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Swirling Vortex of Bathtub Water Reveals an Elusive Mechanism of Black Hole Physics

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When a black hole is active, we tend to focus on the effect it has on the material it’s slurping up. It makes sense to do so; black holes themselves are difficult to probe. But the interaction between the black hole and the material should have an effect on the black hole, too – as it gains material, it should also gain in mass.

 

Such small feedback responses – especially ones previously ignored as trivial – are known as backreactions, and scientists have just observed an analogue of one that’s specific to black holes, and which can be seen in water swirling down a drain.

It’s a detection that could help study black hole phenomena that are too subtle for our current instruments, such as the Hawking radiation that is thought to be emitted by black holes. This is a theoretical type of black-body radiation that would eventually – after a very, very long time – see a black hole completely evaporate, provided it was not growing at all.

In order to study cosmic objects in finer detail than we can across the vast distances of space, scaled-down versions, or analogues, can be created in a lab. Like, for instance, a recent experiment to replicate white dwarf core pressures.

Black hole analogues are an excellent way to find out more about these enigmatic objects, and different kinds can help reveal their secrets in multiple ways.

Optical fibre and Bose-Einstein condensates have both been used to learn more about Hawking radiation. But one of the simplest has to do with how black holes feed: the draining bathtub vortex.

 

Black hole accretion can be compared with water swirling down a drain. Treating matter as a ripple in a field, the water can stand in for spacetime itself, or a field rippling with quantum activity.

Measuring the ripples responses as the water vanishes down a swirling drain might have something to say about waves of energy disappearing into a black hole.

A bathtub vortex black hole analogue. (The University of Nottingham)

From such analogues, we’ve learnt a lot about the effect of black holes on the space and material around them. But with an external water pump keeping the background of the system steady, it was unclear whether a water black hole analogue would have the freedom to be able to react to waves.

This set of experiments is the first time a draining bathtub vortex has demonstrated an effect on the black hole itself.

“We have demonstrated that analogue black holes, like their gravitational counterparts, are intrinsically backreacting systems,” said physicist Sam Patrick of the University of Nottingham in the UK.

“We showed that waves moving in a draining bathtub push water down the plug hole, modifying significantly the drain speed and consequently changing the effective gravitational pull of the analogue black hole.”

 

When waves were sent rippling into the system towards the drain, they pushed extra water in, accelerating the “accretion” process so significantly that the water levels in the tub dropped noticeably, even while a pump maintained the same level of water going in.

This change in the water level corresponds to a change in the properties of the black hole, the researchers said.

This could be extremely useful information, partially because an increase in mass changes the gravitational strength of a black hole – it changes the way the black hole warps its surrounding spacetime, as well as the effect the black hole has on the accretion disc. In addition, it offers a new way to study how waves can affect black hole dynamics.

“What was really striking for us is that the backreaction is large enough that it causes the water height across the entire system to drop so much that you can see it by eye! This was really unexpected,” Patrick said.

“Our study paves the way to experimentally probing interactions between waves and the spacetimes they move through. For example, this type of interaction will be crucial for investigating black hole evaporation in the laboratory.”

The team’s research has been published in Physical Review Letters.

 

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The Earth’s Magnetosphere Might be Creating Water on the Moon

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There’s no doubt that the Moon has water on its surface. Orbiters have spotted deposits of ice persisting in the perpetual shadows of polar craters. And recent research shows that water exists in sunlit parts of the Moon, too.

Over the years, scientists have presented evidence that the Moon’s water came from comets, from asteroids, from inside the Moon, and even from the Sun.

But now new research is pointing the finger directly at Earth as the source of some of the Moon’s water.

The new study is titled “Earth Wind as a Possible Exogenous Source of Lunar Surface Hydration.” The lead author is H.Z. Wang of Shandong University in China, and the paper is published in The Astrophysical Journal Letters. The research suggests that particles from Earth can seed the Moon with water.

That the Moon has water isn’t surprising. Astronomers have detected water in all kinds of places in space, though most of it is ice. The prevailing theory for that water is that it arrives on planets and moons as they form, perhaps delivered by asteroids or comets. But this paper presents evidence that some of the water on the Moon’s surface came from Earth’s wind.

It’s likely that the solar wind is responsible for some of the Moon’s surface water. The lunar regolith contains silicates, and protons in the solar wind are able to reduce the oxygen out of those silicates. That oxygen then readily combines with hydrogen to form water.

The problem with the Sun being the only source of lunar surface water is evaporation. Computer models predict that a large portion of it—up to 50%—should evaporate from high-latitude regions of the lunar surface during the full Moon. For three to five days each cycle the Moon is in Earth’s magnetosphere, meaning that water should disappear from the surface since Earth’s magnetosphere blocks the solar wind from reaching the Moon and replenishing the surface water during that period.

This image from the study shows the Moon in the Earth’s magnetosphere. For 3 to 5 days each month, the Moon is protected from the Solar wind and instead subject to the Earth wind. Image Credit: Wang et al, 2021.

But that’s not what happens. Instead, according to data from India’s Chandrayaan-1 satellite’s Moon Mineralogy Mapper, the water doesn’t disappear during full Moons. The authors of the study say that an “Earth wind” is replenishing it.

The solar wind and the Earth wind are different. The solar wind is primarily plasma consisting of protons and electrons released from the Sun’s upper atmosphere. But the Earth wind is a flow of ions from the magnetosphere, as measured by the THEMIS-ARTEMIS mission.

This figure from the study a north (B) overview and a south (C) overview of the Moon’s polar regions. It shows data from the Chandrayaan-1 satellite’s Moon Mineralogy Mapper which indicates OH/H2O abundance. The red and black bars around the outside of each image shows the Moon subjected to solar wind and Earth wind. The small red square is the Goldschmidt crater, which has an anomalous abundance of OH/H2O due to its composition. Image Credit: Wang et al, 2021.

Japan’s Kaguya mission detected hydrogen ions from Eath’s exosphere embedded in the soil. It also detected high concentrations of oxygen isotopes coming from Earth’s ozone layer and becoming embedded in the lunar surface. This points to the idea of a “water bridge” from the Earth to the Moon. This bridge is active during the days of the month when the Moon is inside Earth’s magnetosphere, and it replenishes water lost to evaporation.

Though these findings go a long way to help explain lunar surface water, they might have broader importance, too. If there’s a bridge between Earth and the Moon that creates water on the Moon, where else in the Solar System might this be happening?

This image from the study shows satellite data for an entire month, including the Full Moon. During the time that the Moon is out of the Solar wind and inside Earth’s magnetosphere, surface water persisted. For a more detailed explanation of this figure, see the study. Image Credit: Wang et al, 2021.

The authors have proposed a mechanism for lunar water that coexists with the solar wind explanation. But it’s not confirmed yet. Future studies may provide further evidence that there’s a water bridge between the Earth and the Moon. China’s Chang’e 5 mission returned lunar samples to Earth back in December. Those samples could hold evidence for the water bridge idea.

If it turns out to be correct, astronomers will immediately begin to wonder (they probably already have) if a similar mechanism is at work elsewhere, maybe right here in our own Solar System.

This study also points out how much more we have to learn about the interactions between planets, their moons, and their stars. The evolution of water in our and other solar systems may depend on these interactions. This research effort could also help us understand the potential habitability of distant exoplanets.

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Backreaction observed for first time in water tank black hole simulation

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Lab experiment using water tank simulation to demonstrate backreaction. Credit: University of Nottingham

Scientists have revealed new insights into the behavior of black holes with research that demonstrates how a phenomenon called backreaction can be simulated.

The team from the University of Nottingham have used their simulation of a black hole, involving a specially designed water tank, for this latest research published in Physical Review Letters. This study is the first to demonstrate that the evolution of black holes resulting from the fields surrounding them can be simulated in a laboratory experiment.

The researchers used a water tank simulator consisting of a draining vortex, like the one that forms when you pull the plug in the bath. This mimics a black hole since a wave which comes too close to the drain gets dragged down the plug hole, unable to escape. Systems like these have grown increasingly popular over the past decade as a means to test gravitational phenomena in a controlled laboratory environment. In particular, Hawking radiation has been observed in an analog black hole experiment involving quantum optics.

Using this technique the researchers showed for the first time that when waves are sent into an analog black hole, the properties of the black hole itself can change significantly. The mechanism underlying this effect in their particular experiment has a remarkably simple explanation. When waves come close to the drain, they effectively push more water down the plug hole causing the total amount of water contained in the tank to decrease. This results in a change in the water height, which in the simulation corresponds to a change in the properties of the black hole.

Lead author, Post-doctoral researcher Dr. Sam Patrick from the University of Nottingham School of Mathematical Sciences explains: “For a long time, it was unclear whether the backreaction would lead to any measurable changes in analog systems where the fluid flow is driven, for example, using a water pump. We have demonstrated that analog black holes, like their gravitational counterparts, are intrinsically backreacting systems. We showed that waves moving in a draining bathtub push water down the plug hole, modifying significantly the drain speed and consequently changing the effective gravitational pull of the analog black hole.

What was really striking for us is that the backreaction is large enough that it causes the water height across the entire system to drop so much that you can see it by eye! This was really unexpected. Our study paves the way to experimentally probing interactions between waves and the spacetimes they move through. For example, this type of interaction will be crucial for investigating black hole evaporation in the laboratory.”

Black hole research at the University of Nottingham has recently received a £4.3 million funding boost for a three-year project that aims to provide further insights into the physics of the early universe and black holes.

The research team will use quantum simulators to mimic the extreme conditions of the early universe and black holes. The Nottingham team will be using a new state laboratory to set up a novel hybrid superfluid optomechanical system to mimic quantum black hole processes in the laboratory.

Black holes gain new powers when they spin fast enough

More information:
Sam Patrick et al, Backreaction in an Analogue Black Hole Experiment, Physical Review Letters (2021). DOI: 10.1103/PhysRevLett.126.041105
Provided by
University of Nottingham

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Backreaction observed for first time in water tank black hole simulation (2021, February 1)
retrieved 1 February 2021
from https://phys.org/news/2021-02-backreaction-tank-black-hole-simulation.html

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Moon could get water from ‘wind’ in the Earth’s magnetosphere: Study

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A new study published in the Astrophysical Journal Letters reveals that solar wind may not be the only source of water-forming ions on the moon. Researchers show that the particles from the moon with water, imply that even other planets can contribute water to their satellites. Water is prevalent in space. It is available from the surface of Mars to Jupiter’s moons and Saturn’s rings, comets, asteroids and Pluto.

Moon could get water from ‘wind’

Water has been detected in clouds which are far away from the solar system. Earlier, it was assumed that water was incorporated into these objects during the formation of the solar system. However, with time, there was evidence that water in space is prevalent and far more dynamic. Various computer models have predicted that up to half of the lunar surface water should evaporate and disappear at high-latitude regions during the time of full moon. 

Read: Mesmerising Picture Of Moon With Rainbow Ring Around It Leaves People Stunned; Pic Inside

The latest analysis of surface hydroxyl/water surface maps by the Chandrayaan-1 satellite’s Moon Mineralogy Mapper revealed that lunar surface water does not disappear during this magnetosphere shielding period. Even though Earth’s  magnetic field was thought to block the solar wind from reaching the moon. However, researchers later found out that this was never the case. 

Read: Moon Rock, From NASA’s Apollo 17 Mission, Displayed In Joe Biden’s Oval Office

The researchers compared the time series of water surface maps before, during and after the magnetosphere transit and they argued that the  lunar water could be replenished by flows of magnetospheric ions. These are called the ‘Earth wind”. Later, Kaguya satellite confirmed the presence of these Earth-derived ions near the moon.

Also, THEMIS-ARTEMIS satellite observations were used to profile the distinctive features of ions. Previous observations by the Kaguya satellite during full moon detected high concentrations of oxygen isotopes. These were leaked out of  Earth’s ozone layer and embedded in lunar soil. Also, this was present with an abundance of hydrogen ions in Earth’s  exosphere.

Read: Full Moon 2021 Schedule: Check Out All The Full Moon Dates With Times Here

Also Read: Scientists Identify Over 1 Lakh Previously Unrecognised Moon Impact Craters

(Image Credits: PedroLastra/Instagram)



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The Moon Could Be Getting Water Thanks to ‘Wind’ From Earth’s Magnetosphere

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Evidence of water in the shadows of craters or locked up in glassy beads like microscopic snow-globes has recently revealed the Moon’s surface is far less desiccated than we ever imagined.

 

Just where this veneer of ice water came from is a mystery astronomers are currently trying to solve. One surprising possibility emerging is an elemental rain from our own atmosphere, delivered by Earth’s magnetic field.

Water isn’t exactly a rare substance in space. Given suitable places to hide, it can be sloshing around inside asteroids, coating comets, and even clinging precariously to the darkness of Mercury’s craters.

It makes sense at least some of it will splash onto the Moon every now and then. But with the Sun’s scorching heat and lacking protection from the vacuum of space, it’s not expected to last very long.

To account for the surprising amount of moisture being found on the lunar surface, researchers have proposed a more dynamic form of production – a constant ‘rain’ of protons driven by the solar wind. These hydrogen ions smack into mineral oxides in the Moon’s dust and rocks, ripping apart chemical bonds and forming a loose, temporary alliance with the oxygen.

It’s a solid hypothesis, one that would be given a boost by observations of the more exposed (and more loosely bound) water molecules quickly succumbing to the vacuum of space whenever the Moon is sheltered from solar wind.

 

Our own planet happens to be pretty well protected from the constant breeze of ions blown from the Sun, thanks to a bubble of magnetism surrounding it. This force field not only surrounds us, it is blown into a tear-drop shape by the solar onslaught.

For a few days each month, the Moon passes through this magnetosphere, receiving a brief respite from the Sun’s proton downpour.

An international team of researchers recently used plasma and magnetic field instruments on the Japanese Kaguya orbiter to pinpoint this precise timing in the Moon’s orbit. Spectral data from Chandrayaan-1’s Moon Mineralogy Mapper (M3) were then used to map the distribution of water across the Moon’s surface at its highest latitudes.

The results weren’t quite what anybody expected.

In short, nothing happened. The time-series of the Moon’s watery signature revealed no appreciable difference in the three to five days spent hidden from the Sun’s wind.

These results could mean a few things. One is that the whole solar wind hypothesis is a bust, and other reservoirs are responsible for replenishing the Moon’s surface water.

 

But another intriguing possibility that doesn’t require us to ditch the solar wind idea is that Earth’s magnetic field simply picks up where the Sun leaves off.

Past research has suggested the sheet of plasma associated with our planet’s magnetosphere could deliver about the same amount of hydrogen ions as the solar wind, especially towards the lunar poles.

It’s not all delivered with quite the same amount of punch, admittedly, but the researchers hypothesise even the occasional heavy-hitting hydrogen ion could potentially create more than its fair share of water. And lower-energy protons might be more easily held in place, therefore less likely to fall apart in the moments after they’re formed.

There’s also every possibility that oxygen from the upper reaches of the atmosphere above our poles is carried across the vast stretch of emptiness to collide with the Moon, especially during periods of enhanced geomagnetic activity.

If this all sounds rather speculative, that’s because it is. Right now, we only have a rather surprising map of water that doesn’t quite align with favoured models.

But it points in some exciting new directions for the emerging field of Moon hydrodynamics. Since the researchers only mapped the water distribution at higher latitudes, it’ll be worth looking closer to the equator for the predicted losses in the future.

On a practical front, we might need to rely heavily on a replenishing supply of lunar frost for fuel and life support one day, should the Moon become a stepping stone for space exploration.

If nothing else, we’re slowly piecing together an understanding of a water cycle in space that helps us better understand the connections between our planet and its only natural satellite.

This research was published in the Astrophysical Journal Letters.

 

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First evidence that water can be created on the lunar surface by Earth’s magnetosphere

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75% of its orbit in the solar wind (yellow), which is blocked by the magnetosphere the rest of the time. Credit: E. Masongsong, UCLA EPSS, NASA GSFC SVS.” width=”800″ height=”496″/>
Artist’s depiction of the Moon in the magnetosphere, with “Earth wind” made up of flowing oxygen ions (gray) and hydrogen ions (bright blue), which can react with the lunar surface to create water. The Moon spends >75% of its orbit in the solar wind (yellow), which is blocked by the magnetosphere the rest of the time. Credit: E. Masongsong, UCLA EPSS, NASA GSFC SVS.

Before the Apollo era, the moon was thought to be dry as a desert due to the extreme temperatures and harshness of the space environment. Many studies have since discovered lunar water: ice in shadowed polar craters, water bound in volcanic rocks, and unexpected rusty iron deposits in the lunar soil. Despite these findings, there is still no true confirmation of the extent or origin of lunar surface water.

The prevailing theory is that positively charged hydrogen ions propelled by the solar wind bombard the lunar surface and spontaneously react to make water (as hydroxyl (OH–) and molecular (H2O)). However, a new multinational study published in Astrophysical Journal Letters proposes that solar wind may not be the only source of water-forming ions. The researchers show that particles from Earth can seed the moon with water, as well, implying that other planets could also contribute water to their satellites.

Water is far more prevalent in space than astronomers first thought, from the surface of Mars to Jupiter’s moons and Saturn’s rings, comets, asteroids and Pluto; it has even been detected in clouds far beyond our solar system. It was previously assumed that water was incorporated into these objects during the formation of the solar system, but there is growing evidence that water in space is far more dynamic. Though the solar wind is a likely source for lunar surface water, computer models predict that up to half of it should evaporate and disappear at high-latitude regions during the approximately three days of the full moon when it passes within Earth’s magnetosphere.

Surprisingly, the latest analysis of surface hydroxyl/water surface maps by the Chandrayaan-1 satellite’s Moon Mineralogy Mapper (M3) showed that lunar surface water does not disappear during this magnetosphere shielding period. Earth’s magnetic field was thought to block the solar wind from reaching the moon so that water could not be regenerated faster than it was lost, but the researchers found this was not the case.

By comparing a time series of water surface maps before, during and after the magnetosphere transit, the researchers argue that lunar water could be replenished by flows of magnetospheric ions, also known as “Earth wind.” The presence of these Earth-derived ions near the moon was confirmed by the Kaguya satellite, while THEMIS-ARTEMIS satellite observations were used to profile the distinctive features of ions in the solar wind versus those within the magnetosphere Earth wind.

Previous Kaguya satellite observations during the full moon detected high concentrations of oxygen isotopes that leaked out of Earth’s ozone layer and embedded in lunar soil, along with an abundance of hydrogen ions in our planet’s vast extended atmosphere, known as the exosphere. These combined flows of magnetosphere particles are fundamentally different from those in the solar wind. Thus, the latest detection of surface water in this study refutes the shielding hypothesis and instead suggest that the magnetosphere itself creates a “water bridge” that can replenish the moon.

The study employed a multidisciplinary team of experts from cosmochemistry, space physics and planetary geology to contextualize the data. Prior interpretations of surface water did not consider the effects of Earth ions and did not examine how surface water changed over time. The only surface maps and particle data available during a full moon in the magnetosphere were in winter and summer 2009, and it took the past several years to analyze and interpret the results. The analysis was especially difficult due to the scarce observations, which were required to compare the same lunar surface conditions over time and to control for temperature and surface composition.

In light of these findings, future studies of the solar wind and planetary winds can reveal more about the evolution of water in our solar system and the potential effects of solar and magnetosphere activity on other moons and planetary bodies. Expanding this research will require new satellites equipped with comprehensive hydroxyl/water mapping spectrometers, and particle sensors in orbit and on the lunar surface to fully confirm this mechanism. These tools can help to predict the best regions for future exploration, mining and eventual settlement on the moon. Practically, this research can influence the design of upcoming space missions to better safeguard humans and satellites from particle radiation hazards, and also improve computer models and laboratory experiments of water formation in space.

Water on the Moon: Research unveils its type and abundance – boosting exploration plans

More information:
Earth wind as a possible source of lunar surface hydration. arxiv.org/abs/1903.04095
Provided by
UCLA Earth, Planetary, and Space Sciences

Citation:
First evidence that water can be created on the lunar surface by Earth’s magnetosphere (2021, January 28)
retrieved 28 January 2021
from https://phys.org/news/2021-01-evidence-lunar-surface-earth-magnetosphere.html

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Ingenious ‘Wrinkled’ Graphene Could Be The Most Promising Water Filter Yet

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Graphene continues to dazzle us with its strength and its versatility – exciting new applications are being discovered for it all the time, and now scientists have found a way of manipulating the wonder material so that it can better filter impurities out of water.

 

The two-dimensional material comprised of carbon atoms has been studied as a way of cleaning up water before, but the new method could offer the most promising approach yet. It’s all down to the exploitation of what are known as van der Waals gaps: the tiny spaces that appear between 2D nanomaterials when they’re layered on top of each other.

These nanochannels can be used in a variety of ways, which scientists are now exploring, but the thinness of graphene causes a problem for filtration: liquid has to spend much of its time travelling along the horizontal plane, rather than the vertical one, which would be much quicker.

To solve this problem, the team behind the new study used an elastic substrate to scrunch up the graphene layer into a microscopic series of peaks and valleys. That means liquid can scoot down the side of a peak vertically, rather than trekking across the open plains horizontally (all at the nanoscale, of course).

(Brown University)

“When you start wrinkling the graphene, you’re tilting the sheets and the channels out of plane,” says materials scientist Muchun Liu from the Massachusetts Institute of Technology (MIT).

“If you wrinkle it a lot, the channels end up being aligned almost vertically.”

 

To finish the effect, the graphene and substrate are fixed in an epoxy substance, before the tops of the peaks and the bottoms of the valleys are trimmed off. It gives liquid a quicker route through the graphene while still enabling filtration to happen.

Liu and her colleagues have given the new materials the name VAGMEs (vertically aligned graphene membranes), and further down the line they could find uses far beyond making water safe to drink.

“What we end up with is a membrane with these short and very narrow channels through which only very small molecules can pass,” says chemical engineer Robert Hurt, from Brown University.

“So, for example, water can pass through, but organic contaminants or some metal ions would be too large to go through. So you could filter those out.”

The next step will be to put this into practice and work out a practical filtering system, but the theory is sound. The material passed one of its first tests by allowing water vapor to flow through, while trapping larger hexane molecules.

 

Eventually these VAGMEs could find uses in industrial or household filtering systems, the scientists say – just one of many promising ways that graphene is being put to use in various different scientific fields.

As for the nanochannels that operate between super-thin 2D materials such as graphene, there’s plenty of potential here too, according to the experts. The closer that scientists look at these nanomaterials, the more they discover.

“In the last decade, a whole field has sprung up to study these spaces that form between 2D nanomaterials,” says Hurt.

“You can grow things in there, you can store things in there, and there’s this emerging field of nanofluidics where you’re using those channels to filter out some molecules while letting others go through.”

The research has been published in Nature Communications.

 

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There’s lots of water in the world’s most explosive volcano

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Shiveluch volcano has had more than 40 violent eruptions over the last 10,000 years. The last gigantic blast occurred in 1964, creating a new crater and covering an area of nearly 100 square kilometers with pyroclastic flows. But Shiveluch is actually currently erupting, as it has been for over 20 years. Credit: Michael Krawczynski, Washington University in St. Louis

There isn’t much in Kamchatka, a remote peninsula in northeastern Russia just across the Bering Sea from Alaska, besides an impressive population of brown bears and the most explosive volcano in the world.

Kamchatka’s Shiveluch volcano has had more than 40 violent eruptions over the last 10,000 years. The last gigantic blast occurred in 1964, creating a new crater and covering an area of nearly 100 square kilometers with pyroclastic flows. But Shiveluch is actually currently erupting, as it has been for over 20 years. So why would anyone risk venturing too close?

Researchers from Washington University in St. Louis, including Michael Krawczynski, assistant professor of earth and planetary sciences in Arts & Sciences and graduate student Andrea Goltz, brave the harsh conditions on Kamchatka because understanding what makes Shiveluch tick could help scientists understand the global water cycle and gain insights into the plumbing systems of other volcanoes.

In a recent study published in the journal Contributions to Mineralogy and Petrology, researchers from the Krawczynski lab looked at small nodules of primitive magma that were erupted and preserved amid other materials.

“The minerals in these nodules retain the signatures of what was happening early in the magma’s evolution, deep in Earth’s crust,” said Goltz, the lead author of the paper.






The researchers found that the conditions inside Shiveluch include roughly 10%-14% water by weight (wt%). Most volcanoes have less than 1% water. For subduction zone volcanoes, the average is usually 4%, rarely exceeding 8 wt%, which is considered superhydrous.

Of particular interest is a mineral called amphibole, which acts as a proxy or fingerprint for high water content at known temperature and pressure. The unique chemistry of the mineral tells researchers how much water is present deep underneath Shiveluch.

“When you convert the chemistry of these two minerals, amphibole and olivine, into temperatures and water contents as we do in this paper, the results are remarkable both in terms of how much water and how low a temperature we’re recording,” Krawczynski said.

“The only way to get primitive, pristine materials at low temperatures is to add lots and lots of water,” he said. “Adding water to rock has the same effect as adding salt to ice; you’re lowering the melting point. In this case, there is so much water that the temperature is reduced to a point where amphiboles can crystallize.”

Water drives explosive eruptions: Magma is wetter than we thought

More information:
Andrea E. Goltz et al, Evidence for superhydrous primitive arc magmas from mafic enclaves at Shiveluch volcano, Kamchatka, Contributions to Mineralogy and Petrology (2020). DOI: 10.1007/s00410-020-01746-5
Provided by
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Citation:
Wet and wild: There’s lots of water in the world’s most explosive volcano (2021, January 23)
retrieved 23 January 2021
from https://phys.org/news/2021-01-wild-lots-world-explosive-volcano.html

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A Horrible Condition Turning Starfish Into Goo Has Finally Been Identified

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In 2013, the lives of millions of sea stars were mysteriously extinguished. Limbs that were once strong, probing arms searching for sustenance, shrivelled and tore themselves away from the rest of their bodies and melted into a sickly goo.

 

“There were arms everywhere,” ecologist Drew Harvell told The Atlantic‘s Ed Yong last year. “It looked like a blast zone.”

The dismal remains of these animals, who are usually capable of regenerating their own limbs, were strewn along the entire West Coast of North America, in one of the largest mass wildlife mortality events ever recorded. Over 20 species of sea stars were perishing.

In some areas, sunflower star (Pycnopodia helianthoides) populations dropped by an average of around 90 percent in weeks, a loss that saw this once common and abundant species vanish from most of its range in just a few years.

The culprit causing this sea star wasting (SSW) even got to starfish in captivity, killing individual animals within days.

Leg of Pisaster ochraceus disintegrating from sea star wasting syndrome. (Elizabeth Cerny-Chipman/Oregon State University/CC BY-SA 2.0)

This led scientists to suspect some sort of pathogen, like a virus or bacterium, was infecting these stunning sea creatures. However, subsequent studies exonerated the lead viral suspect.

Meanwhile, more sea star deaths followed around the globe, including half a world away in Port Phillip Bay, Australia.

 

Now, San Francisco State University marine biologist Citlalli Aquino and colleagues have finally unravelled the mystery, showing something much more complicated was going on. 

By comparing the types of bacteria within healthy sea stars and those suffering from the wasting disease, the researchers found bacteria that thrive in low oxygen environments were abundant in the sick animals, as were copiotrophs – bacteria that like high-nutrient environments.

Experiments back in the lab confirmed that depleting water of oxygen caused tissue-melting lesions in 75 percent of sea stars. Adding excess nutrients or phytoplankton to the water also caused the sea star’s health to decline.

Re-analysing tissue samples from the 2013 event, the researchers detected excess nitrogen – a sign these animals suffocated to death. 

“Sea stars diffuse oxygen over their outer surface through little structures called papulae, or skin gills,” explained Cornell University marine microbiologist Ian Hewson. “If there is not enough oxygen surrounding the papulae, the starfish can’t breathe.”

These microorganisms aren’t directly causing disease, but stealing the sea stars’ oxygen supply when increased levels of organic matter are triggering the microbes to bloom. As a result, the sea stars literally drown in their own environment. Then their decaying bodies further increase nutrients for the microbes, creating a horrible feedback loop of sea star death.

 

Aquino and team noted most SSW events are reported in late fall or summer, when phytoplankton that increase levels of nutrients in the water via photosynthesis are more abundant.

Warmer temperatures are known drivers of phytoplankton blooms, and the sea star wasting event in Australia followed the longest and most intense heat wave on record. Sea star wasting events elsewhere have also followed increased sea temperatures.

“Warmer waters can’t have as much oxygen [compared with colder water] just by physics alone,” Hewson told Erin Garcia de Jesus at Science News.

None of this bodes well for our future on a warming planet.

University of Vermont biologist Melissa Pespeni, who was not involved in the study, told Science News this complicated tangle of biological and environmental factors is “a new kind of idea for [disease] transmission.”

Devastating repercussions from the loss of these precious stars of the sea have already echoed out across entire ecosystems. The sunflower star is a voracious predator with up to 24 arms that span as far as 1 metre (3.3 ft), feeling their way across the seafloor for sea urchins, snails, and other invertebrates to devour.

Without the sunflower and other sea stars keeping sea urchins in check, these herbivores are eating their way through giant kelp forests. By 2016, sea urchins had already reduced kelp populations by 80 percent in some areas, decimating these once thriving underwater forests.

“This is a very clear example of a trophic cascade, which is an ecological domino effect triggered by changes at the end of a food chain,” said Simon Fraser University marine ecologist Isabelle Côté, who investigated the environmental aftermath last year. 

“It’s a stark reminder that everything is connected to everything else.”

This research was published in Frontiers in Microbiology.

 

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Juno maps water ice across northern Ganymede

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Jupiter’s moon Ganymede is the largest planetary satellite in the solar system. It’s also one of the most intriguing: Ganymede is the only moon with its own magnetic field, it is the most differentiated of all moons, and it likely possesses a subsurface ocean of liquid water. It was studied by the early Jupiter flybys made by the Pioneer and Voyager spacecraft, but our understanding today rests largely on observations made by NASA’s Galileo orbiter from 1995 to 2003.

Mura et al. now report some of the first in situ observations of Ganymede since the end of the Galileo mission. They used the Jovian Infrared Auroral Mapper (JIRAM) on board NASA’s Juno spacecraft to take images and spectra of the moon’s north polar region. On 26 December 2019, Juno passed Ganymede at a distance of about 100,000 kilometers, enabling JIRAM to map this region at a spatial resolution of up to 23 kilometers per pixel.

As Juno flies past Ganymede, the spacecraft can observe physical locations on the moon’s surface from a variety of angles. By comparing the brightness of these regions across a range of observation and illumination geometries, the authors developed a photometric model for Ganymede’s surface reflectance. They observed that wavelength-dependent reflectance relationships sometimes break down in the vicinity of relatively fresh craters, perhaps because of a larger average size of ice grains in these regions.

Combining their model with spectral observations of the 2-micrometer water ice absorption band allowed the authors to map the distribution of water ice in the north polar region. Where these estimates overlapped with maps derived from Earth-based telescopic observations, the researchers found largely good agreement. This congruence enabled them to extend the global water ice map for Ganymede to much more northerly latitudes.

Observations in other spectral bands also revealed the presence of nonwater chemical species on the surface of Ganymede, including possible detections of hydrated magnesium salts, ammonia, carbon dioxide, and a range of organic molecules.

NASA Juno takes first images of jovian moon Ganymede’s north pole

More information:
A. Mura et al. Infrared Observations of Ganymede From the Jovian InfraRed Auroral Mapper on Juno, Journal of Geophysical Research: Planets (2020). DOI: 10.1029/2020JE006508

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Juno maps water ice across northern Ganymede (2021, January 21)
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