During a hike around the Root Glacier in Alaska to set up scientific instruments in 2006, a glaciologist at the University of Idaho, Tim Bartholomaus, encountered something quite unexpected.
Scattered across the glacier were seemingly misplaced balls of moss. Not attached to anything, the furry green spheres stood out in a world of white.
Intrigued by their discovery, Bartholomaus and two colleagues began a longitudinal investigation on the existence of the balls, reporting in the journal Polar Biology that they can persist for years and move around in a coordinated and "herdlike fashion" that researchers are yet to explain sufficiently.
The colony of balls appear to navigate at similar speeds and in the same directions - the speeds and directions change over the course of weeks, however.
Image credit: WFAE site
The existence of these strange moss balls was noticed 70 years ago in the Journal of Glaciology, with an Icelandic researcher describing them as "jökla-mýs" or "glacier mice".
The latest work is adding to the very small body of research on these balls even though glaciologists have long known of them and been admired by them.
What we know so far is each ball is a soft, wet and squishy clump of moss. Looking like little mice or rats, the balls can be composed of different moss species and are thought to form around some kind of impurity, like a bit of dust (similar to the formation of a snowflake where a cold water droplet freezes onto a pollen or dust particle in the sky).
Data collection by Bartholomaus and his team has also found that the balls can survive for around six years, but potentially much longer.
The balls have been spotted in Alaska, Iceland, Svalbard and South America, although they will not grow on any glacier - it seems certain conditions are required.
Science indicates the balls must roll around and periodically get exposed to the sun in order for the surface to have live moss coating it.
Assessing the possibility of their rolling, some researchers have noted that the balls have sometimes been found teetering on a pedestal of ice. That pedestal might form as the moss ball insulates the ice underneath it, preventing it from melting as fast as the surrounding ice. Eventually, the ball would tip off the pedestal and roll away.
In terms of their movement, things get more mysterious. The researchers expected the moss balls would travel in random directions once rolling off their pedestals, but the reality was different. The balls moved about an average of an inch a day in a choreographed formation.
With landscape and atmospheric data not complying with the obvious hypotheses that the movement of the balls is due to either rolling downhill or following the dominant direction of the wind, the explanation behind their movement is still unanswered and baffling to researchers.
With possible explanations somewhere in the physics of the energy and heat around the surface of the glacier, this case provides an exciting challenge for scientists and researchers to figure out.