By Liam Mannix
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It’s not often you get to witness a true moment of discovery.
“Oh! I think that’s some there,” says Oskar Lindenmayer, leaning intently into the glass display case and jabbing a finger towards a small green blemish on a huge chunk of space ore. “That little patch there.”
We are staring at an ancient meteorite that hundreds of thousands of museum visitors have walked past – and Lindenmayer has just discovered an exotic mineral almost new to science, right there on its flank.
Oskar Lindenmayer holds a fragment of the Cranbourne meteorites, revealing (in green) the new mineral muonionalustaite.Credit: Tim Carrafa / Supplied
The mineral is called muonionalustaite (pronounced mew-on-en-ulster-ite) and it’s an extraterrestrial jumble of nickel, chlorine, hydrogen and oxygen atoms that scientists first described in 2021.
The find – several patches of green spread across the oxidised crust of a meteorite that slammed into what is now Cranbourne in Melbourne’s south-east thousands of years ago – is just the third natural sample discovered.
A large chunk of the meteorite has been on display at the Melbourne Museum for years – the British stole most of the rest – tucked in a corner behind the toothy Tarbosaurus skeleton.
Lindenmayer and Dr Bill Birch with the larger meteorite fragment, that is on display.Credit: Tim Carrafa / Supplied
Lindenmayer, who manages the geosciences collection at the Museums Victoria Research Institute, points out a small bright-green plaque on the rock’s surface.
Anyone who noticed it over the years probably assumed it was mould growing on the rock. But under a microscope, muonionalustaite reveals itself as a series of microscopic green pearls – hollow, liquid-like, seemingly frozen just before they burst.
Muonionalustaite under the microscopeCredit: Museums Victoria / Supplied
“It’s just this beautiful texture, this little world you never would have expected,” says Lindenmayer.
A history of star-fall
The 13 Cranbourne meteorite fragments – pieces of a single chunk – were picked from the region in the 1850s.
The academic literature records descriptions of First Nations groups holding ceremonies around the rock, dancing and striking it to produce an eerie ring.
The muonionalustaite patches lay undiscovered on several chunks of meteorites spread across the museum’s collection, until Dr Bill Birch read about its discovery on the crust of a meteorite in Sweden.
“It had a picture,” says Birch, a curator emeritus of geosciences at the institute. “I thought to myself, ‘Now, I’ve seen that before.’”
Birch scraped off some samples with a needle and, as the museum was closing on a Friday afternoon in July, ran them through an X-ray diffraction machine. The device fires X-rays at samples and then measures how the atomic structure interferes with the radiation – producing a graph that reveals the atomic make-up.
Oskar Lindenmayer (left) and Bill Birch.Credit: Tim Carrafa / Supplied
“I said to Oskar, ‘Is there a peak?’ Yes. ‘And is there another peak?’ Yes,” says Birch.
Lindenmayer says: “We high-fived.”
They are something of a scientific odd couple. Lindenmayer pulls out a box of meteorite fragments from the museum’s collection where they have also spotted muonionalustaite. They look like tan bark.
“It’s amazing – it’s the sort of thing you’d chuck out”, says Birch.
“No you wouldn’t!” says Lindenmayer, shocked.
“Well, it’s the sort of thing I’d chuck out,” says Birch.
Muonionalustaite is so new no one really understands how it forms. The best guess is that after the meteorite buries itself in the earth, chlorinated water seeps inside, mixing with nickel and iron, and then seeping back out as muonionalustaite.
“It absorbs water and very quickly turns into this liquid. It oozes out of the meteorite,” says Birch. “When it dries out, it forms little droplets. And the contents of the fluid crystallises around the edges – not a bubble, but a globule.”
Once it has been pointed out, the green plaque seems hard to miss. How did it stay hidden in plain sight? “That’s a long story,” says Birch, who suspects it was probably confused for the more common nickel-carbonate zeolite.
“It’s just this beautiful texture,” says Lindenmayer, “this little world you never would have expected.” Credit: Tim Carrafa / Supplied
‘The ingredients Earth is made out of’
Why study meteorites? Because you might find a previously undiscovered mineral, obviously. But meteorites also tell us about how the Earth – and maybe life itself – was formed.
Our planet formed from asteroids that slowly accreted out of the “molecular cloud” of dust and rocks that once surrounded our sun. Many of these meteorites carried large volumes of frozen water in their depths, which would have helped fill the early oceans.
And because they orbited the sun and were directly exposed to its radiation for millions of years, they may have been test beds for cosmic chemistry. Some even carry simple organic molecules, including short-chain amino acids that could have been essential in life’s genesis.
“They are essentially the building blocks, the ingredients Earth is made out of,” says Professor Trevor Ireland, who studies asteroids at the University of Queensland.
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