The surprising signal from Mars Odyssey is that oceans of ice lie in wait just under the surface of the Red Planet. Scientists have found Martian terrain that is hydrogen-rich, an indicator of water ice. The most abundant reservoirs of that near-surface water stretch from the planet’s poles to within about 50 degrees of the equator. The amount of hydrogen detected is huge. So much so that one brimming bucket of ice-rich polar soil, when heated, can yield more than half a bucket of water. That’s big news for Mars water reclamation experts. As a watering hole to sustain an expeditionary crew, Mars must now be approached with an eye on how to tap into the invaluable resource. Scientists and engineers have begun charting how this watery commodity can nourish the human drive to distant Mars.