New Mexico Geological Society Annual Spring Meeting — Abstracts

Preliminary examination of images from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) reveals evidence of possible collapse features associated with impact craters > 1 km diameter in the mid-latitudes of Mars. A theoretical model developed by Stafford & Boston [2005] and expanded by Johnston & Boston [2006] suggests that the energy associated with the cratering process could supply heat sufficient to melt ground ice and allow it to circulate briefly through the fracture system also created by the impact. In the presence of soluble sulfate minerals, which have been found to be abundant at the surface of Mars, this process could create a hydrothermal karst system capable of providing a protected habitat for indigenous subsurface Mars lifeforms that may be either dormant or even active in the subsurface and released to the aboveground environment by the impact event.

Hydrothermal and karst systems are found in the vicinity of certain Earth impact craters such as Haughton (Devon Isl., Nunavut, Canada) and Chicxulub (Yucatan, Mexico) and seem to be preferentially developed along the concentric rather than the radial fractures produced by the impact. A similar pattern seems to be emerging from the examined Mars images. The postulated collapse features are found ringing craters in the middle-latitudes, frequently in combination with gullies on the crater walls. No such features are seen around similar-sized craters in either the equatorial or polar latitudes. This may be explained by the expected distribution of ground ice and permafrost, as outlined by Head et al [2003]. In the absence of permafrost, no water is available to be melted by the cratering process, while in the continuous permafrost zone karst formation is inhibited or obscured by the mantling process.