Mini lunar ice thread. The permanently shadowed regions (PSRs) at the lunar poles are often conflated with cold traps, or a simple relation is drawn where PSR = ice. But actually only ~41% of PSR area at the north pole is permanently <110 K, and ~81% for the south.

110 kelvin is often taken as the "magic temperature" where ice is stable on billion-year timescales. This difference is mostly because even when shadowed from direct sunlight, thermally re-radiated energy off nearby slopes can warm surfaces above 110 K.

So true cold trap area is much smaller than PSR area. But, as shown by J.-P. Williams & J. Kloos in a pair of papers last year, there are vast regions around the permanent cold traps that are seasonally below 110 K due to the Moon's tilt.

And perhaps even more significant, micro cold traps (~1-10 m scale) that can't be easily resolved make up an enormous area of additional cold trap: we estimated ~16,000 square km for each pole in a soon-to-be-submitted paper.

These seasonal and micro cold traps (and there should also be seasonal micro cold traps) create a vast peripheral area around the big cold traps. These are all shown in the figure in the first tweet.

The fact that seasonal/micro cold traps vastly exceed the area of large resolvable cold traps (and surround them) is important for water and other volatile migration. Any studies of volatile transport should take these factors into account or could get completely wrong results.

(Most of the data here came from the DIVINER instrument on LRO)