Man's hunt for gold leads to discovery of rare 4.6 billion-year-old meteorite
In 2015, David Hole was on a hunt for gold in Maryborough Regional Park, Victoria, Australia. Instead, he found a rare red-coloured rock -- from another world.
But Hole did not know it then: he thought the rock was a gold nugget. When he failed to scrape gold out of the 17kg rock, he carried it to the Melbourne Museum. After a series of tests, Dermot Henry and Dr Bill Birch who work at the museum, unveiled its identity: a 4.6 billion-year-old meteorite. This space rock, which has since been named Maryborough meteorite after the town Maryborough, was once a part of a comet or asteroid that fell into the Earth's atmosphere.
"When you consider all the events this chunk of rock has experienced since its formation 4.6 billion years ago, it is really mind-boggling that we get the opportunity to hold it and study it today. How good is that?" says Birch, Museums Victoria Emeritus Curator in Geosciences, in a statement.
Story behind the discovery
It is rare to find meteorites. Of the thousands of rocks Henry, Head of Sciences at Museums Victoria, has examined in his 37 years at the museum, only two have been meteorites, including the Maryborough meteorite. "This is only the 17th meteorite found in Victoria, whereas there has been thousands of gold nuggets found," Henry told 10 daily.
Recalling the events that led up to its identification, Henry told the Sydney Morning Herald, "It had this sculpted, dimpled look to it. That’s formed when they come through the atmosphere, they are melting on the outside, and the atmosphere sculpts them.”
Dr Birch suspected that the rock was not from Earth the moment he lifted it. “If you saw a rock on earth like this, and you picked it up, it shouldn’t be that heavy,” he says.
This meteorite, they suspect, probably belonged to the asteroid belt between Mars and Jupiter. "It has been nudged out of there by some asteroids smashing into each other, then one day it smashes into Earth and some prospector finds it and brings it to us," Henry told Sydney Morning Herald.
The duo of Birch and Henry are not really sure of when the meteorite arrived on Earth. But they do know that it may have entered our planet 100 and 1000 years ago. Also, according to local news reports, people have witnessed multiple meteors in the Maryborough district, between 1889 and 1951.
Unlike most meteorites, Maryborough meteorite has not left a mark on the site. "There was no evidence for the meteorite leaving an impact, and no further pieces had been found in the vicinity," write the authors in a paper on the discovery published in the Proceedings of the Royal Society of Victoria.
What can the rock tell us?
To dig into the rock's past, the team dissected and analyzed the material. The rock had iron, nickel and a lot of chondrules: round grains composed of minerals that melted in the solar nebula -- the cloud of gas and dust -- about 4.5 billion years ago.
When the chondrules cooled, the molten material hardened to form small solid spheres, which later went on to form planets and asteroids. “You’re looking right back to the formation of the solar system here,” says Henry.
Chondrules which are a part of meteorites are called chondrite meteorites, the most common space rocks that have hit Earth. These chondrites are further classified into ordinary and carbonaceous.
Ordinary chondrites are the most common type of stony meteorite, accounting for 86% of all meteorites that have fallen to Earth. Their tests revealed that the rock was a H5 ordinary chondrite meteorite. It is named H5, thanks to its high iron content. Carbonaceous chondrites, on the other hand, are and often contain water.
Studying meteorites can help scientists learn about the origin of life and the solar system. "They transport us back in time, providing clues to the age, formation and chemistry of our Solar System (including the Earth). Some provide a glimpse at the deep interior of our planet. In some meteorites, there is 'stardust' even older than our Solar System, which shows us how stars form and evolve to create elements of the periodic table. Other rare meteorites contain organic molecules such as amino acids; the building blocks of life," explains Henry.