Ozone levels -- measured in Dobson units -- seemed to bottom out over the icy continent back in 1994. The preferred ozone level, for sun-blocking purposes, is somewhere between 250 and 500 units; the record low of four years ago was 88 units; the pole hole is now at 100 and heading south with the Antarctic spring.
"It sounds pretty scary," says TIME science writer Mike Lemonick, "but scientists knew that the ban on ozone-killing chemicals that went into effect in 1996 wouldn't show any results for a while. The chemicals released before then will take a while to be cleared from the atmosphere, and until they are they'll keep destroying ozone. The destruction should ease off, with ozone levels rebounding over the next few decades." Meantime, let's hope NASA scientists remembered to pack their SPF 40.