Marsquakes, Add Water and Shake
An anonymous reader writes "Analysis of Mars orbital data shows northern pit chains as evidence for relatively recent seismic activity. If marsquakes release water-ice to the surface, then such young features may be reshaping and eroding the landscape from below. No modern volcanic or seismic activity has ever been confirmed before. A long-standing mystery is why the northern hemisphere is smooth, while the martian south is so rugged."
I sunk your battleship.