Valley networks are the most common drainage feature on Mars and they are frequently cited as evidence of former clement climate conditions. However, burial and erosion have altered the form of some valley networks, resulting in forms that range from inverted valleys (sinuous ridges), filled valleys, and exhumed negative-relief valleys. The image above shows a sinuous ridge system that terminates in a possible paleolake depression. Planetary geologist Ken Edgett initially identified this system in 2005 and PSI Senior Scientist Rebecca Williams and Research Associate Frank Chuang are now mapping others like this in detail. Mapping is being performed using the ArcGIS Desktop Geographic Information System package on high-resolution Context camera images, approximately 6 meters per pixel. The mapping thus far has resulted in greater numbers of ancient valley networks being identified, expanding the known record of aqueous activity on Mars.
