(Fiona Pepper’s post from the ABC NEWS Australia on 02 October 2019.)
The Secrets Of The Universe: The Murchison
meteorite is one of the most scientifically significant space rocks ever discovered.
It fell to Earth on September 28, 1969, near the town of Murchison in Victoria,
Australia. A bright fireball was seen streaking across the sky before the
meteorite exploded in the atmosphere and scattered fragments across a wide
area.
What makes the Murchison meteorite so extraordinary
is its composition. It's classified as a carbonaceous chondrite, a rare type of
meteorite rich in organic compounds and primitive solar system material.
Scientists believe it is over 4.6 billion years old, meaning it formed during
the very early days of the solar system.
When researchers analyzed the Murchison fragments, they discovered over 70 amino acids—the building blocks of life. Many of these are not found naturally on Earth, strongly suggesting an extraterrestrial origin. In later studies, scientists even identified sugars and nucleobases, which are crucial for RNA and DNA. This raised a profound possibility: the ingredients for life may have been delivered to Earth from space.
Additionally, in 2020, researchers found grains of
stardust in the meteorite that were dated to be up to 7 billion years old,
making them the oldest solid material ever found on Earth. These tiny grains
predate our Sun and were likely formed in ancient stars that exploded as
supernovae.
When a space visitor came to country Victoria
It was a spring Sunday, September 28, 1969. In the
small farming town of Murchison, two hours north of Melbourne, many locals were
making their way to church. One was celebrating his 21st birthday, and the
Gillick brothers were building a ferret cage in their back yard.
But at 10.58am everyone stopped what they were
doing and looked to the sky. They didn’t know it yet but a 4.6-billion-year-old
meteorite had just rained down on their town. Murchison is a farming town on
the Goulburn River with fewer than 1,000 inhabitants. Many locals were making
their way to church when they heard the meteorite. A lot of meteorite samples
were found to the east of the Murchison bridge .
“My husband and I were getting ready for church,”
recalls Marianne Begg. “Our 11-year-old son and our seven-year-old daughter
were out on the front verandah and I heard this ‘ba-boom, ba-boom, ba-boom’.
“I called out, ‘John stop jumping on the verandah!’
and he said, ‘It’s not me mum, it’s up in the sky.’ “We rushed outside and we
could see this puff of blue smoke, right up in the clear blue sky and we
realised something had happened.” Aside from the noise, Marianne says there was
also a strong smell of methylated spirits.
Running late for the 11.00am church service, the
Begg family piled into their car and rolled out of their driveway. “We looked
down the paddock with 115 milking cows and they were all just about heaped in
the corner of the paddock, trying to get away with their ears up,” Marianne
says. Marianne Begg has vivid memories of the meteorite landing.
Over the course of the morning, everyone came up
with their own theory as to what had caused the unusual noise and smell. A
dairy exploding, or maybe a plane crashing. “I jokingly said I thought it was
two spaceships shooting at each other,” says Marianne.
Others thought it was a fire or car accident, and
expected the sirens at the nearby fire station to spring to life. And some
thought it must have come from Puckapunyal, the nearby military training base. “Everybody
was of course speculating … Was it the guns going off, a gas explosion or
something had happened on the [train] track?” says Don Polkinghorne, another
local.
But it was 1969: there was no way of looking up or confirming what had actually happened. “We just went on with what we were doing, because nobody in those days could find out.”
(The
black arrow on the map shows the direction the meteorite travelled.)
That evening, on a farm just minutes from town, the
late Arnold Brisbane went to milk his dairy cows for the second time that
Sunday. “Having left the yard pristine, he noticed this black charcoal substance
on the yard,” explains Beth Brisbane, Arnold’s daughter in-law.
“He had no idea what it was but obviously it had
fallen out of the sky because there was no other reason for it.” Arnold scooped
up the bulk of the “charcoal”, threw it over the fence and then proceeded to
hose the yard down — flushing the unusual substance into the farm’s manure pit.
But the next morning, as Murchison residents continued to corroborate their stories of lights, smoke and noise in the sky, Mr Brisbane decided to take a sample of this strange, black, charcoal-like substance to Shepparton News. Journalists then took the sample to the nearby police station.
After telling the police, the Shepparton News
called the geology department at the University of Melbourne. “That’s when the
fuss started,” says Beth Brisbane.
From moon rocks to Murchison
On the day of the Murchison meteorite landing, John
Lovering, professor of geology at the University of Melbourne, was slightly
preoccupied. “I was coming back in the aircraft from America, having picked up
the first lunar samples to analyse in our labs here in Melbourne,” he recalls.
It was three months after Apollo 11 landed on the moon and Professor Lovering had been nominated as one of the principal Australian investigators for analysing the samples the astronauts brought home.
(Professor Lovering not long after the discovery of
the Murchison meteorite.)
It was as he was standing in Melbourne airport, clutching a bag of moon rock samples, that Professor Lovering first heard about the meteorite landing. “A bloke from The Age came and said, ‘something has fallen out of the sky in a place called Murchison’.” Meanwhile, a group of University of Melbourne geology students had already made their way to the town to start looking for pieces of meteorite.
Andrew Gleadow was a third-year geology student at
the time. Today, he’s an emeritus professor of earth sciences at the University
of Melbourne.
He was designated the grim task of sorting through
the manure pit on the Brisbanes’ farm. “I was assigned to stand in the pit with
gumboots on, sleeves rolled up, sieving through manure, feeling for gritty
little lumps like gravel,” Professor Gleadow recalls.
‘The rarest of meteorites’
It wasn’t until a couple of days after the landing
that the true significance of the meteorite was recognised. Caught up with
official proceedings following his return with the moon rocks, Professor
Lovering hadn’t had the opportunity to go to Murchison.
As it happened, he was in the Melbourne ABC TV
studio, waiting to be interviewed on current affairs program This Day Tonight,
when he finally laid eyes on a piece of the meteorite. “The door flung open and
a bloke came in carrying a plastic bag, all blown up [from the gases coming off
the rock],” he remembers.
I opened it up and I got the smell of all these
very complex organic compounds— an incredible potpourri of all the smells that
you ever imagined. I looked inside and there was this black, coaly looking
material and I said, ‘My god, it’s a carbonaceous chondrite!’
“These are the rarest of meteorites, the most
primitive of them. And here was this beautifully fresh one.” Because the rock
had landed in the daytime and was discovered quickly, its precious cocktail of organic
compounds wasn’t contaminated.
Overwhelmed by the significance of the find,
Professor Lovering began leaping around the TV studio. “[Presenter] Peter
Couchman said ‘hold on, hold on we’re not on the air yet’, but by the time we
got on the air I was all calm and collected,” he says. “As far as I was
concerned, the meteorite was more important than the moon rock that I’d come
back with on that very same day.”
It wasn’t long before scientists and meteorite
collectors from all over the world began to descend upon the tiny town of
Murchison.
An impact without a crater
Carbonaceous chondrites break up as they enter the
atmosphere; the booming the locals reported was these meteorite fragments
breaking the sound barrier. So unlike most meteorites, there was no impact
site, no crater. Instead, the Murchison meteorite was scattered across a swathe
of farmland 11 kilometres long and 3km wide.
With clues like a big piece that went through a hay
shed in Murchison East, people had an idea of where to look, Beth Brisbane
remembers. Countless scientists showed up at the Brisbanes’ farm to take a look
at the dairy. But it wasn’t just scientists looking for meteorite samples: the
locals got involved too.
The Gillick boys became known for their ability to
seek out meteorite pieces. It was the Gillick brothers, Peter and Kim, aged 10
and 11 at the time, who became most dedicated to the cause. The boys were very
methodical in their search efforts.
“We started to piece together where it fell and how
it fell,” Kim Gillick says. “We realised quickly that the small pieces travel
less and fell quicker to the earth, and the large pieces carried and went
further.”
Using maps of the area, the brothers gridded a path
of where the meteorite fell and which direction, and that told them where to
look. Each day at 10 or 11am, when the sun was high in the sky, their mother
would drive them to an area that they had determined as a potential spot for
meteorite fragments.
Peter Gillick and his brother Kim spent much of their school holidays looking for the meteorite, with much success. “We’d just go walking, get in lines and just go up and down, up and down,” Kim says. They sometimes went for long periods without finding any pieces, but Kim says that just made the search all the more satisfying. “Each piece was different. It was a thrill,” he says.
The Gillick brothers quickly gained a reputation
for knowing where to find fragments of meteorite. “Scientists would come down
to Murchison and stay at our house, and they’d go out with Pete and me and find
a piece of meteorite,” Kim says. Professor Lovering was one of these
scientists. In a sort of scientific exchange, he brought along the samples of
moon rock he’d recently brought back from America.
“We had the test tubes in our hands looking at the
moon,” Kim says. “That was unbelievable.” For at least 12 months after the
meteorite landing, the brothers conducted regular searches. And it paid off. Of
the 100 kilograms of Murchison meteorite that was recovered, Kim says he and
Peter recovered roughly a third.
A secret fortune
While the meteorite was obviously of scientific value, it also had a price tag.
Kim Gillick and his mother Emily at the Murchison
post office with their meteorite fragments on display.
In an interview with This Day Tonight in 1970,
Kim’s mother Emily Gillick was asked what was being done with the meteorite
samples. “We have exchanged a lot for different stones and minerals, we have
donated a lot to the Melbourne University and Sydney Museum and we have also
sold a lot to American institutions,” she said.
When asked how much the family had made from the
sale of the meteorite, Emily hesitated. “I really wouldn’t like to say. We
really have got quite a bit and it’s going to educate the children,” she
responded at the time.
To this day, Murchison locals are reluctant to
speak about how much was made from the sale of meteorite fragments, or whether
they souvenired a small chunk for themselves. “Somebody told me it was worth
$3,000 a gram, is that right?” Beth Brisbane asks.
And then of course there are some residents who are
fairly certain there are still pieces of meteorite to be discovered. “They
think that the main piece of it might be in the middle of the Waranga Basin,”
says Marianne Begg. “Of course you’d never find that, it’d be down in the mud.”
50 years of science
Half a century since the fall of the Murchison meteorite, it remains unrivalled in its scientific significance. Philipp Heck is a cosmochemist at the Field Museum in Chicago. He lives thousands of kilometres from Murchison but has spent much of his career studying this particular rock.
Philipp Heck from the Chicago Field Museum has spent much of his career studying the Murchison meteorite.
(The Melbourne Museum rock registry lists when the
earliest Murchison meteorite samples were acquired.)
“The Murchison meteorite was the most important
meteorite for me and for many other scientists who study meteorites,” he says. “I
started studying the meteorite when I was a student and still study it today
and I have my own students working on Murchison.”
This single clump of ancient minerals, Dr Heck explains, is constantly offering scientists fresh insights into the solar system and our origins. “I anticipate in the next 50 years we’ll learn more from Murchison every year.”
Older than our solar system
Carbonaceous chondrites like the Murchison
meteorite are rich in carbon and make up just 4 per cent of meteorites that
fall today. And the 1969 impact in Murchison is the biggest of its type ever
witnessed.
What’s more, at 4.6 billion years old, the
Murchison specimen is older than our solar system; it’s a small, smelly
snapshot of the conditions that set our planetary neighbourhood on the path to
what we recognise today. “Similar to an embryo in an animal developing, what
happens to the embryo determines the future outcome,” Dr Heck explains.
Before our Sun and planets formed, the solar system
was a messy disc of gas, dust and debris. The Murchison meteorite is a mixture
of some of the chunks that were never collected into a planet or a moon.
It probably knocked around in the asteroid belt
beyond Mars, Dr Heck says, until much more recently, something kicked it
towards central Victoria. “The meteorite came from a carbon rich asteroid,
probably from the outer asteroid belt, and it travelled more than a million
years until it reached Earth.”
Filled with a range of organic compounds, the
Murchison meteorite contains “the very origins of life itself” such as amino
acids, water, sugars and alcohol-related compounds. That concentration of
organic molecules is the reason for the stench of methylated spirits that
Murchison locals reported when it first crashed through the atmosphere. The
odour can still be smelled in samples of the rock today.
Dr Heck says a meteorite much like this one could
have hit Earth very early on in its history and “delivered the prebiotic
building blocks that enabled later life to form”.
(Even fifty years after landing, fragments of the meteorite give off their characteristic smell when unwrapped.)
(A total of 4 kilograms of Murchison meteorite sits
in the Melbourne Museum collection.)
Other discoveries from the Murchison meteorite have
taught us about the behaviour of the Sun when it was a very young star. “When
the Sun was in its infancy, it was much more active than today,” Dr Heck says. “That
means there were many more eruptions going on, high-energy particles shooting
out in all directions, hitting everything in their path.”
He says scientists are able to see a record of that
activity in certain minerals contained within the Murchison meteorite. “Quantifying
this will take many more years of studying these different types of minerals
with different techniques, but we can actually do early solar system astronomy
by studying Murchison in the laboratory.”
What’s more, Dr Heck says the Murchison meteorite
is the most prolific source on our planet of pre-solar stardust grains. “These
grains are very rare,” he says, explaining that different grains represent
material from different ancient stars.
“This tells us that our solar system formed from a
multitude of different stars … so we’re essentially a product of these
different stars. At first sight [the meteorite] looks not very spectacular. If
you look at it closer, it is actually a sample of our galaxy and it is
extremely valuable.”
All of these insights might not have materialised,
Dr Heck says, if the rock hadn’t struck in broad daylight, in a populated area
where word passed quickly from the local residents to scientists.