Cause
This orange snow was most likely caused by a heavy sandstorm in neighbouring Kazakhstan. Tests on the snow revealed numerous sand and clay dust particles, which were blown into Russia in the upper stratosphere. The speculation that the colouration was caused by a rocket launch from Baikonur in Kazakhstan was later dismissed, as the last launch before the event took place on 18 January.
Russia's environmental watchdog originally claimed that the coloured snowfall was caused by industrial pollution. It stated that the snow contained four times the normal quantities of acids, nitrates, and iron. However, it would be nearly impossible to pinpoint a culprit if pollution were the cause, as there are various industries nearby, such as the city of Omsk, which is a centre of the oil industry in Russia.
Read more about this topic: 2007 Siberian Orange Snow