An Entire Continent Runs on Rivers You Can't See. Scientists Just Mapped Them - ScienceAlert

Galaxies can contain hundreds of billions of stars, but every one of those stars begins with cold, dense gas. Large galaxies, including the Milky Way, are surrounded by an enormous reservoir of this material known as the circumgalactic medium, or CGM. The CGM extends roughly 10-20 times farther than the visible part of a galaxy. Over time, some of this gas can cool, flow inward, gather into dense clouds, and eventually form new stars. Because stars give rise to planets and the conditions necessary for life, the CGM plays an important role in a galaxy's long term evolution.

Over the past decade, a network of usually pristine blue rivers and lakes that winds through Alaska's breathtaking Brooks Range mountains has been starting to look a little… rusty. Scientists first noticed the unusual orange plumes flowing into the water back in 2018. They began to investigate, collecting water samples from various sites so remote they can only be accessed by helicopter – but at the time, they were only able to get a snapshot of what was going on. "The more we flew around, we started noticing more and more orange rivers and streams," said ecologist Jon O'Donnell, of the US National Park Service. "There are certain sites that look almost like a milky orange juice. "Taylor Evinger holds a bottle of orange water sampled from the Igning River in Gates of the Arctic National Park and Preserve in Alaska. (Brett Poulin/UC Davis)Environmental toxicologist Brett Poulin (of UC Davis) was intrigued at how similar the orange staining looked to the acidic pollution he had seen draining from metal mines.