-called Special Regions on Mars are subject to stricter planetary protection guidelines precisely because they could contain life.  Particularly promising locations are found below ice crusts or within lava tube caves, where life would find natural protection from UV radiation and a higher availability of water.  Regions associated with hydrothermal activity also would be promising, and some of these are likely to be active today.

So despite the new results, the search for life on Mars is by no means over. It will simply become more focused as we learn more about the Martian environment and its variations.