A report proposes an apparatus that would extract water from the atmosphere of Mars and would consume little energy in doing so. The apparatus would include a set of copper plates surrounded by a thermal shield with slots through which atmospheric gas could circulate. At night, the slots would be open and the plates would be cooled to a temperature-170 K by thermally coupling them to a radiator facing the sky. Assuming that in the nighttime Martian atmosphere at ground level, the temperature is ≤200 K and the concentration of water vapor is at or near saturation, the vapor would condense and freeze on the plates. During the day, the slots would be closed and plates would be heated by thermally coupling them to a small solar collector; this would cause the ice to melt, and the water thus produced would be collected.
This work was done by Pramod K. Sharma of Caltech for NASA's Jet Propulsion Laboratory. To obtain a copy of the report, "A Passively Operated Unit for Extraction of Water from the Mars Atmosphere," access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Physical Sciences category.