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STUART GARY: This is Space Time series 26 episode 91 for
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broadcast on the 31st of July 2023. Coming up on Space Time
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could ancient asteroid impacts have fueled Volcanism on Venus.
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A new date for the start of plate tectonics on planet Earth.
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And NASA's Juno spacecraft undertakes its latest and
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closest fly by yet of the volcanic Jovian moon. Io all
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that and more coming up on Space Time.
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GENERIC: Welcome to Space Time with Stuart Garry.
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STUART GARY: A new study claims the early impact history of
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Venus might explain how Earth's sister planet has maintained its
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youthful surface despite lacking plate tectonics. The findings
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reported in the journal Nature astronomy compared the early
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collision histories of the two planets and concluded that Venus
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likely experienced higher speed, higher energy asteroid impacts.
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The authors say these would have created a superheated core that
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promoted extended Volcanism and resurfaced the planet with
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floods of magma.
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The study's lead author Simone Mary from the South West
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Research Institute in Boulder Colorado says one of the
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mysteries of the inner solar system is that despite their
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similar size and bulk density, Earth and Venus are distinctly
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different planets, especially when it comes to the processes
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that move materials through each planet. And the whole thing's
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really funny because let's face it.
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Both planets were made at the same time in the same part of
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the solar system, out of the same materials. And yet they've
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gone on to very different destinies. Earth shifting plate
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tectonics continually reshapes its surface as chunks of the
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crust collide to form mountain ranges and in places promote
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Volcanism while other parts subduct under the continents.
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While new material breaks the surface at mid ocean ridges. On
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the other hand, Venus is no evidence of any type of plate
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tectonic activity, but it has more volcanoes than any other
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planet in the solar system. In fact, there are over 80
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Venusian volcanoes at last count, that's 60 times more than
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the Earth.
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And they've played a major role in renewing Venus's surface
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through floods of lava which appear to be continuing right up
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to this day. Previous simulations have struggled to
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create scenarios which support this level of Volcanism.
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However, new computer modeling suggests that long lived
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Volcanism driven by early energetic collisions on Venus
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does offer a compelling explanation for its junk surface
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age. The massive volcanic activity is fueled by a
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superheated core resulting in vigorous internal melting. While
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Venus and Earth may have formed in the same neighborhood, slight
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differences in the two planets.
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Distances from the sun may have had a major effect, changing the
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impact velocities of asteroids and comets which hit the
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planets. Now, these differences arise because Venus is closer to
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the sun and moves faster around it, thereby energizing impact
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conditions.
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In addition, the tail of collisional growth is typically
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dominated by impactor Orting well beyond Earth's orbit. And
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that requires higher orbital eccentricities to collide with
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Venus rather than the Earth. And that results in far more
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powerful impacts.
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It's a simple equation, higher impact velocities melt more
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material melting as much as 82 per cent of Venus's mantle. And
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this, the authors say produces a mixed mantle of molten materials
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redistributed globally and a superheated core if impacts on
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Venus had significantly higher velocities than on Earth.
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A few large impacts could have drastically different outcomes
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with important implications for the subsequent geophysical
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evolution. The multidisciplinary team involved in the research
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combined expertise in large scale collision modeling and
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geodynamic processes to assess the consequences of these
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collisions for the long term evolution of Venus.
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Venus's internal conditions aren't well known. And before
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considering the role of energetic impacts geo dynamical
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models required special conditions in order to achieve
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the sort of massive Volcanism we see on Venus.
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But the authors found that once you input high energy impact
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scenarios into the model, it easily comes up with the
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extensive and extended Volcanism without needing to tweak the
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parameters. The new findings come in the wake of NASA's
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decision to undertake two new missions to Venus Veritas and Da
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Vinci and the European Space Agency isn't left out either.
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They're planning a new mission to Venus could envision we'll
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keep you informed. This is Space Time still to come. A new date
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for the start of plate tectonics on the Earth. And Juno
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undertakes its closest fly by yet of the volcanic Jovian moon
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Io all that and more still to come on Space Time.
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Well, it seems the ongoing debate about when plate
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tectonics began on planet Earth is continuing with new evidence
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suggesting subduction commenced around 3.2 billion years ago.
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The findings are important because Earth is the only planet
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known in our solar system to have significant plate tectonics
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and perhaps not coincidentally the only planet capable of
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hosting life.
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The findings reported in the journal Earth Science Reviews
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today follows the establishment of a new framework for dating
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Earth's evolution including the formation of the continents and
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of mineral deposits. The researchers studied Australia's
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abundant lead and zinc ore deposits along with a vast
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global database of geology.
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They determined that 3.2 billion years ago was a crucial point in
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Earth's history when the planet changed from what was
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essentially a layer cake structure to a mode of remixing,
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possibly driven by the start of global scale plate tectonics. A
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process which still dominates the Earth's system today.
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The study's lead author Luke Duet from Curtin University says
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one of the main questions to be answered was when continents as
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we know them today were first formed. Now to get an answer,
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the authors had to first determine when the composition
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of the continental crust began to differ significantly from the
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Earth's mantle where the continental material was
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extracted from.
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The challenge was to first understand how the Earth's
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mantle evolved since the great moon formation impact 4.5
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billion years ago.
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That's when a mars sized planet which scientists have called
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thea collided with the early proto Earth, turning both bodies
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into a single molten Magma Ocean with some ejector then flung
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into orbit to form the moon. Meanwhile, the Magma Ocean
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restarted the entire differentiation process which
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would eventually form an inner and outer core surrounded by a
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thick mantle and a thin crust.
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Duet says scientists first need to reconcile this well
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established theory with the composition of the present day
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mantle. The authors use lead isotope compositions from rock
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samples from different parts of the Earth's surface as well as
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from ancient meteorites dating back to the formation of the
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solar system 4.6 billion years ago.
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This allowed them to reconstruct an interpretation of the Earth's
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mantle evolution. They could then compare its mantle
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evolution with that of the Australian continent by using
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measurements from large lead zinc deposits known for tracking
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continental crust deposition through time.
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Australia has an estimated 52 billion tons of lead zinc ore
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making it the second largest reserve in the world just behind
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China. They range from as old as 3.4 billion years in Western
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Australia's Pilbara Region down to relatively young deposits is
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285 million years old and that makes them perfect for study.
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The team's analysis revealed that the lead zinc deposits
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started to exhibit significant differences from the Earth's
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mantle around 3.2 billion years ago. And deet says it's this
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period which is considered to be the point at which plate
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tectonics began to be the dominant driver of continental
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formation on the planet. This is a.
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LUC DOUCET : Huge debate in the community. And if you look at
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the recent papers, so basically, as you said, some people think
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it start just right away after Earth formed and the moon is
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formed. And then there's a paper saying that it can start very,
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very late like at the geological timescale like 500 ago.
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So yeah, very recently. So there's a huge gap when we don't
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know where it starts. So basically, the idea is to try to
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find a way to quantify or find a proxy of when you think plate
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tectonic starts, which is a vast question, right?
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So in our case, what we, what we thought is when you have plate
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tectonics, what we know is to have plate tectonics, you you
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need to have like continental plates. So to form the continent
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and then you need the continent to evolve and to become very
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different from the from the mantle where they have been when
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they have been extracted.
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So to form the continental crust, you need, you have this
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like the planet is formed, then you have the core and then you
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have this layer of rocks, we call the mantle and then you
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need to melt the mantle and then you produce the Contin crust and
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then you need the crust to stay where it is like to float on the
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mantle.
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Yes, the thing is we think that in the beginning, we have
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evidence that in the beginning of the Earth's history, you can
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produce the crust. So we have evidence like in the zero where
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we know there is like constant cross material form very early
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on the question we don't know is is this rock going back to the
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metal already?
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So then you go back where you started and then you just
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remixed and then you put extract and remixed the thing you need
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to have the cross that been formed and then stay where it
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is. So, so to do that, we need to find some proxies, some
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evidence that the mantle and the crust become very different in
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terms of composition. And this is what we try to do this.
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STUART GARY: How did you go about doing that?
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LUC DOUCET : Basically, we are using lead isotopes. So lead
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contain different isotopes. So different, different type of
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lead. We have lead deposits that form throughout Earth's history
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and we just measure the composition of the on these
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deposits because they reflect the composition of the crust.
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The problem we had is we need the evolution of the mantle as
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well.
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So this is what we started to study how no the lead completion
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of the mantle. So to do that, we start from today, when you're on
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the ocean, the ocean crust and the initial ocean crust, it's
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extracted from the mantle as well and we know this has to be
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complied. So then we make a model to see how the lead to be
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completion of the metal evolved since the formation of the
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Earth.
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So we had to use the present day composition of the metal. But we
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have to model how the lead is the composition of the Earth was
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at the beginning. And to do that, we had to understand how
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the giant impact moon formation processes, you know, modify that
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because lead is an element that go to the rocks, but also go to
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the surface and basically can go to the core when you form the
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core.
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So we have to understand all these processes to basically to
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connecting these two points, which is the present day
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accomplishment of the mantle and the completion of the mantle
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back in the day, you know, when this mantle formed right at the
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beginning, right. So we define this model and then we just
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compare this evolution of the of the mantle with the completion
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of the cut of the crust.
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Measuring has to be completion within the lead deposits. And
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then we find that there is at the beginning. So from around
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3.4 billion years old and 3.3 0.8 billion years old until 3.2
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they were the same completion, the metal and the crust is the
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same. But after that, you see a difference, you see that the the
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continent crust is beginning to be more different.
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And these differences then is, is significant after 3.2 until
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today. So that's what we say. Ok, we have the formation of the
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crust at the time and then it has to become more and more
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different with time. So then we say, oh, so then this is at the
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time where we should have what we call something like modern
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like pla formation, starting at the time.
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STUART GARY: It's all complicated. However, by
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thinking, well, especially in wa where you've got this huge u
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shaped craton under that part of the crust, which goes down many
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kilometers into the mantle, got one bit popping up in the south
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west of Western Australia and the other bit popping up in the
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Pilbara Region.
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You've got that as a problem. You've also got the fact that in
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somewhere like Canada, you've got other dates using as a
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dating technique when the continental crust is like at all
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form.
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LUC DOUCET : Yes. Yes. It's a very tough job. So, but the,
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the, the thing that it's I would say originally in our research
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is usually we, we know very little on how the man evolve,
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right? And we have those continental crust, releases, you
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know, like in the Pilbara, in New Y in Canada, in Russia, in
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the United States, Southern America pretty much everywhere,
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right?
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But the thing is when, when you look at these, these relis, you
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mostly have relis of the crust and as I said, so you can form
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the crust very early on. You don't know if this crust. So we
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have some bits of crust, but you don't know how much crust has
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been formed at the time.
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Because if you go to to Jack Hills in the northern, you, you
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say, oh, we have rocks that we can find 4.4 billion, you know,
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small grains. But are those grains representative of like
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huge continents or just small bits of continental crust?
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Right?
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So originally as a researcher, we compare what we know about
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the crust, but also what we know about the mantle. And this is
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really like this crust mantle relationship that's really
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critical to see what happened. This is where we, we managed to
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find this kind of a difference between the mantle and the
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crust, which is until now was quite obscure.
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So that's something we really like in this work is we would be
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able to connect the mantle and the crust. And we find this 3.2
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billion years old time where we think there is extraction and
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what is interesting is we are not the only one saying 3.2 was
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a tipping point.
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For example, there is a paper published in nature, I think
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maybe this week or something using another isotropic systems
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or titanium isotopes, which is a bit novel novel tool people are
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using and they are finding pretty much the same in the same
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time frame.
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So they say after 3.5 I 3.2 we have a major change in iso
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composition between the crust and the mantle. So this is quite
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interesting to see this time period is making more and more
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important in our understanding how platonic and formed. So
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there is a line of evidence. I think that this time is maybe
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the tipping point, we've got.
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STUART GARY: Planet Earth forming 4.6 billion years ago.
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And then about 4.5 billion years ago, the a mars sized body
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slammed into this proto Earth and all the differentiation that
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had taken place up until then that was all wiped out. The
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whole thing became one huge molten Magma Ocean again.
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And then the differentiation process recommenced at 4.5
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billion years, heavy elements heading towards the center,
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lighter elements heading towards the surface and then as it
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cooled, as it slowly cooled and solidified, we have lots of
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radioactive elements in there and lots of heat inside the
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planet. And that then starts this conveyor belt of plate
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tectonics which is still going on today.
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LUC DOUCET : The keyword is cooling. Think right at the
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beginning, the mantle was so dynamic that everything that got
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up, maybe some piece would stay there like in the Pilbara or you
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know, very small pieces, but the majority would go down. And at
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some point because the Earth is cooling, then the convection in
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the metal became less dynamic and then it followed the crust
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to stay there and then to start to evolve to the crust. We know
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today.
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STUART GARY: Now you've got samples from one location.
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LUC DOUCET : So basically for for in our research, we use the
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database for, for the crust, we use the database from the
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science Australia because Australia it's really cool
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because there is lead deposits from 3.8 to not 3.6 sorry to to
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today, right?
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And Australia, the Elco in Australia is the Commonwealth
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survey, but also all the states doing a very good job of, you
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know, documenting all the mineral deposits and doing all
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the geochemical data. So we have like huge database and so we use
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all this wealth of data to constrain what's going on for
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the crest evolution. So that's what we did for the crest and
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for the mantle, what we did.
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So we used an online databases where we have a huge amount of
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data for entire Earth history for the mental mental derived
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rock. So we have a comprehensive database of basically the entire
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Earth history. And for both the crest and the mental recall. So
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that's what we did.
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STUART GARY: That's Luke Duet from Curtin University and this
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is Space Time still to come. NASA's Juno spacecraft
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undertakes its closest fly by yet of the volcanic Jovi moon
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IO. And later in the science report, a preliminary analysis
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by the World Meteorological Organization suggests that July
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2023 will be listed as the hottest month on record for
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planet Earth. All that and more still to come on Space Time.
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NASA's Juno spacecraft has just completed its latest flyby of
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the spectacular volcanic Jovian moon. Io. The spacecraft made
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its closest approach yet to the fiery world coming within 22
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kilometers of its lava covered surface.
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The data collected by Juno's Jovin infrared oral mapper and
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other science instruments will provide a wealth of information
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on the hundreds of erupting volcanoes pouring out molten
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magma and sulfurous gasses over the surface of the volcano.
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Festoon moon.
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Juno principal investigator Scott Bolton from the South West
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Research Institute in San Antonio Texas says while the
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aurora mapper was actually designed to study Jupiter's
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polar aurora, its ability to identify heat sources is proving
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indispensable in the hunt for active volcanoes on IO.
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He says as Juno gets closer with each flyby, the mapper and other
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science instruments all add to science's library of data on the
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moon allowing researchers to not only better resolve surface
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features but to understand how they change over time. Launched
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back in 2011, June has been studying the Jovian system since
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2016 and has just commenced the third year of its extended
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mission in.
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SCOTT J. BOLTON: Roman mythology, which of course is
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rooted from Greek mythology. Juno was the wife and sister
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goddess of Jupiter and Jupiter was sort of being naughty with
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some friends. So he cast a veil of clouds around himself and his
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friends. But of course, Juno was a fairly powerful God herself
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and used her powers to look right through the clouds and see
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the true nature of Jupiter and understand what he was really up
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to.
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And that's exactly what the Juno spacecraft does for us is that
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it goes there with special instruments in a special orbit
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and uses its powers to see right through Jupiter's clouds and
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understand its true nature, which is holding these secrets
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for us about how the solar system formed and where we all
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came from.
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Juno spins like a propeller where the propeller is kind of
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facing the sun because they're all solar powered.
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If you spin something, it stays spinning, it's like a gyroscope.
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We can use a spinning spacecraft to let each instrument get its
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turn to see Jupiter. We get to go very close to the planet
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inside the radiation belts, instead of outside the radiation
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belt, we're in a polar orbit.
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So by small adjustments of the time we can map the entire
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planet, we can get repeated stripes at different longitudes
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as Jupiter spins underneath us, it.
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Does mean that Juno is the polar regions to a greater extent than
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with other spacecraft. But I think the most important thing
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is that it gets in very close to the planet. As part of that
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ellipse brings it in a few 1000 miles above those clouds, very
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close near the equator.
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We go over the poles of Jupiter. That means we can study the
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magnetosphere in a different way.
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A magnetosphere is the sphere of influence of a magnetic field.
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So a planet that has a magnetic field has a magnetosphere when
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its sphere of influence extends beyond the planet out into space
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and affects the region around the magnetosphere of Jupiter is
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vast. So if you think of Jupiter being 10 times the size of the
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Earth and the magnetosphere is 100 times the size of Jupiter.
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I would expect you to know to tell us more about how planets
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work, meaning how the heat gets out what kinds of flows exist
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inside the body, how magnetic fields get generated, learning
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what Jupiter is made of, we will learn such a wide range of
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things for indeed, Jupiter is the most massive planet in the
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solar system. It is the body you want to understand in order to
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understand the architecture of everything else, including.
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STUART GARY: Slightly larger than the Earth's moon. Io is the
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world in constant torment. Not only is Jupiter, the biggest
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planet in our solar system for ever pulling on it
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gravitationally, but so too are Io's Galilean siblings, the ice
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world of Europa and the biggest moon in the solar system,
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Ganymede.
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The result is that Io's constantly being stretched and
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squeezed, generating lots of internal friction in the process
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that friction is super heating the moon's internal structure
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and that's resulted in a volcanic cauldron with dozens of
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volcanoes constantly erupting over its surface.
00:22:24
During Juno's last fly by of AO back in May, the Juno cam imager
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took a picture from 35 kilometers showing a smudge at
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the moon's ver region near the equator. Now these smudges are
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often smoking guns to planetary scientists.
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Jason Perry from the University Of Arizona's High Rise
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Operations Center in Tucson says that when he compared it to
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visible light images taken of the same area during the Galileo
00:22:50
mission and the new horizon fly by in 1999 and 2007, he was
00:22:55
excited to see changes where the lava flow field had expanded to
00:22:59
the west. And another volcano just north of Volland had fresh
00:23:03
lava flows surrounding it during the say May 16th pass.
00:23:07
Juno's Jovin Infra Aro mapper found a smoking gun of its own,
00:23:11
capturing the 202 kilometer wide Loki Patera, the largest
00:23:15
volcanic depression on IO appearing to be active. The
00:23:19
observations showed that lava could be bubbling onto the
00:23:22
surface of the area in the North West in the process creating a
00:23:26
larva lake to the south and East.
00:23:28
It's a fascinating observation and one of many yet to come
00:23:32
thanks to NASA's Juno spacecraft, this Space Time and
00:23:54
time that to take a brief look at some of the other stories
00:23:56
making news in science. This week with the science report, a
00:24:00
preliminary analysis suggests that July 2023 will be listed as
00:24:05
the hottest month on record for the planet.
00:24:08
Largely because of global warming. The World
00:24:11
Meteorological Organization, the European Union funded Copernicus
00:24:15
climate change service and Leipzig University have combined
00:24:19
temperature data for July finding that it will be the
00:24:22
hottest July on record by a wide margin.
00:24:25
July 2023 will be 0.2 °C warmer than the previous warmest July,
00:24:31
which is back in 2019 and it follows on from the planet's
00:24:35
hottest June on record. And the addition of an El Nino event
00:24:39
which began back in May will further boost global
00:24:42
temperatures as a result of this climate pattern's combination
00:24:46
with climate change makes it highly likely that more months
00:24:49
this year will also set new temperature records.
00:24:53
But the authors say that July 2023 won't just be the hottest
00:24:56
month since records began, but it's also likely to be the
00:25:00
hottest month in 120 years.
00:25:03
They base that claim on evidence of past temperatures found in
00:25:07
ancient sediments and layers of ice as well as in other Pado
00:25:10
climate records. The World Meteorological Organization says
00:25:14
these temperatures are related to heat waves in large parts of
00:25:17
North America, Asia and Europe, which along with wildfires in
00:25:21
countries including Canada and Greece have had major impacts on
00:25:25
people's health, the environment and national economies.
00:25:29
On July the sixth, the daily average global surface
00:25:32
temperature on planet Earth surpassed the record set in
00:25:35
August 2016 making it the hottest day on record with July
00:25:40
the fifth and July the seventh only just behind.
00:25:44
Meanwhile, there are now growing fears that the Gulf Stream could
00:25:48
collapse by 2050 because of climate change. A report in the
00:25:53
Journal Nature Communications claims that contrary to recent
00:25:56
IPCC assessments, Dennis, researchers say the Atlantic
00:26:00
Meridiana overturning circulation, that's the large
00:26:03
system of ocean currents that carries warm water from the
00:26:06
tropics to the North Atlantic could collapse any time after
00:26:09
2025.
00:26:10
Under current rates of greenhouse gas emissions. The
00:26:14
team have analyzed sea surface temperatures in the North
00:26:17
Atlantic between 18 70 2020 in order to get a proxy for the
00:26:21
Gulf Stream, finding early warning signals of a big change
00:26:25
in the system which might suggest it could shut down as
00:26:29
early as 2025 and certainly no later than 2095.
00:26:34
They say that the last time this kind of abrupt climate change
00:26:37
happened, it led to average northern hemisphere temperatures
00:26:40
fluctuating by 10 to 15 °C over a decade.
00:26:45
A re analysis of Australian clinical trial data has shown
00:26:49
that healthy people over the age of 70 shouldn't take a daily low
00:26:53
dose aspirin as it could significantly increase the risk
00:26:56
of brain bleeds with no reduction in the risk of a
00:26:59
stroke.
00:27:00
The findings reported in the journal of the American Medical
00:27:03
Association are a re analysis of the Australian Led Asbury study
00:27:07
and extends the trial's findings by focusing on stroke and
00:27:11
bleeding events.
00:27:12
The authors say the study supports recent recommendations
00:27:16
that low dose aspirin should not be prescribed for primary
00:27:19
prevention. In healthy older adults, reports of glasses of
00:27:24
beer falling skidding, sliding or being pushed off a table or
00:27:29
bar by some invisible unknown force.
00:27:31
In other words, a ghost are pretty common in the paranormal
00:27:34
world and the events described are certainly real. However,
00:27:39
while a paranormal explanation may be thrilling, Tim Mendham
00:27:42
from Australian Skeptics points out the world of science offers
00:27:46
a far more rational explanation.
00:27:48
TIM MENDHAM: Right now. You may be surprised to know that at
00:27:51
Skeptic Central, we get sent videos of ghosts and strange
00:27:56
paranormal phenomena all the time like every day and often
00:28:00
they happen in pubs which is interesting because they have
00:28:02
spirits there.
00:28:03
Of course, pubs also have CCTV within the pub and you'll see
00:28:08
these little videos of people sitting in the pub drinking and
00:28:11
then off on a sideboard somewhere or on the bar,
00:28:13
suddenly this glass will seem to move and fall off the side and
00:28:17
smash et cetera.
00:28:17
And people instantly say ghosts, poltergeists are moving the
00:28:21
glasses around and it's interesting and it's fun and you
00:28:23
wonder what the CCTV is doing, looking at the wrong part of the
00:28:26
pub, but never mind, there are explanations for it. It does
00:28:29
happen, but there are explanations for it, which are
00:28:31
quite sort of mundane and one is basically the glass is capturing
00:28:35
air under the bottom.
00:28:36
Now, if you look at most glasses they will have on the bottom, on
00:28:39
the base of the glass, there's a rim and there's a little bit of
00:28:42
indentation underneath. And if you, if you put the glass down,
00:28:46
often not a full glass, it doesn't have to be a full glass.
00:28:48
It's a bit harder to move.
00:28:49
But an empty glass or almost empty glass, you put it down on
00:28:53
the surface of the bar and you're presuming you're not
00:28:55
having a mat or something on the bar, but it's a straight sort of
00:28:58
polished surface and the air gets captured smooth bar top,
00:29:01
doesn't it really ones? No, not the ones you slide down to the
00:29:06
person at the end of the bar.
00:29:07
Yeah, it has to be smooth, very smooth. If there's sunlight on
00:29:11
the glass, it will actually make the air, the air that's
00:29:13
underneath, that's trapped underneath the glass expand,
00:29:16
right? If the surface of the bar is warm, what happens is that
00:29:19
the air expands and therefore creates a little bubble
00:29:21
underneath the glass, which is easier to move to slide.
00:29:23
If its own accord. Right. And if there's an uneven surface or if
00:29:26
there's a push or who knows what it might just move a bit. And if
00:29:29
it happens to be beside the edge of the bar, it will possibly
00:29:32
fall off.
00:29:33
It's not going to move a huge amount. It's not going to move
00:29:35
from one end of the bar to the other, but they do move. And if
00:29:37
you're captured on CCTV, it looks impressive, quite fun
00:29:45
because I can't explain it. It's the old story, I can't explain
00:29:48
it. Therefore, it must be a ghost, which means I've just
00:29:49
explained it.
00:29:50
There's a similar phenomenon called the Leen frost effect.
00:29:53
When there's a heat underneath your sweat, you form a liquid,
00:29:56
say under your foot when fire walking. If you ever try that,
00:29:59
have you tried that?
00:30:00
I have, I know it hurts, but there's a layer of, you don't
00:30:08
stop, keep going, you cannot stop and you have to make sure
00:30:11
that the coals are actually sort of settled down to just glowing.
00:30:14
But if it forms a liquid, this is a suggestion that it forms a
00:30:16
liquid under your feet, which is sweat or vapor or whatever. And
00:30:20
then that will act as a little barrier for a short time, right?
00:30:23
Don't stand on the coals, it's not going to work. But if you
00:30:25
move very quickly across the coal surface and don't try this
00:30:29
at home, that it might give you a sort of very, very short term
00:30:33
protection against being burnt, no guarantees. It doesn't always
00:30:36
work. And it's a similar thing.
00:30:37
Therefore, it's a layer of air or liquid that is sort of acting
00:30:41
as a buffer against gravity or against friction. It acts as a
00:30:44
buffer against friction and therefore the things can move a
00:30:46
bit right off their own accord. And therefore, in a video, it
00:30:49
looks good, but don't take it as evidence of being haunted.
00:30:53
STUART GARY: That's Tim Mendham from Australian Skeptics and
00:31:12
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