Hunting for meteorites

Claire Concannon joins a meteorite hunt on the South Island's West Coast and learns what these rocks from space can tell us about the early formation of our solar system.

In January 1976 Ted Dowie was looking for gold in a river in the mining district of Dunganville near Greymouth when he came across a black, smooth-topped boulder in a dry creek bed. It rang like a bell when he hit it and was unusually heavy. Intrigued, Dowie rolled the boulder up on the stream bank and sent a small sample he had chipped off to New Zealand Geological Survey.

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Mr. Dowie had found a 50.2kg iron meteorite, the name we give to rock or other solid debris that has come from outer space and landed on Earth. The Dunganville meteorite is still the largest of the nine recorded in New Zealand to date, and it is the iron core of a protoplanet from four and a half billion years ago when our solar system was forming.

At that time most of the gas and dust left over from an explosion of a massive star came together to form our sun. Some of the remaining material became protoplanets, with some getting big and hot enough to melt so that they separated out into a dense iron core and a lighter mantle.

A few of these protoplanets went on to become our familiar family of planets, but others got smashed apart before they made it that far. The remnants of these drifted in space, but the odd collision knocked them on a course to land on earth.

A short time after Mr. Dowie's find a further search of the creek bed turned up 68 pieces of the weathered crust. But what if some was overlooked, or if the boulder was just one in a shower of meteorites? Could there be more out there?

These are the questions on the minds of Associate Professor James Scott and students from the Geology department at the University of Otago. Following in Dowie's footsteps, with metal detectors in hand, the team set out to see if they can find a piece of a core of a four and a half billion year old protoplanet in a river on the South Island's West Coast.

To learn more:

Read the 1984 paper that describes the Dunganville meteor here.

Find out more about the recorded New Zealand meteorite falls and finds on the Te Ara website.

Thanks to GNS Science, Te Pū Ao, for providing fragments of the Dunganville meteorite for XRF testing.

Go to this episode on rnz.co.nz for more details