Three new underground lakes have been detected near the south pole of Mars. Scientists also confirmed the existence of a fourth lake - the presence of which was hinted at in 2018. Liquid water is vital for biology, so the finding will be of interest to researchers studying the potential for life elsewhere in the Solar System. But the lakes are also thought to be extremely salty, which could pose challenges to the survival of any microbial life forms. Billions of years ago, water flowed in rivers and pooled in lakes on the Martian surface. But Mars has since lost...