SPACE/COSMOS
Does planetary evolution favor human-like life? Study ups odds we’re not alone
New theory proposes that humans — and analogous life beyond Earth — may represent the probable outcome of biological and planetary evolution
Penn State
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A new model upends the decades-old “hard steps” theory that intelligent life was an incredibly improbable event and suggests that maybe it wasn't all that hard or improbable. The team of researchers said the new interpretation of humanity’s origin increases the probability of intelligent life elsewhere in the universe.
view moreCredit: NASA
UNIVERSITY PARK, Pa. — Humanity may not be extraordinary but rather the natural evolutionary outcome for our planet and likely others, according to a new model for how intelligent life developed on Earth.
The model, which upends the decades-old “hard steps” theory that intelligent life was an incredibly improbable event, suggests that maybe it wasn't all that hard or improbable. A team of researchers at Penn State, who led the work, said the new interpretation of humanity’s origin increases the probability of intelligent life elsewhere in the universe.
“This is a significant shift in how we think about the history of life,” said Jennifer Macalady, professor of geosciences at Penn State and co-author on the paper, which published today (Feb. 14) in the journal Science Advances. “It suggests that the evolution of complex life may be less about luck and more about the interplay between life and its environment, opening up exciting new avenues of research in our quest to understand our origins and our place in the universe.”
Initially developed by theoretical physicist Brandon Carter in 1983, the “hard steps” model argues that our evolutionary origin was highly unlikely due to the time it took for humans to evolve on Earth relative to the total lifespan of the sun — and therefore the likelihood of human-like beings beyond Earth is extremely low.
In the new study, a team of researchers that included astrophysicists and geobiologists argued that Earth's environment was initially inhospitable to many forms of life, and that key evolutionary steps only became possible when the global environment reached a "permissive" state.
For example, complex animal life requires a certain level of oxygen in the atmosphere, so the oxygenation of Earth’s atmosphere through photosynthesizing microbes and bacteria was a natural evolutionary step for the planet, which created a window of opportunity for more recent life forms to develop, explained Dan Mills, postdoctoral researcher at The University of Munich and lead author on the paper.
“We're arguing that intelligent life may not require a series of lucky breaks to exist,” said Mills, who worked in Macalady’s astrobiology lab at Penn State as an undergraduate researcher. “Humans didn't evolve ‘early’ or ‘late’ in Earth’s history, but ‘on time,’ when the conditions were in place. Perhaps it’s only a matter of time, and maybe other planets are able to achieve these conditions more rapidly than Earth did, while other planets might take even longer.”
The central prediction of the “hard steps” theory states that very few, if any, other civilizations exist throughout the universe, because steps such as the origin of life, the development of complex cells and the emergence of human intelligence are improbable based on Carter’s interpretation of the sun's total lifespan being 10 billion years, and the Earth's age of around 5 billion years.
In the new study, the researchers proposed that the timing of human origins can be explained by the sequential opening of “windows of habitability” over Earth's history, driven by changes in nutrient availability, sea surface temperature, ocean salinity levels and the amount of oxygen in the atmosphere. Given all the interplaying factors, they said, the Earth has only recently become hospitable to humanity — it’s simply the natural result of those conditions at work.
“We’re taking the view that rather than base our predictions on the lifespan of the sun, we should use a geological time scale, because that's how long it takes for the atmosphere and landscape to change,” said Jason Wright, professor of astronomy and astrophysics at Penn State and co-author on the paper. “These are normal timescales on the Earth. If life evolves with the planet, then it will evolve on a planetary time scale at a planetary pace.”
Wright explained that part of the reason that the “hard steps” model has prevailed for so long is that it originated from his own discipline of astrophysics, which is the default field used to understand the formation of planets and celestial systems. The team’s paper is a collaboration between physicists and geobiologists, each learning from each other’s fields to develop a nuanced picture of how life evolves on a planet like Earth.
“This paper is the most generous act of interdisciplinary work,” said Macalady, who also directs Penn State’s Astrobiology Research Center. “Our fields were far apart, and we put them on the same page to get at this question of how we got here and are we alone? There was a gulf, and we built a bridge.”
The researchers said they plan to test their alternative model, including questioning the unique status of the proposed evolutionary “hard steps.” The recommended research projects are outlined in the current paper and include such work as searching the atmospheres of planets outside our solar system for biosignatures, like the presence of oxygen. The team also proposed testing the requirements for proposed “hard steps” to determine how hard they actually are by studying uni- and multicellular forms of life under specific environmental conditions such as lower oxygen and temperature levels.
Beyond the proposed projects, the team suggested the research community should investigate whether innovations —such as the origin of life, oxygenic photosynthesis, eukaryotic cells, animal multicellularity and Homo sapiens — are truly singular events in Earth's history. Could similar innovations have evolved independently in the past, but evidence that they happened was lost due to extinction or other factors?
“This new perspective suggests that the emergence of intelligent life might not be such a long shot after all,” Wright said. “Instead of a series of improbable events, evolution may be more of a predictable process, unfolding as global conditions allow. Our framework applies not only to Earth, but also other planets, increasing the possibility that life similar to ours could exist elsewhere.”
The other co-author on the paper is Adam Frank of the University of Rochester. Penn State’s Astrobiology Research Center, the Penn State Center for Exoplanets and Habitable Worlds, the Penn State Extraterrestrial Intelligence Center, the NASA Exobiology program and the German Research Foundation supported this work.
Journal
Science Advances
Method of Research
Systematic review
Subject of Research
Not applicable
Article Title
A reassessment of the “hard-steps” model for the evolution of intelligent life
Article Publication Date
14-Feb-2025
“Game changing” release of Type Ia Supernovae data may hold key to the history of the Universe
Lancaster University
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Nighttime long exposure of the open Samuel Oschin Telescope dome at Palomar Observatory in California
view moreCredit: Palomar/Caltech
A unique dataset of Type Ia Supernovae being released today could change how cosmologists measure the expansion history of the Universe.
Dr Mathew Smith and Dr Georgios Dimitriadis from Lancaster University are both members of the Zwicky Transient Facility (ZTF), a wide-field sky astronomical survey using a new camera attached to the Samuel Oschin Telescope at Palomar Observatory in California.
Type Ia Supernovae are the dramatic explosions of white dwarf stars at the ends of their lives. Cosmologists use them to probe distances across the universe by comparing their fluxes, as further objects appear dimmer.
The ZTF cosmology science working group is today publishing twenty-one articles studying these 3628 Type Ia Supernovae, forming a Special Issue in Astronomy & Astrophysics. https://www.aanda.org/component/toc/?task=topic&id=2090
Lancaster astrophysicist Dr Mathew Smith, co-leader of the ZTF SN Ia DR2 release, said: “This release provides a game-changing dataset for supernova cosmology. It opens the door to new discoveries about both the expansion of the universe and the fundamental physics of supernovae.”
This is the first time that astrophysicists have access to such a large and homogeneous dataset. Type Ia supernovae are rare, occurring approximately once per thousand years in a typical galaxy, but ZTF’s depth and survey strategy enable researchers to detect nearly four per night. In only two and a half years, ZTF has doubled the number available Type Ia Supernovae for cosmology acquired for the last 30 years to almost three thousand.
Head of the ZTF Cosmology Science working group Dr Mickael Rigault from the Institut des deux Infinis de Lyon (CNRS / Claude Bernard University) said: ““For the past five years, a group of thirty experts from around the world have collected, compiled, assembled, and analysed these data. We are now releasing it to the entire community. This sample is so unique in terms of size and homogeneity, that we expect it to significantly impact the field of Supernovae cosmology and to lead to many additional new discoveries in addition to results we have already published.”
The ZTF camera, installed on the 48-inch Schmidt telescope at Palomar Observatory, scans the entire northern sky daily in three optical bands, reaching a depth of 20.5 magnitude—one million times fainter than the dimmest stars visible to the naked eye. This sensitivity allows ZTF to detect nearly all supernovae within 1.5 billion light-years of Earth.
Professor Kate Maguire from Trinity College Dublin, a co-author of the study, said: “Thanks to ZTF’s unique ability to scan the sky rapidly and deeply, we have captured multiple supernovae within days—or even hours—of explosion, providing novel constraints on how they end their lives.”
The acceleration of the expansion of the Universe, awarded by the Nobel prize in 2011, was discovered in the late 90s using approximately a hundred of these Supernovae. Since then, cosmologists are investigating the reason for this acceleration caused by the dark energy that plays the role of an anti-gravity force across the Universe.
Co-author Professor Ariel Goobar, Director of the Oskar Klein Centre in Stockholm, one of the founding institutions of ZTF, and also member of the team that discovered the accelerated expansion of the Universe in 1998 said: “Ultimately, the aim is to address one of our time’s biggest questions in fundamental physics and cosmology, namely what is most of the Universe made of? For that we need the ZTF supernova data.”
One of the key outcomes of these studies is that Type Ia Supernovae intrinsically vary as a function of their host environment, more so than expected before, and the correction mechanism assumed so far has to be revisited. This could change how we measure the expansion history of the Universe and may have important consequences for current deviation observed in the standard model of cosmology.
Dr Rigault said: “With this large and homogeneous dataset, we can explore Type Ia supernovae with an unprecedented level of precision and accuracy. This is a crucial step toward honing the use of Type Ia Supernovae in cosmology and assess if current deviations in cosmology are due to new fundamental physics or unknown problem in the way we derive distances.”
Journal
Astronomy and Astrophysics
Method of Research
Imaging analysis
Subject of Research
Not applicable
Article Title
ZTF SN Ia DR2: Overview
Article Publication Date
14-Feb-2025
From collisions to stellar cannibalism – the surprising diversity of exploding white dwarfs
Trinity College Dublin
image:
the Palomar 48 inch telescope at the Palomar Observatory in California with an image of the Milky Way in the background. The stars represent the number of supernovae discovered in each direction and the inset is an image of a galaxy after (left) and before (right) the supernova exploded.
view moreCredit: Mickael Rigault.
Astrophysicists have unearthed a surprising diversity in the ways in which white dwarf stars explode in deep space after assessing almost 4,000 such events captured in detail by a next-gen astronomical sky survey. Their findings may help us more accurately measure distances in the Universe and further our knowledge of “dark energy”.
The dramatic explosions of white dwarf stars at the ends of their lives have for decades played a pivotal role in the study of dark energy – the mysterious force responsible for the accelerating expansion of the Universe. They also provide the origin of many elements in our periodic table, such as titanium, iron and nickel, which are formed in the extremely dense and hot conditions present during their explosions.
A major milestone has been achieved in our understanding of these explosive transients with the release of a major dataset, and associated 21 publications in an Astronomy & Astrophysics Special Issue, published today.
This unique dataset of nearly 4,000 nearby supernovae is many times larger than previous similar samples and has allowed crucial breakthroughs in understanding how these white dwarfs explode. The sample was obtained by Zwicky Transient Facility (ZTF), a Caltech-led astronomical sky survey, with key involvement of researchers at Trinity College Dublin, led by Prof. Kate Maguire in the School of Physics.
“Thanks to ZTF’s unique ability to scan the sky rapidly and deeply, it has been possible to discover new explosions of stars up to one million times fainter than the dimmest stars visible to the naked eye,” highlights Prof. Kate Maguire.
One of the key results, led by the group at Trinity, is the discovery that there are multiple exotic ways that white dwarfs can explode, including in collisions of two stars in luminous stellar spectacles, as well as the cannibalism of stars by their companions in double star systems.
This is only possible with this sample due to the ability to discover very faint blips combined with large sample sizes. And the surprising diversity may have implications for the use of these supernovae to measure distances in the Universe since the constraints on the properties of dark energy crucially demand that these explosions can be standardised.
“The diversity of ways that white dwarf stars can blow up is much greater than previously expected, resulting in explosions that range from being so faint they are barely visible to others that are bright enough to see for many months to years afterwards,” says Prof. Maguire.
Each star is a SN exploding with the size indicating how bright it appears and the colour indicating the colour of the supernova, they go from blue (hotter) to yellow (cooler) as they grow older and cool.
Journal
Astronomy and Astrophysics
Want some salt with that?
Deposits found on a nearby asteroid point to salty water in the outer Solar System
Kyoto University
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Colorized microscopic image of sodium carbonate deposit on Ryugu sample
view moreCredit: KyotoU/Toru Matsumoto
Kyoto, Japan -- Asteroids that orbit close to the Earth inevitably cause us some anxiety due to the even remote possibility of a collision. But their proximity also offers ample opportunities to learn more about the universe. Ryugu, a 900-meter diameter asteroid in the Apollo belt, has recently proven useful in our search for signs of life's precursors elsewhere in our Solar System.
A team of researchers at Kyoto University have found evidence of salt minerals in samples recovered from Ryugu during the initial phase of Japan's Hayabusa2 mission. The discovery of these deposits, containing sodium carbonate, halite, and sodium sulfates, suggest that liquid saline water once existed within a parent body of Ryugu.
Before examining the samples, the team expected that sample grains returned from the asteroid might contain substances not generally found in meteorites. They anticipated that these could be highly water-soluble materials, which readily react with moisture in Earth's atmosphere and are difficult to detect unless examined in their pristine state as preserved in the vacuum of space.
"Careful handling allowed us to identify the delicate salt minerals, providing a unique glimpse into Ryugu's chemical history," says corresponding researcher Toru Matsumoto.
Experts believe the asteroid was once part of a larger parent body that existed about 4.5 billion years ago, shortly after the formation of the solar system. This parent body would have been heated by radioactive decay, creating an environment of hot water below 100°C. While Ryugu and its grains did not contain any moisture, questions remain about how the liquid water was lost.
"These crystals tell us how liquid water disappeared from Ryugu's parent body," says Matsumoto. The salt crystals dissolve easily in water, suggesting that they could only have precipitated within highly saline water and in conditions with a limited amount of liquid.
"We hypothesized that as fractures exposed the saltwater to space or as the parent body cooled, this liquid could have either evaporated or frozen," Matsumoto explains. "The salt minerals we've found are the crystallized remnants of that water."
The deposits could prove crucial in comparing the evolved water in the dwarf planet Ceres -- located in the Asteroid Belt -- and the moons of Jupiter and Saturn, since researchers believe these icy bodies harbor subsurface oceans or liquid reservoirs. They expect sodium carbonates and halite will be found in surface deposits on Ceres, in water plumes from Saturn's satellite Enceladus, and on the surfaces of Jupiter's satellites Europa and Ganymede.
Since salt production is closely linked to the geological settings and brine chemistry in these aqueous bodies, the discovery of sodium salts in the Ryugu samples provide new insights for comparing the role that water has played in the development of planets and moons in the outer Solar System.
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The paper "Sodium carbonates on Ryugu as evidence of highly saline water in the outer Solar System" appeared on 18 November 2024 in Nature Astronomy, with doi: 10.1038/s41550-024-02418-1
About Kyoto University
Kyoto University is one of Japan and Asia's premier research institutions, founded in 1897 and responsible for producing numerous Nobel laureates and winners of other prestigious international prizes. A broad curriculum across the arts and sciences at undergraduate and graduate levels complements several research centers, facilities, and offices around Japan and the world. For more information, please see: http://www.kyoto-u.ac.jp/en
Journal
Nature Astronomy
Method of Research
Observational study
Subject of Research
Not applicable
Article Title
Sodium carbonates on Ryugu as evidence of highly saline water in the outer Solar System
New technology enhances gravitational-wave detection
Instrument developed at UC Riverside will help answer fundamental questions in physics and cosmology
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The new adaptive optical devices are designed to deliver ring-like targeted heating patterns to the surface of the 34-cm-diameter core optics in LIGO to control the effect of increasing thermal distortion as the laser power is increased toward the megawatt scale.
view moreCredit: Richardson lab, UC Riverside.
RIVERSIDE, Calif. -- In a paper published earlier this month in Physical Review Letters, a team of physicists led by Jonathan Richardson of the University of California, Riverside, showcases how new optical technology can extend the detection range of gravitational-wave observatories such as the Laser Interferometer Gravitational-Wave Observatory, or LIGO, and pave the way for future observatories.
Since 2015, observatories like LIGO have opened a new window on the universe. Plans for future upgrades to the 4-kilometer LIGO detectors and the construction of a next-generation 40-kilometer observatory, Cosmic Explorer, aim to push the gravitational-wave detection horizon to the earliest times in the history of the universe, before the first stars formed. However, realizing these plans hinges on achieving laser power levels exceeding 1 megawatt, far beyond LIGO’s capabilities today.
The research paper reports a breakthrough that will enable gravitational-wave detectors to reach extreme laser powers. It presents a new low-noise, high-resolution adaptive optics approach that can correct the limiting distortions of LIGO’s main 40-kilogram mirrors which arise with increasing laser power due to heating.
Richardson, an assistant professor of physics and astronomy, explains the paper’s findings in the following Q&A:
What are gravitational waves?
Gravitational waves are a new way to observe the universe. They are predicted by the equations of general relativity. When massive objects accelerate or collide in the universe, distortions in the fabric of space-time propagate out like ripples in a pond at the speed of light. These distortions are gravitational waves and, like electromagnetic waves, they carry energy and momentum. We now have a lot of information about the extreme astrophysical objects like black holes that create them and about the physics of the underlying nature of spacetime that these waves travel through to reach us.
How does LIGO work?
LIGO is one of the largest pieces of scientific equipment in the world. It consists of two 4 kilometers by 4 kilometers-long laser interferometers. One of these interferometers is in inland Washington State; the other is outside Baton Rouge, Louisiana. These sister sites operate in tandem, passively listening to any distortions of spacetime that might happen to propagate through Earth as a gravitational wave.
LIGO so far has seen about 200 events of stellar mass compact objects colliding and merging with each other. The overwhelming majority have been mergers of two black holes, but we’ve also seen mergers of neutron stars. I hope we may one day detect some source that is completely unexpected and unpredicted. If you look at the history of astronomy, every time we’ve developed electromagnetic telescopes that can observe a different wavelength of light than has never been observed before, we see the universe literally in a new light and have almost always discovered new types of objects visible in that wavelength band but not in others. I hope the same is true for gravitational waves.
Tell us about the instrument you’ve developed in your lab that has LIGO applications.
My focus at UCR is on developing new types of laser adaptive optical technology to overcome very fundamental physics limitations to how sensitive we can make detectors like LIGO. Across the majority of gravitational wave signal frequencies we can see from the ground, almost all of them are limited in sensitivity by quantum mechanics, by the quantum properties of the laser light itself that we use in the interferometer to bounce off mirrors. The instrument we’ve developed in my lab is designed to deliver precision optical corrections directly to the main mirrors of the LIGO interferometers. Our instrument is designed to sit just centimeters in front of the reflective surface of these mirrors and project very low noise corrective infrared radiation onto the front surface of the mirror. It is the first prototype for a totally new type of approach that uses non-imaging optical principles, which has never been used in gravitational wave detection before.
What is Cosmic Explorer?
Cosmic Explorer is the U.S. concept for a next-generation gravitational-wave observatory, after LIGO. It will be 10 times the size of LIGO, so that’s 40 by 40-kilometer-long interferometer arms. It will be the largest scientific instrument ever built. At their design sensitivity, these detectors will see the universe at earlier times than when the first stars are believed to have formed, when the universe was about 0.1% of its present 14-billion-year age. We will be able to see a snapshot of the universe at a very early stage in time.
Briefly, what does the research paper discuss?
The paper demonstrates that high-precision optical corrections are essential to expanding our gravitational-wave view of the universe. It lays out the potential implications for the impact we expect our new technology to have in the next generation of LIGO and in the years beyond that. Importantly, the paper shows that this type of technology is necessary and adequate to enable much higher levels of circulating laser power in the LIGO detectors than ever before. We expect this technology, and future versions of it, will be able to achieve more power in the interferometer.
Why is it important to do this research?
This research promises to answer some of the deepest questions in physics and cosmology, such as how fast the universe is expanding and the true nature of black holes. There are two contradicting measures right now of the local expansion rate of the universe, which gravitational waves can potentially resolve. Gravitational waves will also provide exquisitely high precision measurements of the detailed dynamics around the event horizons of black holes, allowing us to make direct tests of classical general relativity and alternative theories.
The University of California, Riverside is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California's diverse culture, UCR's enrollment is more than 26,000 students. The campus opened a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual impact of more than $2.7 billion on the U.S. economy. To learn more, visit www.ucr.edu.
Journal
Physical Review Letters
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Expanding the Quantum-Limited Gravitational-Wave Detection Horizon
Article Publication Date
15-Feb-2025
New research sheds light on using multiple CubeSats for in-space servicing and repair missions
University of Illinois Grainger College of Engineering
image:
Fuel-optimal trajectories of four servicing agents transporting modular components between the service vehicle and the target spacecraft, while satisfying anti-collision constraints.
view moreCredit: The Grainger College of Engineering at the University of Illinois Urbana-Champaign
As more satellites, telescopes, and other spacecraft are built to be repairable, it will take reliable trajectories for service spacecraft to reach them safely. Researchers in the Department of Aerospace Engineering in The Grainger College of Engineering, University of Illinois Urbana-Champaign are developing a methodology that will allow multiple CubeSats to act as servicing agents to assemble or repair a space telescope. Their method minimizes fuel consumption, guarantees that servicing agents never come closer to each other than 5 meters, and can be used to solve pathway guidance problems that aren’t space related.
“We developed a scheme that allows the CubeSats to operate efficiently without colliding,” said aerospace Ph.D. student Ruthvik Bommena. “These small spacecrafts have limited onboard computation capabilities, so these trajectories are precomputed by mission design engineers.”
Bommena and his faculty adviser Robyn Woollands demonstrated the performance of the algorithm by simulating two, three or four vehicle swarms simultaneously transporting modular components between a service vehicle and a space telescope undergoing in-space servicing.
“These are difficult trajectories to compute and calculate, but we came up with a novel technique that guarantees its optimality,” Bommena said.
Bommena said the most difficult aspect is the scale of the distances. The James Webb Space Telescope’s orbit is about 1.5 million kilometers away, at the Sun-Earth Lagrange Point 2. It’s where the gravitational force of the Sun and Earth balance each other, making it the perfect place in space for deep-space observation satellites to maintain orbit while facing away from the Sun.
“Without getting too technical, we used indirect optimization methods to guarantee that the output solution is fuel optimal. Direct methods do not guarantee that."
“We also incorporated the anti-collision path inequality constraints into the optimal control formulation as a hard constraint, so the spacecraft do not violate the constraint at any point during the trajectory.”
Bommena explained that traditional direct or indirect methods with constraints, such as collision-avoidance, break the trajectory into multiple arcs, increasing the complexity exponentially.
“Our methodology allows the trajectories to be solved as single arcs. We are just going from the starting point directly to the destination point. It’s more fuel optimal and more computationally efficient.”
Another major outcome from the research is the development of a novel target-relative circular restricted three-body problem dynamical model.
“We needed to mitigate the numerical challenges that come from the large distance between the Sun and the Earth,” Bommena said. “To do that, we first shifted the center of the frame along the x-axis from the Sun-Earth barycenter to the location of Lagrange point L2 and then derived the equations of motion relative to the target spacecraft. We also introduced a new distance unit by applying a scaling factor that proportionally adjusts in relation to the original distance measurement.”
Bommena said he and Woollands worked on this project for about a year and a half. His breakthrough came on a long-distance flight.
“The math was working on paper. The major problem we had was wrestling with numerics. I was coding during a long flight. I tried a couple of things and suddenly the solution converged. At first, I didn't believe it. That was a very exciting moment and the next few days felt awesome.”
Bommena said although the application for this work is to make in-space servicing and assembly safer and more efficient, the methodology they developed is very versatile and can be used in other trajectory optimization scenarios with different constraints.
This work was partially supported by Ten One Aerospace through a NASA STTR Phase I research grant.
The study, “Indirect Trajectory Optimization with Path Constraints for Multi-Agent Proximity Operations,” was written by Ruthvik Bommena and Robyn Woollands. It is published in The Journal of the Astronautical Sciences. DOI: 10.1007/s40295-024-00470-7
Journal
The Journal of the Astronautical Sciences
Article Title
Indirect Trajectory Optimization with Path Constraints for Multi-Agent Proximity Operations
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