this is a good story
Prospectors’ mystery rock was no nugget, but something much rarer
Liam MannixJuly 17, 2019 — 12.49am
Dave Hole had tried everything. Rock saw. Drill. They all just bounced off. The damn rock would not crack. This was his last shot.
He gripped the sledgehammer with two hands, raised it above his head, and brought it down as hard as he could. CLANGGG.
Nothing. Not even a scratch. “What the hell is this thing?”, Mr Hole thought to himself.
The answer, it turned out, was something not of this Earth.
He had come across the large reddish rock while hunting for gold near Maryborough, where he lives, in 2015. It was extremely heavy, far heavier than it looked, so Mr Hole thought there had to be a nugget inside.
He was wrong. This was no nugget. It contained something much rarer than gold: metal raindrops from the dawn of our solar system.
Dr Bill Burch, senior curator emeritus and Dermot Henry, head of sciences at Museums Victoria.Sim Schluter
People bring rocks to Melbourne Museum all the time, hoping they are meteorites. It is the job of museum geologists Dermot Henry and Bill Birch to gently let them down. Of the thousands of rocks Mr Henry has examined in his 37 years at the museum, only two have been meteorites.
But the moment Mr Hole brought his rock in, packed inside a backpack, they started to get very excited.
“It had this sculpted, dimpled look to it,” Mr Henry recalled. “That’s formed when they come through the atmosphere, they are melting on the outside, and the atmosphere sculpts them.”
The moment he lifted it, Dr Birch knew. “If you saw a rock on earth like this, and you picked it up, it shouldn’t be that heavy.”
Testing quickly confirmed their suspicions. Mr Hole’s rock was a 4.6 billion-year-old meteorite.
The rock – now known as the Maryborough meteorite – is so heavy because, unlike standard Earth rocks, it is filled with very dense forms of iron and nickel.
Mr Henry used a super-hard diamond saw to slice the edge off, revealing a cross-section of little silver raindrops.
These were once droplets of silicate minerals that crystallised from the super-hot cloud of gas that formed our solar system. “You’re looking right back to the formation of the solar system here,” says Mr Henry.
It is called an “H5 chondrite”, which is similar to the rocks the Earth was built from.
About 4.6 billion years ago our solar system consisted of lumps of this chondrite circling the sun. Gravity slowly clumped those rocks together to make Earth and the other rocky planets.
Some lumps of chondrite were left over. Most of them now orbit in the asteroid belt between Mars and Jupiter.
Occasionally, two asteroids in the belt will crash into each other, sending shards of rock flying. That’s how the Maryborough meteorite would have started its life – as a shard sent racing toward Earth.
After travelling for years through space, it entered the Earth’s atmosphere. Friction would have superheated the rock and turned its surface red and molten. It would have streaked across the sky before landing with a thud in the dense scrub where, years later, Mr Hole found it.
The lack of weathering on the rock suggests it has been on Earth for less than 200 years, says Mr Henry. That means someone probably saw it fall. There are records in local newspapers of fireballs streaking across the sky above Maryborough, including one from The Age in June 1951.
The meteorite will go on display at Melbourne Museum on August 11 during National Science Week. Mr Hole plans to travel down to take a look at the rock, which travelled for 4.6 billion years to wind up on his doorstep.
“It was just pot luck, mate. A billion to one – bigger, a trillion to one,” he marvels. “Got more chance of being struck by lightning twice.”
The moment he lifted it, Dr Birch knew. “If you saw a rock on earth like this, and you picked it up, it shouldn’t be that heavy.”Simon Schluter
