Extinct ape gets a facelift, 12 million years later

New study reconstructs the face of Pierolapithecus catalaunicus, a key fossil in the story of great ape and human evolution

Peer-Reviewed Publication

AMERICAN MUSEUM OF NATURAL HISTORY

 

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FROM LEFT, THE PIEROLAPITHECUS CRANIUM SHORTLY AFTER DISCOVERY, AFTER INITIAL PREPARATION, AND AFTER VIRTUAL RECONSTRUCTION.

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CREDIT: © DAVID ALBA (LEFT), SALVADOR MOYÀ-SOLÀ (MIDDLE), KELSEY PUGH (RIGHT)

A new study led by scientists at the American Museum of Natural History, Brooklyn College, and the Catalan Institute of Paleontology Miquel Crusafont has reconstructed the well-preserved but damaged skull of a great ape species that lived about 12 million years ago. The species, Pierolapithecus catalaunicus, may be crucial to understanding great ape and human evolution. The researchers describe their findings today in the journal Proceedings of the National Academy of Sciences.

Pierolapithecus catalaunicus, a species from northeastern Spain first described in 2004, was one of a diverse group of now-extinct ape species that lived in Europe around 15 to 7 million years ago. The species is key to understanding the mosaic nature of hominid (great ape and human) evolution because it is known from a cranium and partial skeleton of the same individual—a rarity in the fossil record.

“Features of the skull and teeth are extremely important in resolving the evolutionary relationships of fossil species, and when we find this material in association with bones of the rest of the skeleton, it gives us the opportunity to not only accurately place the species on the hominid family tree, but also to learn more about the biology of the animal in terms of, for example, how it was moving around its environment,” said lead author Kelsey Pugh, a research associate in the Museum’s Division of Anthropology and a lecturer at Brooklyn College.

Previous work on Pierolapithecus suggests that an upright body plan preceded adaptations that allowed hominids to hang from tree branches and move among them. However, debate persists about the species’ evolutionary place, partly due to damage to the cranium.

“One of the persistent issues in studies of ape and human evolution is that the fossil record is fragmentary, and many specimens are incompletely preserved and distorted,” said co-author Ashley Hammond, associate curator and chair of the Museum’s Division of Anthropology. “This makes it difficult to reach a consensus on the evolutionary relationships of key fossil apes that are essential to understanding ape and human evolution.”

In an effort to bring clarity to these questions, the researchers used CT scans to virtually reconstruct the cranium of Pierolapithecus, compare it to other primate species, and model the evolution of key features of ape facial structure. They found that Pierolapithecus shares similarities in overall face shape and size with both fossilized and living great apes, but it also has distinct facial features not found in other Middle Miocene apes. The results are consistent with the idea that this species represents one of the earliest members of the great apes and human family.

“An interesting output of the evolutionary modeling in the study is that that the cranium of Pierolapithecus is closer in shape and size to the ancestor from which living great apes and humans evolved. On the other hand, gibbons and siamangs (the ‘lesser apes’) seem to be secondarily derived in relation to size reduction,” said co-author Sergio Almécija, a senior research scientist in the Museum’s Division of Anthropology.

Other authors on this study include Santiago Catalano, from the Fundación Miguel Lillo (Argentina); Miriam Pérez de los Ríos, from the Universidad Complutense de Madrid; Josep Fortuny, from the Catalan Institute of Paleontology Miquel Crusafont (ICP); Brian Shearer, from New York University; Alessandra Vecino Gazabón, from the American Museum of Natural History; Salvador Moyà-Solà, from the ICP and ICREA; and David Alba, from the ICP.

DOI: https://doi.org/10.1073/pnas.2218778120

 

ABOUT THE AMERICAN MUSEUM OF NATURAL HISTORY (AMNH)

The American Museum of Natural History, founded in 1869 with a dual mission of scientific research and science education, is one of the world’s preeminent scientific, educational, and cultural institutions. The Museum encompasses more than 40 permanent exhibition halls, galleries for temporary exhibitions, the Rose Center for Earth and Space including the Hayden Planetarium, and the Richard Gilder Center for Science, Education, and Innovation. The Museum’s scientists draw on a world-class permanent collection of more than 34 million specimens and artifacts, some of which are billions of years old, and on one of the largest natural history libraries in the world. Through its Richard Gilder Graduate School, the Museum offers two of the only free-standing, degree-granting programs of their kind at any museum in the U.S.: the Ph.D. program in Comparative Biology and the Master of Arts in Teaching (MAT) Earth Science residency program. Visit amnh.org for more information.

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JOURNAL

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2218778120 

ARTICLE TITLE

The reconstructed cranium of Pierolapithecus and the evolution of the great ape face

 

Critical step made for managing brushtail possums

Peer-Reviewed Publication

UNIVERSITY OF OTAGO

Common Brushtail Possum - The Australian Museum

Researchers say mapping the genetic code of the brushtail possum will benefit those working to both conserve and control the animal.

 

In a five-year long study, just published in Nature Communications, an international group of researchers led by the University of Otago, has assembled the entire genetic code of the marsupial mammal.

 

The work also uncovered where and when their genes are expressed, and revealed surprising details about their population diversity, reproduction, and origins. 

 

Study lead Associate Professor Tim Hore, of Otago’s Department of Anatomy, describes possums as “a fascinating animal that is loved in one country and a cause of concern in another”.

 

“They are hunted in Aotearoa New Zealand for their fur, and controlled for conservation, but treasured and protected in Australia. Having their full genetic code is important for both countries as efforts to manage their respective populations are being held back by the lack of this knowledge,” he says.

 

“In New Zealand, where the possum is a harmful introduced species, we can use the information to help guide control and eradication strategies, by tracking and monitoring target populations on the basis of their genes; but in the same way our work will also be useful for its conservation in Australia, where it is a valued native species.”

 

A potential novel way to improve possum population management has also been revealed by the DNA sequencing, based on chemical communication genes the researchers have discovered. 

 

“Possums are nocturnal, so non-visual means of communication are really important. We uncovered possum genes responsible for carrying scent in urine, and found that although they are silenced in newborns, they are switched on in adults, particularly males. Molecules produced from these genes could be used to lure possums towards a trap or keep them away from pest-free areas,” he says.

 

Professor Dan Tompkins, Science Director at the study co-funder Predator Free 2050 Limited, was excited about the results for the research and development pathways they open up.

 

“Through the Predator Free 2050 mission we are driving to eradicate possums – along with rats and stoats – from the whole of Aotearoa to protect native biodiversity, and we are always on the lookout for more targeted, efficient and humane ways of getting the job done,” Professor Tompkins says.

 

“Deciphering their genetic code provides us with an invaluable new knowledge base that underpins and enables exploration of a range of better approaches to do just that, from possum-species toxins to fertility control, and the exciting new ideas leveraging scent communication proposed here.”

 

Researchers also uncovered new details regarding the establishment of possums in New Zealand from Australian populations. 

 

Introduced in the late 19th century to establish a fur trade, possums went on to become serious pests, damaging many forest ecosystems and killing native birds and some insects.

 

As carriers of bovine tuberculosis, they also threaten biosecurity and trade. The New Zealand government alone spends more than $150 million per year controlling possum numbers.

 

In comparison, they are a cultural and ecological treasure in their native range, where Southern Aboriginal tribes use their skins for cloaks, depicting images and stories on them throughout life.

 

Study co-first author Dr Donna Bond, also of Otago’s Department of Anatomy, says possums from the study were collected from Otago Peninsula and other sites near Dunedin, but were genetic hybrids tracing back to discrete populations in Tasmania and the Australian mainland.

 

“Although the possums introduced in the 19th century were low in numbers, perhaps a few hundred, because they are mixed up from at least four different Australian populations, the New Zealand animals we tested had more genetic diversity than those from Australia,” she says.

 

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JOURNAL

Nature Communications

DOI

10.1038/s41467-023-41784-8 

ARTICLE TITLE

The admixed brushtail possum genome reveals invasion history in New Zealand and novel imprinted genes

ARTICLE PUBLICATION DATE

17-Oct-2023

 

Marine mammal longevity study reveals remarkable advances in animal welfare

Just as humans are now living longer lives as a result of advances in medicine and care, so too are marine mammals in modern zoos and aquariums, according to a new study

Peer-Reviewed Publication

SPECIES360

 

IMAGE: 

A COMMON BOTTLENOSE DOLPHIN AT PLANÈTE SAUVAGE, FRANCE. STUDY AUTHORS EXAMINED 200 YEARS' WORTH OF DATA ON FOUR MARINE MAMMAL SPECIES INCLUDING BOTTLENOSE DOLPHINS. 

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CREDIT: A. MONNIER – PLANÈTE SAUVAGE, FRANCE

A new study provides compelling evidence that animal care and management practices at zoos and aquariums have significantly improved over time. The study, led by Species360 and University of Southern Denmark Research Scientist Dr. Morgane Tidière in collaboration with 41 co-authors from academic, governmental, and zoological institutions around the world, is the first to examine life expectancy and lifespan equality together as a proxy of population welfare in marine mammal species. 

The study also found that marine mammal species live longer in zoological institutions than in the wild as a result of advances in animal care practices centered on animal welfare. The results have been published in Proceedings of the Royal Society B: Biological Sciences. 

Study authors used the same statistical methods used to assess improvements in human population welfare to analyze data from the world’s largest database of information on wildlife in human care – the Species360 Zoological Information Management System (ZIMS).

The study examined 200 years’ worth of data from ZIMS, dating as far back as the early 1800s up until 2020, to look at whether four marine mammal species – the harbor seal, California sea lion, polar bear, and common bottlenose dolphin – have seen improved conditions of life in human care, and whether that can be observed through a progressive concentration of individuals reaching old age.

Applying the same methodology using additional data sources for wild populations, the authors examine whether these four marine mammal species are living longer lives in zoos and aquariums, compared to their counterparts in the wild. 

The study authors found that the life expectancy of the four marine mammal species has increased by over three times, and that the rate of deaths in the first year of life has declined by up to 31% over the last century in zoos and aquariums included in the study. Additionally, the life expectancy of these species in zoos and aquariums is currently two to three times longer than their counterparts in the wild. 

In addition to looking at how long these four species are living, researchers looked at how many of them are living well by examining lifespan equality, which can show if a population is consistently living longer lives and avoiding less predictable, earlier causes of death. Researchers found conclusively that the four species have a progressively increasing lifespan equality across time in zoological institutions. They also highlight that current populations of the four species living in zoological institutions included in the study have a higher lifespan equality than their counterparts in the wild.
The researchers found a significant improvement in longevity and lifespan equality for the four species from the 1990s onwards, which is believed to be a result of advancements in zoological practices, such as implementing advanced veterinary, environmental, nutritional and enrichment measures, as well as the voluntary cooperation of animals in routine examinations through positive reinforcement training. 

These improvements in how progressive zoos and aquariums care for animals are a result of the establishment of regional and national zoo associations, accreditation standards, coordinated breeding programs, shared databases and professional networks which foster knowledge sharing – thereby collectively improving animal welfare. 

Lead study author, Dr. Morgane Tidière, Species360, commented on the significance of the study, saying; “Our findings indicate that significant progress has been made in enhancing the welfare of marine mammals in zoological institutions, as a result of improvements in management practices in progressive zoos and aquariums. Professional zoos and aquariums of today cannot be compared to zoos 30 years ago.” Dr. Tidière continues: “This kind of research is possible as a result of the standardized data collected and shared by Species360 member zoos and aquariums around the world.” 

The study authors note that these results reflect the average welfare of marine mammals in Species360 member facilities, rather than demonstrating a global minimum standard achieved by all zoos and aquariums worldwide. Nonetheless, these findings serve as evidence of positive progress in the management and care of animals within leading  zoological facilities. The researchers hope the findings inspire other institutions, which are not part of professional zoo and aquarium bodies, to invest time and resources into enhancing their animal management practices.

The results of this study contribute to the ongoing dialogue surrounding the wellbeing of animals in zoos and aquariums and may help inform future policy decisions. It demonstrates the importance of scientific research in understanding and improving the lives of animals in zoological institutions. The preliminary results have already informed legislative decisions in France and Spain, guiding evidence-based choices regarding the care of marine mammals in these settings.

The full study can be read here: https://royalsocietypublishing.org/doi/10.1098/rspb.2023.1895. 

 

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JOURNAL

Proceedings of the Royal Society B Biological Sciences

DOI

10.1098/rspb.2023.1895 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Survival improvements of marine mammals in zoological institutions mirror historical advances in human longevity

ARTICLE PUBLICATION DATE

18-Oct-2023

COI STATEMENT

In accordance with our ethical obligations as researchers, we hereby disclose that the Species360 ConservationScience Alliance received funding from our Species360 members, which share their data by means of the Species360 Zoological Information Management System (ZIMS). Our members include over 1300 zoos, aquariums, rescue centres, sanctuaries and other worldwide wildlife organizations that believe in sharing standardized records of more than 22 000 species through ZIMS. One of the main aims of data standards and sharing is to obtain sufficient sample sizes to develop research and analytics to support evidence-based decisions on animal care and species conservation. In addition, 25 co-authors work in zoological or aquarium organizations, including non-Species360 members.

A new study study has found that marine mammal species, like polar bears, live longer in zoological institutions than in the wild as a result of advances in animal care practices centered on animal welfare.

Polar bear (IMAGE)

SPECIES360

 

A new study examined 200 years’ worth of data from the Species360 Zoological Information Management System (ZIMS), dating as far back as the early 1800s up until 2020, to look at whether four marine mammal species – the harbor seal, California sea lion, polar bear, and common bottlenose dolphin – have seen improved conditions of life in human care, and whether that can be observed through a progressive concentration of individuals reaching old age.

 

CREDIT

Andrew Derocher – University of Alberta

Common bottlenose dolphins at Planète Sauvage, France. Study authors examined 200 years' worth of data on four marine mammal species including bottlenose dolphins and found that their life expectancy has increased by over three times, and is currently two to three times longer than their counterparts in the wild. 

A study published in Proceedings of the Royal Society B: Biological Sciences has found that marine mammal species in zoos and aquariums like common bottlenose dolphins live longer lives than their counterparts in the wild. 

CREDIT

Aurélie Monnier – Planète Sauvage, France

Researchers found a significant improvement in longevity and lifespan equality for four marine mammal species from the 1990s onwards, which is believed to be a result of advancements in zoological practices, such as implementing advanced veterinary, environmental, nutritional and enrichment measures, as well as the voluntary cooperation of animals in routine examinations through positive reinforcement training

CREDIT

Assiniboine Park Conservancy

A new study has found that marine mammal species, like harbor seals, live longer in zoological institutions than in the wild as a result of advances in animal care practices centered on animal welfare.

CREDIT

Georgia Aquarium

 

MIT design would harness 40% of the sun’s heat to produce clean hydrogen fuel

Conventional systems for producing hydrogen depend on fossil fuels, but the new system uses only solar energy.

Peer-Reviewed Publication

MASSACHUSETTS INSTITUTE OF TECHNOLOGY

 

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MIT ENGINEERS HAVE DEVELOPED A DESIGN FOR A SYSTEM THAT EFFICIENTLY HARNESSES THE SUN’S HEAT TO SPLIT WATER AND GENERATE HYDROGEN.

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CREDIT: COURTESY OF AHMED GHONIEM, ANIKET PATANKAR, ET. AL

MIT engineers aim to produce totally green, carbon-free hydrogen fuel with a new, train-like system of reactors that is driven solely by the sun. 

In a study appearing today in Solar Energy Journal, the engineers lay out the conceptual design for a system that can efficiently produce “solar thermochemical hydrogen.” The system harnesses the sun’s heat to directly split water and generate hydrogen — a clean fuel that can power long-distance trucks, ships, and planes, while in the process emitting no greenhouse gas emissions. 

Today, hydrogen is largely produced through processes that involve natural gas and other fossil fuels, making the otherwise green fuel more of a “grey” energy source when considered from the start of its production to its end use. In contrast, solar thermochemical hydrogen, or STCH, offers a totally emissions-free alternative, as it relies entirely on renewable solar energy to drive hydrogen production. But so far, existing STCH designs have limited efficiency: Only about 7 percent of incoming sunlight is used to make hydrogen. The results so far have been low-yield and high-cost.

In a big step toward realizing solar-made fuels, the MIT team estimates its new design could harness up to 40 percent of the sun’s heat to generate that much more hydrogen. The increase in efficiency could drive down the system’s overall cost, making STCH a potentially scalable, affordable option to help decarbonize the transportation industry. 

“We’re thinking of hydrogen as the fuel of the future, and there’s a need to generate it cheaply and at scale,” says the study’s lead author, Ahmed Ghoniem, the Ronald C. Crane Professor of Mechanical Engineering at MIT. “We’re trying to achieve the Department of Energy’s goal, which is to make green hydrogen by 2030, at $1 per kilogram. To improve the economics, we have to improve the efficiency and make sure most of the solar energy we collect is used in the production of hydrogen.”

Ghoniem’s study co-authors are Aniket Patankar, first author and MIT postdoc; Harry Tuller, MIT professor of materials science and engineering; Xiao-Yu Wu of the University of Waterloo; and Wonjae Choi at Ewha Womans University in South Korea.

Solar stations 

Similar to other proposed designs, the MIT system would be paired with an existing source of solar heat, such as a concentrated solar plant (CSP) — a circular array of hundreds of mirrors that collect and reflect sunlight to a central receiving tower. An STCH system then absorbs the receiver’s heat and directs it to split water and produce hydrogen. This process is very different from electrolysis, which uses electricity instead of heat to split water. 

At the heart of a conceptual STCH system is a two-step thermochemical reaction. In the first step, water in the form of steam is exposed to a metal. This causes the metal to grab oxygen from steam, leaving hydrogen behind. This metal “oxidation” is similar to the rusting of iron in the presence of water, but it occurs much faster. Once hydrogen is separated, the oxidized (or rusted) metal is reheated in a vacuum, which acts to reverse the rusting process and regenerate the metal. With the oxygen removed, the metal can be cooled and exposed to steam again to produce more hydrogen. This process can be repeated hundreds of times. 

The MIT system is designed to optimize this process. The system as a whole resembles a train of box-shaped reactors running on a circular track. In practice, this track would be set around a solar thermal source, such as a CSP tower. Each reactor in the train would house the metal that undergoes the redox, or reversible rusting, process. 

Each reactor would first pass through a hot station, where it would be exposed to the sun’s heat at temperatures of up to 1,500 degrees Celsius. This extreme heat would effectively pull oxygen out of a reactor’s metal. That metal would then be in a “reduced” state — ready to grab oxygen from steam. For this to happen, the reactor would move to a cooler station at temperatures around 1,000 C, where it would be exposed to steam to produce hydrogen. 

Rust and rails

Other similar STCH concepts have run up against a common obstacle: what to do with the heat released by the reduced reactor as it is cooled. Without recovering and reusing this heat, the system’s efficiency is too low to be practical.

A second challenge has to do with creating an energy-efficient vacuum where metal can de-rust. Some prototypes generate a vacuum using mechanical pumps, though the pumps are too energy-intensive and costly for large-scale hydrogen production. 

To address these challenges, the MIT design incorporates several energy-saving workarounds. To recover most of the heat that would otherwise escape from the system, reactors on opposite sides of the circular track are allowed to exchange heat through thermal radiation; hot reactors get cooled while cool reactors get heated. This keeps the heat within the system. The researchers also added a second set of reactors that would circle around the first train, moving in the opposite direction. This outer train of reactors would operate at generally cooler temperatures and would be used to evacuate oxygen from the hotter inner train, without the need for energy-consuming mechanical pumps. 

These outer reactors would carry a second type of metal that can also easily oxidize. As they circle around, the outer reactors would absorb oxygen from the inner reactors, effectively de-rusting the original metal, without having to use energy-intensive vacuum pumps. Both reactor trains would  run continuously and would enerate separate streams of pure hydrogen and oxygen. 

The researchers carried out detailed simulations of the conceptual design, and found that it would significantly boost the efficiency of solar thermochemical hydrogen production, from 7 percent, as previous designs have demonstrated, to 40 percent. 

“We have to think of every bit of energy in the system, and how to use it, to minimize the cost,” Ghoniem says. “And with this design, we found that everything can be powered by heat coming from the sun. It is able to use 40 percent of the sun’s heat to produce hydrogen.” 

In the next year, the team will be building a prototype of the system that they plan to test in concentrated solar power facilities at laboratories of the Department of Energy, which is currently funding the project. 

“When fully implemented, this system would be housed in a little building in the middle of a solar field,” Patankar explains. “Inside the building, there could be one or more trains each having about 50 reactors. And we think this could be a modular system, where you can add reactors to a conveyor belt, to scale up hydrogen production.”

This work was supported by the Centers for Mechanical Engineering Research and Education at MIT and SUSTech. 

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Written by Jennifer Chu, MIT News

Paper: “A comparative analysis of integrating thermochemical oxygen pumping in water-splitting redox cycles for hydrogen production”

https://www.sciencedirect.com/science/article/abs/pii/S0038092X23005935

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JOURNAL

Solar Energy

DOI

10.1016/j.solener.2023.111960 

ARTICLE TITLE

“A comparative analysis of integrating thermochemical oxygen pumping in water-splitting redox cycles for hydrogen production”

REAL CHEMTRAILS

Signatures of the Space Age: Spacecraft metals left in the wake of humanity’s path to the stars

Airplane-based research by Purdue scientists detects unprecedented levels of alloy aerosols in the atmosphere

Peer-Reviewed Publication

PURDUE UNIVERSITY

 

IMAGE: 

DAN CZICZO, PROFESSOR AND HEAD OF THE DEPARTMENT OF EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES IN PURDUE’S COLLEGE OF SCIENCE, WAS PART OF THE RESEARCH TEAM THAT DISCOVERED SIGNIFICANT AMOUNTS OF METALS IN AEROSOLS IN THE ATMOSPHERE, LIKELY FROM INCREASINGLY FREQUENT LAUNCHES AND RETURNS OF SPACECRAFT AND SATELLITES. DATA WAS COLLECTED MORE THAN 11 MILES ABOVE THE PLANET’S SURFACE USING SAMPLING TOOLS HITCHED TO THE NOSE CONE OF RESEARCH PLANES.

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CREDIT: PURDUE UNIVERSITY PHOTO/JOHN UNDERWOOD

WEST LAFAYETTE, Ind. – The Space Age is leaving fingerprints on one of the most remote parts of the planet — the stratosphere — which has potential implications for climate, the ozone layer and the continued habitability of Earth. 

Using tools hitched to the nose cone of their research planes and sampling more than 11 miles above the planet’s surface, researchers have discovered significant amounts of metals in aerosols in the atmosphere, likely from increasingly frequent launches and returns of spacecraft and satellites. That mass of metal is changing atmospheric chemistry in ways that may impact Earth’s atmosphere and ozone layer.

“We are finding this human-made material in what we consider a pristine area of the atmosphere,” said Dan Cziczo, one of a team of scientists who published a study on these results in the Proceedings of the National Academy of Sciences. “And if something is changing in the stratosphere — this stable region of the atmosphere — that deserves a closer look.” Cziczo, professor and head of the Department of Earth, Atmospheric, and Planetary Sciences in Purdue’s College of Science, is an expert in atmospheric science who has spent decades studying this rarefied region.

Led by Dan Murphy, an adjunct professor in the Department of Earth, Atmospheric, and Planetary Sciences and a researcher at the National Oceanic and Atmospheric Administration, the team detected more than 20 elements in ratios that mirror those used in spacecraft alloys. They found that the mass of lithium, aluminum, copper and lead from spacecraft reentry far exceeded those metals found in natural cosmic dust. Nearly 10% of large sulfuric acid particles — the particles that help protect and buffer the ozone layer — contained aluminum and other spacecraft metals.

Scientists estimate that as many as 50,000 more satellites may reach orbit by 2030. The team calculates that means that, in the next few decades, up to half of stratospheric sulfuric acid particles would contain metals from reentry. What effect that could have on the atmosphere, the ozone layer and life on Earth is yet to be understood.

Scientists have long suspected that spacecraft and satellites were changing the upper atmosphere, but studying the stratosphere, where we don’t live and even the highest flights enter only briefly, is challenging.

As part of NASA’s Airborne Science Program, Murphy and his group fly a WB-57 airplane to sample the atmosphere 11.8 miles (19 km) above the ground in Alaska, where circumpolar clouds tend to form. Similar measurements were made by Cziczo and his group from an ER-2 aircraft over the continental United States. Both groups use instruments hitched to the nose cone to ensure that only the freshest, most undisturbed air is sampled.

The sheltering sky

Like the view of the unruffled surface of the ocean, the stratosphere appears untroubled — at least to human eyes. Life and civilization take place mostly on the planet’s surface and in the troposphere, the atmosphere’s very lowest layer. The stratosphere is a surprisingly stable and seemingly serene layer of the atmosphere.

The stratosphere is also the realm of the ozone layer: that gaseous marvel that acts as a global tent to shield the planet and all life on it from the searing, scorching rays of ultraviolet radiation. Without the ozone layer, life would likely never have arisen on Earth. And without it, life is unlikely to be able to continue.

The last decades have been eventful for the stratosphere. The ozone layer came under threat from chlorofluorocarbons in the 1980s, and only coordinated, sustained global efforts of governments and corporations have begun to bear fruit in repairing and replenishing it. 

“Shooting stars streak through the atmosphere,” Cziczo said. “Often, the meteor burns up in the atmosphere and doesn’t even become a meteorite and reach the planet. So the material it was made from stays in the atmosphere in the form of ions. They form very hot gas, which starts to cool and condense as molecules and fall into the stratosphere. The molecules find each other and knit together and form what we call meteorite smoke. Scientists recently started noticing that the chemical fingerprint of these meteoritic particles was starting to change, which made us ask, ‘Well, what changed?’ because meteorite composition hasn’t changed. But the number of spacecraft has.”

What goes up

Spacecraft launches, and returns, were once international events. The launches of Sputnik and the Mercury missions were front-page news. Now, a quickening tide of innovation and loosening regulation means that dozens of countries and corporations are able to launch satellites and spacecraft into orbit. All those satellites have to be sent up on rockets — and most of that material, eventually, comes back down.

Like the wakes of great ships trolling through the ocean, rockets leave behind them a trail of metals that may change the atmosphere in ways scientists don’t yet understand. 

“Just to get things into orbit, you need all this fuel and a huge body to support the payload,” Cziczo said. “There are so many rockets going up and coming back and so many satellites falling back through the atmosphere that it’s starting to show up in the stratosphere as these aerosol particles.”

Of course, shooting stars were the first space-delivery system. Meteorites fall through the atmosphere every day. The heat and friction of the atmosphere peel material off them, just as they do off human-made artifacts. However, while hundreds of meteors enter the Earth’s atmosphere every day, they are increasingly being rivaled by the mass of metals that comprise the tons of Falcon, Ariane and Soyuz rockets that boost spacecraft into space and return again to Earth’s surface.  

“Changes to the atmosphere can be difficult to study and complex to understand,” Cziczo said. “But what this research shows us is that the impact of human occupation and human spaceflight on the planet may be significant — perhaps more significant than we have yet imagined. Understanding our planet is one of the most urgent research priorities there is.”

Writer: Brittany Steff, bsteff@purdue.edu 

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JOURNAL

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2313374120 

ARTICLE TITLE

Metals from spacecraft reentry in stratospheric aerosol particles

ARTICLE PUBLICATION DATE

16-Oct-2023