ASU Microscopes Uncover Decades-Old Mystery of Ancient Asteroids
A geologist's passion for exotic rocks led him to a groundbreaking discovery. Axel Wittmann, a geologist with a penchant for unique specimens, found himself captivated by suevite, a rock formed from intense meteorite collisions. But it was a chance encounter with fellow geologist Philippe Lambert during an excursion to the Rochechouart impact structure in southern France that unveiled a new, enigmatic rock formation. This discovery would challenge conventional understanding and keep Wittmann intrigued for over a decade.
In 1972, Lambert stumbled upon a peculiar rock during his PhD fieldwork. He named it impactoclastite, a unique formation found exclusively at the Rochechouart impact structure. Impactoclastite was believed to be composed of debris that fell back from the asteroid's impact plume. However, what set it apart was its remarkable survival. Unlike other impact deposits that faded over time, impactoclastite persisted in the suevite rock layers, forming veins up to 27 meters deep and occurring in various orientations. This longevity of millions of years remained unexplained until a high-resolution microscope examination at Arizona State University's Eyring Materials Center.
Wittmann's curiosity led him to analyze a sample of impactoclastite using the center's advanced JEOL JXA-8530F electron microprobe. This instrument's precision revealed compositional signatures in the impactoclastite, indicating the presence of asteroid metals formed at extreme temperatures. This discovery led to a groundbreaking theory: 'debris inhalation.'
The theory posits that after the Rochechouart asteroid impact, a hot vapor and molten droplet plume rose into the sky. The central crater peak, formed in minutes, created a vast cave beneath the existing rock slab. Hours to a day later, the slab collapsed into this cave, causing cracks in the partially cooled suevite. As the plume rained ash and droplets back onto the crater, a temporary vacuum formed, sucking the falling debris into the cracks. This process, akin to the ground's breath, preserved the impactoclastite for millions of years.
Wittmann's 16-year analysis culminated in a publication in Earth and Planetary Science Letters. The research team's findings not only explain the impactoclastite's formation but also enhance our understanding of impact craters, asteroid materials, and ancient environments. Moreover, it contributes to planetary defense science by enabling more accurate modeling of atmospheric consequences and hazard zones for future asteroid impacts.
Lambert emphasizes the importance of communicating these scientific discoveries to the public, as it is crucial for safeguarding our planet. This research highlights the power of interdisciplinary collaboration and the potential for groundbreaking discoveries through advanced microscopy and geological exploration.
