̽��ֱ�� of Cambridge - geology

Ancient seafloor vents spewed tiny, life-giving minerals into Earth’s early oceans

cmm201 — Fri, 02 Feb 2024 16:38:44 +0000

Their study, published in Science Advances, examined 3.5-billion-year-old rocks from western Australia in previously unseen detail and identified large quantities of a mineral called greenalite, which is thought to have played a role in early biological processes. ̽��ֱ��researchers also found that the seafloor vents would have seeded the oceans with apatite, a mineral rich in the life-essential element phosphorus.

̽��ֱ��earliest lifeforms we know of—single-celled microorganisms, or microbes—emerged around 3.7 billion years ago. Most of the rocks that contain traces of them and the environment they lived in have, however, been destroyed. Some of the only evidence we have of this pivotal time comes from an outcrop of sediments in the remote Australian outback.

̽��ֱ��so-called Dresser Formation has been studied for years but, in the new study, researchers re-examined the rocks in closer detail, using high magnification electron microscopes to reveal tiny minerals that were essentially hidden in plain sight.

̽��ֱ��greenalite particles they observed measured just a few hundred nanometres in size—so small that they would have been washed over thousands of kilometres, potentially finding their way into a range of environments where they may have kick-started otherwise unfavourable chemical reactions, such as those involved in building the first DNA and RNA molecules.

“We’ve found that hydrothermal vents supplied trillions upon trillions of tiny, highly-reactive greenalite particles, as well as large quantities of phosphorus,” said Professor Birger Rasmussen, lead author of the study from the ̽��ֱ�� of Western Australia.

Rasmussen said scientists are still unsure as to the exact role of greenalite in building primitive cells, “but this mineral was in the right place at the right time, and also had the right size and crystal structure to promote the assembly of early cells.”

̽��ֱ��rocks the researchers studied contain characteristic layers of rusty-red, iron-rich jasper which formed as mineral-laden seawater spewed from hydrothermal vents. Scientists had thought the jaspers got their distinctive red colour from particles of iron oxide which, just like rust, form when iron is exposed to oxygen.

But how did this iron oxide form when Earth’s early oceans lacked oxygen? One theory is that photosynthesising cyanobacteria in the oceans produced the oxygen, and that it wasn’t until later, around 2.4 billion years ago, that this oxygen started to skyrocket in the atmosphere.

̽��ֱ��new results change that assumption, however, “the story is completely different once you look closely enough,” said study co-author Professor Nick Tosca from Cambridge’s Department of Earth Sciences.

̽��ֱ��researchers found that tiny, drab, particles of greenalite far outnumbered the iron oxide particles which give the jaspers their colour. ̽��ֱ��iron oxide was not an original feature, discounting the theory that they were formed by the activity of cyanobacteria.

“Our findings show that iron wasn’t oxidised in the oceans; instead, it combined with silica to form tiny crystals of greenalite,” said Tosca. “That means major oxygen producers, cyanobacteria, may have evolved later, potentially coinciding with the soar in atmospheric oxygen during the Great Oxygenation Event.”

Birger said that more experiments are needed to identify how greenalite might facilitate prebiotic chemistry, “but it was present in such vast quantities that, under the right conditions its surfaces could have synthesized an enormous number of RNA-type sequences, addressing a key question in origin of life research – where did all the RNA come from?”

Reference:
Rasmussen, B, Muhling, J, Tosca, N J. 'Nanoparticulate apatite and greenalite in oldest, well-preserved hydrothermal vent precipitates.' Science Advances (2024). DOI: 10.1126/sciadv.adj4789

Researchers from the universities of Cambridge and Western Australia have uncovered the importance of hydrothermal vents, similar to underwater geysers, in supplying minerals that may have been a key ingredient in the emergence of early life.

MARUM − Zentrum für Marine Umweltwissenschaften, Universität Bremen

̽��ֱ��hydrothermal vent 'Candelabra' in the Logatchev hydrothermal field on the Mid-Atlantic Ridge at a water depth of 3300 metres.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Scottish rocks to play a key role in Mars space mission

sc604 — Fri, 28 Jul 2023 15:48:18 +0000

A group of scientists, including from the ̽��ֱ�� of Cambridge, have this week been collecting samples of rock from the NatureScot National Nature Reserve (NNR) as part of the NASA and European Space Agency (ESA)’s Mars Sample Return Program.

̽��ֱ��programme is gathering samples of rocks from around the world that bear a similarity to those on Mars, ahead of rock samples from the Red Planet being brought back to Earth in 2033.

Rum has been selected as the only UK site for sampling, and is a high priority in the programme, as some of its igneous rocks have a very similar mineral and chemical content to those that have been collected by NASA’s Perseverance Rover during its exploration of an ancient lakebed on Mars.

Intensive study of the rocks from Rum and around the globe will crucially help scientists understand what methods of testing and analysis will work best in readiness for when the Martian rocks return to Earth.

As the first samples from another world, the Mars rocks are thought to present the best opportunity to reveal clues about the early evolution of the planet, including the potential for past life.

̽��ֱ��Rum sampling is being led by Dr Lydia Hallis, a geologist and planetary scientist from the ̽��ֱ�� of Glasgow, and member of the programme’s Science Group. ̽��ֱ��team also includes scientists from the ̽��ֱ�� of Cambridge, the ̽��ֱ�� of Leicester and Brock ̽��ֱ�� in Canada.

“These Rum rocks are an excellent comparison to one particular Martian rock sample, which the NASA Perseverance Rover collected from the igneous Séítah Formation within Jezero crater,” said Hallis. “Not only is the mineralogy and chemistry similar, but the two rocks appear to have a similar amount of weathering.

“This seems strange when we think how wet and warm Rum is compared to present-day Mars, but billions of years ago when the Séítah formation crystallised on Mars the difference in environment would not have been so pronounced. At this time Mars was much wetter and warmer, with a thicker atmosphere that may even have produced rain (though not as much as we get in Scotland!). Over time the Martian atmosphere thinned, leaving the surface much dryer and colder, essentially halting any further weathering within Séítah and preserving the rocks at Jezero Crater for us to investigate today.

“ ̽��ֱ��rocks on Rum are much younger, but their exposure to the Scottish elements has produced roughly the same amount of weathering as was produced in the Séítah Formation during Mars’ early wet and warm climate. Because of all these similarities, analysis of the Rum rocks should give us a good head start and help the samples from the Red Planet achieve their full potential when they are returned to Earth.”

“It’s amazing to think that somewhere right here in the UK might be able to tell us something about the geology of a different planet,” said team member Professor Helen Williams from Cambridge’s Department of Earth Sciences. “We’ve still got several years left to wait before we can study the real Mars rocks, but in the meantime, our Scottish samples will provide scientists with the perfect material to test and refine the analytical techniques they will be using to investigate material returned from the Red Planet.”

Lesley Watt, NatureScot’s Rum NNR reserve manager, said: “With its extinct volcanoes and dramatic mountains, Rum has always been one of the best places to discover Scotland's world-class geology, but we didn’t quite realise that the rocks here were of interplanetary significance as well.

“It has been fascinating to learn more about the NASA/ESA mission, and really exciting for the island to play a small part in this truly historic endeavour to find out more about Mars. We hope it will add yet another element of interest for visitors to this special place.”

Adapted from a NatureScot press release.

Ancient rocks from the Isle of Rum in northwest Scotland are playing an important role in an international space mission to discover more about Mars.

It’s amazing to think that somewhere right here in the UK might be able to tell us something about the geology of a different planet

Helen Williams

NASA/JPL-Caltech

Illustration of NASA's Perseverance rover operating on the surface of Mars.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Seawater could have provided phosphorous required for emerging life

cmm201 — Tue, 27 Sep 2022 13:40:56 +0000

Their results, published in the journal Nature Communications, show that seawater might be the missing source of phosphate, meaning that it could have been available on a large enough scale for life without requiring special environmental conditions.

“This could really change how we think about the environments in which life first originated,” said co-author Professor Nick Tosca from Cambridge's Department of Earth Sciences.

̽��ֱ��study, which was led by Matthew Brady, a PhD student from Cambridge's Department of Earth Sciences, shows that early seawater could have held one thousand to ten thousand times more phosphate than previously estimated — as long as the water contained a lot of iron.

Phosphate is an essential ingredient in creating life’s building blocks — forming a key component of DNA and RNA — but it is one of the least abundant elements in the cosmos in relation to its biological importance. When in its mineral form, phosphate is also relatively inaccessible — it can be hard to dissolve in water so that life can use it.

Scientists have long suspected that phosphorus became part of biology early on, but they have only recently begun to recognize the role of phosphate in directing the synthesis of molecules required by life on Earth. “Experiments show it makes amazing things happen – chemists can synthesize crucial biomolecules if there is a lot of phosphate in solution,” said Tosca.

But the exact environment needed to produce phosphate has been a topic of discussion. Some studies have suggested that when iron is abundant then phosphate should actually be even less accessible to life. This is, however, controversial because early Earth would have had an oxygen-poor atmosphere where iron would have been widespread.

To understand how life came to depend on phosphate, and the sort of environment that this element would have formed in, they carried out geochemical modelling to recreate early conditions on Earth.

“It’s exciting to see how simple experiments in a bottle can overturn our thinking about the conditions that were present on the early Earth,” said Brady.

In the lab, they made up seawater with the same chemistry thought to have existed in Earth’s early history. They also ran their experiments in an atmosphere starved of oxygen, just like on ancient Earth.

̽��ֱ��team’s results suggest that seawater itself could have been a major source of this essential element.

“This doesn’t necessarily mean that life on Earth started in seawater,” said Tosca, “It opens up a lot of possibilities for how seawater could have supplied phosphate to different environments— for instance, lakes, lagoons, or shorelines where sea spray could have carried the phosphate onto land.”

Previously scientists had come up with a range of ways of generating phosphate, some theories involving special environments such as acidic volcanic springs or alkaline lakes, and rare minerals found only in meteorites.

“We had a hunch that iron was key to phosphate solubility, but there just wasn’t enough data,” said Tosca. ̽��ֱ��idea for the team’s experiments came when they looked at waters that bathe sediments deposited in the modern Baltic Sea. “It is unusual because it's high in both phosphate and iron — we started to wonder what was so different about those particular waters.”

In their experiments, the researchers added different amounts of iron to a range of synthetic seawater samples and tested how much phosphorous it could hold before crystals formed and minerals separated from the liquid. They then built these data points into a model that could predict how much phosphate ancient seawater could hold.

̽��ֱ��Baltic Sea pore waters provided one set of modern samples they used to test their model. “We could reproduce that unusual water chemistry perfectly,” said Tosca. From there they went on to explore the chemistry of seawater before any biology was around.

̽��ֱ��results also have implications for scientists trying to understand the possibilities for life beyond Earth. “If iron helps put more phosphate in solution, then this could have relevance to early Mars,” said Tosca.

Evidence for water on ancient Mars is abundant, including old river beds and flood deposits, and we also know that there was a lot of iron at the surface and the atmosphere was at times oxygen-poor, said Tosca.

Their simulations of surface waters filtering through rocks on the Martian surface suggest that iron-rich water might have supplied phosphates in this environment too.

“It’s going to be fascinating to see how the community uses our results to explore new, alternative pathways for the evolution of life on our planet and beyond,” said Brady.

Reference:
Matthew P Brady et al. 'Marine phosphate availability and the chemical origins of life on Earth.' Nature Communications (2022). DOI: 10.1038/s41467-022-32815-x

̽��ֱ��problem of how phosphorus became a universal ingredient for life on Earth may have been solved by researchers from the ̽��ֱ�� of Cambridge and the ̽��ֱ�� of Cape Town, who have recreated primordial seawater containing the element in the lab.

This could really change how we think about the environments in which life first originated

Nick Tosca

NASA

Artist Concept of an Early Earth

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Lava from 2021 Icelandic eruption gives rare view of deep churnings beneath volcano

cmm201 — Fri, 16 Sep 2022 14:30:00 +0000

̽��ֱ��study, published in the journal Nature and led by the ̽��ֱ�� of Iceland, reports that the eruption was unusual because it was supplied by a particularly deep reservoir of magma originating around 15 kilometres beneath the surface, at the base of Earth’s crust.

Their results also show that volcanoes like this can be fed by complex plumbing systems, where different batches of magma can mix and travel to the surface in just a matter of days or weeks.

̽��ֱ��researchers took measurements of lava and volcanic gases during the first 50 days of the eruption — giving them a near-real time report on the changing magma supply.

“I never expected to see the chemical composition of erupting lava change this quickly, showing us just how fast things can change in the depths beneath volcanoes,” said Simon Matthews from the ̽��ֱ�� of Iceland.

̽��ֱ��chemical fingerprint of lavas and the crystals inside them — together with the volcanic gases erupted — helped the researchers decode where the magma originated from and its journey to the surface. Until now, there has been a lack of information about the deepest parts of magmatic systems.

̽��ֱ��results showed that, during the initial phases of the eruption, the lava was predominately coming from around the boundary between the crust and underlying mantle – the thick, rocky layer that makes up most of Earth’s interior. But over the following weeks, the composition of the lava changed, indicating the eruption was directly tapping magma from greater depths.

“Ever since Enlightenment thinkers started writing about volcanoes, scientists have drawn cross-sections to visualise how they might work below ground,” said co-author Professor Clive Oppenheimer from Cambridge’s Department of Geography. “This study draws together different strands of information from monitoring the chemistry of lava and gas emissions to describe what is happening up to 20 kilometres down.”

They used indicators including the magnesium contents of the lava and carbon dioxide levels in the volcanic gases as barometers to gauge how hot and deep the magma feeding the eruption was. They suggest that, for the magma to come from 15 kilometres below the surface, the eruption was fed by something like a high-speed train direct to the mantle.

“We’ve known for a while that magma coming from the mantle is variable,” said co-author Professor John Maclennan from Cambridge’s Department of Earth Sciences, “But we’ve had to work hard to find clues as to how this complex mixing happens.”

̽��ֱ��authors point out that it has long been argued that different kinds of magma can mix deep in magmatic systems before an eruption. ̽��ֱ��new research shows that new magma can flow into a deep reservoir and mix with existing magma rapidly, in as little as 20 days.

Normally scientists use lavas erupted from old or extinct volcanoes to get a below ground view of volcanoes. But these samples are often too old to unravel processes happening over the course of a few days, “I’ve looked at hundreds of samples from dead volcanoes, but never had the chance to observe such a spectacular example of magma mixing in real-time,” said Maclennan.

Magma mixing has been shown to be an important process in triggering volcanic eruptions, so the study findings could have implications for understanding what drove the eruption and for future monitoring of volcanic activity in Iceland and at similar volcanoes.

Reference:
Sæmundur A. Halldórsson et al. ‘Rapid shifting of a deep magmatic source at Fagradalsfjall volcano, Iceland.’ Nature (2022). DOI: 10.1038/s41586-022-04981-x.

After centuries without volcanic activity, Iceland’s Reykjanes peninsula sprang to life in 2021 when lava erupted from the Fagradalsfjall volcano. New research involving the ̽��ֱ�� of Cambridge helps us see what is going on deep beneath the volcano by reading the chemistry of lavas and volcanic gases almost as they were erupted.

I’ve looked at hundreds of samples from dead volcanoes, but never had the chance to observe such a spectacular example of magma mixing in real-time

John Maclennan

Fagradalsfjall volcano

Yes

Scientists 'see' puzzling features deep in Earth’s interior

cmm201 — Thu, 19 May 2022 09:00:00 +0000

̽��ֱ��enigmatic area of rock, which is located almost directly beneath the Hawaiian Islands, is one of several ultra-low velocity zones – so-called because earthquake waves slow to a crawl as they pass through them.

̽��ֱ��research, published in Nature Communications, is the first to reveal the complex internal variability of one of these pockets in detail, shedding light on the landscape of Earth’s deep interior and the processes operating within it.

“Of all Earth’s deep interior features, these are the most fascinating and complex. We’ve now got the first solid evidence to show their internal structure - it’s a real milestone in deep earth seismology,” said lead author Zhi Li, PhD student at Cambridge’s Department of Earth Sciences.

Earth’s interior is layered like an onion: at the centre sits the iron-nickel core, surrounded by a thick layer known as the mantle, and on top of that a thin outer shell — the crust we live on. Although the mantle is solid rock, it is hot enough to flow extremely slowly. These internal convection currents feed heat to the surface, driving the movement of tectonic plates and fuelling volcanic eruptions.

Scientists use seismic waves from earthquakes to 'see' beneath Earth’s surface — the echoes and shadows of these waves reveal radar-like images of deep interior topography. But, until recently, 'images' of the structures at the core-mantle boundary, an area of key interest for studying our planet’s internal heat flow, have been grainy and difficult to interpret.

̽��ֱ��researchers used the latest numerical modelling methods to reveal kilometre-scale structures at the core-mantle boundary. According to co-author Dr Kuangdai Leng, who developed the methods while at the ̽��ֱ�� of Oxford, “We are really pushing the limits of modern high-performance computing for elastodynamic simulations, taking advantage of wave symmetries unnoticed or unused before.” Leng, who is currently based at the Science and Technology Facilities Council, says that this means they can improve the resolution of the images by an order of magnitude compared to previous work.

̽��ֱ��researchers observed a 40% reduction in the speed of seismic waves travelling at the base of the ultra-low velocity zone beneath Hawaii. This supports existing proposals that the zone contains much more iron than the surrounding rocks – meaning it is denser and more sluggish. “It’s possible that this iron-rich material is a remnant of ancient rocks from Earth’s early history or even that iron might be leaking from the core by an unknown means,” said project lead Dr Sanne Cottaar from Cambridge Earth Sciences.

̽��ֱ��research could also help scientists understand what sits beneath and gives rise to volcanic chains like the Hawaiian Islands. Scientists have started to notice a correlation between the location of the descriptively-named hotspot volcanoes, which include Hawaii and Iceland, and the ultra-low velocity zones at the base of the mantle. ̽��ֱ��origin of hotspot volcanoes has been debated, but the most popular theory suggests that plume-like structures bring hot mantle material all the way from the core-mantle boundary to the surface.

With images of the ultra-low velocity zone beneath Hawaii now in hand, the team can also gather rare physical evidence from what is likely the root of the plume feeding Hawaii. Their observation of dense, iron-rich rock beneath Hawaii would support surface observations. “Basalts erupting from Hawaii have anomalous isotope signatures which could either point to either an early-Earth origin or core leaking, it means some of this dense material piled up at the base must be dragged to the surface,” said Cottaar.

More of the core-mantle boundary now needs to be imaged to understand if all surface hotspots have a pocket of dense material at the base. Where and how the core-mantle boundary can be targeted does depend on where earthquakes occur, and where seismometers are installed to record the waves.

̽��ֱ��team’s observations add to a growing body of evidence that Earth’s deep interior is just as variable as its surface. “These low-velocity zones are one of the most intricate features we see at extreme depths – if we expand our search, we are likely to see ever-increasing levels of complexity, both structural and chemical, at the core-mantle boundary,” said Li.

They now plan to apply their techniques to enhance the resolution of imaging of other pockets at the core-mantle boundary, as well as mapping new zones. Eventually they hope to map the geological landscape across the core-mantle boundary and understand its relationship with the dynamics and evolutionary history of our planet.

Reference:
Zhi Li, Kuangdai Leng, Jennifer Jenkins, Sanne Cottaar. 'Kilometer-scale structure on the core–mantle boundary near Hawaii.' Nature Communications (2022), DOI: 10.1038/s41467-022-30502-5

New research led by the ̽��ֱ�� of Cambridge is the first to obtain a detailed 'image' of an unusual pocket of rock at the boundary layer with Earth’s core, some three thousand kilometres beneath the surface.

Of all Earth’s deep interior features, these are the most fascinating and complex

Zhi Li

gnuckx

Etna volcano eruption, 12 January 2011

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‘Slushy’ magma ocean led to formation of the Moon’s crust

sc604 — Thu, 13 Jan 2022 14:00:00 +0000

̽��ֱ��scientists, from the ̽��ֱ�� of Cambridge and the Ecole normale supérieure de Lyon, have proposed a new model of crystallisation, where crystals remained suspended in liquid magma over hundreds of millions of years as the lunar ‘slush’ froze and solidified. ̽��ֱ��results are reported in the journal Geophysical Research Letters.

Over fifty years ago, Apollo 11 astronauts collected samples from the lunar Highlands. These large, pale regions of the Moon – visible to the naked eye – are made up of relatively light rocks called anorthosites. Anorthosites formed early in the history of the Moon, between 4.3 and 4.5 billion years ago.

Similar anorthosites, formed through the crystallisation of magma, can be found in fossilised magma chambers on Earth. Producing the large volumes of anorthosite found on the Moon, however, would have required a huge global magma ocean.

Scientists believe that the Moon formed when two protoplanets, or embryonic worlds, collided. ̽��ֱ��larger of these two protoplanets became the Earth, and the smaller became the Moon. One of the outcomes of this collision was that the Moon was very hot – so hot that its entire mantle was molten magma, or a magma ocean.

“Since the Apollo era, it has been thought that the lunar crust was formed by light anorthite crystals floating at the surface of the liquid magma ocean, with heavier crystals solidifying at the ocean floor,” said co-author Chloé Michaut from Ecole normale supérieure de Lyon. “This ‘flotation’ model explains how the lunar Highlands may have formed.”

However, since the Apollo missions, many lunar meteorites have been analysed and the surface of the Moon has been extensively studied. Lunar anorthosites appear more heterogeneous in their composition than the original Apollo samples, which contradicts a flotation scenario where the liquid ocean is the common source of all anorthosites.

̽��ֱ��range of anorthosite ages – over 200 million years – is difficult to reconcile with an ocean of essentially liquid magma whose characteristic solidification time is close to 100 million years.

“Given the range of ages and compositions of the anorthosites on the Moon, and what we know about how crystals settle in solidifying magma, the lunar crust must have formed through some other mechanism,” said co-author Professor Jerome Neufeld from Cambridge’s Department of Applied Mathematics and Theoretical Physics.

Michaut and Neufeld developed a mathematical model to identify this mechanism.

In the low lunar gravity, the settling of crystal is difficult, particularly when strongly stirred by the convecting magma ocean. If the crystals remain suspended as a crystal slurry, then when the crystal content of the slurry exceeds a critical threshold, the slurry becomes thick and sticky, and the deformation slow.

This increase of crystal content occurs most dramatically near the surface, where the slushy magma ocean is cooled, resulting in a hot, well-mixed slushy interior and a slow-moving, crystal-rich lunar ‘lid’.

“We believe it’s in this stagnant ‘lid’ that the lunar crust formed, as lightweight, anorthite-enriched melt percolated up from the convecting crystalline slurry below,” said Neufeld. “We suggest that cooling of the early magma ocean drove such vigorous convection that crystals remained suspended as a slurry, much like the crystals in a slushy machine.”

Enriched lunar surface rocks likely formed in magma chambers within the lid, which explains their diversity. ̽��ֱ��results suggest that the timescale of lunar crust formation is several hundreds of million years, which corresponds to the observed ages of the lunar anorthosites.

Serial magmatism was initially proposed as a possible mechanism for the formation of lunar anorthosites, but the slushy model ultimately reconciles this idea with that of a global lunar magma ocean.

̽��ֱ��research was supported by the European Research Council.

Jerome Neufeld is also affiliated with the Department of Earth Sciences. He is a Fellow of Trinity College.

Reference:
Chloé Michaut and Jerome A Neufeld. ‘Formation of the lunar primary crust from a long-lived slushy magma ocean.’ Geophysical Research Letters (2022). DOI: 10.1029/2021GL095408

Adapted from an ENS-Lyon press release.

Scientists have shown how the freezing of a ‘slushy’ ocean of magma may be responsible for the composition of the Moon’s crust.

Cooling of the early magma ocean drove such vigorous convection that crystals remained suspended as a slurry, like the crystals in a slushy machine.

Jerome Neufeld

NASA/Goddard Space Flight Center

Magma ocean and first rocky crust on the Moon

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Earth's interior is swallowing up more carbon than thought

cmm201 — Mon, 26 Jul 2021 09:59:43 +0000

They found that the carbon drawn into Earth’s interior at subduction zones - where tectonic plates collide and dive into Earth’s interior - tends to stay locked away at depth, rather than resurfacing in the form of volcanic emissions.

Their findings, published in Nature Communications, suggest that only about a third of the carbon recycled beneath volcanic chains returns to the surface via recycling, in contrast to previous theories that what goes down mostly comes back up.

One of the solutions to tackle climate change is to find ways to reduce the amount of CO₂ in Earth’s atmosphere. By studying how carbon behaves in the deep Earth, which houses the majority of our planet’s carbon, scientists can better understand the entire lifecycle of carbon on Earth, and how it flows between the atmosphere, oceans and life at the surface.

̽��ֱ��best-understood parts of the carbon cycle are at or near Earth’s surface, but deep carbon stores play a key role in maintaining the habitability of our planet by regulating atmospheric CO₂ levels. “We currently have a relatively good understanding of the surface reservoirs of carbon and the fluxes between them, but know much less about Earth’s interior carbon stores, which cycle carbon over millions of years,” said lead author Stefan Farsang, who conducted the research while a PhD student at Cambridge's Department of Earth Sciences.

There are a number of ways for carbon to be released back to the atmosphere (as CO₂) but there is only one path in which it can return to the Earth’s interior: via plate subduction. Here, surface carbon, for instance in the form of seashells and micro-organisms which have locked atmospheric CO₂ into their shells, is channelled into Earth’s interior. Scientists had thought that much of this carbon was then returned to the atmosphere as CO₂ via emissions from volcanoes. But the new study reveals that chemical reactions taking place in rocks swallowed up at subduction zones trap carbon and send it deeper into Earth’s interior - stopping some of it coming back to Earth’s surface.

̽��ֱ��team conducted a series of experiments at the European Synchrotron Radiation Facility, “ ̽��ֱ��ESRF has world-leading facilities and the expertise that we needed to get our results,” said co-author Simon Redfern, Dean of the College of Science at NTU Singapore, “ ̽��ֱ��facility can measure very low concentrations of these metals at the high pressure and temperature conditions of interest to us.” To replicate the high pressures and temperatures of subductions zones, they used a heated ‘diamond anvil’, in which extreme pressures are achieved by pressing two tiny diamond anvils against the sample.

̽��ֱ��work supports growing evidence that carbonate rocks, which have the same chemical makeup as chalk, become less calcium-rich and more magnesium-rich when channelled deeper into the mantle. This chemical transformation makes carbonate less soluble – meaning it doesn’t get drawn into the fluids that supply volcanoes. Instead, the majority of the carbonate sinks deeper into the mantle where it may eventually become diamond.

“There is still a lot of research to be done in this field,” said Farsang. “In the future, we aim to refine our estimates by studying carbonate solubility in a wider temperature, pressure range and in several fluid compositions.”

̽��ֱ��findings are also important for understanding the role of carbonate formation in our climate system more generally. “Our results show that these minerals are very stable and can certainly lock up CO₂ from the atmosphere into solid mineral forms that could result in negative emissions,” said Redfern. ̽��ֱ��team have been looking into the use of similar methods for carbon capture, which moves atmospheric CO₂ into storage in rocks and the oceans.

“These results will also help us understand better ways to lock carbon into the solid Earth, out of the atmosphere. If we can accelerate this process faster than nature handles it, it could prove a route to help solve the climate crisis,” said Redfern.

Reference:
Farsang, S, Louvel, M, Zhao, C et al. Deep carbon cycle constrained by carbonate solubility. Nature Communications (2021). DOI: 10.1038/s41467-021-24533-7

Adapted from a news release by the ESRF

Scientists from Cambridge ̽��ֱ�� and NTU Singapore have found that slow-motion collisions of tectonic plates drag more carbon into Earth’s interior than previously thought.

We currently have a relatively good understanding of the surface reservoirs of carbon and the fluxes between them, but know much less about Earth’s interior carbon stores, which cycle carbon over millions of years

Stefan Farsang

NASA Goddard Space Flight Center

Alaska’s Pavlof Volcano: NASA’s View from Space

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Early humans were sheltered from worst effects of volcanic supereruption

sc604 — Mon, 05 Jul 2021 19:00:00 +0000

̽��ֱ��eruption of the Toba volcano was the largest volcanic eruption in the past two million years, but its impacts on climate and human evolution have been unclear. Resolving this debate is important for understanding environmental changes during a key interval in human evolution.

“We were able to use a large number of climate model simulations to resolve what seemed like a paradox,” said lead author Benjamin Black from Rutgers ̽��ֱ��. “We know this eruption happened and that past climate modeling has suggested the climate consequences could have been severe, but archaeological and palaeoclimate records from Africa don’t show such a dramatic response.

“Our results suggest that we might not have been looking in the right place to see the climate response. Africa and India are relatively sheltered, whereas North America, Europe and Asia bear the brunt of the cooling. One intriguing aspect of this is that Neanderthals and Denisovans were living in Europe and Asia at this time, so our paper suggests evaluating the effects of the Toba eruption on those populations could merit future investigation.”

̽��ֱ��researchers analysed 42 global climate model simulations in which they varied magnitude of sulphur emissions, time of year of the eruption, background climate state and sulfur injection altitude to make a probabilistic assessment of the range of climate disruptions the Toba eruption may have caused.

̽��ֱ��results suggest there was likely significant regional variation in climate impacts. ̽��ֱ��simulations predict cooling in the Northern Hemisphere of at least 4°C, with regional cooling as high as 10°C depending on the model parameters.

In contrast, even under the most severe eruption conditions, cooling in the Southern Hemisphere -- including regions populated by early humans – was unlikely to exceed 4°C, although regions in southern Africa and India may have seen decreases in precipitation at the highest sulphur emission level.

̽��ֱ��results explain independent archaeological evidence suggesting the Toba eruption had modest effects on the development of hominid species in Africa. According to the authors, their ensemble simulation approach could be used to better understand other past and future explosive eruptions.

“Our work is not only a forensic analysis of Toba’s aftermath some 74,000 years ago, but also a means of understanding the unevenness of the effects such very large eruptions may have on today’s society,” said co-author Dr Anja Schmidt from the ̽��ֱ�� of Cambridge. “Ultimately, this will help to mitigate the environmental and societal hazards from future volcanic eruptions.”

̽��ֱ��study included researchers from the US National Center for Atmospheric Research, the ̽��ֱ�� of Leeds and ̽��ֱ�� of Cambridge in the UK, and was supported by the National Center for Atmospheric Research and the National Science Foundation.

Reference:
Benjamin A Black et al. ‘Global climate disruption and regional climate shelters after the Toba supereruption.’ PNAS (2021). DOI: 10.1073/pnas.2013046118 |

Adapted from a Rutgers ̽��ֱ�� press release.

A massive volcanic eruption in Indonesia about 74,000 years ago likely caused severe climate disruption in many areas of the globe, but early human populations were sheltered from the worst effects, suggests a new study published in the journal PNAS.

Ultimately, this will help to mitigate the environmental and societal hazards from future volcanic eruptions

Anja Schmidt

Clive Oppenheimer

Site of the Toba supereruption, in present-day Indonesia

Yes