Categories: interesting-sites, astronomy-space
Date: 17 July 2009 03:18:35
From spaceweather.com [a new site for me to be addicted to] via an article on crikey.com.au.
Noctilucent clouds are still rather mysterious [from the article: "traces of ice crystals have been detected in them"; "seem to grow in frequency during solar cycle minimums"; "may be related to the severe upper atmosphere cooling which is the flip side of the warming caused by the green house gas effect in the lower atmosphere"...] So, in the words of the article, no complete answers as yet, 'but they "sure are pretty."'
Superb photos and interesting descriptions. Take a look.