Pena Blanca Spring

Peña Blanca Spring is an aubrite, a rare type of achondrite meteorite dominated by the magnesium silicate mineral enstatite. Aubrites formed under extremely reducing conditions, meaning they contain almost no iron in oxidized minerals, giving them a strikingly pale, light-colored appearance unlike most other meteorite types.

The Peña Blanca Spring meteorite fell in 1946 in Brewster County, Texas, near the spring that gives it its name. It was an observed fall, meaning witnesses saw the meteorite arrive, which allowed researchers to recover fresh specimens relatively quickly after impact.

Aubrites are among the rarest meteorite types in the world's collections, making up only a small fraction of all known meteorite falls. Peña Blanca Spring is one of a very small number of observed aubrite falls, which makes it scientifically valuable for studying this unusual class of extraterrestrial material.

The highly reducing conditions under which aubrites formed indicate they originated in a parent body with almost no available oxygen, so iron exists as metal or sulfide rather than in oxide minerals. This chemistry points to formation conditions very different from most terrestrial and asteroidal rocks, and helps researchers link aubrites to specific parent bodies such as the asteroid 3103 Eger.