The formation and evolution of Earth and other planets in the solar system have long been a topic of interest for planetary scientists. One way to gain insight into this process is by studying rocks from space.
However, obtaining these rocks is a challenging task. Sending spacecraft to asteroids or other planets to collect samples is possible but extremely difficult and expensive.
Another option is to study meteorites, which are rocks that fall to Earth from space. However, meteorites are relatively rare, and their journey through the Earth’s atmosphere and collision with the ground often leaves them in poor condition.
Despite these challenges, meteorites can provide valuable information. In a recent study, researchers analyzed glass fragments found near a 5,000-year-old meteorite impact site in the Northern Territory. The analysis revealed a significant amount of metal from the meteorite itself, confirming that the craters at the site were formed by a cosmic object and providing clues about its composition.
Natural glass, like the kind found in windowpanes and kitchenware, also occurs in nature. Most of it is obsidian, which is produced in volcanoes. A smaller amount of natural glass is created by lightning strikes and asteroid impacts. Determining the origin of natural glass requires careful forensic analysis, but it can provide valuable information about its source.
In this study, the researchers analyzed glass samples from the Henbury crater field in the Northern Territory. This site contains at least 13 impact craters formed around 5,000 years ago. The meteorites recovered from this site are IIIAB irons, which are remnants of the metallic core of a shattered ancient world. These meteorites are essentially lumps of metal composed mainly of iron, nickel, and cobalt.
When a meteorite strikes the ground, the heat of the impact melts the meteorite and surrounding rock. Some of this melted material forms droplets that cool and solidify into glass-like lumps. The researchers used laser technology to heat the glass samples and analyze their composition. The analysis revealed that the glass contained elements from the local sandstone as well as high levels of iron, nickel, and cobalt, indicating a significant contribution from the meteorite.
The Henbury glass also contained elevated levels of chromium, iridium, and other elements from the platinum group, which are rare in most rocks on Earth’s surface. This further supports the cosmic origin of the glass.
Similar glass has been found at other impact sites around the world, such as the Kamil crater in Egypt and the Wabar crater in Saudi Arabia. However, the high levels of meteorite residue found in the Henbury glass are unique to this site.
The researchers believe that meteorite-rich glass forms in all craters, regardless of size. However, it is best preserved in young craters that have not been eroded. The presence of meteorite residue in glass is a clear indication of an asteroid strike and provides valuable evidence for impact events.
There are many reports of enigmatic natural glasses whose origins are unclear. Determining whether these glasses have an impact origin requires careful investigation.
While obtaining rocks from space is a challenging task, ongoing missions to asteroids, Mars, and the Moon offer hope for collecting fresh samples. In the meantime, studying bush glasses like those found at the Henbury crater field can provide valuable insights into our cosmic heritage.
