"They really do look like little mammals, little mice or chipmunks or rats or something running around on the glacier, although they run in obviously very slow motion," says wildlife biologist
Sophie Gilbert, also at the University of Idaho.
Each ball is like a soft, wet, squishy pillow of moss. The balls can be composed of different moss species and are thought to form around some kind of impurity, like a bit of dust. They've been seen in Alaska, Iceland, Svalbard and South America, although they won't grow on just any glacier — it seems that conditions have to be just right.
Their motion is what interested Gilbert and Bartholomaus, as well as their Washington State University colleague
Scott Hotaling.
"Most people who would look at them would immediately wonder, 'Well, I wonder if they roll around out here in some way,' " says Gilbert. "Tumbleweeds come to mind, which are obviously totally different, but also round and roll around."
She notes that the entire surface of the ball must periodically get exposed to the sun. "These things must actually roll around or else that moss on the bottom would die," says Gilbert.
The possibility of their rolling had been noted by other researchers, who previously observed that the balls sometimes could be found teetering on a pedestal of ice. That pedestal might form as the moss ball insulated the ice underneath it, preventing it from melting as fast as the surrounding ice. Scientists suspected that the ball would eventually tip off of the pedestal and roll away.
