What is this formation on the Mars rock?:
http://mars.jpl.nasa.gov/msl-raw-images/...1_DXXX.jpg
http://mars.jpl.nasa.gov/msl-raw-images/...1_DXXX.jpg
http://mars.jpl.nasa.gov/msl-raw-images/...1_DXXX.jpg
http://mars.jpl.nasa.gov/msl-raw-images/...1_DXXX.jpg