Venus may harbour life some 50km above its surface, we learned a couple of weeks ago. Now a new paper, published in Nature Astronomy, reveals that the best place for life on Mars might be more than a kilometre below its surface, where an entire network of subglacial lakes has been discovered.
Mars was not always so cold and dry as it is now. There are abundant signs that water flowed across its surface in the distant past, but today you’d struggle to find even any crevices that you could call moist.
There is nevertheless plenty of water on Mars today, but it’s virtually all frozen, so not much use for life. Even in places where the noon-time temperature creeps above freezing, surface signs of liquid water are frustratingly rare. This is because the atmospheric pressure on Mars is too slight to confine water in its liquid state, so ice usually turns directly into vapour when heated.