Extensional Fractures

In this 0.25 m/pixel NAC frame we found narrow fractures that extend across the lunar surface, in the mare basalt of Lacus Somniorum. Narrow fractures like these are probably extensional features caused by tensional stress that pulls the rocks apart in opposite directions. Similar fractures have been found before on top of wrinkle ridges. The fractures in today's Featured Image are also associated with a small wrinkle ridge. In the LROC WAC 100 m/pixel context image below, you can see the ridge (white arrow) between two hills of non-mare material. The fractures are located to the east of the ridge (white asterisk). There are a number of other wrinkle ridges in the area as well.

LROC WAC mosaic of the region surrounding the narrow fractures. The white asterisk marks the location of the fractures, while the white arrow points to a ridge that may be related to the fractures [NASA/GSFC/Arizona State University].

Examine the rest of the narrow fractures in the NAC frame! 

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Stress and pull

Fractures in the mare of Tsiolkovskiy crater