Many of the MVACS investigations focus on water. The complete water cycle involves exchanges between the surface and atmosphere, exchanges between different forms of water, and transport within the atmosphere. Of these, previous spacecraft missions have observed only the latter. While the total amount of atmospheric water is extremely small (ten thousand times less than in Earth's atmosphere), it has a strong seasonal variation. The Mars Atmospheric Water Detection (MAWD) experiments on each of the Viking orbiters revealed how water vapor is released from near-surface ice each spring. MVACS will measure, for the first time, all the important aspects of the water cycle at one point on the surface. Where is it? In what forms does it exist? What is the present water cycle, and was it different in the past? MVACS will look for answers to these questions by measuring the amounts of water in the form of vapor, ice, and water-bearing minerals. MVACS will also measure the physical parameters that control water, like pressure, temperature, and wind. These direct measurements from a point on the surface will complement the present global view of the atmospheric water cycle derived from orbiting spacecraft.