In very low Earth orbit there are (at least) two problems; aerodynamic drag, and atomic oxygen (O rather than O2). Drag can be compensated with a low thrust from an ion engine.
Question: But what exactly makes atomic oxygen "bad". How exactly does atomic oxygen cause problems for spacecraft in VLEO? I assume it has something to do with the higher reactivity of single oxygen atoms compared to oxygen molecules, but what are the specific problems?
Does it just slowly eat the whole spacecraft, or are there specific materials or devices that are particularly sensitive?
Does it get inside and munch on insulation and rubber seals like the Andromeda Strain?
People might want to put Earth-viewing telescopes in VLEO to be closer. Since the glass in lenses and reflective aluminum coatings on mirrors are pretty much fully oxidized, is it the thin optical coatings on their surfaces that get "eaten" for example?