Atmosphere of Earth sublimated into polar-mesospheric noctilucent clouds. These are the highest clouds in the atmosphere and may be visible to the naked eye if sunlight reflects off them about an hour or two after sunset or a similar length of time before sunrise. They are most readily visible when the Sun is around 4 to 16 degrees below the horizon. Lightning-induced discharges known as transient luminous events (TLEs) occasionally form in the mesosphere above tropospheric thunderclouds. The mesosphere is also the layer where most meteors burn up upon atmospheric entrance. It is too high above Earth to be accessible to jet-powered aircraft
Last Day on Earth (The Walking Dead) 10 in his review and commented, "For all that "Last Day on Earth" was really about, and what was important about it, it went on too long. And then failed to deliver a satisfying exclamation point. Instead, we got another fake out/cliffhanger. A technique this show is absolutely over indulging in. Jeffrey Dean Morgan was terrific as Negan though." Zack Handlen of "The A.V. Club" gave the episode a C, the lowest grade given by the website for the show to date, faulting the episode for awkward, drawn-out writing and forced story arcs which couldn't maintain an atmosphere of suspense