Connect with us

TOP SCEINCE

Geoscientists map changes in atmospheric CO2 over past 66 million years

Published

on

Geoscientists map changes in atmospheric CO2 over past 66 million years


Today atmospheric carbon dioxide is at its highest level in at least several million years thanks to widespread combustion of fossil fuels by humans over the past couple centuries.

But where does 419 parts per million (ppm) — the current concentration of the greenhouse gas in the atmosphere — fit in Earth’s history?

That’s a question an international community of scientists, featuring key contributions by University of Utah geologists, is sorting out by examining a plethora of markers in the geologic record that offer clues about the contents of ancient atmospheres. Their initial study was published this week in the journal Science, reconstructing CO2 concentrations going back through the Cenozoic, the era that began with the demise dinosaurs and rise of mammals 66 million years ago.

Glaciers contain air bubbles, providing scientists direct evidence of CO2 levels going back 800,000 years, according to U geology professor Gabe Bowen, one of the study’s corresponding authors. But this record does not extend very deep into the geological past.

“Once you lose the ice cores, you lose direct evidence. You no longer have samples of atmospheric gas that you can analyze,” Bowen said. “So you have to rely on indirect evidence, what we call proxies. And those proxies are tough to work with because they are indirect.”

“Proxies” in the geologic record

These proxies include isotopes in minerals, the morphology of fossilized leaves and other lines of geological evidence that reflect atmospheric chemistry. One of the proxies stems from the foundational discoveries of U geologist Thure Cerling, himself a co-author on the new study, whose past research determined carbon isotopes in ancient soils are indicative of past CO2 levels.

But the strength of these proxies vary and most cover narrow slices of the past. The research team, called the Cenozoic CO2 Proxy Integration Project, or CenCO2PIP, and organized by Columbia University climate scientist Bärbel Hönisch, set out to evaluate, categorize and integrate available proxies to create a high-fidelity record of atmospheric CO2.

“This represents some of the most inclusive and statistically refined approaches to interpreting CO2 over the last 66 million years,” said co-author Dustin Harper, a U postdoctoral researcher in Bowen’s lab. “Some of the new takeaways are we’re able to combine multiple proxies from different archives of sediment, whether that’s in the ocean or on land, and that really hasn’t been done at this scale.”

The new research is a community effort involving some 90 scientists from 16 countries. Funded by dozens of grants from multiple agencies, the group hopes to eventually reconstruct the CO2 record back 540 million years to the dawn of complex life.

At the start of the Industrial Revolution — when humans began burning to coal, then oil and gas to fuel their economies — atmospheric CO2 was around 280 ppm. The heat-trapping gas is released into the air when these fossil fuels burn.

Looking forward, concentrations are expected to climb up to 600 to 1,000 ppm by the year 2100, depending on the rate of future emissions. It is not clear exactly how these future levels will influence the climate.

But having a reliable map of past CO2 levels could help scientists more accurately predict what future climates may look like, according to U biology professor William Anderegg, director the U’s Wilkes Center for Climate & Policy.

“This is an incredibly important synthesis and has implications for future climate change as well, particularly the key processes and components of the Earth system that we need to understand to project the speed and magnitude of climate change,” Anderegg said.

Today’s 419 ppm is the highest CO2 in 14 million years

At times in the past when Earth was a far warmer place, levels of CO2 were much higher than now. Still, the 419 ppm recorded today represents a steep and perhaps dangerous spike and is unprecedented in recent geologic history.

“By 8 million years before present, there’s maybe a 5% chance that CO2 levels were higher than today,” Bowen said, “but really we have to go back 14 million years before we see levels we think were like today.”

In other words, human activity has significantly altered the atmosphere within the span of a few generations. As a result, climate systems around the globe are showing alarming signs of disruption, such as powerful storms, prolonged drought, deadly heat waves and ocean acidification.

A solid understanding of atmospheric CO2 variation through geological time is also essential to deciphering and learning from various features of Earth’s history. Changes in atmospheric CO2 and climate likely contributed to mass extinctions, as well as evolutionary innovations.

During the Cenozoic, for example, long-term declines in CO2 and associated climate cooling may have driven changes to plant physiology, species competition and dominance, which in turn impacted mammalian evolution.

“A more refined understanding of past trends in CO2 is therefore central to understanding how modern species and ecosystems arose and may fare in the future,” the study states.



Source link

Continue Reading
Click to comment

Leave a Reply

TOP SCEINCE

Inherited predisposition for higher muscle strength may protect against common morbidities

Published

on

By

Inherited predisposition for higher muscle strength may protect against common morbidities


A study conducted at the Faculty of Sport and Health Sciences at the University of Jyväskylä showed that a genetic predisposition for higher muscle strength predicts a longer lifespan and a lower risk for developing common diseases. This is the most comprehensive international study to date on hereditary muscle strength and its relationship to morbidity. The genome and health data of more than 340,000 Finns was used in the research.

Muscle strength, especially hand grip strength, can indicate an individual’s physiological resources to protect against age-related diseases and disabilities, as well as their ability to cope with them. Age-related loss of muscle strength is individual and influenced not only by lifestyle but also by genetics.

The study revealed that individuals with a genetic predisposition for higher muscle strength have a slightly lower risk for common noncommunicable diseases and premature mortality. However, it did not predict better survival after acute adverse health events compared to the time before illness onset.

“It seems that a genetic predisposition for higher muscle strength reflects more on an individual’s intrinsic ability to resist and protect oneself against pathological changes that occur during aging than the ability to recover or completely bounce back after severe adversity,” says doctoral researcher Päivi Herranen from the Faculty of Sport and Health Sciences.

The research utilized a unique study population

Muscle strength is a multifactorial trait influenced by lifestyle and environmental factors but also by numerous genetic variants, each with a very small effect on muscle strength. In this study, the genetic predisposition for muscle strength was defined by constructing a polygenic score for muscle strength, which summarizes the effects of hundreds of thousands of genetic variants into a single score. The polygenic score makes it possible to compare participants with an exceptionally high or low genetic predisposition for muscle strength, and to investigate associations with inherited muscle strength and other phenotypes, in this case, common diseases.

“In this study, we were able to utilize both genetic information and health outcomes from over 340,000 Finnish men and women,” Herranen explains.

“To our knowledge, this is the first study to investigate the association between a genetic predisposition for muscle strength and various diseases on this scale.”

Further research on the effects of lifestyles is still needed

Information about the genetic predisposition for muscle strength could be used alongside traditional risk assessment in identifying individuals who are at particularly high risk of common diseases and health adversities. However, further research on the topic is still needed.

“Based on these results, we cannot say how lifestyle factors, such as physical activity, modify an individual’s intrinsic ability to resist diseases and whether their impact on health differs among individuals due to genetics,” Herranen notes.

The study utilized the internationally unique FinnGen dataset, compiled through the collaboration of Finnish biobanks. The dataset consisted of 342,443 Finns who had given their consent and provided a biobank sample. The participants were aged 40 to 108 years, and 53% of them were women. The diagnoses selected for the study were based on the leading causes of death and the most significant noncommunicable diseases in Finland. Selected diagnoses included the most common cardiometabolic and pulmonary diseases, musculoskeletal and connective tissue diseases, falls and fractures, mental health and cognitive disorders, cancers, as well as overall mortality and mortality from cardiovascular diseases.

The study is the second publication of Päivi Herranen’s doctoral thesis, which investigates how genetics and environmental factors affect biological aging, particularly the weakening of muscle strength and functional capacity with age. The research is part of the GenActive project, funded by the Research Council of Finland and the Juho Vainio and Päivikki and Sakari Sohlberg foundations. The project is led by Assistant Professor and Academy Research Fellow Elina Sillanpää. The research was conducted in collaboration with the Gerontology Research Center (GEREC), the Institute for Molecular Medicine Finland (FIMM), and the FinnGen research project.



Source link

Continue Reading

TOP SCEINCE

Brightest gamma-ray burst of all time came from the collapse of a massive star

Published

on

By

Brightest gamma-ray burst of all time came from the collapse of a massive star


In October 2022, an international team of researchers, including Northwestern University astrophysicists, observed the brightest gamma-ray burst (GRB) ever recorded, GRB 221009A.

Now, a Northwestern-led team has confirmed that the phenomenon responsible for the historic burst — dubbed the B.O.A.T. (“brightest of all time”) — is the collapse and subsequent explosion of a massive star. The team discovered the explosion, or supernova, using NASA’s James Webb Space Telescope (JWST).

While this discovery solves one mystery, another mystery deepens.

The researchers speculated that evidence of heavy elements, such as platinum and gold, might reside within the newly uncovered supernova. The extensive search, however, did not find the signature that accompanies such elements. The origin of heavy elements in the universe continues to remain as one of astronomy’s biggest open questions.

The research will be published on Friday (April 12) in the journal Nature Astronomy.

“When we confirmed that the GRB was generated by the collapse of a massive star, that gave us the opportunity to test a hypothesis for how some of the heaviest elements in the universe are formed,” said Northwestern’s Peter Blanchard, who led the study. “We did not see signatures of these heavy elements, suggesting that extremely energetic GRBs like the B.O.A.T. do not produce these elements. That doesn’t mean that all GRBs do not produce them, but it’s a key piece of information as we continue to understand where these heavy elements come from. Future observations with JWST will determine if the B.O.A.T.’s ‘normal’ cousins produce these elements.”

Blanchard is a postdoctoral fellow at Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), where he studies superluminous supernovae and GRBs. The study includes co-authors from the Center for Astrophysics | Harvard & Smithsonian; University of Utah; Penn State; University of California, Berkeley; Radbound University in the Netherlands; Space Telescope Science Institute; University of Arizona/Steward Observatory; University of California, Santa Barbara; Columbia University; Flatiron Institute; University of Greifswald and the University of Guelph.

Birth of the B.O.A.T.

When its light washed over Earth on Oct. 9, 2022, the B.O.A.T. was so bright that it saturated most of the world’s gamma-ray detectors. The powerful explosion occurred approximately 2.4 billion light-years away from Earth, in the direction of the constellation Sagitta and lasted a few hundred seconds in duration. As astronomers scrambled to observe the origin of this incredibly bright phenomenon, they were immediately hit with a sense of awe.

“As long as we have been able to detect GRBs, there is no question that this GRB is the brightest we have ever witnessed by a factor of 10 or more,” Wen-fai Fong, an associate professor of physics and astronomy at Northwestern’s Weinberg College of Arts and Sciences and member of CIERA, said at the time.

“The event produced some of the highest-energy photons ever recorded by satellites designed to detect gamma rays,” Blanchard said. “This was an event that Earth sees only once every 10,000 years. We are fortunate to live in a time when we have the technology to detect these bursts happening across the universe. It’s so exciting to observe such a rare astronomical phenomenon as the B.O.A.T. and work to understand the physics behind this exceptional event.”

A ‘normal’ supernova

Rather than observe the event immediately, Blanchard, his close collaborator Ashley Villar of Harvard University and their team wanted to view the GRB during its later phases. About six months after the GRB was initially detected, Blanchard used the JWST to examine its aftermath.

“The GRB was so bright that it obscured any potential supernova signature in the first weeks and months after the burst,” Blanchard said. “At these times, the so-called afterglow of the GRB was like the headlights of a car coming straight at you, preventing you from seeing the car itself. So, we had to wait for it to fade significantly to give us a chance of seeing the supernova.”

Blanchard used the JWST’s Near Infrared Spectrograph to observe the object’s light at infrared wavelengths. That’s when he saw the characteristic signature of elements like calcium and oxygen typically found within a supernova. Surprisingly, it wasn’t exceptionally bright — like the incredibly bright GRB that it accompanied.

“It’s not any brighter than previous supernovae,” Blanchard said. “It looks fairly normal in the context of other supernovae associated with less energetic GRBs. You might expect that the same collapsing star producing a very energetic and bright GRB would also produce a very energetic and bright supernova. But it turns out that’s not the case. We have this extremely luminous GRB, but a normal supernova.”

Missing: Heavy elements

After confirming — for the first time — the presence of the supernova, Blanchard and his collaborators then searched for evidence of heavy elements within it. Currently, astrophysicists have an incomplete picture of all the mechanisms in the universe that can produce elements heavier than iron.

The primary mechanism for producing heavy elements, the rapid neutron capture process, requires a high concentration of neutrons. So far, astrophysicists have only confirmed the production of heavy elements via this process in the merger of two neutron stars, a collision detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2017. But scientists say there must be other ways to produce these elusive materials. There are simply too many heavy elements in the universe and too few neutron-star mergers.

“There is likely another source,” Blanchard said. “It takes a very long time for binary neutron stars to merge. Two stars in a binary system first have to explode to leave behind neutron stars. Then, it can take billions and billions of years for the two neutron stars to slowly get closer and closer and finally merge. But observations of very old stars indicate that parts of the universe were enriched with heavy metals before most binary neutron stars would have had time to merge. That’s pointing us to an alternative channel.”

Astrophysicists have hypothesized that heavy elements also might be produced by the collapse of a rapidly spinning, massive star — the exact type of star that generated the B.O.A.T. Using the infrared spectrum obtained by the JWST, Blanchard studied the inner layers of the supernova, where the heavy elements should be formed.

“The exploded material of the star is opaque at early times, so you can only see the outer layers,” Blanchard said. “But once it expands and cools, it becomes transparent. Then you can see the photons coming from the inner layer of the supernova.”

“Moreover, different elements absorb and emit photons at different wavelengths, depending on their atomic structure, giving each element a unique spectral signature,” Blanchard explained. “Therefore, looking at an object’s spectrum can tell us what elements are present. Upon examining the B.O.A.T.’s spectrum, we did not see any signature of heavy elements, suggesting extreme events like GRB 221009A are not primary sources. This is crucial information as we continue to try to pin down where the heaviest elements are formed.”

Why so bright?

To tease apart the light of the supernova from that of the bright afterglow that came before it, the researchers paired the JWST data with observations from the Atacama Large Millimeter/Submillimeter Array (ALMA) in Chile.

“Even several months after the burst was discovered, the afterglow was bright enough to contribute a lot of light in the JWST spectra,” said Tanmoy Laskar, an assistant professor of physics and astronomy at the University of Utah and a co-author on the study. “Combining data from the two telescopes helped us measure exactly how bright the afterglow was at the time of our JWST observations and allow us to carefully extract the spectrum of the supernova.”

Although astrophysicists have yet to uncover how a “normal” supernova and a record-breaking GRB were produced by the same collapsed star, Laskar said it might be related to the shape and structure of the relativistic jets. When rapidly spinning, massive stars collapse into black holes, they produce jets of material that launch at rates close to the speed of light. If these jets are narrow, they produce a more focused — and brighter — beam of light.

“It’s like focusing a flashlight’s beam into a narrow column, as opposed to a broad beam that washes across a whole wall,” Laskar said. “In fact, this was one of the narrowest jets seen for a gamma-ray burst so far, which gives us a hint as to why the afterglow appeared as bright as it did. There may be other factors responsible as well, a question that researchers will be studying for years to come.”

Additional clues also may come from future studies of the galaxy in which the B.O.A.T. occurred. “In addition to a spectrum of the B.O.A.T. itself, we also obtained a spectrum of its ‘host’ galaxy,” Blanchard said. “The spectrum shows signs of intense star formation, hinting that the birth environment of the original star may be different than previous events.”

Team member Yijia Li, a graduate student at Penn State, modeled the spectrum of the galaxy, finding that the B.O.A.T.’s host galaxy has the lowest metallicity, a measure of the abundance of elements heavier than hydrogen and helium, of all previous GRB host galaxies. “This is another unique aspect of the B.O.A.T. that may help explain its properties,” Li said.

The study, “JWST detection of a supernova associated with GRB 221009A without an r-process signature,” was supported by NASA (award number JWST-GO-2784) and the National Science Foundation (award numbers AST-2108676 and AST-2002577). This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope.



Source link

Continue Reading

TOP SCEINCE

Stellar winds of three sun-like stars detected for the first time

Published

on

By

Stellar winds of three sun-like stars detected for the first time


An international research team led by a researcher from the University of Vienna has for the first time directly detected stellar winds from three Sun-like stars by recording the X-ray emission from their astrospheres, and placed constraints on the mass loss rate of the stars via their stellar winds. The study is currently published in Nature Astronomy.

Astrospheres, stellar analogues of the heliosphere that surrounds our solar system, are very hot plasma bubbles blown by stellar winds into the interstellar medium, a space filled with gas and dust. The study of the stellar winds of low-mass stars similar to the Sun allows us to understand stellar and planetary evolution, and ultimately the history and future of our own star and solar system. Stellar winds drive many processes that evaporate planetary atmospheres into space and therefore lead to atmospheric mass loss.

Although escape rates of planets over an hour or even a year are tiny, they operate over long geological periods. The losses accumulate and can be a decisive factor for a planet evolving into a habitable world or an airless rock. Despite their importance for the evolution of both stars and planets, winds of Sun-like stars are notoriously difficult to constrain. Mainly composed of protons and electrons, they also contain a small quantity of heavier highly charged ions (e.g. oxygen, carbon). It is these ions which, by capturing electrons from the neutrals of the interstellar medium around the star, emit X-rays.

X-ray emission from astropheres detected

An international research team led by Kristina Kislyakova, Senior Scientist at the Department of Astrophysics of the University of Vienna, has detected for the first time the X-ray emission from the astrospheres around three sun-like stars, so called main sequence stars which are stars in the prime of their life, and has thus recorded such winds for the first time directly, allowing them to place constraints on the mass loss rate of the stars via their stellar winds.

These results, based on observations with the XMM-Newton space telescope, are currently published in Nature Astronomy. The researchers observed the spectral fingerprints (so-called spectral lines) of the oxygen ions with XMM-Newton and were able to determine the quantity of oxygen and ultimately the total mass of stellar wind emitted by the stars. For the three stars with detected astrospheres, named 70 Ophiuchi, epsilon Eridani, and 61 Cygni, the researchers estimated their mass loss rates to be 66.5±11.1, 15.6±4.4, and 9.6±4.1 times the solar mass loss rate, respectively. This means that the winds from these stars are much stronger than the solar wind, which might be explained by stronger magnetic activity of these stars.

“In the solar system, solar wind charge exchange emission has been observed from planets, comets, and the heliosphere and provides a natural laboratory to study the solar wind’s composition,” explains the lead author of the study, Kristina Kislyakova. “Observing this emission from distant stars is much more tricky due to the faintness of the signal. In addition to that, the distance to the stars makes it very difficult to disentangle the signal emitted by the astrosphere from the actual X-ray emission of the star itself, part of which is “spread” over the field-of-view of the telescope due to instrumental effects. We have developed a new algorithm to disentangle the stellar and the astrospheric contributions to the emission and detected charge exchange signals originating from stellar wind oxygen ions and the surrounding neutral interstellar medium of three main-sequence stars. This has been the first time X-ray charge exchange emission from astrospheres of such stars has been detected. Our estimated mass loss rates can be used as a benchmark for stellar wind models and expand our limited observational evidence for the winds of Sun-like stars.”

Co-author Manuel Güdel, also of the University of Vienna, adds, “there have been world-wide efforts over three decades to substantiate the presence of winds around Sun-like stars and measure their strengths, but so far only indirect evidence based on their secondary effects on the star or its environment alluded to the existence of such winds; our group previously tried to detect radio emission from the winds but could only place upper limits to the wind strengths while not detecting the winds themselves. Our new X-ray based results pave the way to finding and even imaging these winds directly and studying their interactions with surrounding planets.”

“In the future, this method of direct detection of stellar winds in X-rays will be facilitated thanks to future high resolution instruments, like the X-IFU spectrometer of the European Athena mission. The high spectral resolution of X-IFU will resolve the finer structure and emission ratio of the oxygen lines (as well as other fainter lines), that are hard to distinguish with XMM’s CCD resolution, and provide additional constraints on the emission mechanism; thermal emission from the stars, or non-thermal charge exchange from the astrospheres.” — explains CNRS researcher Dimitra Koutroumpa, a co-author of the study.



Source link

Continue Reading

Trending

Copyright © 2017 Zox News Theme. Theme by MVP Themes, powered by WordPress.