cted from the Sun by walls of ancient rock, something extraordinary has accumulated over the eons. Water ice.
Scientists have known for some years now that these polar craters contain frozen water, delivered over billions of years by comets and asteroids and preserved in the permanent cold by the absence of sunlight. The temperatures in these crater floors can drop below negative 200 degrees Celsius, among the coldest places in the entire solar system. This ice is important for many reasons. Wa