I've noticed a lot of stressing over how the water remains frozen during Mercury's day (assertions such as 'Mercury must have a very cold night' spring to mind).
Mercury is almost tidally locked to the Sun, which means there are parts of its surface that are always 'dark'. Anything frozen there will basically remain frozen until the Sun starts to die/Mercury gets hit by an asteroid/the 1% chance that Mercury will collide with Venus in the next 5billion years happens.
Mercury is almost tidally locked to the Sun, which means there are parts of its surface that are always 'dark'. Anything frozen there will basically remain frozen until the Sun starts to die/Mercury gets hit by an asteroid/the 1% chance that Mercury will collide with Venus in the next 5billion years happens.