IMPACT CRATER LAKES ON MARS

The robotic search for life on Mars centers on identifying accessible environments where the biological catalyst, water, has existed. The fo rmation of large impact craters on Mars (>65 km diameter) may have res ulted in the creation of ice-covered impact crater lakes, which would not freeze for thousands of years, even under present climatic conditi ons. Water could be supplied from deep confined aquifers penetrated by the impact craters, without the need for surface melt water. Freezing of the lakes is postponed owing to heat from impact generated melt-be aring deposits, from impact-related uplift of hotter rocks from depth, and from the latent heat of freezing of a deep crater lake. Abundant morphologic evidence for ancient crater lakes has not been found in Vi king images, except for craters associated with outflow channels. Howe ver ice-covered crater lakes could have formed, and further searches f or evidence of these lakes are warranted. The lake deposits from disse cted impact craters may represent one of the best targets for future s urface exobiology investigations or sample return missions from Mars.