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Understanding Meteorites: The Ongoing Quest
Over the years, shooting stars have fascinated the imagination of people across the world. Also known as fallen stars, they are frequently viewed as symbols of hope, enchantment and good fortune by different cultures, yet for many, these blazing streaks of light are merely moments of astonishment. However, for a nine-year-old girl from Nqweba, South Africa’s Eastern Cape province, this curiosity became a physical reality. On a calm Sunday morning in late August 2024, Eli-zé du Toit was sitting on her grandparents’ veranda, when suddenly a rumble shook the ground and a mysterious rock plummeted from a fig tree right in front of her. On closer inspection, the rock, still warm on the surface, had a blackened crust with a grey inside that resembled concrete, but the interior was noticeably frigid. A meteorite.
But what exactly is a meteorite, and where does it come from?
A meteorite is a piece of extraterrestrial rock that survives after colliding into Earth’s atmosphere. They originate primarily from the asteroid belt, a region between Mars and Jupiter where remnants of the early solar system formation reside. The majority of meteorites come from asteroids, but some come from the Moon or Mars. These space pebbles are pulled to Earth by its gravitational attraction, which pulls objects from space. As meteoroids – the term used for meteorites before they enter the atmosphere – approach Earth, they encounter the atmosphere, where frictional heating causes them to glow and create a visible streak of light known as a meteor or “shooting star”. The meteoroid’s extreme heat and pressure frequently force it to break and disintegrate, with just a portion of the debris reaching the ground as meteorites. Meteorite research offers important insights into the early solar system, planetary body formation and space conditions prior to meteorite entry into Earth’s atmosphere.
The Nqweba meteorite is not the first meteorite hitting Earth’s surface this year. On 21 January, the Ribbeck meteorite, an aubrite categorised as asteroid 2024 BX1, fell in Ribbeck, Germany. Aubrites are a rare type of achondrite meteorite, known for their unique mineralogical composition. This meteorite’s arrival has piqued the interest of academics, who want to investigate its composition and obtain insights into the differentiation processes of asteroids. The Ribbeck meteorite’s impact site, located in a rural area, provided a remarkably intact sample, which is crucial for comprehending the early solar system. This occurrence was followed by the Angers meteorite, which fell in France on 4 June this year. Although the meteorite’s exact classification is unknown, the lack of initial classification has not reduced its scientific value. Researchers are currently analysing the meteorite to determine its type and origin. The Angers meteorite’s fall was significant for its influence on the local population and the resulting surge in scientific activity. As for the Nqweba meteorite, which is of the HED type, thorough investigations into its composition and origin are still going on.
While the meteorites of 2024 are remarkable in their own way, history is full of extraordinary space rocks that have left indelible traces on our planet. One of the most well-known is the Hoba meteorite, the largest intact meteorite ever discovered on Earth. The Hoba meteorite was discovered in 1920 on a property called Hoba West, 19 kilometres west of Grootfontein in northern Namibia. It weighs roughly 60 tonnes. It is thought to have entered Earth’s atmosphere less than 80,000 years ago and has never been moved since its discovery. The meteorite was first identified by farmer Jacobus Hermanus Brits, who, upon discovering the massive, unusual rock surrounded by white limestone, brought a sample to the South West Africa Company office in Grootfontein, where it was confirmed as a meteorite. The true scale of the Hoba meteorite was revealed only after digging around the rock. The meteorite has a huge, generally rectangular shape with a flat top and is about 2.7 metres (9 feet) wide. Its composition is mostly iron (82.3%), with nickel (16.4%) and cobalt (0.8%). The shallow angle of its atmospheric entry and low impact speed produced a small crater, which has since eroded away.
The Gibeon meteorites, which fell over a broad elliptical area of around 275 by 100 kilometres centred on Brukkaros in Namibia, are well-known for their widespread dispersion and scientific significance. These meteorites were initially discovered in the early nineteenth century, when James Alexander collected little metal bits in 1838, which were later confirmed as meteoritic by chemist John Herschel. The Gibeon meteorites are classed as octahedrites, which are predominantly made up of taenite and kamacite, two crystalline forms of an iron- nickel alloy. Their unique Widmannstätten structure, which features alternating bands of these two minerals, provides intricate data about their genesis and temperature history. The meteorites show distinct thermal alterations from their high-speed atmospheric entry, including smooth outer layers and deep, spherical cavities, indicating an extended atmospheric flight. Their composition, which includes an average of 8% nickel and traces of other elements such as cobalt and phosphorus, makes them crucial for studying the processes that shaped their parent body and their subsequent journey through space.
Their research not only improves our understanding of the materials and processes that contributed to the formation of planets and celestial bodies, but it also gives a direct link to the early cosmos.
Meteorites act as cosmic time capsules, retaining crucial information about the solar system’s formation and history. Their research not only improves our understanding of the materials and processes that contributed to the formation of planets and celestial bodies, but it also gives a direct link to the early cosmos. Scientists can solve the riddles of planetary formation and determine the possibility of extraterrestrial life by analysing these spaceborne debris. Meteorites continue to enrich our understanding of the universe, providing a profound connection between Earth and the furthest reaches of space.
