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Rogue visitors from space have appeared recently. An asteroid passed within 3,600km of Earth on January 27 and a ‘pale green’ comet made its closest pass in 50,000 years on St Bridget’s day. Meteors we have always with us, but they are in the news also; five meteorites have been found during an expedition to Antarctica.

About the size of a truck, Asteroid 2023 would be too small to cause mayhem were it to strike even a built-up area. Most such objects burn up and disintegrate due to friction with the Earth’s atmosphere but, as the dinosaurs discovered, space debris reaches the ground occasionally. The arrival of a lethal missile can’t be predicted accurately, but not to worry: according to NASA a five-metre-wide object hits the Earth only about once a year. A 50m-wide fragment arrives every 1,000 years or so.

The St Bridget’s day comet hailed from the Oort Cloud — “an icy hinterland on the outskirts of the solar system where hundreds of millions to trillions of comets lurk,” writes Michael Greshko in National Geographic.

The Hoba Meteorite is the largest known meteorite and likewise the largest known single mass of native iron known on earth. The meteorite came down about 20 km west of Grootfontein about 80,000 years ago and still remains at the same place. Picture: Namibia Tourism Board
The Hoba Meteorite is the largest known meteorite and likewise the largest known single mass of native iron known on earth. The meteorite came down about 20 km west of Grootfontein about 80,000 years ago and still remains at the same place. Picture: Namibia Tourism Board

In 1920, a Namibian farmer’s ox-drawn plough struck something in the soil. He had a piece of the offending obstacle analysed. The object turned out to be no ordinary meteorite, but the largest one ever found. The lump of iron and nickel, 3m square and 1m thick, may have crashed to earth less than 80,000 years ago.

The meteorite was not moved from where it fell at Hoba West off the beaten track between Grootfontain and Otavi. Oddly, no crater resulted from the impact. The surrounding soil has been removed and a mini-amphitheatre created for viewing. Astronomers differ as to the age of the meteorite, declared a national monument in 1955, but touching something that hurtled through the cosmos for 200 to 400 million years is almost a mystical experience.

The Hoba Meteorite site was declared a National Heritage on March 15, 1955. Picture: Hoba Meteorite National Heritage Site
The Hoba Meteorite site was declared a National Heritage on March 15, 1955. Picture: Hoba Meteorite National Heritage Site

The Hoba ‘fallen star’ weighed around 66 tonnes at impact but pieces were chipped off by vandals, reducing it to about 60 tonnes. The announcement that five meteorites, the largest of them weighing just 7.1kg, have been found in Antarctica seems ‘small beer’ by comparison. However, of the 45,000 extra-terrestrial objects recovered worldwide in the last century, only 100 or so are this heavy. According to the Field Museum, “even the smallest fragments from space tell a big story. Meteorites can contain minerals that are older than the sun and the planets”.

Antarctica is the ideal place in which to find such objects — they are easy to spot against the snowy landscape. Meteorites falling elsewhere tend to plough into the soil or become hidden by vegetation. They strike the Earth in prodigious numbers, only a tiny fraction reaching the ground as ‘meteorites’.

Nor has Ireland escaped them.

The National Museum lists eight ‘meteorite falls’ here since 1779. The most recent notable ‘event’ occurred in Leighlinbridge, County Carlow. At 10.10pm on the night of November 28, 1999, ‘a fireball’ exploded over the town. Loud bangs were heard several seconds later. Four fragments were recovered in the locality. Their total weight was 271 grams.

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