Evidence for Liquid Surface Water on Mars

A northern Noachis venting site

Composition of Themis visual and thermal image, 200% original size, therefore 50 m/pix. The small venting crater is located near 17°S 358.5°E in northern Noachis. The bright white structre is a cliff down to a very large crater basin. In the visible image the dark ejecta around the vent are probably due to water/soil interaction. In the thermal image it is cooling from evaporating liquid water. The water had to be liquid because as ice it could not chemicaly react with the soil. The crater has a diameter of about 100 m, the ejecta are up to 1.5 km away. There is considerable stereo parallax between the visual and the thermal image as the movement of the right image border shows. But the black area on both images seems quite similar, especially the fingers to the East. It is unclear whether after 26 days, the thermal image still shows the evaporation of an eruption as long ago. If the crater is a continous vent, the shape of the ejecta would represent the daily wind speed and directions. As the Viking Landers found, Martian winds are repetitive and predictable. The continous vent idea is supported by the thermal image as it shows a hot cloud over the crater. In the visible image such a cloud could be more transparent. Notable is the position of the vent close to a cliff. Erosion by the exit of liquid water there seems a posibility. It could be similar to the gullies of the Aerobrake Crater. The visual image is I06517002, from 2003-06-04 at INA 77° LST 17.3. The thermal is I06835006, from 2003-06-30 at INA 98° LST 5.4