These clouds appear when ice-crystal-laden clouds for high in the
atmosphere, high enough that the sun strikes the clouds while the
ground is in darkness.
This photograph was produced by NASA’s Aeronomy
of Ice in the Mesosphere project. The AIM satellite
is designed specifically to study the phenomenon of noctilucent clouds.
The photo is the first one released by the Project.
The Project website has a different terrestrial photo, even
more striking than the one I posted previously.
It is awe-inspiring, truly, but it is also just ice.