While cruising high above the Sahara desert (around 400 kilometers), an astronaut aboard the International Space Station (ISS) spotted a giant ghostly skull staring back at them. Fortunately, it isn’t the bones of an ancient giant, nor the entrance to the lair of an evil genus, but a strangely shaped volcanic crater.
The image was shared by NASA Earth Observatory on Halloween, but it was taken on February 12, 2023, by an ISS astronaut simply using a Nikon D5 digital camera.
It shows the Trou au Natron in northern Chad, a 1,000-meter (3,300-foot) deep volcanic caldera with an irregular diameter of 6 to 8 kilometers (4 to 5 miles) Most of the gaping pit’s base is caked in a layer of a white salt known as natron, which is a mixture of sodium carbonate, sodium bicarbonate, sodium chloride, and sodium sulfate. The black pits that make up the eyes and nose are actually towering cinder cones that have built up around volcanic vents.
Trou au Natron is found among the Tibesti Mountains, the highest mountain massif in the Sahara at an elevation of 2,450 meters (8,040 feet). Considered to be one of the most remote and isolated parts of the planet, these mountains are an eerie and mysterious place.
Despite its harsh environment, the Tibesti Mountains harbor some interesting biodiversity, including golden jackals, fennec foxes, gazelles, African wildcats, and various bird species. It’s also the ancestral homeland of the semi-nomadic Toubou people.
Trou au Natron is not deeply understood by scientists because it’s so far-flung, not to mention surrounded by a dangerous area wracked by political violence. No one knows how or when Trou au Natron was formed. The volcano is extinct, although is not known when it last erupted. It is known, however, that it was a deep glacial lake some 14,000 years ago.