Many types of craters exist on Mars. Most are generated by impacts of asteroids and comets.
In this area though, we think these craters may be due to steam explosions. This happens on the Earth when hot lava runs over icy ground.
HiRISE is one of six instruments on NASA's Mars Reconnaissance Orbiter. The University of Arizona, Tucson, operates the orbiter's HiRISE camera, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter Project for the NASA Science Mission Directorate, Washington.