Twenty Years Ago Today: The Iron Heart of a Meteorite Exposed

See all that gas and dust swirling around the sun? In four and a half billion years time, some of that will be you. Four and a half billion years ago (or thereabouts), the sun ignited. But there was more to the solar system than just the sun. The disc of gas and dust that swirled around the new star began to clump together to make planets and moons and asteroids. They melted under the pressure of their own increasing gravity and became so hot that the heavier elements sank within them down to their cores, leaving them with deposits of iron right at the heart of each one.

One such body flew on in its orbit around the sun for untold millions of years, cooling off until it was solid through and through. It could have gone on forever, until the heat-death of the universe put an end to all light; but it was not to be. The solar system was stuffed to the gills with lumps of rock and iron, so many that they smashed into each other over and over. Sometimes this would make a bigger chunk of rock and iron. This time it just smashed the asteroid apart, breaking up the iron core into tiny pieces that swung on around the sun in new orbits, going on for more millions of years...

Until one of them hit China.

In 1516, a fireball was observed over Nantan county in the province of Guangxi. The meteor flared bright, but it was too big and heavy to vapourise. It broke apart into a shower of meteoritic chunks weighing nine and a half tons between them. They smacked into the ground across the county, each one too small to do much damage or even to be noticed. And there they lay for centuries - ignored, forgotten, perhaps occasionally uncovered, but never desired so much that anyone went looking for them.

Until one day China had a desperate need for iron.

Mao Zedong, a man who counted his successes in terms of how many millions of people died as a result

By 1958, Mao Zedong had already removed all opposition to Communist rule by the simple expedient of asking for suggestions on how things could be improved, and then purging the half a million or so people who actually replied. So he was now free to push forward with his ideological campaign to industrialise China by forcing the heroic peasants to make a Great Leap Forward in production of all goods - including steel.

But the campaign was woefully mismanaged. Steel production couldn't be conjured from nothing, with no infrastructure. So to fulfil the ever-increasing quotas, people would melt down pots, pans and anything else they could lay their hands on - which included any meteoritic iron that happened to be lying around. And so the lumps of metal that fell from the sky centuries before were uncovered, and dragged off to makeshift furnaces. But they wouldn't melt. The iron had been mixed with nickel when it was formed, and the resulting alloy had a melting point far beyond the capability of the peasants struggling to meet their quotas. The meteorites were put to one side while 36 million people died in the famines caused by the disaster that was the Great Leap Forward.

The Nantan meteorite, once it had been sliced open.

By 1994, China was finally making rapid progress towards real industrialisation, mainly because Mao and his old supporters had died off, leaving the more practically minded (if still somewhat brutal) Deng Xiaoping in charge. Contact with the rest of the world blossomed, and some of the haul of meteorites from Nantan were sold off - one of them to a consortium of European museums for the princely sum of $25,000.

And so, twenty years ago today, a lump of iron and nickel weighing 255kg was sliced up into five pieces at a specialist cutting firm in Redditch, which was surprised but overjoyed to get the chance to prepare the meteorite for the Natural History Museum. The resulting shard was briefly put on display before being given over to research that would help to explain the story of the early solar system, and how dust and gas could go on to form the planets and moons and asteroids that we know today...