Grimy biofilm covering Jefferson Memorial baffles scientists

WASHINGTON (AP) — It’s black, grimy and growing, but what exactly is engulfing one of the nation’s most hallowed monuments?
The Washington Post reports conservationists are baffled as to how to stop a microbial invasion that’s been slowly covering the Jefferson Memorial, causing the 73-year-old white neoclassical structure to take on a dingy look.
National Mall and Memorial Parks Chief of Resource Management Catherine Dewey says the biofilm became noticeable less than a d