Venus has a negligible magnetic field è solar wind can disturb its atmosphere directly and blow away fractions of its upper atmosphere (including airborne particulate matter) in comet-like fashion. (Added 15 February 2003.)

http://www.ebicom.net/~rsf1/vel/1918.htm

Donald R. Barber (Norman Lockyer Observatory News 01/1997): a peculiar sequence of air-borne/rain-water-borne yeast-like bacterial attacks on astronomical photographic plate emulsions at a British observatory from 1932 to 1963 …