You'll Never Guess What Made This Saint Bernard's Fur Turn Green Overnight

“The story begins with a lot of drool,” Dr. Stephanie Olson said in a viral Twitter thread on Sunday.

The assistant professor in Purdue University’s Department of Earth, Atmosphere, and Planetary Science noticed something odd on her Saint Bernard’s fur. Olive’s neck had turned green overnight!

As an “early Earth geochemist,” Dr. Olson was intent on unearthing the cause of the color (pun intended).

It’s no secret that Saint Bernards drool. But after Olive had surgery and was sentenced to the cone of shame, all that slobber collected around her collar.

“Dog saliva contains iron porphyrins,” Olson explained in a subsequent tweet. “Upon contact with oxygen, the iron is oxidized to iron oxide nanoparticles. Rust, essentially. This is why Olive and many other drooly dogs have rusty red staining by their mouths.”

But there’s a reason Olive’s neck turned green instead of the red we see so often on doggie eyes and mouths. According to Olson, this chemical reaction turned into the perfect storm when Olive laid down to rest (as tired pups do), isolating her slobber underneath her neck folds. The lack of oxygen prevented red staining and instead caused green rust to form.

The result was an odd ombré effect, with Olive’s muzzle retaining red stains and blending into the pale green rust matted in her neck fur.

Ironically enough, Olive derives from olivine, a notoriously green mineral with a gorgeous emerald hue. Olson jokes that maybe her pup is just honoring her namesake.

As an astrobiologist with a special interest in Earth’s evolution, Olson of course had to connect her pup’s phenomenon to the world around us. She explained that green rust is uncommon today because of the presence of oxygen, but our planet’s conditions were different in the past.

“…it may have been common on the ancient Earth before our atmosphere became oxygenated,” Olson said. “The ocean may have even appeared green instead of blue 2.5 billion years ago!”

Though Olson isn’t sure how to remove the rust from Olive’s neck, she ended her adorable exposé with a call to fellow geochemists for possible solutions. If she can’t remove it, at least Olive will have quite the trademark look!