My Pick of Pic's December 14, 2003 Hydrothermal Activity on Mars? Galle Crater is a large impact crater located in the Mars southern hemisphere on the eastern edge of the Argire Impact Basin. This image covers a small area on the crater floor. There is a group of gullies in the upper left part of the picture. Mars has a great variety of channels and gullies. While none of them have been 100% linked to liquid water runoff, some of them would be hard to explain by any other process. The gullies seen here fall into that category. This scene is exciting for an additional reason. It would appear that the water has erupted from a subsurface source. It also appears to be very resent. One interpration is that hydrothermal energy is driving the water to the surface where it has erupted. It then flowed down the shallow slope, meandering as it went. The liquid state is unstabile on Mars and would quickly evaporate. This is consistant with the decrease in gully width as it flowed down slope. If one were standing on Mars to witness one of these eruptions, it might very well be similar to the gysers of Yellowstone National Park - which are also driven by hydrothermal activity. The many twisting, winding, and criss-crossing dark streeks in the picture are the result of dust devil activity. There also are what appears to be some smaller gullies on the edge of some of the dark regions in the middle of the picture. ASU Context USGS Context