Nacreous Clouds!

By Peter Kimball

Yesterday evening, Britney came into the office and excitedly asked "have you guys seen what's going on outside?"  Exiting the lab building, we were greeted by a spectacle that I'd heard about, and very much hoped to see during these early weeks:  nacreous clouds.  Also called polar stratospheric clouds, these clouds are very beautiful and very interesting.  From their Wikipedia entry:

Polar stratospheric clouds or PSCs, also known as nacreous clouds (/ˈneɪkriː.əs/, from nacre, or mother of pearl, due to its iridescence), are clouds in the winter polar stratosphere at altitudes of 15,000–25,000 meters (49,000–82,000 ft). They are best observed during civil twilight when the sun is between 1 and 6 degrees below the horizon. They are implicated in the formation of ozone holes.
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I had hoped we'd see these at some point before darkness leaves us altogether.  I did not expect we'd see them six hours after getting here!  Between the epic C-17 flight, our arrival on station, and seeing these clouds, we will remember yesterday for quite some time.