Making alien worlds on Earth

Want to get up close to the swirling methane seas on
Saturn’s satellite Titan or check out the subsurface salty
oceans of Ganymede, Jupiter’s largest moon? For Helen
Brand at ANSTO’s Australian Synchrotron in Melbourne and
Helen Maynard-Casely at the Australian Centre for Neutron
Scattering in Sydney, there’s no need to wait for a probe to
dive or drill in. The planetary science pair explores alien
worlds by making tiny bits of them on Earth.

Using a technique called powder diffraction, Brand and
Maynard-Casely mix the compounds that are thought to
comprise our companions in the solar system, squash them
to mimic those otherworldly pressures and watch how their
crystal structure changes. For work such as this, Brand and
Maynard-Casely shared the 2017 ANSTO Early Career
Award in Nuclear Science and Technology.

Their collaboration spans decades. They met at age 18
as undergraduates at University College London. “We’ve
known each other for a very long time!” Maynard-Casely says.
And even though both are London-born and work closely in
Australia today, their journeys from childhood through school
to university took different paths.

Maynard-Casely grew up in rural Cambridgeshire, her
parents a mechanic and a teacher. But she had her sights set
on space early on. At eight years old, she watched chemist
Helen Sharman blast off and become the first British
astronaut and first woman to visit the Mir space station.
“Family legend is I walked up to dad and said, ‘I want to go
to space because that’s what Helens do!’” Maynard-Casely
laughs.

That drive for outer space was brought back to earth
when, not long after, she discovered volcanoes. She became
enamoured with the spate of volcano-disaster films of the
time, such as the 1997 thrillers Volcano and Dante’s Peak.
And at around 15 or 16 years old, she “found out about
volcanoes made of ice [on other planets], and thought: ‘That’s
where I want to be’.”

After high school, she enrolled in a planetary science
degree at University College London, the first in her family to
go to university. Meanwhile, Brand – with a physics teacher mother and maths teacher father – “had no chance” of not
being a scientist, she says. Her dad, a hobby geologist, “took
a geological hammer on his honeymoon, much to my mum’s
annoyance!”

Luckily, the younger Brand liked geology too – not to
mention space. Growing up in south London, she remembers
frequenting the London Science Museum. There, she
admired the bronze command module of Apollo 10, which
flew around the moon in a dress rehearsal of the historic
Apollo 11 landing in 1969.

It was a school trip to Iceland, led around the bleak, icy,
otherworldly landscapes by a geologist teacher, that really
glued her love of rocks and space together. She decided to
apply for the general physical sciences degree at University
College London.

“On the first day, they give you a timetable and tell you to
choose eight subjects,” she says. But after around six weeks,
she realised she was in the same classes as the planetary
science students – including Maynard-Casely – so she
transferred to their course.

After graduating, both embarked on PhDs. Brand
stayed at University College London, unravelling the crystal
structure of hydrated minerals in Jupiter’s four largest moons:
Io, Europa, Ganymede and Callisto. Maynard-Casely’s
studies took her to the University of Edinburgh in Scotland,
where she examined how methane’s structure changes in the
crushing pressures of gas giants Uranus and Neptune.

When Brand moved to Australia in 2009 to take up a position at CSIRO in Melbourne, she worked on a problem
extremely relevant to the mining boom of the time: how a
hydrated mineral called jarosite forms.

Ore dug from the ground is often a mix of loads of metals
and impurities. To end up with pure zinc, for instance, a
refinery must get rid of iron. This is done by mixing ore with
water and adding an alkaline. The alkaline binds to iron,
creating jarosite, which “precipitates and blobs to the top, and
can then be scooped off,” Brand says.

X-ray powder diffraction can tell mining companies the
best way to crystallise different types of jarosite and do it
more efficiently.

“But the same thing happens on Mars,” Brand says – not
in mines, of course, but naturally (as it does on Earth). In
2004, the Opportunity rover found jarosite on the Martian
surface – the first hydrated mineral discovered on the red
planet.

Jarosite needs lots of water to form. Its presence was
another piece of evidence that, at some point, Mars had vast
liquid oceans.

 

 

When Brand moved to the Australian Synchrotron
powder diffraction beamline, she wanted to see how jarosite
forms in conditions like the Martian crust and surface. The
chemistry could be plugged into geological models of Martian
evolution and help planetary scientists reveal the planet’s
history.

Maynard-Casely made the move to Australia too, in 2011,
first working with Brand at ANSTO’s Australian Synchrotron
before moving to ANSTO in Sydney. (“She followed me!”
Brand laughs. “I was here first.”)

Among other things, Maynard-Casely is looking at how
the structure of small hydrocarbons and ices shift when
placed under pressure. Recently, she’s taken an interest in the
asteroid belt – a ring of asteroids and dwarf planets between
Mars and Jupiter.

NASA’s Dawn spacecraft swung by asteroid Vesta before
settling into orbit around Ceres, the largest body in the
asteroid belt, last year. There, it found the topmost metre
of Ceres’ surface to be hydrogen-rich, consistent with huge
expanses of water ice tucked away below.

“We’ve gone from thinking these bodies are completely
dry, there’s no water there, to the realisation that Ceres sits
neatly on the ice line, which is the point where it got cold
enough for water to condense straight away [when the solar
system formed],” Maynard-Casely says.

She’ll try different combinations of salts to emulate
Ceres conditions and see what structures appear. Then,
she’ll compare her data with that taken by Dawn (which, like
all NASA research, is open-access). It might tell us about
the water situation on Ceres, she says, “but in reality, we’ll
probably make it a bit more complicated!” At the very least,
she will have accumulated a comprehensive diffraction
catalogue of different salty solutions from minus 269 °C to
room temperature.

Brand, too, has turned her attention to asteroids – but
those that made it to Earth. Last year, a friend asked if she
would use the X-ray diffractometer to examine sand-sized
2.7-billion-year-old meteorites found embedded in limestone
in the Pilbara. What they found was evidence that the early
Earth’s upper atmosphere’s oxygen levels were similar to that
of today.

Since finishing their degrees, Maynard-Casely and Brand
have forged their own paths using data that didn’t exist when
they were at university.

And while they’ve been interested in science since
childhood, neither had an idea of where it would take them
– or the solar system’s secrets they’d reveal. They simply
pursued what they loved.

“When people say to me, ‘I don’t know what to do’, I say,
‘do what you enjoy’,” Maynard-Casely says. “I tend to give
that advice to a lot of people.”

Brand agrees. When enrolling in her general maths and
physics undergraduate degree, “I didn’t really know what I
was doing or where I was going to end up,” she says. “I just
liked space and rocks – and here I am.”

To learn more about ANSTO visit www.ansto.gov.au