the subsurface of mars. >> liquid water is a critical distinction. we have known about ice on larson's 2008 when nasa's lander found it and we've known about seasonal running water since 2011. thanks to nasa's mars reconnaissance orbiter. a standing, stable body of water, that is something else entirely. >> the discoveries have mostly been there is water ice, there is ice here, i stare. maybe there is transcendent droplets forming on the legs of robotic landers are frost on rocks. this is the mother load, real liquid water in large amounts underneath the south polar ice cap of mars. >> that would be a game-changer in the search for life on mars because it's long been believed that where there is water, there is life. now the challenge is getting there, getting a rover they control down deep inside the polar ice cap to see what kind of life could potentially be locked inside the lake. >> shannon: fascinating.