Some places in the Ismenius Lacus quadrangle display large numbers of cracks and pits.
 It is widely believed that these are the result of ground ice sublimating (changing directly from a solid to a gas).
 After the ice leaves, the ground collapses in the shape of pits and cracks.
 The pits may come first.
 When enough pits form, they unite to form cracks.
Some places in the Ismenius Lacus quadrangle display large numbers of cracks and pits.  It is widely believed that these are the result of ground ice sublimating (changing directly from a solid to a gas).  After the ice leaves, the ground collapses in the shape of pits and cracks.  The pits may come first.  When enough pits form, they unite to form cracks.
Ismenius Lacus quadrangle