Pyramid of light to appear in the west on Feb. 21, 2011 (Sky Tonight: Zodiacal light)
"Clouds" over Olympic Valley, California in August of 2010 (Matt Saal)... or chemtrails?
Clouds, jet condensation, or Chemtrails?
(Berthoud Recorder) Explanation: What’s happened to these clouds? Normal cloud bottoms are flat because moist warm air that rises and cools will condense into water droplets at a very specific temperature, which usually corresponds to a very specific height. After water droplets form that air becomes an opaque cloud. Under some conditions, however, cloud pockets can develop that contain large droplets of water or ice that fall into clear air as they evaporate. Such pockets may occur in turbulent air near a thunderstorm, being seen near the top of an anvil cloud, for example. Resulting mammatus clouds can appear especially dramatic if sunlit from the side. These mammatus clouds were photographed last August  over Olympic Valley, California.
- NASA/JPL: Astronomy Pictures of the Day
Persistent "contrails" made of chemicals visible from space (Paolo Nespoli/NASA/ESA)
This picture, innocently taken by an astronaut who assumes that what he is photographing are contrails (momentary condensation behind high flying aircraft), paints a hazy picture.
(Telegraph.co.uk) Aurora Borealis and the Aurora Australis from space: City lights and atmospheric optical phenomena were captured in this exposure from the Space Shuttle Endeavour in December 2001. More Twitpics from space>>