geophysical science

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The Science Has Spoken: Pluto Will Never Be A Planet Again

“What’s perhaps most remarkable is that we can make a simple, mathematical relationship between a world’s mass and its orbital distance that can be scaled and applied to any star. If you’re above these lines, you’re a planet; if you’re below it, you’re not. Note that even the most massive dwarf planets would have to be closer to the Sun than Mercury is to reach planetary status. Note by how fantastically much each of our eight planets meets these criteria… and by how much all others miss it. And note that if you replaced the Earth with the Moon, it would barely make it as a planet.”

It was a harsh lesson in astronomy for all of us in 2006, when the International Astronomical Union released their official definition of a planet. While the innermost eight planets made the cut, Pluto did not. But given the discovery of large numbers of worlds in the Kuiper belt and beyond our Solar System, it became clear that we needed something even more than what the IAU gave us. We needed a way to look at any orbiting worlds around any star and determine whether they met a set of objective criteria for reaching planetary status. Recently, Alan Stern spoke up and introduced a geophysical definition of a planet, which would admit more than 100 members in our Solar System alone. But how does this stand up to what astronomers need to know?

As it turns out, not very well. But the IAU definition needs improving, too, and modern science is more than up to the challenge. See who does and doesn’t make the cut into true planetary status, and whether Planet Nine – if real – will make it, too!

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Engineer school: Done ✔
End of research masted: D-7 ⏳👍

Can’t wait to be done with all of this ! Studying for my oral exam on geophysical fluids dynamics 🌊 and trying to remember all these lessons I had months ago 😮💪

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Turbidity currents are a gravity-driven, sediment-laden flow, like a landslide or avalanche that occurs underwater. They are extremely turbulent flows with a well-defined leading edge, called a head. Turbidity currents are often triggered by earthquakes, which shake loose sediments previously deposited in underwater mountains and canyons. Once suspended, these sediments make the fluid denser than surrounding water, causing the turbidity current to flow downhill until its energy is expended and its sediment settles to form a turbidite deposit. By sampling cores from the seafloor, scientists studying turbidites can determine when and where magnitude 8+ earthquakes have occurred over the past 12,000+ years!  (Video credit: A. Teijen et al.; submitted by Simon H.)

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Inge Lehmann (1888-1993) was a Danish geophysicist and seismologist who, in 1936, discovered that the Earth has a solid inner core surrounded by a molten outer core. This overturned the previous belief that the Earth’s core was a single molten sphere.

She began her higher education by studying mathematics at the University of Copenhagen, and later at Cambridge. She made important investigations of the Earth’s structure, discovering, among other elements, a seismic discontinuity that was named after her. Today, the American Geophysical Society awards a medal in her honor.

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One of the factors that complicates geophysical flows is that both the atmosphere and the ocean are stratified fluids with many stacked layers of differing densities. These variations in density can generate instabilities, trap rising or sinking fluids, and transmit waves. The animations above show flow over two ridges with dye visualization (top), velocity (middle), and contours of density (bottom). The upstream influence of the left ridge creates a smooth, focused flow that quickly becomes turbulent after the crest. The jet rebounds as a turbulent hydraulic jump before slowing again upstream of the second ridge. Like the first ridge, the second ridge also generates a hydraulic jump on the lee side. Clearly both stratification and the local topography play a big role in how air moves over and between the ridges. If prevailing winds favor these kinds of flows, it can help generate local microclimates. (Image credit and submission: K. Winters, source videos)

Major volcanic eruptions can be accompanied by pyroclastic flows, a mixture of rock and hot gases capable of burying entire cities, as happened in Pompeii when Mt. Vesuvius erupted in 79 C.E. For even larger eruptions, such as the one at Peach Spring Caldera some 18.8 million years ago, the pyroclastic flow can be powerful enough to move half-meter-sized blocks of rock more than 150 km from the epicenter. Through observations of these deposits, experiments like the one above, and modeling, researchers were able to deduce that the Peach Spring pyroclastic flow must have been quite dense and flowed at speeds between 5 - 20 m/s for 2.5 - 10 hours! Dense, relatively slow-moving pyroclastic flows can pick up large rocks (simulated in the experiment with large metal beads) both through shear and because their speed generates low pressure that lifts the rocks so that they get swept along by the current. (Image credit: O. Roche et al., source)

He Lavas Me, He Lavas Me Not

This Heart is a Stone - Chapter 32

It hasn’t been an easy 15 years since since the barrier atop Mt. Ebott broke and monsters were reintroduced to the surface world. The uneasy acceptance of monsterkind was hard won by many sacrifices though over the years tensions have settled into a general, though in some cases begrudging, acceptance.

You are a grad student at the local university, eagerly pursuing a degree in Geophysics and Planetary Sciences in hopes of returning to the National Park Service. One step closer to the future you’ve had planned out since you were 17.

Plans change, though… and along the way, you might undergo a metamorphosis too.
*Please do not assume this is just a student/teacher kink fic, because it is not :)

Astronomers perform largest-ever survey of high-mass binary star systems

In addition to solo stars like our Sun, the universe contains binary systems comprising two massive stars that interact with each other. In many binaries the two stars are close enough to exchange matter and may even merge, producing a single high-mass star that spins at great speed.

Until now the number of known high-mass binaries has been very small, basically confined to those identified in our galaxy, the Milky Way.

An international group of astronomers led by researchers at the University of São Paulo’s Institute of Astronomy, Geophysics & Atmospheric Sciences (IAG-USP) in Brazil, have just extended the list of by identifying and characterizing 82 new high-mass binaries located in the Tarantula Nebula, also known as 30 Doradus, in the Large Magellanic Cloud. The LMC is a satellite galaxy of the Milky Way and is about 160,000 light years from Earth.

The results of the study are described in article published in the journal Astronomy & Astrophysics.

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What did Earth’s ancient magnetic field look like?

New work from Carnegie’s Peter Driscoll suggests Earth’s ancient magnetic field was significantly different than the present day field, originating from several poles rather than the familiar two. It is published in Geophysical Research Letters.
Earth generates a strong magnetic field extending from the core out into space that shields the atmosphere and deflects harmful high-energy particles from the Sun and the cosmos. Without it, our planet would be bombarded by cosmic radiation, and life on Earth’s surface might not exist. The motion of liquid iron in Earth’s outer core drives a phenomenon called the geodynamo, which creates Earth’s magnetic field. This motion is driven by the loss of heat from the core and the solidification of the inner core.
But the planet’s inner core was not always solid. What effect did the initial solidification of the inner core have on the magnetic field? Figuring out when it happened and how the field responded has created a particularly vexing and elusive problem for those trying to understand our planet’s geologic evolution, a problem that Driscoll set out to resolve.
Here’s the issue: Scientists are able to reconstruct the planet’s magnetic record through analysis of ancient rocks that still bear a signature of the magnetic polarity of the era in which they were formed. This record suggests that the field has been active and dipolar–having two poles–through much of our planet’s history. The geological record also doesn’t show much evidence for major changes in the intensity of the ancient magnetic field over the past 4 billion years. A critical exception is in the Neoproterozoic Era, 0.5 to 1 billion years ago, where gaps in the intensity record and anomalous directions exist. Could this exception be explained by a major event like the solidification of the planet’s inner core?
In order to address this question, Driscoll modeled the planet’s thermal history going back 4.5 billion years. His models indicate that the inner core should have begun to solidify around 650 million years ago. Using further 3-D dynamo simulations, which model the generation of magnetic field by turbulent fluid motions, Driscoll looked more carefully at the expected changes in the magnetic field over this period.
“What I found was a surprising amount of variability,” Driscoll said. “These new models do not support the assumption of a stable dipole field at all times, contrary to what we’d previously believed.”
His results showed that around 1 billion years ago, Earth could have transitioned from a modern-looking field, having a “strong” magnetic field with two opposite poles in the north and south of the planet, to having a “weak” magnetic field that fluctuated wildly in terms of intensity and direction and originated from several poles. Then, shortly after the predicted timing of the core solidification event, Driscoll’s dynamo simulations predict that Earth’s magnetic field transitioned back to a “strong,” two-pole one.
“These findings could offer an explanation for the bizarre fluctuations in magnetic field direction seen in the geologic record around 600 to 700 million years ago,” Driscoll added. “And there are widespread implications for such dramatic field changes.”
Overall, the findings have major implications for Earth’s thermal and magnetic history, particularly when it comes to how magnetic measurements are used to reconstruct continental motions and ancient climates. Driscoll’s modeling and simulations will have to be compared with future data gleaned from high quality magnetized rocks to assess the viability of the new hypothesis.

IMAGE….This is an illustration of ancient Earth’s magnetic field compared to the modern magnetic field courtesy of Peter Driscoll. Credit: Peter Driscoll

Misconception About Tsunamis

Tsunamis in the middle of the ocean are usually just centimeters in height, not the 10m killer waves they are when they reach the shore.

This is due to the conservation of momentum - 

The velocity of a wave, V, is proportional to the depth of the water it is travelling over, so in deep seas waves are travelling very quickly, and naturally have large Wavelengths, L.

Because the wave has a large wavelength it will also have a large mass, even if its only a few centimeters tall, as Mass is proportional to L and H. and Momentum = Mass X Velocity.

So a large Mass X large Velocity = Large momentum.

But as the wave approaches the shore, depth decreases.

V = SqRt( Gravity X Depth )  so if the depth is 4 times shallower, velocity is halved.

So now we have Mass X (Velocity / 2) = Momentum, But momentum must be conserved! so Mass is doubled, but if the Wavelength is not changed how can the wave gain mass? 

So, as a Tsunami approaches the shore, ocean depth obviously decreases. Which in turn decreases Velocity, meaning mass must increase which means Height must increase!

Which is why those movies of boats being flung out of the ocean and capsized by massive waves in the middle of the ocean is incorrect. You probably wouldn’t even noticed it! 

Astronomers perform largest-ever survey of high-mass binary star systems

An international group of researchers led by Brazilians has identified and characterized 82 binaries in a satellite galaxy of the Milky Way

In addition to solo stars like our Sun, the universe contains binary systems comprising two massive stars that interact with each other.

In many binaries the two stars are close enough to exchange matter and may even merge, producing a single high-mass star that spins at great speed.

Until now the number of known high-mass binaries has been very small, basically confined to those identified in our galaxy, the Milky Way.

An international group of astronomers led by researchers at the University of São Paulo’s Institute of Astronomy, Geophysics & Atmospheric Sciences (IAG-USP) in Brazil, have just extended the list of by identifying and characterizing 82 new high-mass binaries located in the Tarantula Nebula, also known as 30 Doradus, in the Large Magellanic Cloud.

The LMC is a satellite galaxy of the Milky Way and is about 160,000 light years from Earth.

The results of the study are described in article published in the journal Astronomy & Astrophysics.

“By identifying and characterizing these 82 high-mass binaries, we have more than doubled the number of these objects, and in a completely new region with very different conditions from those found in the Milky Way,” said Leonardo Andrade de Almeida, a postdoctoral fellow at IAG-USP and first author of the study.

In research supervised by Augusto Damineli Neto, a full professor at IAG and a co-author of the article, Almeida analyzed the data obtained during the VLT-FLAMES Tarantula Survey and Tarantula Massive Binary Monitoring observation campaigns performed by the European Southern Observatory (ESO) from 2011.

Using FLAMES/GIRAFFE, a spectrograph coupled to ESO’s Very Large Telescope (VLT), which has four 8 m primary mirrors and operates in Chile’s Atacama Desert, the observation campaigns collected spectral data for over 800 high-mass objects in the region of the Tarantula Nebula, so named because its glowing filaments resemble spider legs.

From this total of 800 observed objects, the astronomers who worked on the two surveys identified 100 candidate binaries of spectral type O (very hot and massive) in a sample of 360 stars based on parameters such as the amplitude of variations in their radial velocity (the velocity of motion away from or toward an observer).

For the last two years, Almeida has collaborated with colleagues in other countries on an analysis of these 100 candidate high-mass binaries using the FLAMES/GIRAFFE spectrograph and has managed to characterize 82 of them completely.

“This represents the largest survey and spectroscopic characterization of massive binary systems every performed,” he said.

“It was only possible thanks to the technological capabilities of the FLAMES/GIRAFFE spectrograph.”

The scientific instrument developed by ESO can be used to obtain spectra for a number of objects simultaneously, and weaker objects can be observed because it is coupled to the VLT, which has large mirrors and captures more light, Almeida explained.

“We can collect 136 spectra in a single observation using FLAMES/GIRAFFE,” he said.

“Nothing similar could be done before.

Our instruments could only observe individual objects and it took much longer to characterize them.”

Spectroscopic analysis of the 82 binaries showed that properties such as mass ratio, orbital period (the time taken to complete one orbit) and orbital eccentricity (the amount by which the orbit deviates from a perfect circle) were highly similar to those observed in the Milky Way.

This was unexpected since the LMC embodies a phase of the universe prior to the Milky Way when the largest number of high-mass stars were formed.

For this reason, its metallicity - the proportion of its matter made up of chemical elements different from hydrogen and helium, the primordial atoms that gave rise to the first stars - is only half that of the binaries found in the Milky Way, whose metallicity is very close to the Sun’s.

“At the beginning of the universe, stars were metal-poor but chemical evolution increased their metallicity,” Almeida said.

This analysis of binaries in the LMC, he added, provides the first direct constraints on the properties of massive binaries in galaxies whose stars were formed in the early universe and have the LMC’s metallicity.

“The discoveries made during the study may provide better measurements for use in more realistic simulations of how high-mass stars evolved in the different phases of the universe.

If so, we’ll be able to obtain more precise estimates of the rate at which black holes, neutron stars and supernovae were formed in each phase, for example,” he said.

High-mass stars are the most important drivers of the chemical evolution of the universe. Because they are more massive, they produce more heavy metals, evolve more rapidly, and end their lives as supernovae, ejecting all their matter into the interstellar medium. This matter is recycled to form a new population of stars.

However, Almeida went on, estimates of the chemical evolution of the universe and astrophysical predictions of the number of black holes usually take into account sole stars like our Sun, which evolve more simply.

According him, when you include binaries in computing these projections, the result changes dramatically.

So when making astrophysical predictions you need to consider these massive objects.

NASA Mission Reveals Speed of Solar Wind Stripping Martian Atmosphere

NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) mission has identified the process that appears to have played a key role in the transition of the Martian climate from an early, warm and wet environment that might have supported surface life to the cold, arid planet Mars is today.

MAVEN data have enabled researchers to determine the rate at which the Martian atmosphere currently is losing gas to space via stripping by the solar wind. The findings reveal that the erosion of Mars’ atmosphere increases significantly during solar storms. The scientific results from the mission appear in the Nov. 5 issues of the journals Science and Geophysical Research Letters.

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New light shed on end of Snowball Earth period

The second ice age during the Cryogenian period was not followed by the sudden and chaotic melting-back of the ice as previously thought, but ended with regular advances and retreats of the ice, according to research published by scientists from the University of Birmingham in the journal Nature Geoscience today (24 August 2015).

The researchers also found that the constant advance and retreat of ice during this period was caused by the Earth wobbling on its axis.

These ice ages are explained by a theory of Snowball Earth, which says that they represent the most extreme climatic conditions the world has ever known and yet they ended quite abruptly 635 million years ago. Little was known about how they ended – until now.

For the study, the scientists analyzed sedimentary rocks from Svalbard, Norway that were laid down in that ice age. The deposits preserved a chemical record which showed high levels of CO2 were present in the atmosphere. Carbon dioxide was low when the ice age started, and built up slowly over millions of years when the whole Earth was very cold – this period is represented only by frost-shattered rubble under the sediments.

Eventually the greenhouse warmth in the atmosphere from carbon dioxide caused enough melting for glaciers to erode, transport and deposit sediment. The sedimentary layers showed ice retreat and advance as well as cold arid conditions. They reveal a time when glacial advances alternated with even more arid, chilly periods and when the glaciers retreated, rivers flowed, lakes formed, and yet simple life survived.

As theory predicts, this icy Earth with a hot atmosphere rich in carbon dioxide had reached a ‘Goldilocks’ zone – too warm to stay completely frozen, too cold to lose its ice, but just right to record more subtle underlying causes of ancient climate change.

The geological researchers invited a French group of physicists who produce sophisticated climate models to test their theory that the advances and retreats of ice during this period were caused by the Earth wobbling on its axis in 20,000 year periods. The rocks and the models agreed: slight wobbles of the Earth on its spin axis caused differences in the heat received at different places on the Earth’s surface. These changes were small, but enough over thousands of years to cause a change in the places where snow accumulated or melted, leading the glaciers to advance and retreat. During this time the whole Earth would have looked like the Dry Valley regions of Antarctica – a very dry landscape, with lots of bare ground, but also containing glaciers up to 3 km thick.

Professor Ian Fairchild, lead investigator from the University of Birmingham’s School of Geography, Earth and Environmental Sciences, said: 'We now have a much richer story about what happened at the end of the Snowball Earth period. The sediment analysis has given us a unique window on what happened so many millions of years ago. We know that the Earth’s climate is controlled by its orbit, and we can now see the effect of that in this ancient ice age too.’


Lightning linked to solar wind

Correlation suggests answer to longstanding question about what triggers bolts.

Lightning has been around since the dawn of time, but what triggers it is still an enigma. Now, researchers propose that the answer could lie in solar particles that penetrate the atmosphere and ionize the air, releasing free electrons and leading to a massive discharge.

Thunderclouds become electrically charged from the collisions of microscopic ice particles in their midst, and from air currents that push the negative and positive charges apart. The air is a good insulator, keeping electrons from jumping back and equilibrating the electrostatic charges. But if a pathway of ionized air molecules forms that can act as a conductor between different parts of a cloud, or between the cloud and the ground, the result is a lightning bolt.

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The Cambrian Explosion

The Cambrian explosion, or Cambrian radiation, was the relatively rapid appearance, around 542 million years ago, of most major animal phyla, as demonstrated in the fossil record. This was accompanied by major diversification of other organisms. Before about 580 million years ago, most organisms were simple, composed of individual cells occasionally organized into colonies. Over the following 70 or 80 million years, the rate of evolution accelerated by an order of magnitude and the diversity of life began to resemble that of today. Ancestors of many of the present phyla appeared during this period, with the exception of Bryozoa, which made its earliest known appearance in the Lower Ordovician.

The Cambrian explosion has generated extensive scientific debate. The seemingly rapid appearance of fossils in the “Primordial Strata” was noted as early as the 1840s, and in 1859 Charles Darwin discussed it as one of the main objections that could be made against his theory of evolution by natural selection. The long-running puzzlement about the appearance of the Cambrian fauna, seemingly abruptly and from nowhere, centers on three key points: whether there really was a mass diversification of complex organisms over a relatively short period of time during the early Cambrian; what might have caused such rapid change; and what it would imply about the origin and evolution of animals. Interpretation is difficult due to a limited supply of evidence, based mainly on an incomplete fossil record and chemical signatures remaining in Cambrian rocks.

Phylogenetic analysis has supported the view that during the Cambrian radiation metazoa evolved monophyletically from a single common ancestor: flagellated colonial protists similar to modern choanoflagellates.

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nature.com
Magnetic mystery of Earth's early core explained
Competing ideas suggest how sloshing motions could maintain a primordial magnetic field.

Geophysicists call it the new core paradox: They can’t quite explain how the ancient Earth could have sustained a magnetic field billions of years ago, as it was cooling from its fiery birth.

Now, two scientists have proposed two different ways to solve the paradox. Each relies on minerals crystallizing out of the molten Earth, a process that would have generated a magnetic field by churning the young planet’s core. The difference between the two explanations comes in which particular mineral does the crystallizing.

Silicon dioxide is the choice of Kei Hirose, a geophysicist at the Tokyo Institute of Technology who runs high-pressure experiments to simulate conditions deep within the Earth. “I’m very confident in this,” he reported on 17 December at a meeting of the American Geophysical Union in San Francisco, California.

But David Stevenson, a geophysicist at the California Institute of Technology in Pasadena, says that magnesium oxide — not silicon dioxide — is the key to solving the problem. In unpublished work, Stevenson proposes that magnesium oxide, settling out of the molten early Earth, could have set up the buoyancy differences that would drive an ancient geodynamo.

The core paradox arose in 2012, when several research teams reported that Earth’s core loses heat at a faster rate than once thought1, 2. More heat conducting away from the core means less heat available to churn the core’s liquid. That’s important because some studies suggest Earth could have had a magnetic field more than 4 billion years ago —  just half a billion years after it coalesced from fiery debris swirling around the newborn Sun. “We need a dynamo more or less continuously,” Peter Driscoll, a geophysicist at the Carnegie Institution for Science in Washington DC, said at the meeting.

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