Part 3582 - Freefall - Translations

"Kessler Syndrome" - A theoretical scenario in which the density of objects in low Earth orbit due to space pollution is high enough that collisions between objects could cause a cascade in which each collision generates space debris that increases the likelihood of further collisions. (https://en.wikipedia.org/wiki/Kessler_syndrome)

A "Kessler event", in this comic, refers to the initial scattering that leads to this cascade.