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Island arcs study reveals ancient connections between ocean chemistry and volcanic rocks

VOLCANOES

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22/10/2024

Island arcs study reveals ancient connections between ocean chemistry and volcanic rocks

Bringing a novel approach to a classic problem, researchers have revealed how changes in ocean chemistry over the past 2 billion years have left an imprint on volcanic rocks formed in island arcs. Island arcs, which arise from volcanic activity along subduction zones where one tectonic plate dives beneath another, play a crucial role in the formation of the continental crust.

The study sheds light on how these arcs have interacted with the ocean’s chemistry through deep-time connections that are only now being uncovered. The research was published in the Proceedings of the National Academy of Sciences on October 18.

The study, resulting from a collaboration between the laboratory of Professor of Geology Claire Bucholz and UC Berkeley, has shown that the strontium isotopic compositions of island arc magmas have varied in tandem with seawater strontium composition over geologic time.

Specifically, the study proposes a model for this covariation involving transfer of seawater strontium to island arcs through hydrothermal alteration of the ocean floor, which is ultimately subducted into the mantle source regions of island arc magmas and then incorporated into the resulting island arc basalts.

Bucholz studies how different reservoirs on Earth, from the surface to the mantle, interact and how these interactions have changed over time. Subduction zones are an excellent place to ask such questions because they represent an interface between major reservoirs: the ocean, the crust, and the mantle, and because subduction processes have been operating on Earth for billions of years.

The subducting plate is composed of oceanic crust, which is imprinted with the chemistry of seawater through hydrothermal alteration. When the subducting plate descends into the mantle, it heats up and releases water-rich fluids and melts that carry this seawater-derived chemical signature into the overlying mantle. In turn, this influx of fluids causes the mantle to melt, producing magmas that ultimately ascend and erupt on the surface of the Earth.

This process creates island arc volcanoes like those found in the Aleutians or elsewhere in the Pacific Ring of Fire. The magmatic rocks found in these island arcs carry the original fingerprint of seawater in their chemical makeup and thus, by studying them, researchers can learn about their connection to the ocean.

When it comes to the modern Earth, geochemists generally accept that there is a connection between seawater and island arc basalts. For example, a well-known characteristic of modern island arc basalts is their enrichment in radiogenic strontium relative to basalts formed at mid-ocean ridges, which are spreading apart rather than subducting.

The typical explanation for this enrichment is that the “extra” radiogenic strontium is supplied by the subducting oceanic crust, which incorporated radiogenic seawater strontium before it subducted.

The use of radiogenic isotopes (those produced through radioactive decay) to study arc magmas has a rich history that was pioneered by co-author Donald DePaolo, who received his Ph.D. at Caltech in 1978 and is now on the faculty at UC Berkeley.

During his time at Caltech, DePaolo developed the methodology to make the first neodymium isotope measurements on terrestrial rocks and explored their variations in island arc magmas in conjunction with that of strontium isotopes.

This work was foundational for the development of radiogenic isotopic studies of rocks and has been a cornerstone of geochemical studies since. The new study, led by current Caltech graduate student Amanda Bednarick, builds on this foundation and connects researchers who have worked at Caltech over four decades, including co-author Daniel Stolper (Ph.D. ’14).

The new work required meticulous combing of past literature data of strontium isotopes in island arc rocks. Although this data has existed for decades, no one had undertaken the task of compiling and analyzing it because the original strontium ratios in magmatic rocks are easily altered and often obscured. However, with careful assessment of existing datasets to select only the most reliable measurements, Bednarick was able to document a clear signal.

“The literature review and compilation that Amanda undertook was time and labor intensive,” says Bucholz. “However, it is only through these efforts that the highest-quality datasets emerge and we are able to say something consequential about the geologic past.”

“We understand the connections between seawater strontium and island arc volcanic rocks only in a general way, but the correlations found by carefully assessing the data are undeniable,” adds DePaolo.

Bednarick showed that the isotopic ratios of strontium in island basalts correlate well with those of seawater through the geologic past, which have varied due to changes in the amount of strontium put into the oceans from the continents (radiogenic) versus the mantle (unradiogenic). Most strikingly, a significant increase in strontium isotope ratios in island arcs coincides with a known shift in ocean chemistry during the late Neoproterozoic era, around 600 million years ago.

To understand this relationship, Bednarick and co-authors developed a model incorporating the known record of seawater chemistry and strontium input into island arc magmas. These models indicate that the strontium isotope ratios in island arc basalts can be explained solely by changes in seawater chemistry, which in turn reflects broader geologic and climatic shifts.

“This study highlights how changes at Earth’s surface, particularly in ocean chemistry, are recorded in the deep Earth through the volcanic rocks formed in subduction zones. It’s a great example of how interconnected Earth’s systems are, even over billions of years,” explains Bednarick.

Understanding the ancient geochemical processes that govern island arc formation is critical for reconstructing the history of Earth’s tectonics and oceans. The study suggests that the patterns observed today have deep roots and that the strontium isotope signatures of ancient island arcs can provide valuable clues about the planet’s long-term evolution.

Next, Bednarick aims to examine sequences of rock called ophiolites, which represent fragments of hydrothermally altered oceanic crust now preserved on continents, to further understand the chemistry of seawater from more than 1 billion years ago.

More information: Amanda L. Bednarick et al, Temporal covariation of island arc Sr isotopes and seawater chemistry over the past 2 billion years, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2401832121

Journal information: Proceedings of the National Academy of Sciences

Provided by California Institute of Technology

Rare fossils of extinct elephant document the earliest known instance of butchery in India

PALEONTOLOGY

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22/10/2024

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Rare fossils of extinct elephant document the earliest known instance of butchery in India

During the late middle Pleistocene, between 300 and 400 thousand years ago, at least three ancient elephant relatives died near a river in the Kashmir Valley of South Asia. Not long after, they were covered in sediment and preserved along with 87 stone tools made by the ancestors of modern humans.

The remains of these elephants were first discovered in 2000 near the town of Pampore, but the identity of the fossils, cause of death and evidence of human intervention remained unknown until now.

A team of researchers including Advait Jukar, a curator of vertebrate paleontology at the Florida Museum of Natural History, published two new papers on fossils from the Pampore site. In one, researchers describe their discovery of elephant bone flakes which suggests that early humans struck the bones to extract marrow, an energy-dense fatty tissue. The findings are the earliest evidence of animal butchery in India. The research is published in the journal Quaternary Science Reviews.

The fossils themselves are also rare. In a second study published in the Journal of Vertebrate Paleontology, the researchers described the bones, which belong to an extinct genus of elephants called Palaeoloxodon, whose members were more than twice the weight of today’s African elephants. Only one set of Palaeoloxodon bones for this species had been discovered previously, and the fossils from this study are by far the most complete.

To date, only one fossil hominin—the Narmada human—has ever been found on the Indian subcontinent. Its mix of features from older and more recent hominin species indicate the Indian subcontinent must have played an important role in early human dispersal. Prior to the fossil’s discovery in 1982, paleontologists only had stone tool artifacts to give a rough sketch of our ancestors’ presence on the subcontinent.

Smallest dinosaur egg ever found confirmed in China

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22/10/2024

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Smallest dinosaur egg ever found confirmed in China

A team of paleontologists, geoscientists and evolutionary specialists affiliated with multiple institutions in China has found that a fossilized egg unearthed in 2021 is the smallest dinosaur egg ever found. In their paper published in the journal Historical Biology, the group describes where the eggs were found, the techniques used to study them, and what the researchers learned about them.

Prior to this new find, the smallest dinosaur egg ever found was 45.5 mm by 40.4 mm by 34.4 mm. The smallest of the new eggs uncovered in this new effort has a length of just 29 mm—it was also the most complete of the group discovered.

The eggs were found at a construction site near the city of Ganzhou in 2021 in southeast China—the region is known to paleontologists as one of the best in the world for finding dinosaur eggs. Six eggs were fossilized together, forming a single unit. All were in relatively good condition.

After three years of careful analysis, which included use of an electron microscope, the research team found that the creatures inside the eggs were from a non-avian therapod. They also found evidence that they belonged to an unknown ootaxon, which the team has named Minioolithus ganzhouensis. The team has also dated the eggs to 80 million years ago, putting them in the Late Cretaceous.

The researchers used electron backscatter diffraction techniques to gain an overall image of both the egg shells and the creatures inside of them. They state that all their study techniques thus far have been nondestructive—the eggs are still in the same condition in which they were found.

The research team plans to continue studying the eggs, including a new analysis of the discovery site, which was well preserved—it has already provided new information regarding how dinosaurs built their nests. The researchers are hoping to figure out which sort of dinosaur laid them, and from there, to learn more about the formation process as dinosaurs grew inside their eggs. They also suspect they might be able to learn more about the dinosaur reproductive process in general.

More information: Rui Wu et al, The smallest known complete dinosaur fossil eggs from the Upper Cretaceous of South China, Historical Biology (2024). DOI: 10.1080/08912963.2024.2409873

Journal information: Historical Biology

Giant meteorite impact 3.26 billion years ago may have aided early life

ASTRONOMY

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22/10/2024

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Giant meteorite impact 3.26 billion years ago may have aided early life

Billions of years ago, long before anything resembling life as we know it existed, meteorites frequently pummeled the planet. One such space rock crashed down about 3.26 billion years ago, and even today, it’s revealing secrets about Earth’s past.

Nadja Drabon, an early-Earth geologist and assistant professor in the Department of Earth and Planetary Sciences, is insatiably curious about what our planet was like during ancient eons rife with meteoritic bombardment, when only single-celled bacteria and archaea reigned—and when it all started to change. When did the first oceans appear? What about continents? Plate tectonics? How did all those violent impacts affect the evolution of life?

A study in Proceedings of the National Academy of Sciences sheds light on some of these questions, in relation to the inauspiciously named “S2” meteoritic impact of over 3 billion years ago, and for which geological evidence is found in the Barberton Greenstone belt of South Africa today.

Through the painstaking work of collecting and examining rock samples centimeters apart and analyzing the sedimentology, geochemistry, and carbon isotope compositions they leave behind, Drabon’s team paints the most compelling picture to date of what happened the day a meteorite the size of four Mount Everests paid Earth a visit.

“Picture yourself standing off the coast of Cape Cod, in a shelf of shallow water. It’s a low-energy environment without strong currents. Then all of a sudden, you have a giant tsunami, sweeping by and ripping up the sea floor,” said Drabon.

The S2 meteorite, estimated to have been up to 200 times larger than the one that killed the dinosaurs, triggered a tsunami that mixed up the ocean and flushed debris from the land into coastal areas. Heat from the impact caused the topmost layer of the ocean to boil off, while also heating the atmosphere. A thick cloud of dust blanketed everything, shutting down any photosynthetic activity taking place.

What happened when a meteorite the size of four Mount Everests hit Earth? — Nadja Drabon, right, with students David Madrigal Trejo and Öykü Mete during fieldwork in South Africa. Credit: Nadja Drabon

But bacteria are hardy, and following impact, according to the team’s analysis, bacterial life bounced back quickly. With this came sharp spikes in populations of unicellular organisms that feed off the elements phosphorus and iron.

Iron was likely stirred up from the deep ocean into shallow waters by the aforementioned tsunami, and phosphorus was delivered to Earth by the meteorite itself and from an increase of weathering and erosion on land.

Drabon’s analysis shows that iron-metabolizing bacteria would thus have flourished in the immediate aftermath of the impact. This shift toward iron-favoring bacteria, however short-lived, is a key puzzle piece depicting early life on Earth. According to Drabon’s study, meteorite impact events—while reputed to kill everything in their wake (including, 66 million years ago, the dinosaurs)—carried a silver lining for life.

“We think of impact events as being disastrous for life,” Drabon said. “But what this study is highlighting is that these impacts would have had benefits to life, especially early on … these impacts might have actually allowed life to flourish.”

These results are drawn from the backbreaking work of geologists like Drabon and her students, hiking into mountain passes that contain the sedimentary evidence of early sprays of rock that embedded themselves into the ground and became preserved over time in the Earth’s crust. Chemical signatures hidden in thin layers of rock help Drabon and her students piece together evidence of tsunamis and other cataclysmic events.

The Barberton Greenstone Belt in South Africa, where Drabon concentrates most of her current work, contains evidence of at least eight impact events including the S2. She and her team plan to study the area further to probe even deeper into Earth and its meteorite-enabled history.

More information: Drabon, Nadja et al, Effect of a giant meteorite impact on Paleoarchean surface environments and life, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2408721121. doi.org/10.1073/pnas.2408721121

Journal information: Proceedings of the National Academy of Sciences

Provided by Harvard University

Each glacier has a unique organic matter composition, study reveals

OCEANOGRAPHY

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19/10/2024

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Each glacier has a unique organic matter composition, study reveals

Melting glaciers release more than just water. Organic matter once trapped in ice can run into streams and rivers, where it becomes food for microbes. These organisms respire the organic matter back to the atmosphere in the form of carbon dioxide, with potential implications for climate change.

Despite its importance in the carbon cycle, glacial organic matter is not well understood. Holt and colleagues addressed this gap by using ultrahigh-resolution mass spectrometry to characterize the organic matter in 136 glacial meltwater rivers across six continents. They focused specifically on dissolved organic matter less than 0.7 micrometers across.

The team’s analysis revealed a vast array of organic molecules with more than 35,000 distinct chemical formulas—each of which may be broken down to different extents and at different rates—with no two glaciers carrying exactly the same suite of molecules.

Human activity around glaciers often affected the kinds of organic matter they released, the researchers noted. Some places, including Alaska and Nepal, contained signatures of fossil fuel combustion because they receive material from industrial centers. Others, such as those in remote regions of Greenland and New Zealand, appeared to carry mostly organic matter made by microbes living within the glacier’s ecosystem.

Glacial melting is accelerating around the world, creating a growing source of greenhouse gases in the atmosphere. But this work demonstrates that the contributions from glaciers are not all the same. When assessing how glaciers will influence climate and ecosystem change, scientists must consider different glaciers independently, the authors suggest.

The paper is published in the journal Global Biogeochemical Cycles.

More information: Amy D. Holt et al, Gradients of Deposition and In Situ Production Drive Global Glacier Organic Matter Composition, Global Biogeochemical Cycles (2024). DOI: 10.1029/2024GB008212

Journal information: Global Biogeochemical Cycles

Provided by Eos

This story is republished courtesy of Eos, hosted by the American Geophysical Union. Read the original story here.

New research shows most space rocks crashing into Earth come from a single source

ASTRONOMY

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19/10/2024

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New research shows most space rocks crashing into Earth come from a single source

The sight of a fireball streaking across the sky brings wonder and excitement to children and adults alike. It’s a reminder that Earth is part of a much larger and incredibly dynamic system.

Each year, roughly 17,000 of these fireballs not only enter Earth’s atmosphere, but survive the perilous journey to the surface. This gives scientists a valuable chance to study these rocky visitors from outer space.

Scientists know that while some of these meteorites come from the Moon and Mars, the majority come from asteroids. But two separate studies published in Nature today have gone a step further. The research was led by Miroslav Brož from Charles University in the Czech Republic, and Michaël Marsset from the European Southern Observatory in Chile.

The papers trace the origin of most meteorites to just a handful of asteroid breakup events—and possibly even individual asteroids. In turn, they build our understanding of the events that shaped the history of the Earth—and the entire solar system.

What is a meteorite?

Only when a fireball reaches Earth’s surface is it called a meteorite. They are commonly designated as three types: stony meteorites, iron meteorites, and stony-iron meteorites.

Stony meteorites come in two types.

The most common are the chondrites, which have round objects inside that appear to have formed as melt droplets. These comprise 85% of all meteorites found on Earth.

Most are known as “ordinary chondrites”. They are then divided into three broad classes—H, L and LL—based on the iron content of the meteorites and the distribution of iron and magnesium in the major minerals olivine and pyroxene. These silicate minerals are the mineral building blocks of our solar system and are common on Earth, being present in basalt.

“Carbonaceous chondrites” are a distinct group. They contain high amounts of water in clay minerals, and organic materials such as amino acids. Chondrites have never been melted and are direct samples of the dust that originally formed the solar system.

The less common of the two types of stony meteorites are the so-called “achondrites”. These do not have the distinctive round particles of chondrites, because they experienced melting on planetary bodies.

The asteroid belt

Asteroids are the primary sources of meteorites.

Most asteroids reside in a dense belt between Mars and Jupiter. The asteroid belt itself consists of millions of asteroids swept around and marshaled by the gravitational force of Jupiter.

The interactions with Jupiter can perturb asteroid orbits and cause collisions. This results in debris, which can aggregate into rubble pile asteroids. These then take on lives of their own.

It is asteroids of this type which the recent Hayabusa and Osiris-REx missions visited and returned samples from. These missions established the connection between distinct asteroid types and the meteorites that fall to Earth.

S-class asteroids (akin to stony meteorites) are found on the inner regions of the belt, while C-class carbonaceous asteroids (akin to carbonaceous chondrites) are more commonly found in the outer regions of the belt.

But, as the two Nature studies show, we can relate a specific meteorite type to its specific source asteroid in the main belt.

One family of asteroids

The two new studies place the sources of ordinary chondrite types into specific asteroid families—and most likely specific asteroids. This work requires painstaking back-tracking of meteoroid trajectories, observations of individual asteroids, and detailed modeling of the orbital evolution of parent bodies.

The study led by Miroslav Brož reports that ordinary chondrites originate from collisions between asteroids larger than 30 kilometers in diameter that occurred less than 30 million years ago.

The Koronis and Massalia asteroid families provide appropriate body sizes and are in a position that leads to material falling to Earth, based on detailed computer modeling. Of these families, asteroids Koronis and Karin are likely the dominant sources of H chondrites. Massalia (L) and Flora (LL) families are by far the main sources of L- and LL-like meteorites.

The study led by Michaël Marsset further documents the origin of L chondrite meteorites from Massalia.

It compiled spectroscopic data—that is, characteristic light intensities which can be fingerprints of different molecules—of asteroids in the belt between Mars and Jupiter. This showed that the composition of L chondrite meteorites on Earth is very similar to that of the Massalia family of asteroids.

The scientists then used computer modeling to show an asteroid collision that occurred roughly 470 million years ago formed the Massalia family. Serendipitously, this collision also resulted in abundant fossil meteorites in Ordovician limestones in Sweden.

In determining the source asteroid body, these reports provide the foundations for missions to visit the asteroids responsible for the most common outerspace visitors to Earth. In understanding these source asteroids, we can view the events that shaped our planetary system.

Journal information: Nature

Provided by The Conversation

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Extremely well-preserved fossil sawfly sheds new light on co-evolution of insects and toxic plants

PALEONTOLOGY

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18/10/2024

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Extremely well-preserved fossil sawfly sheds new light on co-evolution of insects and toxic plants

A team of Australian researchers has described a new species of now-extinct sawfly from an extremely well-preserved fossil found in central NSW.

This fossilized sawfly, which is between 11 and 16 million years old from the Miocene Period, was the first of its kind discovered in Australia and only the second discovered in the world. It was found by a team of paleontologists in 2018 who were exploring McGraths Flat, a fossil site in central NSW that has since yielded many other detailed fossils.

This research was published in the journal Systematic Entomology.

Despite the name, sawflies are not flies, but a type of wasp, with spitfires the most widely recognized group of sawfly species in Australia. They are called sawflies because they have a saw-like ovipositor that is used to lay eggs, and they could be mistaken as flies because they lack a typical “wasp waist.”

With the approval of the Mudgee Local Aboriginal Land Council, Wiradjuri words were used to name the newly described species of sawfly Baladi warru. “Baladi” means “saw” and “warru” means “wasp.” This name honors the Traditional Owners of the lands on which the fossil was located.

Researchers from Australia’s national science agency, CSIRO, the University of Canberra, Australian Museum and Queensland Museum have analyzed the sawfly’s wing venation and other features preserved in the fossil and determined its taxonomic (scientific naming) placement within sawflies. This allowed them to describe it as a new species.

Fossil sawfly discovery 16 million years in the making — The fossil is believed to be between 11 and 16 million years old, from the Miocene Period. Credit: Michael Frese, University of Canberra

CSIRO research scientist, Dr. Juanita Rodriguez, helped describe the new sawfly species.

“We looked at the fossil and its morphology and then put this information together with molecular and morphological data from a wide sample of current sawfly species. This helped us decipher the fossil’s placement in the sawfly tree of life,” Dr. Rodriguez said.

“We used the fossil’s age and its placement to establish that sawflies originated in the Cretaceous Period, around 100 million years ago, which means their ancient ancestors lived in Gondwana. When this supercontinent split up, sawflies ended up distributed in Australia and South America.

“When we examined the fossil, we identified pollen grains on the sawfly’s head which revealed it had visited a flowering Quintinia plant. This helped our team trace complex species interactions in the palaeoenvironment of McGraths Flat.”

University of Canberra paleontologist and CSIRO visiting scientist, Dr. Michael Frese, who found the fossil sawfly, said this discovery would help researchers track the evolution and distribution of sawflies.

“In particular, this find has helped us in understanding the incredible ability of sawflies to feed on toxic plants,” Dr. Frese said.

“They eat the leaves of Myrtaceae—a family of woody plants that includes eucalypts—because they have mouthparts with which they can separate toxic oils or a chemical detoxification system inside their gut when feeding on myrtaceous leaves. This enables the larvae, sometimes called spitfires, to use the oils as a defensive weapon.

“In terms of the bigger picture, our work is helping researchers make sense of their current distribution across Australia and the Americas. Although this particular species, Baladi warru, has been extinct for millions of years, it provides information on native pollinators so we can understand their evolution and impact in the present.”

More information: Juanita Rodriguez et al, A new exceptionally preserved sawfly fossil (Hymenoptera: Pergidae) and an evaluation of its utility for divergence time estimation and biogeography, Systematic Entomology (2024). DOI: 10.1111/syen.12653

Provided by CSIRO

Could life exist below Mars ice? Study proposes possibilities

MARS

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17/10/2024

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Could life exist below Mars ice? Study proposes possibilities

While actual evidence for life on Mars has never been found, a new NASA study proposes microbes could find a potential home beneath frozen water on the planet’s surface.

Through computer modeling, the study’s authors have shown that the amount of sunlight that can shine through water ice would be enough for photosynthesis to occur in shallow pools of meltwater below the surface of that ice. Similar pools of water that form within ice on Earth have been found to teem with life, including algae, fungi, and microscopic cyanobacteria, all of which derive energy from photosynthesis.

“If we’re trying to find life anywhere in the universe today, Martian ice exposures are probably one of the most accessible places we should be looking,” said the paper’s lead author, Aditya Khuller of NASA’s Jet Propulsion Laboratory in Southern California.

Mars has two kinds of ice: frozen water and frozen carbon dioxide. For their paper, published in Communications Earth & Environment, Khuller and colleagues looked at water ice, large amounts of which formed from snow mixed with dust that fell on the surface during a series of Martian ice ages in the past million years. That ancient snow has since solidified into ice, still peppered with specks of dust.

Although dust particles may obscure light in deeper layers of the ice, they are key to explaining how subsurface pools of water could form within ice when exposed to the sun: Dark dust absorbs more sunlight than the surrounding ice, potentially causing the ice to warm up and melt up to a few feet below the surface.

Mars scientists are divided about whether ice can actually melt when exposed to the Martian surface. That’s due to the planet’s thin, dry atmosphere, where water ice is believed to sublimate—turn directly into gas—the way dry ice does on Earth. But the atmospheric effects that make melting difficult on the Martian surface wouldn’t apply below the surface of a dusty snowpack or glacier.

Thriving microcosms

On Earth, dust within ice can create what are called cryoconite holes—small cavities that form in ice when particles of windblown dust (called cryoconite) land there, absorb sunlight, and melt farther into the ice each summer. Eventually, as these dust particles travel farther from the sun’s rays, they stop sinking, but they still generate enough warmth to create a pocket of meltwater around them. The pockets can nourish a thriving ecosystem for simple lifeforms..

“This is a common phenomenon on Earth,” said co-author Phil Christensen of Arizona State University in Tempe, referring to ice melting from within. “Dense snow and ice can melt from the inside out, letting in sunlight that warms it like a greenhouse, rather than melting from the top down.”

Christensen has studied ice on Mars for decades. He leads operations for a heat-sensitive camera called THEMIS (Thermal Emission Imaging System) aboard NASA’s 2001 Mars Odyssey orbiter. In past research, Christensen and Gary Clow of the University of Colorado Boulder used modeling to demonstrate how liquid water could form within dusty snowpack on the Red Planet. That work, in turn, provided a foundation for the new paper focused on whether photosynthesis could be possible on Mars.

In 2021, Christensen and Khuller co-authored a paper on the discovery of dusty water ice exposed within gullies on Mars, proposing that many Martian gullies form by erosion caused by the ice melting to form liquid water.

This new paper suggests that dusty ice lets in enough light for photosynthesis to occur as deep as 9 feet (3 meters) below the surface. In this scenario, the upper layers of ice prevent the shallow subsurface pools of water from evaporating while also providing protection from harmful radiation. That’s important, because unlike Earth, Mars lacks a protective magnetic field to shield it from both the sun and radioactive cosmic ray particles zipping around space.

The white edges along these gullies in Mars’ Terra Sirenum are believed to be dusty water ice. Scientists think meltwater could form beneath the surface of this kind of ice, providing a place for possible photosynthesis. This is an enhanced-color image; the blue color would not actually be perceptible to the human eye. Credit: NASA/JPL-Caltech/University of Arizona
Radiatively habitable zones within ice in the southern hemisphere of Mars. Credit: Communications Earth & Environment (2024). DOI: 10.1038/s43247-024-01730-y
The white edges along these gullies in Mars’ Terra Sirenum are believed to be dusty water ice. Scientists think meltwater could form beneath the surface of this kind of ice, providing a place for possible photosynthesis. This is an enhanced-color image; the blue color would not actually be perceptible to the human eye. Credit: NASA/JPL-Caltech/University of Arizona
Radiatively habitable zones within ice in the southern hemisphere of Mars. Credit: Communications Earth & Environment (2024). DOI: 10.1038/s43247-024-01730-y

The study authors say the water ice that would be most likely to form subsurface pools would exist in Mars’ tropics, between 30 degrees and 60 degrees latitude, in both the northern and southern hemispheres.

Khuller next hopes to re-create some of Mars’ dusty ice in a lab to study it up close. Meanwhile, he and other scientists are beginning to map out the most likely spots on Mars to look for shallow meltwater—locations that could be scientific targets for possible human and robotic missions in the future.

More information: Aditya Khuller, Potential for photosynthesis on Mars within snow and ice, Communications Earth & Environment (2024). DOI: 10.1038/s43247-024-01730-y. www.nature.com/articles/s43247-024-01730-y

Journal information: Nature Communications Earth & Environment , Communications Earth & Environment

Provided by NASA

La Nina could soon arrive. Here’s what that means for winter weather

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17/10/2024

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La Nina could soon arrive. Here’s what that means for winter weather

The National Oceanic and Atmospheric Administration’s Climate Prediction Center says there is a 60% chance that a weak La Niña event will develop this autumn and could last until March.

La Niña is part of a natural climate cycle that can cause extreme weather across the planet—and its effects vary from place to place.

Although there is no guarantee how this La Niña will play out, there are some general trends. Experts say northern parts of South America could see more rain than usual. Southern regions of the U.S. and parts of Mexico could be drier than average. The northern tier of the U.S. and southern Canada could be wetter than average.

La Niña is the cool phase of the El Niño-Southern Oscillation, a naturally occurring global climate pattern that involves changes in wind and ocean temperatures in the Pacific and can cause extreme weather across the planet.

El Niño is the warm phase and happens when trade winds that typically blow across the Pacific toward Asia weaken, allowing warm ocean waters to pile up along the western edge of South America. But during La Niña, the trade winds intensify and cold water from the depths of the sea rises up, resulting in cooler than average ocean temperatures in the eastern Pacific.

These cold ocean temperatures and changes in the atmosphere affect the position of the jet stream—a narrow band of fast moving air flowing from west to east around the planet—by bumping it northward. The jet stream sits over the ocean and can tap into its moisture, influence the path storms take and boost precipitation.

Just recently Earth experienced a “triple-dip” La Niña event from 2020 to 2023. “We had three back to back winters where we had La Niña conditions, which was unusual because the only other case of that happening was back in 1973 to 1976,” said Michelle L’Heurex, a climate scientist at NOAA. L’Heurex said that La Niña’s tend to last longer and be more recurrent than El Niño events.

“It’s unusual although it’s not unprecedented,” said Ben Cook, climate scientist at the NASA Goddard Institute for Space Studies affiliated with Columbia University, about the forecast for a possible La Niña this year.

Cook noted that the frequency of La Niña events can be stressful for regions that have been dealing with drought lately, such as East Africa. “If we’re moving into another La Niña event, it means kind of a continuation of those really bad conditions.”

La Niña weather impacts

The influence La Niña has on the weather varies based on location and the season, said L’Heurex. Parts of South America, such as eastern Argentina, can be drier than average while Colombia, Venezuela and northern parts of Brazil can be wetter than normal.

“It depends exactly where you are. Part of that is because there’s a monsoon cycle, wet and dry season, that goes through Central America and South America, so La Niña is basically modifying the intensity and placement of those monsoon cycles,” explained L’Heurex.

In the U.S., the Northeast and Ohio Valley typically see wetter than normal conditions with an active storm track due to the position of the jet stream, said Samantha Borisoff, climate scientist at NOAA’s Northeast Regional Climate Center based at Cornell University.

The waviness of the jet stream can also cause more frequent cold outbreaks, particularly in the central and southern U.S. Borisoff said snowfall is difficult to predict and highly dependent on the storm and path it takes, but noted that New England, New York and the Great Lakes region tend to be snowier during La Niña winters, but that is never a guarantee. The southern and southeastern regions of the U.S. are farther away from the active storm track and tend to be drier and warmer than normal.

La Niña, El Niño and climate change

Scientists say the link between climate change and La Niña and El Niño is not entirely clear.

Paul Roundy, climate scientist at the University of Albany, said climate models tend to indicate more frequent El Ninos and less frequent La Ninas, but not all models agree. Computer models also struggle to separate normal variation in the El Niño and La Niña phases from climate change’s warming influence on the oceans and atmosphere.

“I would not infer from that that climate change isn’t actually causing more El Niño emergence,” Roundy said. “It’s just that nature itself has such strong swings on its own. So we can get multiple La Niña events, and maybe in 40 or 50 years we’ll be seeing the opposite.”

Giant prehistoric elephant skull from India belongs to mysterious extinct species

PALEONTOLOGY

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16/10/2024

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Giant prehistoric elephant skull from India belongs to mysterious extinct species

The giant fossil skull of an extinct elephant, discovered in northern India’s Kashmir Valley in 2000, sheds light on a poorly known episode in elephant evolutionary history.

The elephant skull was buried with 87 stone tools used by prehistoric humans, and all the materials were excavated under the leadership of Dr. Ghulam Bhat at the University of Jammu.

Recently, an international team of scientists from the Florida Museum of Natural History, the British Museum, the University of York, and the Natural History Museum (London), along with the University of Helsinki’s Dr. Steven Zhang, studied the Kashmir skull to uncover the age and evolutionary context of this megaherbivore. The paper is published in the Journal of Vertebrate Paleontology.

“From the general shape of the skull, it’s quite apparent that the elephant belonged to Palaeoloxodon, or straight-tusked elephants, among the largest land mammals that ever lived. Full-grown adults easily stood around 4m tall at the shoulder and weighed 9–10 tonnes,” says Zhang, a paleontologist from the University’s Department of Geosciences and Geography.

“Yet what’s puzzled experts for some time is that the Kashmir skull lacks a thickened, forward-projecting crest at the skull roof which typifies other Palaeoloxodon skulls found in India.”

Over recent decades, whether the developmental extent of this crest could tell apart different species of Palaeoloxodon and the relative position of these species on the evolutionary tree of elephants has remained controversial. However, recent research concluded that the skull crest in these extinct elephants became more prominent with developmental and sexual maturity. This means that, once specimens can be aged by examining their teeth, it would be possible to compare skulls from individuals with similar levels of maturity.

“From the size, the wisdom teeth and a few other telltale features of the skull, it is evident that the animal was a majestic bull elephant in the prime of its life, but the lack of a well-developed skull crest, particularly in comparison with other mature male skulls from Europe and from India, tells us we have a different species on our hands here,” Zhang explained.

Instead, the research team noticed how the Kashmir skull’s features conform best with another obscure skull from Turkmenistan studied in the 1950s, which was proposed to represent a distinct species, Palaeoloxodon turkmenicus.

“What’s always been puzzling about the Turkmen skull is that, besides the lack of a prominent crest at the skull roof, its other features are highly similar to the already well-known European species, P. antiquus. And this led a number of experts to suggest that the Turkmen specimen is simply an aberrant individual of the European species,” says Zhang.

“But with the Kashmir skull added to the mix, it becomes clear now that the two specimens can be theorized to represent a distinct species that we previously knew very little about, with a broad distribution from Central Asia to the northern Indian Subcontinent,” added Dr. Advait Jukar, the study’s lead author, currently based at the Florida Museum of Natural History.

By measuring protein decomposition in the tooth enamel of the Kashmir Palaeoloxodon skull, and examining stone tools buried alongside the elephant remains, the team concluded that the Kashmir skull dates to the Middle Pleistocene period 300,000–400,000 years ago, very similar to the estimated age of the Turkmen skull. This supports the belief that the two skulls represent a species distinct from other Eurasian Palaeoloxodon.

Palaeoloxodon first evolved in Africa around 1 million years ago; this early African form had a narrow, convex forehead and underdevelopment of the skull crest. Later Palaeoloxodon, best-known from fossils discovered in Europe and India, have very wide, flattened forehead often associated with a thick crest that juts forward from the roof of the skull.

The team thus concluded that with a wide, flat forehead with only the faintest trace of a skull crest, P. turkmenicus may represent a poorly-known missing link that fills a gap in our understanding of how these prodigious prehistoric megaherbivores evolved.

More information: Advait M. Jukar et al, A remarkable Palaeoloxodon (Mammalia, Proboscidea) skull from the intermontane Kashmir Valley, India, Journal of Vertebrate Paleontology (2024). DOI: 10.1080/02724634.2024.2396821

Journal information: Journal of Vertebrate Paleontology

Provided by University of Helsinki