Water, water somewhere – we think – on Mars The Christian Science Monitor

The Odyssey spacecraft, now settling into orbit around Mars, will be hunting for water – the key nutrient for past or present life. But the spacecraft can neither see nor smell its quarry. How will Odyssey scientists know when they have found it? This part of the mission is an exercise in indirect detection. Instead of looking for water itself, a suite of instruments will look for gamma rays and neutrons emitted by hydrogen. The Odyssey team assumes that hydrogen at or near the Martian surface probably will be locked in water molecules. It’s the “H” in “H2O.”