On April 21, 1908, near Earth's North Pole, the Arctic explorer Frederick Albert Cook scrawled in his diary a memorable phrase: "We were the only pulsating creatures in a dead world of ice." These words may soon take on new significance for humankind in another dead world of hidden ice, submerged beneath the red sand of its frigid deserts. This dead world is Mars, and the desert is the planet's mid-latitude region known as Arcadia Planitia.