|A sheet of carbon paper, with the coating side down.|
Wednesday, 7 October 2015
In 1806, Englishman Ralph Wedgwood secured the first patent for carbon paper, which he described as an “apparatus for producing duplicates of writings.” In his process, thin paper was saturated with printer's ink, then dried between sheets of blotting paper.
His idea for the carbon paper was a byproduct of his invention of a machine to help blind people write, and the “black paper” was really just a substitute for ink. In its original form, Wedgwood's “Stylographic Writer” employed a metal stylus instead of a quill for writing, with the carbon paper placed between two sheets of paper in order to transfer a copy onto the bottom sheet.
The manufacture of carbon paper was formerly the largest consumer of montan wax. In 1954 the Columbia Ribbon & Carbon Manufacturing Company filed a patent for what became known in the trade as solvent carbon paper: the coating was changed from wax-based to polymer-based.
The manufacturing process changed from a hot-melt method to a solvent-applied coating or set of coatings. It was then possible to use polyester or other plastic film as a substrate, instead of paper, although the name remained carbon paper.
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Wednesday, 30 September 2015
New findings from NASA's Mars Reconnaissance Orbiter (MRO) provide the strongest evidence yet that liquid water flows intermittently on present-day Mars.
Using an imaging spectrometer on MRO, researchers detected signatures of hydrated minerals on slopes where mysterious streaks are seen on the Red Planet. These darkish streaks appear to ebb and flow over time. They darken and appear to flow down steep slopes during warm seasons, and then fade in cooler seasons. They appear in several locations on Mars when temperatures are above minus 10 degrees Fahrenheit (minus 23 Celsius), and disappear at colder times.
|Martian slopes. Credit: NASA/JPL-Caltech/Univ. of Arizona|
"Our quest on Mars has been to 'follow the water,' in our search for life in the universe, and now we have convincing science that validates what we've long suspected," said John Grunsfeld, astronaut and associate administrator of NASA's Science Mission Directorate in Washington. "This is a significant development, as it appears to confirm that water -- albeit briny -- is flowing today on the surface of Mars."
These downhill flows, known as recurring slope lineae (RSL), often have been described as possibly related to liquid water. The new findings of hydrated salts on the slopes point to what that relationship may be to these dark features. The hydrated salts would lower the freezing point of a liquid brine, just as salt on roads here on Earth causes ice and snow to melt more rapidly. Scientists say it's likely a shallow subsurface flow, with enough water wicking to the surface to explain the darkening.
"We found the hydrated salts only when the seasonal features were widest, which suggests that either the dark streaks themselves or a process that forms them is the source of the hydration. In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks," said Lujendra Ojha of the Georgia Institute of Technology (Georgia Tech) in Atlanta, lead author of a report on these findings published Sept. 28 by Nature Geoscience.
Ojha first noticed these puzzling features as a University of Arizona undergraduate student in 2010, using images from the MRO's High Resolution Imaging Science Experiment (HiRISE). HiRISE observations now have documented RSL at dozens of sites on Mars. The new study pairs HiRISE observations with mineral mapping by MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM).
The spectrometer observations show signatures of hydrated salts at multiple RSL locations, but only when the dark features were relatively wide. When the researchers looked at the same locations and RSL weren't as extensive, they detected no hydrated salt.
Ojha and his co-authors interpret the spectral signatures as caused by hydrated minerals called perchlorates. The hydrated salts most consistent with the chemical signatures are likely a mixture of magnesium perchlorate, magnesium chlorate and sodium perchlorate. Some perchlorates have been shown to keep liquids from freezing even when conditions are as cold as minus 94 degrees Fahrenheit (minus 70 Celsius). On Earth, naturally produced perchlorates are concentrated in deserts, and some types of perchlorates can be used as rocket propellant.
Perchlorates have previously been seen on Mars. NASA's Phoenix lander and Curiosity rover both found them in the planet's soil, and some scientists believe that the Viking missions in the 1970s measured signatures of these salts. However, this study of RSL detected perchlorates, now in hydrated form, in different areas than those explored by the landers. This also is the first time perchlorates have been identified from orbit.
MRO has been examining Mars since 2006 with its six science instruments.
"The ability of MRO to observe for multiple Mars years with a payload able to see the fine detail of these features has enabled findings such as these: first identifying the puzzling seasonal streaks and now making a big step towards explaining what they are," said Rich Zurek, MRO project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.
For Ojha, the new findings are more proof that the mysterious lines he first saw darkening Martian slopes five years ago are, indeed, present-day water.
"When most people talk about water on Mars, they're usually talking about ancient water or frozen water," he said. "Now we know there's more to the story. This is the first spectral detection that unambiguously supports our liquid water-formation hypotheses for RSL."
The discovery is the latest of many breakthroughs by NASA's Mars missions.
"It took multiple spacecraft over several years to solve this mystery, and now we know there is liquid water on the surface of this cold, desert planet," said Michael Meyer, lead scientist for NASA's Mars Exploration Program at the agency's headquarters in Washington. "It seems that the more we study Mars, the more we learn how life could be supported and where there are resources to support life in the future."
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Wednesday, 23 September 2015
An extremely rare meteorite that has the same make-up as the primordial solar system goes on public display for the first time on Friday at the Natural History Museum in London.
The Ivuna meteorite landed in Tanzania in 1938 and has since been broken up into samples, the rest of which remain in the hands of private collectors. The Natural History Museum bought the largest lump in 2008 from a private enthusiast in the US.
The black, satsuma-sized space rock dates back to the birth of the solar system some 4.6bn years ago, before the Earth had formed. It is one of only five in the world with a ratio of chemical elements that, save for hydrogen and helium, almost exactly matches that of the sun.
The meteorite is a carbonaceous chondrite and has a lot of water locked up in its minerals. Up to a fifth of the rock’s weight is bound water, with other constituents being organic compounds that are considered the building blocks of life.
Meteorites like the Ivuna rock may have brought water and vital compounds for life on Earth when they slammed into the surface of the fledgling planet billions of years ago.
Ashley King, a postdoctoral researcher at the Natural History Museum in London, said: “These meteorites are a unique record of conditions that existed at the time over 4.5 billion years ago, before the Earth had formed. They are the primordial building blocks of our Solar System.”
When carbonaceous chondrites reach the Earth, they start to react in the air. But the museum’s Ivuna sample has been stored in a case in pure nitrogen for most of its life to preserve the pristine material.
Researchers at the Natural History Museum believe that studying the meteorite might give them a more accurate record of the sun’s composition than measuring the sun’s surface itself.
“Ivuna is actively used in our research, and it is fantastic to be able to show visitors a unique specimen that is older than Earth itself,” said King. The speciment will go on display at the museum’s free after-hours event, Science Uncovered, on 25 September.
Sara Russell, head of mineral and planetary sciences at the museum, said the Ivuna meteorite had recently been used to cast doubt on claims that the orbiting XMM-Newton observatory had seen dark matter streaming from a distant cluster of galaxies.
“It highlights that we need to learn more about our own galactic back yard. By studying the solar system we can learn abut how matter behaves in distant galaxies. At the Natural History Museum, we are using meteorites such as Ivuna, which dates from a time before planets existed, to understand the composition of primordial material at that time,” she said.
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Tuesday, 15 September 2015
On 15th September 1998, the rings around the planet Jupiter were declared to be made of dust from the impacts of cosmic bodies that crashed into Jupiter's moons. The idea came from studies of the rings made by scientists at several institutions.
Jupiter is the fifth planet from the Sun and the largest planet in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, but is two and a half times that of all the other planets in the Solar System combined. Jupiter is a gas giant, along with Saturn (Uranus and Neptune are ice giants).
Jupiter was known to astronomers of ancient times. The Romans named it after their god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, bright enough to cast shadows, and making it on average the third-brightest object in the night sky after the Moon and Venus.
|A portrait of Jupiter. Source: NASA|
Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, although helium only comprises about a tenth of the number of molecules. It may also have a rocky core of heavier elements, but like the other giant planets, Jupiter lacks a well-defined solid surface. Because of its rapid rotation, the planet's shape is that of an oblate spheroid (it has a slight but noticeable bulge around the equator).
The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope.
Surrounding Jupiter is a faint planetary ring system and a powerful magnetosphere. Jupiter has at least 67 moons, including the four large Galilean moons discovered by Galileo Galilei in 1610. Ganymede, the largest of these, has a diameter greater than that of the planet Mercury.
Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early Pioneer and Voyager flyby missions and later by the Galileo orbiter. The most recent probe to visit Jupiter was the New Horizons spacecraft in late February 2007 en route to Pluto, using the gravity from Jupiter to increase its speed and bend its trajectory. Future targets for exploration in the Jovian system include the possible ice-covered liquid ocean on the moon Europa.
The Galileo orbiter, which went into orbit around Jupiter on December 7, 1995 orbited the planet for over seven years, conducting multiple flybys of all the Galilean moons and Amalthea. The spacecraft also witnessed the impact of Comet Shoemaker–Levy 9 as it approached Jupiter in 1994, giving a unique vantage point for the event. While the information gained about the Jovian system from Galileo was extensive, its originally designed capacity was limited by the failed deployment of its high-gain radio transmitting antenna.
A 340-kilogram titanium atmospheric probe was released from the spacecraft in July 1995, entering Jupiter's atmosphere on December 7. It parachuted through 150 km (93 mi) of the atmosphere at speed of about 2,575 km/h (1600 mph) and collected data for 57.6 minutes before it was crushed by the pressure of about 23 atmospheres at a temperature of 153 °C. It would have melted thereafter, and possibly vaporized. The Galileo orbiter itself experienced a more rapid version of the same fate when it was deliberately steered into the planet on September 21, 2003, at a speed of over 50 km/s, to avoid any possibility of it crashing into and possibly contaminating Europa—a moon which has been hypothesized to have the possibility of harboring life.
Data from this mission revealed that hydrogen composes up to 90% of Jupiter's atmosphere. The temperatures data recorded was more than 300 °C (>570 °F) and the windspeed measured more than 644 kmph (>400 mph) before the probes vapourised.
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Wednesday, 9 September 2015
Scientists may be closer to solving the mystery of how Mars changed from a world with surface water billions of years ago to the arid Red Planet of today.
A new analysis of the largest known deposit of carbonate minerals on Mars suggests that the original Martian atmosphere may have already lost most of its carbon dioxide by the era of valley network formation.
"The biggest carbonate deposit on Mars has, at most, twice as much carbon in it as the current Mars atmosphere," said Bethany Ehlmann of the California Institute of Technology and NASA Jet Propulsion Laboratory, both in Pasadena. "Even if you combined all known carbon reservoirs together, it is still nowhere near enough to sequester the thick atmosphere that has been proposed for the time when there were rivers flowing on the Martian surface."
Carbon dioxide makes up most of the Martian atmosphere. That gas can be pulled out of the air and sequestered or pulled into the ground by chemical reactions with rocks to form carbonate minerals. Years before the series of successful Mars missions, many scientists expected to find large Martian deposits of carbonates holding much of the carbon from the planet's original atmosphere. Instead, these missions have found low concentrations of carbonate distributed widely, and only a few concentrated deposits. By far the largest known carbonate-rich deposit on Mars covers an area at least the size of Delaware, and maybe as large as Arizona, in a region called Nili Fossae.
Christopher Edwards, a former Caltech researcher now with the U.S. Geological Survey in Flagstaff, Arizona, and Ehlmann reported the findings and analysis in a paper posted online by the journal Geology. Their estimate of how much carbon is locked into the Nili Fossae carbonate deposit uses observations from numerous Mars missions, including the Thermal Emission Spectrometer (TES) on NASA's Mars Global Surveyor orbiter, the mineral-mapping Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and two telescopic cameras on NASA's Mars Reconnaissance Orbiter, and the Thermal Emission Imaging System (THEMIS) on NASA's Mars Odyssey orbiter.
Edwards and Ehlmann compare their tally of sequestered carbon at Nili Fossae to what would be needed to account for an early Mars atmosphere dense enough to sustain surface waters during the period when flowing rivers left their mark by cutting extensive river-valley networks. By their estimate, it would require more than 35 carbonate deposits the size of the one examined at Nili Fossae. They deem it unlikely that so many large deposits have been overlooked in numerous detailed orbiter surveys of the planet. While deposits from an even earlier time in Mars history could be deeper and better hidden, they don't help solve the thin-atmosphere conundrum at the time the river-cut valleys formed.
The modern Martian atmosphere is too tenuous for liquid water to persist on the surface. A denser atmosphere on ancient Mars could have kept water from immediately evaporating. It could also have allowed parts of the planet to be warm enough to keep liquid water from freezing. But if the atmosphere was once thicker, what happened to it? One possible explanation is that Mars did have a much denser atmosphere during its flowing-rivers period, and then lost most of it to outer space from the top of the atmosphere, rather than by sequestration in minerals.
"Maybe the atmosphere wasn't so thick by the time of valley network formation," Edwards said. "Instead of Mars that was wet and warm, maybe it was cold and wet with an atmosphere that had already thinned. How warm would it need to have been for the valleys to form? Not very. In most locations, you could have had snow and ice instead of rain. You just have to nudge above the freezing point to get water to thaw and flow occasionally, and that doesn't require very much atmosphere."
NASA's Curiosity Mars rover mission has found evidence of ancient top-of-atmosphere loss, based on the modern Mars atmosphere's ratio of heavier carbon to lighter carbon. Uncertainty remains about how much of that loss occurred before the period of valley formation; much may have happened earlier. NASA's MAVEN orbiter, examining the outer atmosphere of Mars since late 2014, may help reduce that uncertainty.
Arizona State University, Tempe, provided the TES and THEMIS instruments. The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland., provided CRISM. JPL, a division of Caltech, manages the Mars Reconnaissance Orbiter and Mars Odyssey project for NASA's Science Mission Directorate, Washington, and managed the Mars Global Surveyor project through its nine years of orbiter operations at Mars. Lockheed Martin Space Systems in Denver built the three orbiters.
For more information about the Mars Reconnaissance Orbiter mission, visit:
For more information about the Mars Odyssey mission, visit:
The above post is reprinted from materials provided by NASA/Jet Propulsion Laboratory. Note: Materials may be edited for content and length.
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Wednesday, 2 September 2015
At the bottom of a frigid Antarctic lake, a thin layer of green slime is generating a little oasis of oxygen, a team including UC Davis researchers has found. It's the first modern replica discovered of conditions on Earth two and a half billion years ago, before oxygen became common in the atmosphere. The discovery is reported in a paper in the journal Geology.
The switch from a planet with very little available oxygen to one with an atmosphere much like today's was one of the major events in Earth's history, and it was all because some bacteria evolved the ability to photosynthesize. By about 2.4 billion years ago, geochemical records show that oxygen was present all the way to the upper atmosphere, as ozone.
What is not clear is what happened in between, or how long the transition - called the Great Oxidation Event - lasted, said Dawn Sumner, professor and chair of earth and planetary sciences at UC Davis and an author on the paper. Scientists have speculated that here may have been "oxygen oases," local areas where was abundant before it became widespread around the planet.
The new discovery in Lake Fryxell in the McMurdo Dry Valleys could be a modern example of such an ancient oxygen oasis, and help geochemists figure out what to look for in ancient rocks, Sumner said.
|Lake Fryxell. Credit: Tyler Mackey, UC Davis|
Sumner and collaborators including Ian Hawes of the University of Canterbury, New Zealand have been studying life in these ice-covered lakes for several years. The microbes that survive in these remote and harsh environments are likely similar to the first forms of life to appear on Earth, and perhaps on other planets.
The discovery occurred "a little by accident," Sumner said. Hawes and Tyler Mackey, a UC Davis graduate student working with Sumner, were helping out another research team by diving in Lake Fryxell. The lakes of the Dry Valleys typically contain oxygen in their upper layers, but are usually anoxic further down, Sumner said. Lake Fryxell is unusual because it becomes anoxic at a depth where light can still penetrate.
During their dives below the oxygen zone, Hawes and Mackey noticed some bright green bacteria that looked like they could be photosynthesizing. They took measurements and found a thin layer of oxygen, just one or two millimeters thick, being generated by the bacteria.
Something similar could have been happening billions of years ago, Sumner said.
"The thought is, that the lakes and rivers were anoxic, but there was light available, and little bits of oxygen could accumulate in the mats," she said.
The researchers now want to know more about the chemical reactions between the "oxygen oasis" and the anoxic water immediately above it and sediments below. Is the oxygen absorbed? What reactions occur with minerals in the water?
Understanding how this oxygen oasis reacts with the environment around it could help identify chemical signatures preserved in rocks. Researchers could then go looking for similar signatures in rocks from ancient lake beds to find "whiffs of oxygen" prior to the Great Oxidation Event.
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Tuesday, 25 August 2015
Humans have been all over the Earth. We've conquered the lands, flown through the air and dived to the deepest trenches in the ocean. We've even been to the Moon. But we've never been to the planet's core.
We haven't even come close. The central point of the Earth is over 6,000km down, and even the outermost part of the core is nearly 3,000 km below our feet. The deepest hole we've ever created on the surface is the Kola Superdeep Borehole in Russia, and it only goes down a pitiful 12.3 km.
All the familiar events on Earth also happen close to the surface. The lava that spews from volcanoes first melts just a few hundred kilometres down. Even diamonds, which need extreme heat and pressure to form, originate in rocks less than 500km deep.
What's down below all that is shrouded in mystery. It seems unfathomable. And yet, we know a surprising amount about the core. We even have some idea about how it formed billions of years ago – all without a single physical sample. This is how the core was revealed.
One good way to start is to think about the mass of the Earth, says Simon Redfern of the University of Cambridge in the UK.
We can estimate Earth's mass by observing the effect of the planet's gravity on objects at the surface. It turns out that the mass of the Earth is 5.9 sextillion tonnes: that's 59 followed by 20 zeroes.
There's no sign of anything that massive at the surface.
"The density of the material at the Earth's surface is much lower than the
average density of the whole Earth, so that tells us there's something much denser," says Redfern. "That's the first thing."
Essentially, most of the Earth's mass must be located towards the centre of the planet. The next step is to ask which heavy materials make up the core.
The answer here is that it's almost certainly made mostly of iron. The core is thought to be around 80% iron, though the exact figure is up for debate.
The main evidence for this is the huge amount of iron in the universe around us. It is one of the ten most common elements in our galaxy, and is frequently found in meteorites.
Given how much there is of it, iron is much less common at the surface of the Earth than we might expect. So the theory is that when Earth formed 4.5 billion years ago, a lot of iron worked its way down to the core.
That's where most of the mass is, and it's where most of the iron must be too. Iron is a relatively dense element under normal conditions, and under the extreme pressure at the Earth's core it would be crushed to an even higher density, so an iron core would account for all that missing mass.
But wait a minute. How did that iron get down there in the first place?
The iron must have somehow gravitated – literally – towards the centre of the Earth. But it's not immediately obvious how.
Most of the rest of the Earth is made up of rocks called silicates, and molten iron struggles to travel through them. Rather like how water on a greasy surface forms droplets, the iron clings to itself in little reservoirs, refusing to spread out and flow.
A possible solution was discovered in 2013 by Wendy Mao of Stanford University in California and her colleagues. They wondered what happened when the iron and silicate were both exposed to extreme pressure, as happens deep in the earth.
By pinching both substances extremely tightly using diamonds, they were able to force molten iron through silicate.
"The pressure actually changes the properties of how iron interacts with the silicate," says Mao. "At higher pressures a 'melt network' is formed."
This suggests the iron was gradually squeezed down through the rocks of the Earth over millions of years, until it reached the core.
At this point you might be wondering how we know the size of the core. What makes scientists think it begins 3000km down? There's a one-word answer: seismology.
When an earthquake happens, it sends shockwaves throughout the planet. Seismologists record these vibrations. It's as if we hit one side of the planet with a gigantic hammer, and listened on the other side for the noise.
"There was a Chilean earthquake in the 1960s that generated a huge amount of data," says Redfern. "All the seismic stations dotted all over the Earth recorded the arrival of the tremors from that earthquake."
Depending on the route those vibrations take, they pass through different bits of the Earth, and this affects how they "sound" at the other end.
Early in the history of seismology, it was realised that some vibrations were going missing. These "S-waves" were expected to show up on one side of the Earth after originating on the other, but there was no sign of them.
The reason for this was simple. S-waves can only reverberate through solid material, and can't make it through liquid.
They must have come up against something molten in the centre of the Earth. By mapping the S-waves' paths, it turned out that rocks became liquid around 3000km down.
That suggested the entire core was molten. But seismology had another surprise in store.
In the 1930s, a Danish seismologist named Inge Lehmann noticed that another kind of waves, called P-waves, unexpectedly travelled through the core and could be detected on the other side of the planet.
She came up with a surprising explanation: the core is divided into two layers. The "inner" core, which begins around 5,000km down, was actually solid. It was only the "outer" core above it that was molten.
Lehmann's idea was eventually confirmed in 1970, when more sensitive seismographs found that P-waves really were travelling through the core and, in some cases, being deflected off it at angles. Sure enough, they still ended up on the other side of the planet.
It's not just earthquakes that sent useful shockwaves through the Earth. In fact, seismology owes a lot of its success to the development of nuclear weapons.
A nuclear detonation also creates waves in the ground, so nations use seismology to listen out for weapons tests. During the Cold War this was seen as hugely important, so seismologists like Lehmann got a lot of encouragement.
Rival countries found out about each other's nuclear capabilities and along the way we learned more and more about the core of the Earth. Seismology is still used to detect nuclear detonations today.
We can now draw a rough picture of the Earth's structure. There is a molten outer core, which begins roughly halfway to the planet's centre, and within it is the solid inner core with a diameter of 1,220 km.
But there is a lot more to try and tease out, especially about the inner core. For starters, how hot is it?
This turns out to be quite tricky to determine, and baffled scientists until quite recently, says Lidunka Vočadlo of University College London in the UK. We can't put a thermometer down there, so the only solution is to create the correct crushing pressure in the lab.
In 2013 a team of French researchers produced the best estimate to date. They subjected pure iron to pressures a little over half that at the core, and extrapolated from there. They concluded that the melting point of pure iron at core temperatures is around 6,230 °C. The presence of other materials would bring the core's melting point down a bit, to around 6,000 °C. But that's still as hot as the surface of the Sun.
A bit like a toasty jacket potato, Earth's core has stayed warm thanks to heat retained from the formation of the planet. It also gets heat from friction as denser materials shift around, as well as from the decay of radioactive elements. Still, it is cooling by about 100 °C every billion years.
Knowing the temperature is useful, because it affects the speed at which vibrations travel through the core. That is handy, because there is something odd about the vibrations.
P-waves travel unexpectedly slowly as they go through the inner core – slower than they would if it was made of pure iron.
"Wave velocities that the seismologists measure in earthquakes and whatnot are significantly lower [than] anything that we measure in an experiment or calculate on a computer," says Vočadlo. "Nobody as yet knows why that is."
That suggests there is another material in the mix.
It could well be another metal, called nickel. But scientists have estimated how seismic waves would travel through an iron-nickel alloy, and it doesn't quite fit the readings either.
Vočadlo and her colleagues are now considering whether there might be other elements down there too, like sulphur and silicon. So far, no-one has been able to come up with a theory for the inner core's composition that satisfies everyone. It's a Cinderella problem: no shoe will quite fit.
Vočadlo is trying to simulate the materials of the inner core on a computer. She hopes to find a combination of materials, temperatures and pressures that would slow down the seismic waves by the right amount.
She says the secret might lie in the fact that the inner core is nearly at its melting point. As a result, the precise properties of the materials might be different from what they would be if they were safely solid.
That could explain why the seismic waves pass through more slowly than expected.
"If that's the real effect, we would be able to reconcile the mineral physics results with the seismological results," says Vocadlo. "People have not been able to do that yet."
There are plenty of riddles about the earth's core still to solve. But without ever digging to those impossible depths, scientists have figured out a great deal about what is happening thousands of kilometres beneath us.
Those hidden processes in the depths of the Earth are crucial to our daily lives, in a way many of us don't realise.
Earth has a powerful magnetic field, and that is all thanks to the partially molten core. The constant movement of molten iron creates an electrical current inside the planet, and that in turn generates a magnetic field that reaches far out into space.
The magnetic field helps to shield us from harmful solar radiation. If the core of the Earth wasn't the way it is, there would be no magnetic field, and we would have all sorts of problems to contend with.
None of us will ever set eyes on the core, but it's good to know it's there.
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