A meteorite found in the Sahara desert, named Sidi El Habib 001, contains blue halite (common salt) that records a prolonged period of exposure to space. The study, published in Nature, analyses these salt crystals as natural archives of the meteorite's history before it fell to Earth.

Halite is a mineral that forms through the evaporation of saline water and can trap gases and compounds from its surrounding environment within its structure. In the case of Sidi El Habib 001, the halite crystals show a blue coloration attributed to irradiation experienced during their time in space, a process that leaves measurable chemical and structural traces.

The researchers examined the crystals to reconstruct how long the meteorite was exposed to cosmic radiation and the vacuum of interplanetary or interstellar space. Halite thus acts as a geological clock that complements the information provided by other meteorite components, such as silicate minerals.

The finding is significant because halite-bearing meteorites are rare and offer a unique window into the interaction between volatile materials and the space environment. Understanding how salts are altered in space helps to better interpret the history of solar system bodies and the conditions they were subjected to before reaching Earth.