We are all in the Fog
Well, I guess the elliptical arc of a rainbow is not really caused by light or the sun, bla, bla, bla. SCRATCH THAT SCIENCE. All it takes is a little moisture to condense in the atmosphere AT ANY TEMPERATURE and the elliptical Kepler orbit of a weakly interacting massive energetic particle to collapse the atmosphere around it. Looks like whatever is hiding in this arc can CREATE CLOUDS.
Godspeed
References
Copyright 2012 Stewart D. Simonson All Rights Reserved
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Dark Matters a Lot 
Isn’t a local, sometimes toxic, mist reported as the one effect of a meteor or asteroid ( or dark matter) hitting the Earth? Such stories accompany outbreaks of ‘plague’ throughout history.
Yes,
Also during the New Madrid earthquakes for 3 months, which was proceeded by the great comet of 1811. I believe the toxic mist may contain lots of ionizing radiation from protons, etc.
Probably destroyed immune systems and DNA