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View Full Version : Mudcracks at Vostok?



aldo12xu
2005-Mar-10, 06:48 PM
We're seeing the same polygonal fracture pattern that we saw at Endurance on the rocks Wopmay, Earhart and Escher. NASA did not rule out the possibility that the fractures represent mudcracks http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20041007a.html

http://qt.exploratorium.edu/mars/opportunity/pancam/2005-03-10/1P163699129EFF5000P2384L7M1.JPG

http://qt.exploratorium.edu/mars/opportunity/pancam/2005-03-10/1P163698928EFF5000P2384R1M1.JPG

http://qt.exploratorium.edu/mars/opportunity/pancam/2005-03-10/1P163700005EFF5000P2384L7M1.JPG

JonClarke
2005-Mar-10, 09:21 PM
The Endurance features were certainly polygonal fractures, but they should not be referred to as mudcracks. Mudcracks are a very specific term applied to bedding parallel formed during or shortly after deposition by water loss, either desiccation or syneresis. The Endurancer features were on the surface of boulders and clearly cross cut bedding. Thus they are a weathering phenomenon, not depositional or early diagenetic. A non-genetic term is polygonal cracking, a range of terms has been applied to such features - pachydermal, elephant skin, or tortoise shell cracking/weathering.

Jon

aldo12xu
2005-Mar-11, 12:04 AM
Point taken........polygonal fractures formed by some dehydration process. Pachydermal weathering usually refers to clays, doesn't it? So does that imply the rock matrix might have a clay component? Or would you get the same effect if some of the hydrated sulphates making up the rock lost their molecular water (eg. epsomite "dehydrating" to kieserite)?