On Monday, December 19, a mysterious shockwave in a gust of solar wind crashed into the Earth’s magnetic field, opening up a crack in the magnetosphere. According to Space Weather – an organization keeping track of such events – the barrage of plasma that penetrated the magnetosphere has led to a geomagnetic storm.
Although the shockwave’s origins are not exactly known, scientists believe it could have come from a coronal mass ejection (CME) launched by the sunspot AR3165, an area on the Sun’s surface which already released at least eight solar flares on December 14, causing a brief radio blackout over the Atlantic Ocean.
Sunspots are areas on the Sun’s surface where strong magnetic fields, created through the flow of electrical charges, entangle before suddenly snapping and releasing bursts of radiation called solar flares, or plumes of solar material called coronal mass ejections. Once launched, these CMEs can travel at extremely high speeds (often millions of miles per hour), sweeping up charged particles from the solar wind which, if pointed toward the Earth, can trigger geomagnetic storms.
These storms occur when solar debris consisting of electrons, protons, and alpha particles gets absorbed by the Earth’s magnetic field. If they are strong enough, they can create cracks in the magnetosphere which remain open for several hours, enabling some solar material to stream through and disrupt power systems, satellites, and radio communications.
Fortunately, the current storm was rather weak, causing only minor fluctuations in the power grids and impairing some satellite functions, such as those for mobile devices and GPS systems. However, scientists anticipate that in the following years, more powerful geomagnetic storms could warp our planet’s magnetic field to such an extent that satellites may tumble to Earth, electrical systems could be severely disrupted, and the Internet might stop working completely, thus causing trillions of dollars’ worth of damage, while triggering widespread blackouts and endangering thousands of lives.
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By Andrei Ionescu, Earth.com Staff Writer
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An explosion of extremely rare pink auroras recently lit up the night sky above Norway after a solar storm slammed into Earth and ripped a hole in the planet’s magnetic field. The breach enabled highly energetic solar particles to penetrate deeper into the atmosphere than normal, triggering the unusual colored lights.
The stunning light show was spotted Nov. 3 by a tour group led by Markus Varik, a northern lights tour guide from the Greenlander tour company (opens in new tab) based near Tromsø in Norway. The vibrant auroras emerged at around 6 p.m. local time and lasted for around 2 minutes, Varik told Live Science in an email.
“These were the strongest pink auroras I have seen in more than a decade of leading tours,” Varik said. “It was a humbling experience.”
The pink auroras emerged shortly after a small crack appeared in the magnetosphere — an invisible magnetic field surrounding Earth that is generated by the planet’s fluid metal core. Scientists detected the breach after a minor G-1 class solar storm slammed into Earth on Nov. 3, according to Spaceweather.com (opens in new tab).
Related: Do extraterrestrial auroras occur on other planets?
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Pink auroras are extremely rare compared to the more common green lights. (Image credit: Markus Varik/Greenlander)
Pink and green auroras shone in the sky together. (Image credit: Markus Varik/Greenlander)
The crack in Earth’s magnetosphere also enabled strong green auroras throughout the night. (Image credit: Markus Varik/Greenlander)
Auroras are formed when streams of highly energetic charged particles, known as solar wind, pass around the magnetosphere. The planet’s magnetic field protects us from cosmic radiation, but the shield is naturally weaker at the North and South Poles, which enables the solar wind to skim through the atmosphere — usually between 62 and 186 miles (100 and 300 kilometers) above Earth’s surface. As solar particles pass through the atmosphere, they superheat gases, which then vibrantly glow in the night sky, according to NASA (opens in new tab).
Auroras most commonly appear green, because oxygen atoms, which are abundant in the part of the atmosphere that solar wind normally reaches, emit that hue when they are excited. However, during the recent solar storm, the crack in Earth’s magnetosphere enabled the solar wind to penetrate below 62 miles, where nitrogen is the most abundant gas, according to Spaceweather.com. As a result, the auroras gave off a neon pink glow as the supercharged particles smashed mostly into nitrogen atoms.
The crack in Earth’s magnetosphere also helped to generate strong green auroras throughout the night, Varik said.
The magnetosphere hole closed around 6 hours after it first opened. During this time, a strange ribbon of blue light also emerged in the skies above Sweden, where it hung motionless in the sky for around 30 minutes, according to Spaceweather.com (opens in new tab).
However, experts are unsure if this unusual phenomenon was some never-before-seen type of aurora caused by the compromised magnetosphere, or if it was the result of something else. One expert suggested that the ribbon could have been made up of frozen fuel from a Russian rocket, but no rockets were spotted in the area, according to Spaceweather.com.
There are water molecules and ice up on the Moon, so how did they get there? Asteroid and comet collisions are likely to have produced some of it, but a new study suggests another source of lunar water: the Earth’s atmosphere.
Hydrogen and oxygen ions escaping from our planet’s upper atmosphere and then combining on the Moon could have created as much as 3,500 cubic kilometers (840 cubic miles) of surface permafrost or subsurface liquid water, scientists say.
The thinking is that hydrogen and oxygen ions are driven into the lunar surface as the Moon passes through the tail of the Earth’s magnetosphere (the teardrop-shaped bubble around Earth affected by its magnetic field). That occurs five days in every lunar month.
Because of the Sun’s solar wind pushing against this bubble, some of Earth’s magnetic field lines are broken: only tethered to the planet at one end.
When the Moon interferes with the tail of Earth’s magnetosphere, some of these broken connections get fixed, which leads to hydrogen and oxygen ions that had previously escaped Earth’s atmosphere suddenly rushing back towards it.
“It is like the Moon is in the shower – a shower of water ions coming back to Earth, falling on the Moon’s surface,” says geophysicist Gunther Kletetschka from the University of Alaska Fairbanks.
There’s no Moon magnetosphere, so as the ions smack into the lunar surface, permafrost is created, the researchers suggest. Some of that frost, through a variety of geological processes, could be driven below the surface and turned into liquid water.
The suggestion by the researchers is that there’s been a slow accumulation of these ions over the billions of years since the Late Heavy Bombardment, that period of time when the early Earth and Moon were peppered with heavy impacts from other celestial bodies hurtling through space.
Gravitational data from NASA’s Lunar Reconnaissance Orbiter was used to look closely at the Moon’s polar regions and several major craters. The team spotted anomalies that could indicate rock fractures capable of trapping permafrost.
“Crater impacts, forming structural extensions and fractures, allow suitable pore space networks for hosting large subsurface liquid water reservoirs,” write the researchers in their published paper.
“Back of envelope calculations suggested several thousands of cubic kilometers of water phase may have accumulated this way into the subsurface of the Moon over the past 3.5 billions of years.”
The distribution of surface ice at the Moon’s south pole, left, and north pole, right. (NASA)
While it’s likely that the water on the Moon comes from several sources – including hydrogen and oxygen reactions triggered by solar winds, scientists think – a lot of it may well have arrived through this method.
The predicted accumulation would be enough to fill Lake Huron in North America. The cover provided by craters and rock fractures would then give the necessary cover to prevent the water from evaporating back out into space.
NASA is keen to set up a long-term human presence on the Moon, and for that to happen there needs to be a suitable lunar station with a nearby water source. This latest research could help experts to decide where to put that station.
“As NASA’s Artemis team plans to build a base camp on the Moon’s south pole, the water ions that originated many eons ago on Earth can be used in the astronauts’ life support system,” says Kletetschka.
The research has been published in Scientific Reports.
Mars is a parched planet ruled by global dust storms. It’s also a frigid world, where night-time winter temperatures fall to minus 140 C (minus 220 F) at the poles.
But it wasn’t always a dry, barren, freezing, inhospitable wasteland. It used to be a warm, wet, almost inviting place, where liquid water flowed across the surface, filling up lakes, carving channels, and leaving sediment deltas.
But then it lost its magnetic field, and without the protection it provided, the Sun stripped away the planet’s atmosphere. Without its atmosphere, the water went next.
Now Mars is the Mars we’ve always known: A place that only robotic rovers find hospitable.
How exactly did it lose its magnetic shield? Scientists have puzzled over that for a long time.
A magnetic shield is critical to preserving Earth’s atmosphere and habitability. Without it, Earth would resemble Mars. But Earth kept its protection, and Mars didn’t. So Earth is “rippling with life,” as Carl Sagan said, while Mars is likely wholly devoid of life.
Mars has a weak remnant of a magnetic field emanating from its crust, but it’s a feeble phenomenon that provides little protection.
The loss of its magnetosphere was catastrophic for Mars. How did it happen?
A new study published in Nature Communications tries to answer that question, like many studies before. The title is “Stratification in planetary cores by liquid immiscibility in Fe-S-H.” The leading authors are Kei Hirose from the University of Tokyo’s Department of Earth and Planetary Science and Ph.D. student Shunpei Yokoo in the Hirose lab.
Earth’s core creates a magneto effect that generates our planet’s magnetic fields. There’s a solid inner core and an outer liquid core.
Heat flows from the inner core to the outer core, generating convective currents in the outer liquid core. The convective currents flow in patterns generated by the planet’s rotation, the inner core, and the Coriolis effect. This creates the planet’s magnetosphere.
The magnetosphere swaddles Earth like a protective blanket. The Sun’s solar wind strikes the magnetosphere, and the magnetosphere forces it to flow around the planet instead of reaching the atmosphere or the surface.
The magnetosphere isn’t a sphere: The solar wind moves the magnetosphere into an asymmetrical shape. The magnetosphere prevents the solar wind from stripping away Earth’s atmosphere. Without it, Earth would be dry, dead, and barren, just like Mars.
So what happened to Mars?
“Earth’s magnetic field is driven by inconceivably huge convection currents of molten metals in its core. Magnetic fields on other planets are thought to work the same way,” Hirose said in a press release.
“Though the internal composition of Mars is not yet known, evidence from meteorites suggests it is molten iron enriched with sulfur. Furthermore, seismic readings from NASA’s InSIGHT probe on the surface tell us Mars’ core is larger and less dense than previously thought. These things imply the presence of additional lighter elements such as hydrogen.”
NASA’s InSIGHT lander struggled to meet all of its scientific objectives. But it has gathered some critical evidence regarding Mars’ interior structure. If InSIGHT’s results are correct, and if the implied hydrogen is there, there’s a basis for experiments that could reveal more about Mars’ lost magnetic shield.
(NASA/Goddard/MAVEN/CU Boulder/SVS/Cindy Starr)
Above: A visualization of the electric currents around Mars. Electric currents (blue and red arrows) envelop Mars in a nested, double-loop structure that wraps continuously around the planet from its dayside to its night side. These current loops distort the solar wind magnetic field (not pictured), which drapes around Mars to create an induced magnetosphere around the planet.
“With this detail, we prepare iron alloys that we expect to constitute the core and subject them to experiments,” Hirose said.
Previous experiments investigated the behavior of planetary cores at differing pressures and temperatures. But they didn’t focus on hydrogen.
“Recent planet formation theories demonstrate that a large amount of water was delivered to both Mars and the Earth during their accretions, suggesting that hydrogen is possibly a major light element in the core,” the authors explain in their paper. “Despite its importance, so far the Fe-S-H system has been little investigated at high pressures.”
But if data from InSIGHT is correct, the hydrogen in the Fe-S-H core might play a role in the collapse of Mars’ magnetic field.
The researchers prepared a material sample matching what they think Mars’ core was once composed of. It contained iron, sulfur, and hydrogen – Fe-S-H. They placed the sample in a device called a diamond anvil, or diamond anvil cell (DAC).
The diamond anvil cell used in the experiments. (Yokoo et al.)
A diamond anvil compresses samples between two small diamond plates. Diamonds can withstand extreme pressures inside the anvil because they’re forged in extreme pressure deep inside the Earth.
The DAC can subject microscopic samples to pressures of hundreds of gigapascals. A laser heated the sample so that the conditions simulated Mars’ core. As the team subjected the sample to higher temperatures and pressures, they observed it with X-ray and electron beams to track changes in the material. Not only did the Fe-S-H sample melt, but it also changed its composition.
The experiment’s results center on the idea of miscibility. When materials are added together and create a homogenous mixture, they’re miscible. When materials are added together and don’t make a homogenous mixture, they’re immiscible. Fe-S-H’s immiscibility at high temperatures and pressures played a significant role in Martian planetary history.
“We were very surprised to see a particular behavior that could explain a lot,” Hirose said in a press release. “The initially homogeneous Fe-S-H separated out into two distinct liquids with a level of complexity that has not been seen before under these kinds of pressures,” said Hirose. “One of the iron liquids was rich in sulfur, the other rich in hydrogen, and this is key to explaining the birth and eventual death of the magnetic field around Mars.”
Hirose and his team think that initially, two immiscible liquids became separated in Mars’ core.
“While separated denser liquids stayed at the deepest part, lighter liquids migrated upward and mixed with the bulk liquid core, which could drive Martian core convection,” they write.
But in the region where the two liquids separated, something else happened. “At the same time, gravitationally stable, compositional stratification should have developed in a region where liquid separation took place. Eventually, Mars’ entire core became stratified, which ceased convection.”
(Yokoo et al., Nat. Commun., 2022)
Above: This figure from the paper shows how Mars’ core and Earth’s core started similarly, then changed over time. Light- and dark-blue represent buoyant and dense liquids, respectively.
Scientists already knew when convection ceased and Mars lost its magnetic shield. That happened about 4 billion years ago. This study explains why convection ended, leading to the loss of the magnetic shield.
It also explains how it began. “The separation of immiscible S-rich and H-rich liquids could have been responsible for both the onset and termination of Martian core convection and dynamo action,” they write in their paper.
Once the two liquids separated, Mars was doomed. There was no more convection, no more magnetism, no more atmosphere, and no more water. The exact timeframe is unknown, but the result was a dead planet.
However, this is just one study, and we don’t have the complete picture. “With our results in mind, the further seismic study of Mars will hopefully verify the core is indeed in distinct layers as we predict,” said Hirose. “If that is the case, it would help us complete the story of how the rocky planets, including Earth, formed and explain their composition.”
We know Earth won’t remain habitable forever. In about 5 billion years, the Sun will enter its red giant phase and destroy the Earth. But our protective magnetic shield won’t last forever, either, and we’re doomed without it. What will happen first? Doom by loss of magnetosphere? Or doom by a red giant?
“And you might be thinking that the Earth could one day lose its magnetic field as well,” Hirose said, “but don’t worry, that won’t happen for at least a billion years.”
So we have a billion years. Let’s not waste it.
This article was originally published by Universe Today. Read the original article.
It’s been half a century since the Apollo missions returned from the Moon, and yet the lunar samples they brought home continue to baffle us.
Some of these rocks are more than 3 billion years old and appear to have been formed in the presence of a strong geomagnetic field, like the one on Earth. But the Moon today doesn’t have a magnetosphere; it’s too small and dense, frozen right through to the core.
Unlike Earth, the Moon’s insides aren’t constantly churning with electrically conductive material, which produces a geomagnetic field in the first place. So, why do lunar rocks tell us otherwise?
It’s possible the Moon didn’t freeze over as quickly as we thought; a few billion years ago, its core might have still been slightly molten.
But even if the field was sustained for a surprisingly long time, the strength of this field – given the Moon’s size – is unlikely to match what the surface rocks are telling us.
Some scientists suggest the Moon used to wobble more, which kept the liquid in its belly sloshing away for slightly longer. Constant meteorites could have also given the Moon a boost in energy.
Researchers have previously entertained a new angle to the question, suggesting patches of the lunar surface were exposed to short bursts of intense magnetic activity.
In this latest study, a duo from Stanford and Brown University in the US has proposed a model describing just how these short-lived but powerful fields might form.
“[I]nstead of thinking about how to power a strong magnetic field continuously over billions of years, maybe there’s a way to get a high-intensity field intermittently,” explains planetary scientist Alexander Evans.
“Our model shows how that can happen, and it’s consistent with what we know about the Moon’s interior.”
In the first billion years or so of the Moon’s existence, its core was not much hotter than the mantle above. This meant the heat from the Moon’s interior didn’t have anywhere to dissipate, which is what usually causes molten material to move. The lighter, hotter bits tend to rise until they cool, while the denser, colder bits sink until they heat, and so on, and so forth.
Something else must have been stirring the pot, generating a magnetic field.
In its youth, an ocean of molten rock likely covered the Moon, and as the object cooled, this rock would have solidified at slightly different rates.
The densest minerals, such as olivine and pyroxene, would have sunk to the bottom and cooled first, while lighter elements like titanium would have floated to the top and cooled last.
Titanium-rich rock, however, would have weighed more than the solids below, causing chunks near the Moon’s crust to drop through the mantle, right into the core.
Researchers think this sinking effect continued until at least 3.5 billion years ago, with at least a hundred blobs of titanium-rich material hitting ‘rock bottom’ in a billion years.
Each time one of these massive slabs, about 60 kilometers (37 miles) in radius,connected with the core, the mismatch in temperature would have temporarily reignited a surprising convection current, one strong enough to generate a strong pulse of magnetism.
“You can think of it a little bit like a drop of water hitting a hot skillet,” says Evans.
“You have something really cold that touches the core, and suddenly a lot of heat can flux out. That causes churning in the core to increase, which gives you these intermittently strong magnetic fields.”
The new models could help explain why different lunar rocks show different magnetic signatures. The Moon’s magnetosphere may not have been a constant or consistent phenomenon.
The authors are now testing their explanation by looking back at lunar rocks to see if they can detect a weak magnetic background that is only occasionally pierced by a stronger force. The presence of a weaker magnetic hum would suggest a stronger magnetosphere was the exception and not the rule.
Terraforming Mars is one of the great dreams of humanity. Mars has a lot going for it. Its day is about the same length as Earth’s, it has plenty of frozen water just under its surface, and it likely could be given a reasonably breathable atmosphere in time. But one of the things it lacks is a strong magnetic field. So if we want to make Mars a second Earth, we’ll have to give it an artificial one.
The reason magnetic fields are so important is that they can shield a planet from solar wind and ionizing particles. Earth’s magnetic field prevents most high-energy charged particles from reaching the surface. Instead, they are deflected from Earth, keeping us safe. The magnetic field also helps prevent solar winds from stripping Earth’s atmosphere over time. Early Mars had a thick, water-rich atmosphere, but it was gradually depleted without the protection of a strong magnetic field.
Unfortunately, we can’t just recreate Earth’s magnetic field on Mars. Our field is generated by a dynamo effect in Earth’s core, where the convection of iron alloys generates Earth’s geomagnetic field. The interior of Mars is smaller and cooler, and we can’t simply “start it up” to create a magnetic dynamo. But there are a few ways we can create an artificial magnetic field, as a recent study shows.
Ideas for generating a Martian magnetic field have been proposed before, and usually involve either ground-based or orbital solenoids that create some basic level of magnetic protection. In the TV series *The Expanse*, you can see a couple of scenes where you catch a glimpse of them. While this latest study acknowledges that might work, it proposes an even better solution.
A torus of charged particles could give Mars a magnetic field. Credit: Ruth Bamford
As the study points out, if you want a good planetary magnetic field, what you really need is a strong flow of charged particles, either within the planet or around the planet. Since the former isn’t a great option for Mars, the team looks at the latter. It turns out you can create a ring of charged particles around Mars, thanks to its moon Phobos.
Phobos is the larger of the two Martian moons, and it orbits the planet quite closely. So closely that it makes a trip around Mars every 8 hours. So the team proposes using Phobos by ionizing particles from its surface, then accelerating them so they create a plasma torus along the orbit of Phobos. This would create a magnetic field strong enough to protect a terraformed Mars.
It’s a bold plan, and while it seems achievable the engineering hurdles would be significant. But as the authors point out, this is the time for ideas. Start thinking about the problems we need to solve, and how we can solve them, so when humanity does reach Mars, we will be ready to put the best ideas to the test.
Reference: Bamford, R. A., et al. “How to create an artificial magnetosphere for Mars.” Acta Astronautica 190 (2022): 323-333.
Buffeted by a constant stream of charged particles from the solar wind, Earth is not without its protection. Our planet is wrapped in a bubble of magnetism called the magnetosphere, spun out from deep inside the planet’s interior.
As the solar wind blows, scientists assumed that the edges of this bubble would ripple in a series of energy waves in the plasma, generated by the interaction between the solar wind and magnetosphere, along the direction that the wind is blowing. But now they’ve discovered a surprise: some of the waves generated stand still.
Space physicist Martin Archer of Imperial College London has been exploring the boundary of Earth’s magnetosphere for several years.
“Understanding the boundaries of any system is a key problem,” he says. “That’s how stuff gets in: energy, momentum, matter.”
Recently, Archer and his colleagues discovered that the boundary of the magnetosphere, called the magnetopause, behaves like the membrane of a drum: Strike it with a pulse from the solar wind, and waves, called magnetosonic waves, propagate along the magnetopause towards the poles, and are reflected back towards the source.
Now, using data from NASA’s Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission, a team of researchers led by Archer have discovered that, not only do these magnetosonic waves bounce back, they can do so traveling against the direction of the solar wind.
So what happens when these waves encounter the opposing wind? According to modelling conducted by the researchers, the two forces can reach an impasse, with the push of the solar wind cancelling out the push of the wave. A lot of energy is being applied, but nothing is going anywhere.
“It’s similar to what happens if you try walking up a downwards escalator,” Archer says. “It’s going to look like you’re not moving at all, even though you’re putting in loads of effort.”
Because these standing waves hang around longer in Earth’s magnetosphere, they could have a more significant effect on particle acceleration, which in turn affects Earth. We know that plasma waves have an accelerating effect on electrons, which can “surf” the plasma waves like a wakesurfer uses water waves to accelerate.
Particles that accelerate along the magnetic field towards the poles are responsible for the gorgeous aurora that light up our skies (as well as communications problems in the ionosphere).
Earth’s radiation belts, confined by the magnetosphere, could also be affected. More research will be required to understand what effects these standing waves have on particle acceleration.
Meanwhile, the researchers also translated the standing waves into sound. Archer and his colleagues have done this before, translating the sound of the magnetopause’s drum-like responses to the solar wind.
It’s not just a fascinating thing to experience; translating space data into a different medium can help scientists reveal information that might have otherwise passed us by.
“While in a simulation we can see what’s going on everywhere, satellites can only measure these waves where they are giving us only time-series, wiggly lines. This sort of data is actually best suited to our sense of hearing than sight, so listening to the data can often give us a more intuitive idea of what’s going on,” Archer explains.
“You can hear the deep breathing sound of the standing surface waves persist throughout, rising in volume as each pulse hits. Higher pitched sounds, associated with other types of waves, don’t last nearly as long.”
The research has been published in Nature Communications.
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.
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.
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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.
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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.
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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.
