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GEOPHYSICS
March 2023 ESRFnews
and then use it to constrain model predictions of the
outer-core composition. As for the anisotropy of
seismic waves, Kupenko will turn to the diffraction
beamlines. Here, data will expose how the materials
deform under extreme conditions and whether the
deformation can produce that anisotropy of wave
velocities which is observed seismically.
Kupenko began his project back in September, and
it will run for five years – not so long to wait, given that
the first evidence of a metallic core was found about a
century ago. Knowing the core composition is crucial
for understanding the past, the present and the future
of our planet. For instance, the change in the chemical
composition of the core over time might be essential
for the generation of the Earths magnetosphere that
vital shield which protects life from the Suns harmful
highenergy radiation Other researchers will be
keen to know whether the core does indeed contain
elements such as silicon as it is strangely depleted in the
mantle compared with most primitive meteorites the
building blocks of rocky planets that have been
studied If silicon is in the core then its problem
solved says Kupenko But if we find out theres no
silicon then the missing silicon problem is still there
Where is it
Jon Cartwright
portable system. Housing two 100 W-powered lasers
– guided to the laser-cutting heads that are more often
used to cut holes in metal by the aviation industry – it
is unique in providing three routes to a sample within
a DAC using the same optical path: one for the laser
light, one for temperature monitoring and one for visual
inspection. It can also be rotated during an experiment
so that Kupenko and his colleagues can measure
scattering signals at different angles. He has already
tested it at the ID18 nuclear-resonance beamline for
measurements of shear-wave velocity of sample alloys.
Later, he will develop a similar system for ID28 for
measurements of compression-wave velocity, as well as
those of density, which can be backed up with data from
ID27 and ID15B
He will have to take these measurements for different
ironnickel alloys until he finds one whose wave
transmitting properties closely match seismic data for
the core For the inner core which is solid this will
be tricky enough he says however the outer core is
molten and so his samples exposed outercore condi
tions will easily escape the laser and the Xray beams
heating spot in the DAC Spectroscopy can take 8 to
10 hours per pressuretemperature point he says To
keep a melt inside a DAC at the same place that long
is extremely challenging He believes the solution
is to determine the innercore composition first
Ilya Kupenko
has developed
a portable laser-
heating system to
answer questions
about the
composition of
the Earth’s core.
S T E F C A N D É
If silicon
is in the
core then
its problem
solved