Meteorites, the remnants of space rocks that have impacted Earth’s surface, are windows to ancient times. These beautiful assemblages of mineralogical marvels formed around the same time as the Solar System’s rocky worlds and asteroids, which hints at how these terrestrial titans originally came to be.
That’s why meteorite Northwest Africa (NWA) 11119 is so exciting a find. As explained in a stunning Nature Communications paper, it’s 4.564 billion years old, give or take a few hundred thousand years. Earth is around 4.54 billion years old, which means that this former meteor was potentially zipping around the early Solar System before our world even crystallized into being.
That means that it’s not just an insight into how precisely the terrestrial planets appeared from the miasma, but what type of processes were occurring even before then. Turns out that, according to the University of New Mexico (UNM)-led team, there was a decent amount of advanced volcanism taking place back then.
In order to understand why, though, we need to explore what NWA 11119 actually is, and what it isn’t.
Found back in 2016 within a sand dune in Mauritania, it was quickly snapped up by a meteorite collector. It was then sent to Carl Agee, the director of the UNM Institute of Meteoritics, who gave it to his graduate student – and lead author on the new paper, Poorna Srinivasan, to study.
1119 is part of a class of meteorites known as achondrites. They’re best understood, methinks, when contrasted with another type of meteorite. Their counterparts, chondrites, often contain spherical, silica-rich inclusions – called chondrules – whose glassy forms betray their origin story: they only underwent sudden, sporadic heating and melting events, which indicates they were never part of a larger planetesimal or even a fully-grown planet.
Achrondrites, as the name suggests, lack these glassy inclusions. Instead, their textures and minerals indicate that they underwent long-term, high-temperature (and pressure) melting.
This suggests that they spent much of their lives within larger objects, from asteroids (asteroidal achondrites) to planets (primitive achondrites). Lunar and Martian meteorites are types of achondrites too.