Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Jack Oughton - Galaxy Formation Journal 02.docJack Oughton
1) The document discusses theories of galaxy formation from the early universe following the Big Bang.
2) It describes the top-down and bottom-up theories of galaxy formation, where top-down suggests the first objects to form were large irregular structures that later broke apart, and bottom-up suggests smaller dense areas first combined together to form galaxies.
3) The author argues the bottom-up theory of smaller areas hierarchically clustering together is most credible given current evidence of hierarchical clustering in the universe, but knowledge in this area remains limited.
1) New measurements of tungsten isotopes in lunar rocks indicate that the Moon formed later than previously thought, between 62-150 million years after the formation of the solar system, challenging current models of early planetary formation.
2) This later formation of the Moon requires revising our understanding of the timing of events like the giant impact that formed the Earth-Moon system and the solidification of the lunar magma ocean.
3) The new timeline suggests Earth's core may have formed independently of the giant impact and that magma oceans on Earth and other terrestrial planets took longer to solidify than models predicted.
First emergence of cold accretion and supermassive star formation in the earl...Sérgio Sacani
We investigate the first emergence of the so-called cold accretion, the accretion flows deeply penetrating a halo, in the early
universe with cosmological N-body/SPH simulations. We study the structure of the accretion flow and its evolution within
small halos with . 108 M with sufficiently high spatial resolutions down to ∼ 1 pc scale. While previous studies only
follow the evolution for a short period after the primordial cloud collapse, we follow the long-term evolution until the cold
accretion first appears, employing the sink particle method. We show that the cold accretion emerges when the halo mass
exceeds ∼ 2.2×107 M {(1 + 𝑧) /15}
−3/2
, the minimum halo masses above which the accretion flow penetrates halos. We further
continue simulations to study whether the cold accretion provides the dense shock waves, which have been proposed to give
birth to supermassive stars (SMSs). We find that the accretion flow eventually hits a compact disc near the halo centre, creating
dense shocks over a wide area of the disc surface. The resulting post-shock gas becomes dense and hot enough with its mass
comparable to the Jeans mass 𝑀J ∼ 104−5 M, a sufficient amount to induce the gravitational collapse, leading to the SMS
formation.
Large-scale Volcanism and the Heat Death of Terrestrial WorldsSérgio Sacani
This document discusses the potential for large igneous provinces (LIPs) to cause the "heat death" of terrestrial planets through massive volcanic eruptions that overwhelm the climate system. It examines the timing of LIP events on Earth to estimate the likelihood of nearly simultaneous eruptions. Statistical analysis of Earth's LIP record finds that eruptions within 0.1-1 million years of each other are likely. Simultaneous LIPs could have driven Venus into a runaway greenhouse effect like its current state. The timing of LIP events on Earth provides insight into potential past LIP activity on Venus that may have ended its hypothesized earlier temperate climate.
This document discusses evidence that the Moon-forming impact occurred later than previously thought, at around 95 million years after the formation of the solar system. The study uses simulations of planetary formation to show a correlation between the timing of the last giant impact and the amount of mass later accreted by the planet. Comparing this to highly siderophile element abundances in Earth's mantle, which constrain the amount of late-accreted mass, the study determines the Moon-forming impact was most likely 95 million years after solar system formation. Earlier times of 40 million years or less are ruled out at a 99.9% confidence level. The simulations include both classical scenarios and scenarios where Jupiter and Saturn migrated inward early in the solar
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
1) High-resolution gravity data from NASA's GRAIL mission shows distinctive "bulls-eye" patterns of gravity anomalies over lunar impact basins, with a central positive anomaly surrounded by a negative collar and outer positive annulus.
2) The document uses hydrocode modeling and finite element modeling to show that these mascon gravity patterns naturally result from the excavation and collapse of an impact crater, followed by post-impact isostatic adjustment and cooling/contraction of the melt pool.
3) The modeling is able to replicate the observed gravity anomalies of the Freundlich-Sharanov and Humorum basins, supporting the theory that mascons form through this impact and relaxation process rather than
Jack Oughton - Galaxy Formation Journal 02.docJack Oughton
1) The document discusses theories of galaxy formation from the early universe following the Big Bang.
2) It describes the top-down and bottom-up theories of galaxy formation, where top-down suggests the first objects to form were large irregular structures that later broke apart, and bottom-up suggests smaller dense areas first combined together to form galaxies.
3) The author argues the bottom-up theory of smaller areas hierarchically clustering together is most credible given current evidence of hierarchical clustering in the universe, but knowledge in this area remains limited.
1) New measurements of tungsten isotopes in lunar rocks indicate that the Moon formed later than previously thought, between 62-150 million years after the formation of the solar system, challenging current models of early planetary formation.
2) This later formation of the Moon requires revising our understanding of the timing of events like the giant impact that formed the Earth-Moon system and the solidification of the lunar magma ocean.
3) The new timeline suggests Earth's core may have formed independently of the giant impact and that magma oceans on Earth and other terrestrial planets took longer to solidify than models predicted.
First emergence of cold accretion and supermassive star formation in the earl...Sérgio Sacani
We investigate the first emergence of the so-called cold accretion, the accretion flows deeply penetrating a halo, in the early
universe with cosmological N-body/SPH simulations. We study the structure of the accretion flow and its evolution within
small halos with . 108 M with sufficiently high spatial resolutions down to ∼ 1 pc scale. While previous studies only
follow the evolution for a short period after the primordial cloud collapse, we follow the long-term evolution until the cold
accretion first appears, employing the sink particle method. We show that the cold accretion emerges when the halo mass
exceeds ∼ 2.2×107 M {(1 + 𝑧) /15}
−3/2
, the minimum halo masses above which the accretion flow penetrates halos. We further
continue simulations to study whether the cold accretion provides the dense shock waves, which have been proposed to give
birth to supermassive stars (SMSs). We find that the accretion flow eventually hits a compact disc near the halo centre, creating
dense shocks over a wide area of the disc surface. The resulting post-shock gas becomes dense and hot enough with its mass
comparable to the Jeans mass 𝑀J ∼ 104−5 M, a sufficient amount to induce the gravitational collapse, leading to the SMS
formation.
Large-scale Volcanism and the Heat Death of Terrestrial WorldsSérgio Sacani
This document discusses the potential for large igneous provinces (LIPs) to cause the "heat death" of terrestrial planets through massive volcanic eruptions that overwhelm the climate system. It examines the timing of LIP events on Earth to estimate the likelihood of nearly simultaneous eruptions. Statistical analysis of Earth's LIP record finds that eruptions within 0.1-1 million years of each other are likely. Simultaneous LIPs could have driven Venus into a runaway greenhouse effect like its current state. The timing of LIP events on Earth provides insight into potential past LIP activity on Venus that may have ended its hypothesized earlier temperate climate.
This document discusses evidence that the Moon-forming impact occurred later than previously thought, at around 95 million years after the formation of the solar system. The study uses simulations of planetary formation to show a correlation between the timing of the last giant impact and the amount of mass later accreted by the planet. Comparing this to highly siderophile element abundances in Earth's mantle, which constrain the amount of late-accreted mass, the study determines the Moon-forming impact was most likely 95 million years after solar system formation. Earlier times of 40 million years or less are ruled out at a 99.9% confidence level. The simulations include both classical scenarios and scenarios where Jupiter and Saturn migrated inward early in the solar
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
1) High-resolution gravity data from NASA's GRAIL mission shows distinctive "bulls-eye" patterns of gravity anomalies over lunar impact basins, with a central positive anomaly surrounded by a negative collar and outer positive annulus.
2) The document uses hydrocode modeling and finite element modeling to show that these mascon gravity patterns naturally result from the excavation and collapse of an impact crater, followed by post-impact isostatic adjustment and cooling/contraction of the melt pool.
3) The modeling is able to replicate the observed gravity anomalies of the Freundlich-Sharanov and Humorum basins, supporting the theory that mascons form through this impact and relaxation process rather than
Interior Heating of Rocky Exoplanets from Stellar Flares with Application to ...Sérgio Sacani
Many stars of different spectral types with planets in the habitable zone are known to emit flares. Until now, studies
that address the long-term impact of stellar flares and associated coronal mass ejections (CMEs) assumed that the
planet’s interior remains unaffected by interplanetary CMEs, only considering the effect of plasma/UV
interactions on the atmosphere of planets. Here, we show that the magnetic flux carried by flare-associated CMEs
results in planetary interior heating by ohmic dissipation and leads to a variety of interior–exterior interactions. We
construct a physical model to study this effect and apply it to the TRAPPIST-1 star whose flaring activity has been
constrained by Kepler observations. Our model is posed in a stochastic manner to account for uncertainty and
variability in input parameters. Particularly for the innermost planets, our results suggest that the heat dissipated in
the silicate mantle is both of sufficient magnitude and longevity to drive geological processes and hence facilitate
volcanism and outgassing of the TRAPPIST-1 planets. Furthermore, our model predicts that Joule heating can
further be enhanced for planets with an intrinsic magnetic field compared to those without. The associated
volcanism and outgassing may continuously replenish the atmosphere and thereby mitigate the erosion of the
atmosphere caused by the direct impact of flares and CMEs. To maintain consistency of atmospheric and
geophysical models, the impact of stellar flares and CMEs on atmospheres of close-in exoplanetary systems needs
to be studied in conjunction with the effect on planetary interiors.
Western US volcanism due to intruding oceanic mantle driven by ancient Farall...Sérgio Sacani
The origin of late Cenozoic intraplate volcanism over the western United States is debated. One important reason is the lack
of a clear understanding of the mantle dynamics during this volcanic history. Here we reconstruct the mantle thermal states
beneath North America since 20 million years ago using a hybrid inverse geodynamic model with data assimilation. The model
simultaneously satisfies the past subduction kinematics, present mantle tomographic image and the volcanic history. We find
that volcanism in both the Yellowstone volcanic province and the Basin and Range province corresponds to a similar eastwardintruding
mantle derived from beneath the Pacific Ocean and driven mostly by the sinking Farallon slab below the centraleastern
United States. The hot mantle that forms the Columbia River flood basalt and subsequent Yellowstone–Newberry
hotspot tracks first enters the western United States through tears within the Juan de Fuca slab. Subsequent coexistence of the
westward asthenospheric flow above the retreating Juan de Fuca slab and eastward-propagating mantle beyond the back-arc
region reproduces the bifurcating hotspot chains. A similar but weaker heat source intrudes below the Basin and Range around
the southern edge of the slab, and can explain the diffuse basaltic volcanism in this region. According to our models, the putative
Yellowstone plume contributes little to the formation of the Yellowstone volcanic province.
Our Sun. V. A Bright Young Sun Consistent with Helioseismology and Warm Temp...XequeMateShannon
The relatively warm temperatures required on early Earth and Mars have been difficult to account for via warming from greenhouse gases. We tested whether this problem can be resolved for both Earth and Mars by a young Sun that is brighter than predicted by the standard solar model. We computed high-precision solar evolutionary models with slightly increased initial masses of M_i = 1.01 to 1.07 M_sun; for each mass, we considered three different mass loss scenarios. We then tested whether these models were consistent with the current high-precision helioseismic observations. The relatively modest mass loss rates in these models are consistent with observational limits from young stars and estimates of the past solar wind obtained from lunar rocks, and do not significantly affect the solar lithium depletion. For appropriate initial masses, all three mass loss scenarios are capable of yielding a solar flux 3.8 Gyr ago high enough to be consistent with water on ancient Mars. We find that all of our mass-losing solar models are consistent with the helioseismic observations. The early solar mass loss of a few percent does indeed leave a small fingerprint on the Sun's internal structure. However, for helioseismology to significantly constrain early solar mass loss would require higher accuracy in the observed solar parameters and input physics, namely, by a factor of about 3 for the observed solar surface composition, and a factor of 2 for the solar interior opacities, the pp nuclear reaction rate, and the diffusion constants for gravitational settling.
Betelgeuse as a Merger of a Massive Star with a CompanionSérgio Sacani
This document summarizes a study that uses 3D hydrodynamic simulations and 1D stellar evolution modeling to investigate the merger of a 16 solar mass star with a 4 solar mass companion star. The simulations show the companion spirals inward and merges with the primary star's helium core. Approximately 0.6 solar masses of material is ejected in an asymmetric, bipolar outflow. The post-merger structure is then modeled in 1D stellar evolution, showing in some cases the star evolves to have surface properties similar to Betelgeus, with rapid rotation and enhanced nitrogen at the surface. This pioneering study aims to comprehensively model stellar mergers across dynamical, thermal, and nuclear evolutionary timescales.
Fizzy Super-Earths: Impacts of Magma Composition on the Bulk Density and Stru...Sérgio Sacani
Lava worlds are a potential emerging population of Super-Earths that are on close-in orbits around their host stars,
with likely partially molten mantles. To date, few studies have addressed the impact of magma on the observed
properties of a planet. At ambient conditions, magma is less dense than solid rock; however, it is also more
compressible with increasing pressure. Therefore, it is unclear how large-scale magma oceans affect planet
observables, such as bulk density. We update ExoPlex, a thermodynamically self-consistent planet interior
software, to include anhydrous, hydrous (2.2 wt% H2O), and carbonated magmas (5.2 wt% CO2). We find that
Earth-like planets with magma oceans larger than ∼1.5 R⊕ and ∼3.2 M⊕ are modestly denser than an equivalentmass
solid planet. From our model, three classes of mantle structures emerge for magma ocean planets: (1) a
mantle magma ocean, (2) a surface magma ocean, and (3) one consisting of a surface magma ocean, a solid rock
layer, and a basal magma ocean. The class of planets in which a basal magma ocean is present may sequester
dissolved volatiles on billion-year timescales, in which a 4 M⊕ mass planet can trap more than 130 times the mass
of water than in Earth’s present-day oceans and 1000 times the carbon in the Earth’s surface and crust.
- The document discusses two potential causes of the mass extinction event that wiped out the dinosaurs - massive volcanic activity from the Deccan Traps (in present-day India), and a large asteroid impact in what is now the Gulf of Mexico.
- Through climate and habitat modeling, the researchers found that scenarios involving prolonged global cooling from the asteroid impact led to a substantial reduction in suitable habitats for dinosaurs worldwide.
- In contrast, simulations of Deccan volcanism, even those with major global warming effects from carbon dioxide release, did not produce conditions severe enough to cause a dinosaur extinction.
- The asteroid impact may have been the primary driver of the non-avian dinosaur extinction, though volcanic warming likely reduced
Jack Oughton - Galaxy Formation Journal 02.docxJack Oughton
This document discusses theories of galaxy formation from the early universe following the Big Bang. It describes how small fluctuations in the initially uniform hydrogen/helium gas may have led to denser regions that accreted more mass over time through either a "top-down" or "bottom-up" process. The bottom-up theory, in which smaller clumps merged into larger structures, best matches current observational evidence of hierarchical galaxy clustering. However, fully explaining galaxy formation remains challenging due to uncertainties around gas dynamics and dark matter.
Hot Earth or Young Venus? A nearby transiting rocky planet mysterySérgio Sacani
Venus and Earth provide astonishingly different views of the evolution of a rocky planet, raising the question of why these two rock y worlds evolv ed so differently. The recently disco v ered transiting Super-Earth LP 890-9c (TOI-4306c, SPECULOOS-2c) is a key to the question. It circles a nearby M6V star in 8.46 d. LP890-9c receives similar flux as modern Earth, which puts it very close to the inner edge of the Habitable Zone (HZ), where models differ strongly in their prediction of how long rocky planets can hold onto their water. We model the atmosphere of a hot LP890-9c at the inner edge of the HZ, where the planet could sustain several very different environments. The resulting transmission spectra differ considerably between a hot, wet exo-Earth, a steamy planet caught in a runaway greenhouse, and an exo-Venus. Distinguishing these scenarios from the planet’s spectra will provide critical new insights into the evolution of hot terrestrial planets into exo-Venus. Our model and spectra are available online as a tool to plan observations. They show that observing LP890-9c can provide key insights into the evolution of a rocky planet at the inner edge of the HZ as well as the long-term future of Earth.
Compositional and thermal state of the lower mantle from joint 3D inversion w...Sérgio Sacani
This study jointly inverted seismic tomography and mineral elasticity data to constrain the 3D compositional and thermal structure of Earth's lower mantle. The results show a silica-enriched lower mantle with a Mg/Si ratio lower than the upper mantle. Temperature distributions in the upper lower mantle follow a Gaussian profile, while the lowermost mantle does not. Compositional anomalies in the upper lower mantle are mainly thermal, while the lowermost mantle anomalies are mainly compositional or phase variations. The large low shear velocity provinces in the lowermost mantle have higher temperatures and densities than the surrounding mantle, supporting the hypothesis that they originate from an ancient basal magna ocean.
The magma ocean stage in the formation of rocky-terrestrial planetsAdvanced-Concepts-Team
1) The document discusses the magma ocean stage in the early formation of rocky terrestrial planets like Earth. A magma ocean is a liquid layer at the surface after giant impacts melt the mantle.
2) Energy input from impacts and radioactive decay in the early solar system led to magma oceans. The talk analyzes how atmospheric thermal blanketing could prolong the magma ocean stage for millions of years.
3) The model results show that on Earth, the magma ocean likely lasted a few million years. During this stage, CO2 degassed from the interior early while H2O degassed later, and the atmosphere switched from being CO2-dominated to H2O-dominated over
X-Ray-luminous Supernovae: Threats to Terrestrial BiospheresSérgio Sacani
The spectacular outbursts of energy associated with supernovae (SNe) have long motivated research into their
potentially hazardous effects on Earth and analogous environments. Much of this research has focused primarily on
the atmospheric damage associated with the prompt arrival of ionizing photons within days or months of the initial
outburst, and the high-energy cosmic rays that arrive thousands of years after the explosion. In this study, we turn
the focus to persistent X-ray emission, arising in certain SNe that have interactions with a dense circumstellar
medium and observed months and/or years after the initial outburst. The sustained high X-ray luminosity leads to
large doses of ionizing radiation out to formidable distances. We assess the threat posed by these X-ray-luminous
SNe for Earth-like planetary atmospheres; our results are rooted in the X-ray SN observations from Chandra, Swift-
XRT, XMM-Newton, NuSTAR, and others. We find that this threat is particularly acute for SNe showing evidence
of strong circumstellar interaction, such as Type IIn explosions, which have significantly larger ranges of influence
than previously expected and lethal consequences up to ∼50 pc away. Furthermore, X-ray-bright SNe could pose a
substantial and distinct threat to terrestrial biospheres and tighten the Galactic habitable zone. We urge follow-up
X-ray observations of interacting SNe for months and years after the explosion to shed light on the physical nature
and full-time evolution of the emission and to clarify the danger that these events pose for life in our galaxy and
other star-forming regions.
The document describes simulations of a collision between the Moon and a companion moon approximately 1/3 the diameter of the Moon. The simulations found that at the modeled subsonic impact velocity, the companion moon did not form an impact crater but was instead accreted onto the Moon's surface. This added material contributed a hemispheric layer comparable to the extent and thickness of the lunar farside highlands. The collision also displaced the Moon's magma ocean to the opposite hemisphere, potentially explaining the observed concentration of KREEP materials. The findings suggest this late accretion event could explain the geological dichotomy between the lunar near and farside regions.
1) New data from the GRAIL gravity mission and LOLA altimetry is helping to determine the structure of the lunar highlands crust.
2) Preliminary GRAIL gravity models show noise levels are lower than expected, indicating signals exist at even shorter wavelengths than planned.
3) Combined analysis of gravity and topography data can provide insights into crustal thickness, elastic properties of the lithosphere, and the thermal state during and after bombardment.
Os astrônomos descobriram um processo único sobre como as maiores galáxias elípticas do universo continuam gerando estrelas muito tempo depois do anos de pico de nascimentos estelares. A alta resolução e a sensibilidade à radiação ultravioleta do Hubble, permitiu aos astrônomos observarem nós brilhantes de estrelas azuis, quentes, se formando juntamente com jatos de buracos negros ativos encontrados nos centros das gigantescas galáxias elípticas.
Combinando dados do Huubble com observações feitas por um conjunto de telescópios baseados tanto em Terra como no espaço, duas equipes independentes descobriram que os jatos dos buracos negros, e as estrelas recém-nascidas são todos partes de um ciclo auto-regulado. Jatos de alta energia atirados do buraco negro aquecem um halo de gás circulante, controlando a taxa com a qual o gás esfria e cai na galáxia.
“Pense no gás ao redor da galáxia como uma atmosfera”, explicou o líder do primeiro estudo, Megan Donahue, da Universidade Estadual do Michigan. “Essa atmosfera pode conter material em diferentes estados, do mesmo modo que a nossa atmosfera tem gás, nuvens e chuva. O que nós estamos vendo é um processo parecido com uma tempestade. À medida que os jatos impulsionam o gás para fora do centro da galáxia, parte do gás esfria e precipita em aglomerados frios que caem de volta para o centro da galáxia como gotas de chuvas”.
“As gotas de chuva eventualmente esfriam o suficiente para tornar-se nuvens de formação de estrelas de gás frio molecular, e a capacidade de observar no ultravioleta distante do Hubble, nos permitiu observar diretamente esses chuviscos de formação de estrelas”, explicou o líder do segundo estudo, Grant Tremblay, da Universidade de Yale. “Nós sabemos que esses chuviscos estão linkados com os jatos, pois eles foram encontrados em filamentos que se dobram ao redor dos jatos, ou abraçam as bordas de bolhas gigantes que os jatos inflaram”, disse Tremblay. “E eles terminam fazendo um redemoinho de gás de formação de estrelas ao redor do buraco negro central”.
1. The formation and evolution of the Solar System began about 4.57 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center to form the Sun, while the rest flattened into a protoplanetary disk from which the planets, moons, asteroids and other small bodies formed.
2. According to the nebular hypothesis, Earth formed about 4.54 billion years ago from accretion of planetary material in the solar nebula. Within the first 100-200 million years, early Earth had formed extensive oceans and seas.
3. Key events in the development of early Earth included the formation of its layered internal structure through the sinking of
Exploring Martian Magnetic Fields with a HelicopterSérgio Sacani
The era of helicopter-based surveys on Mars has already begun, creating opportunities for future aerial science
investigations with a range of instruments. We argue that magnetometer-based studies can make use of aerial
technology to answer some of the key questions regarding early Mars evolution. As such, we discuss mission
concepts for a helicopter equipped with a magnetometer on Mars, measurements it would provide, and survey
designs that could be implemented. For a range of scenarios, we build magnetization models and test how well
structures can be resolved using a range of different inversion approaches. With this work, we provide modeling
ground work and recommendations to plan the future of aerial Mars exploration.
Timeless Cosmology: Towards a Geometric Origin of Cosmological CorrelationsDanielBaumann11
The document summarizes a colloquium talk about the origin of structure in the universe. It discusses how cosmological correlations provide clues about early universe physics before the hot Big Bang, including evidence that primordial fluctuations were scale invariant. Recent work has developed a "cosmological bootstrap" approach to derive correlation functions by imposing physical consistency conditions rather than directly computing time integrals. This approach reveals differential equations whose solutions encode particle production during inflation and emerge time evolution, providing a new perspective on cosmology without time.
La historia de la vida en la Tierra y en otras plataformas planetarios potenciales portadoras de vida están profundamente ligadas a la historia del Universo. Puesto que la vida, tal como la conocemos, se basa en elementos químicos forjados en estrellas pesadas moribundas, el Universo tiene que ser lo suficientemente antiguo para que las estrellas se formaran y evolucionaran. La teoría cosmológica actual indica que el Universo es de 13,7 ± 0,13 mil millones de años y que las primeras estrellas se formaron cientos de millones de años después del Big Bang. En este trabajo, se argumenta que podemos dividir la historia cosmológica en cuatro edades, desde el Big Bang a la vida inteligente.
The document summarizes key evidence that supports the Big Bang theory of the origin and evolution of the universe. It describes how the Big Bang resulted in the rapid expansion and cooling of the early universe from an incredibly dense and hot state approximately 13.7 billion years ago. It explains how elements like hydrogen, helium, and lithium were formed during nucleosynthesis in the first moments after the Big Bang, and how their cosmic abundances match predictions. It also discusses the cosmic microwave background radiation and redshifts of distant galaxies as further evidence for the Big Bang.
The document summarizes the Rare Earth Hypothesis, which argues that the emergence of complex life on Earth required an improbable combination of astrophysical and geophysical events. It outlines various finely tuned parameters needed for a planet to support life, including properties of the star, planet, atmosphere, water, and biochemistry. The probability of these factors aligning on a planet is estimated to be as low as 1 in 1024, suggesting that complex life is uniquely rare in the universe.
Compositions of iron-meteorite parent bodies constrainthe structure of the pr...Sérgio Sacani
Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System,and they preserve information about conditions and planet-forming processes in thesolar nebula. In this study, we include comprehensive elemental compositions andfractional-crystallization modeling for iron meteorites from the cores of five differenti-ated asteroids from the inner Solar System. Together with previous results of metalliccores from the outer Solar System, we conclude that asteroidal cores from the outerSolar System have smaller sizes, elevated siderophile-element abundances, and simplercrystallization processes than those from the inner Solar System. These differences arerelated to the formation locations of the parent asteroids because the solar protoplane-tary disk varied in redox conditions, elemental distributions, and dynamics at differentheliocentric distances. Using highly siderophile-element data from iron meteorites, wereconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across theprotoplanetary disk within the first million years of Solar-System history. CAIs, the firstsolids to condense in the Solar System, formed close to the Sun. They were, however,concentrated within the outer disk and depleted within the inner disk. Future modelsof the structure and evolution of the protoplanetary disk should account for this dis-tribution pattern of CAIs.
Signatures of wave erosion in Titan’s coastsSérgio Sacani
The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it isunclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theo-retical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion,but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titanremain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively dis-cern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combinelandscape evolution models with measurements of shoreline shape on Earth to characterize how differentcoastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that theshorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded bywaves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates atfetch lengths of tens of kilometers.
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Interior Heating of Rocky Exoplanets from Stellar Flares with Application to ...Sérgio Sacani
Many stars of different spectral types with planets in the habitable zone are known to emit flares. Until now, studies
that address the long-term impact of stellar flares and associated coronal mass ejections (CMEs) assumed that the
planet’s interior remains unaffected by interplanetary CMEs, only considering the effect of plasma/UV
interactions on the atmosphere of planets. Here, we show that the magnetic flux carried by flare-associated CMEs
results in planetary interior heating by ohmic dissipation and leads to a variety of interior–exterior interactions. We
construct a physical model to study this effect and apply it to the TRAPPIST-1 star whose flaring activity has been
constrained by Kepler observations. Our model is posed in a stochastic manner to account for uncertainty and
variability in input parameters. Particularly for the innermost planets, our results suggest that the heat dissipated in
the silicate mantle is both of sufficient magnitude and longevity to drive geological processes and hence facilitate
volcanism and outgassing of the TRAPPIST-1 planets. Furthermore, our model predicts that Joule heating can
further be enhanced for planets with an intrinsic magnetic field compared to those without. The associated
volcanism and outgassing may continuously replenish the atmosphere and thereby mitigate the erosion of the
atmosphere caused by the direct impact of flares and CMEs. To maintain consistency of atmospheric and
geophysical models, the impact of stellar flares and CMEs on atmospheres of close-in exoplanetary systems needs
to be studied in conjunction with the effect on planetary interiors.
Western US volcanism due to intruding oceanic mantle driven by ancient Farall...Sérgio Sacani
The origin of late Cenozoic intraplate volcanism over the western United States is debated. One important reason is the lack
of a clear understanding of the mantle dynamics during this volcanic history. Here we reconstruct the mantle thermal states
beneath North America since 20 million years ago using a hybrid inverse geodynamic model with data assimilation. The model
simultaneously satisfies the past subduction kinematics, present mantle tomographic image and the volcanic history. We find
that volcanism in both the Yellowstone volcanic province and the Basin and Range province corresponds to a similar eastwardintruding
mantle derived from beneath the Pacific Ocean and driven mostly by the sinking Farallon slab below the centraleastern
United States. The hot mantle that forms the Columbia River flood basalt and subsequent Yellowstone–Newberry
hotspot tracks first enters the western United States through tears within the Juan de Fuca slab. Subsequent coexistence of the
westward asthenospheric flow above the retreating Juan de Fuca slab and eastward-propagating mantle beyond the back-arc
region reproduces the bifurcating hotspot chains. A similar but weaker heat source intrudes below the Basin and Range around
the southern edge of the slab, and can explain the diffuse basaltic volcanism in this region. According to our models, the putative
Yellowstone plume contributes little to the formation of the Yellowstone volcanic province.
Our Sun. V. A Bright Young Sun Consistent with Helioseismology and Warm Temp...XequeMateShannon
The relatively warm temperatures required on early Earth and Mars have been difficult to account for via warming from greenhouse gases. We tested whether this problem can be resolved for both Earth and Mars by a young Sun that is brighter than predicted by the standard solar model. We computed high-precision solar evolutionary models with slightly increased initial masses of M_i = 1.01 to 1.07 M_sun; for each mass, we considered three different mass loss scenarios. We then tested whether these models were consistent with the current high-precision helioseismic observations. The relatively modest mass loss rates in these models are consistent with observational limits from young stars and estimates of the past solar wind obtained from lunar rocks, and do not significantly affect the solar lithium depletion. For appropriate initial masses, all three mass loss scenarios are capable of yielding a solar flux 3.8 Gyr ago high enough to be consistent with water on ancient Mars. We find that all of our mass-losing solar models are consistent with the helioseismic observations. The early solar mass loss of a few percent does indeed leave a small fingerprint on the Sun's internal structure. However, for helioseismology to significantly constrain early solar mass loss would require higher accuracy in the observed solar parameters and input physics, namely, by a factor of about 3 for the observed solar surface composition, and a factor of 2 for the solar interior opacities, the pp nuclear reaction rate, and the diffusion constants for gravitational settling.
Betelgeuse as a Merger of a Massive Star with a CompanionSérgio Sacani
This document summarizes a study that uses 3D hydrodynamic simulations and 1D stellar evolution modeling to investigate the merger of a 16 solar mass star with a 4 solar mass companion star. The simulations show the companion spirals inward and merges with the primary star's helium core. Approximately 0.6 solar masses of material is ejected in an asymmetric, bipolar outflow. The post-merger structure is then modeled in 1D stellar evolution, showing in some cases the star evolves to have surface properties similar to Betelgeus, with rapid rotation and enhanced nitrogen at the surface. This pioneering study aims to comprehensively model stellar mergers across dynamical, thermal, and nuclear evolutionary timescales.
Fizzy Super-Earths: Impacts of Magma Composition on the Bulk Density and Stru...Sérgio Sacani
Lava worlds are a potential emerging population of Super-Earths that are on close-in orbits around their host stars,
with likely partially molten mantles. To date, few studies have addressed the impact of magma on the observed
properties of a planet. At ambient conditions, magma is less dense than solid rock; however, it is also more
compressible with increasing pressure. Therefore, it is unclear how large-scale magma oceans affect planet
observables, such as bulk density. We update ExoPlex, a thermodynamically self-consistent planet interior
software, to include anhydrous, hydrous (2.2 wt% H2O), and carbonated magmas (5.2 wt% CO2). We find that
Earth-like planets with magma oceans larger than ∼1.5 R⊕ and ∼3.2 M⊕ are modestly denser than an equivalentmass
solid planet. From our model, three classes of mantle structures emerge for magma ocean planets: (1) a
mantle magma ocean, (2) a surface magma ocean, and (3) one consisting of a surface magma ocean, a solid rock
layer, and a basal magma ocean. The class of planets in which a basal magma ocean is present may sequester
dissolved volatiles on billion-year timescales, in which a 4 M⊕ mass planet can trap more than 130 times the mass
of water than in Earth’s present-day oceans and 1000 times the carbon in the Earth’s surface and crust.
- The document discusses two potential causes of the mass extinction event that wiped out the dinosaurs - massive volcanic activity from the Deccan Traps (in present-day India), and a large asteroid impact in what is now the Gulf of Mexico.
- Through climate and habitat modeling, the researchers found that scenarios involving prolonged global cooling from the asteroid impact led to a substantial reduction in suitable habitats for dinosaurs worldwide.
- In contrast, simulations of Deccan volcanism, even those with major global warming effects from carbon dioxide release, did not produce conditions severe enough to cause a dinosaur extinction.
- The asteroid impact may have been the primary driver of the non-avian dinosaur extinction, though volcanic warming likely reduced
Jack Oughton - Galaxy Formation Journal 02.docxJack Oughton
This document discusses theories of galaxy formation from the early universe following the Big Bang. It describes how small fluctuations in the initially uniform hydrogen/helium gas may have led to denser regions that accreted more mass over time through either a "top-down" or "bottom-up" process. The bottom-up theory, in which smaller clumps merged into larger structures, best matches current observational evidence of hierarchical galaxy clustering. However, fully explaining galaxy formation remains challenging due to uncertainties around gas dynamics and dark matter.
Hot Earth or Young Venus? A nearby transiting rocky planet mysterySérgio Sacani
Venus and Earth provide astonishingly different views of the evolution of a rocky planet, raising the question of why these two rock y worlds evolv ed so differently. The recently disco v ered transiting Super-Earth LP 890-9c (TOI-4306c, SPECULOOS-2c) is a key to the question. It circles a nearby M6V star in 8.46 d. LP890-9c receives similar flux as modern Earth, which puts it very close to the inner edge of the Habitable Zone (HZ), where models differ strongly in their prediction of how long rocky planets can hold onto their water. We model the atmosphere of a hot LP890-9c at the inner edge of the HZ, where the planet could sustain several very different environments. The resulting transmission spectra differ considerably between a hot, wet exo-Earth, a steamy planet caught in a runaway greenhouse, and an exo-Venus. Distinguishing these scenarios from the planet’s spectra will provide critical new insights into the evolution of hot terrestrial planets into exo-Venus. Our model and spectra are available online as a tool to plan observations. They show that observing LP890-9c can provide key insights into the evolution of a rocky planet at the inner edge of the HZ as well as the long-term future of Earth.
Compositional and thermal state of the lower mantle from joint 3D inversion w...Sérgio Sacani
This study jointly inverted seismic tomography and mineral elasticity data to constrain the 3D compositional and thermal structure of Earth's lower mantle. The results show a silica-enriched lower mantle with a Mg/Si ratio lower than the upper mantle. Temperature distributions in the upper lower mantle follow a Gaussian profile, while the lowermost mantle does not. Compositional anomalies in the upper lower mantle are mainly thermal, while the lowermost mantle anomalies are mainly compositional or phase variations. The large low shear velocity provinces in the lowermost mantle have higher temperatures and densities than the surrounding mantle, supporting the hypothesis that they originate from an ancient basal magna ocean.
The magma ocean stage in the formation of rocky-terrestrial planetsAdvanced-Concepts-Team
1) The document discusses the magma ocean stage in the early formation of rocky terrestrial planets like Earth. A magma ocean is a liquid layer at the surface after giant impacts melt the mantle.
2) Energy input from impacts and radioactive decay in the early solar system led to magma oceans. The talk analyzes how atmospheric thermal blanketing could prolong the magma ocean stage for millions of years.
3) The model results show that on Earth, the magma ocean likely lasted a few million years. During this stage, CO2 degassed from the interior early while H2O degassed later, and the atmosphere switched from being CO2-dominated to H2O-dominated over
X-Ray-luminous Supernovae: Threats to Terrestrial BiospheresSérgio Sacani
The spectacular outbursts of energy associated with supernovae (SNe) have long motivated research into their
potentially hazardous effects on Earth and analogous environments. Much of this research has focused primarily on
the atmospheric damage associated with the prompt arrival of ionizing photons within days or months of the initial
outburst, and the high-energy cosmic rays that arrive thousands of years after the explosion. In this study, we turn
the focus to persistent X-ray emission, arising in certain SNe that have interactions with a dense circumstellar
medium and observed months and/or years after the initial outburst. The sustained high X-ray luminosity leads to
large doses of ionizing radiation out to formidable distances. We assess the threat posed by these X-ray-luminous
SNe for Earth-like planetary atmospheres; our results are rooted in the X-ray SN observations from Chandra, Swift-
XRT, XMM-Newton, NuSTAR, and others. We find that this threat is particularly acute for SNe showing evidence
of strong circumstellar interaction, such as Type IIn explosions, which have significantly larger ranges of influence
than previously expected and lethal consequences up to ∼50 pc away. Furthermore, X-ray-bright SNe could pose a
substantial and distinct threat to terrestrial biospheres and tighten the Galactic habitable zone. We urge follow-up
X-ray observations of interacting SNe for months and years after the explosion to shed light on the physical nature
and full-time evolution of the emission and to clarify the danger that these events pose for life in our galaxy and
other star-forming regions.
The document describes simulations of a collision between the Moon and a companion moon approximately 1/3 the diameter of the Moon. The simulations found that at the modeled subsonic impact velocity, the companion moon did not form an impact crater but was instead accreted onto the Moon's surface. This added material contributed a hemispheric layer comparable to the extent and thickness of the lunar farside highlands. The collision also displaced the Moon's magma ocean to the opposite hemisphere, potentially explaining the observed concentration of KREEP materials. The findings suggest this late accretion event could explain the geological dichotomy between the lunar near and farside regions.
1) New data from the GRAIL gravity mission and LOLA altimetry is helping to determine the structure of the lunar highlands crust.
2) Preliminary GRAIL gravity models show noise levels are lower than expected, indicating signals exist at even shorter wavelengths than planned.
3) Combined analysis of gravity and topography data can provide insights into crustal thickness, elastic properties of the lithosphere, and the thermal state during and after bombardment.
Os astrônomos descobriram um processo único sobre como as maiores galáxias elípticas do universo continuam gerando estrelas muito tempo depois do anos de pico de nascimentos estelares. A alta resolução e a sensibilidade à radiação ultravioleta do Hubble, permitiu aos astrônomos observarem nós brilhantes de estrelas azuis, quentes, se formando juntamente com jatos de buracos negros ativos encontrados nos centros das gigantescas galáxias elípticas.
Combinando dados do Huubble com observações feitas por um conjunto de telescópios baseados tanto em Terra como no espaço, duas equipes independentes descobriram que os jatos dos buracos negros, e as estrelas recém-nascidas são todos partes de um ciclo auto-regulado. Jatos de alta energia atirados do buraco negro aquecem um halo de gás circulante, controlando a taxa com a qual o gás esfria e cai na galáxia.
“Pense no gás ao redor da galáxia como uma atmosfera”, explicou o líder do primeiro estudo, Megan Donahue, da Universidade Estadual do Michigan. “Essa atmosfera pode conter material em diferentes estados, do mesmo modo que a nossa atmosfera tem gás, nuvens e chuva. O que nós estamos vendo é um processo parecido com uma tempestade. À medida que os jatos impulsionam o gás para fora do centro da galáxia, parte do gás esfria e precipita em aglomerados frios que caem de volta para o centro da galáxia como gotas de chuvas”.
“As gotas de chuva eventualmente esfriam o suficiente para tornar-se nuvens de formação de estrelas de gás frio molecular, e a capacidade de observar no ultravioleta distante do Hubble, nos permitiu observar diretamente esses chuviscos de formação de estrelas”, explicou o líder do segundo estudo, Grant Tremblay, da Universidade de Yale. “Nós sabemos que esses chuviscos estão linkados com os jatos, pois eles foram encontrados em filamentos que se dobram ao redor dos jatos, ou abraçam as bordas de bolhas gigantes que os jatos inflaram”, disse Tremblay. “E eles terminam fazendo um redemoinho de gás de formação de estrelas ao redor do buraco negro central”.
1. The formation and evolution of the Solar System began about 4.57 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center to form the Sun, while the rest flattened into a protoplanetary disk from which the planets, moons, asteroids and other small bodies formed.
2. According to the nebular hypothesis, Earth formed about 4.54 billion years ago from accretion of planetary material in the solar nebula. Within the first 100-200 million years, early Earth had formed extensive oceans and seas.
3. Key events in the development of early Earth included the formation of its layered internal structure through the sinking of
Exploring Martian Magnetic Fields with a HelicopterSérgio Sacani
The era of helicopter-based surveys on Mars has already begun, creating opportunities for future aerial science
investigations with a range of instruments. We argue that magnetometer-based studies can make use of aerial
technology to answer some of the key questions regarding early Mars evolution. As such, we discuss mission
concepts for a helicopter equipped with a magnetometer on Mars, measurements it would provide, and survey
designs that could be implemented. For a range of scenarios, we build magnetization models and test how well
structures can be resolved using a range of different inversion approaches. With this work, we provide modeling
ground work and recommendations to plan the future of aerial Mars exploration.
Timeless Cosmology: Towards a Geometric Origin of Cosmological CorrelationsDanielBaumann11
The document summarizes a colloquium talk about the origin of structure in the universe. It discusses how cosmological correlations provide clues about early universe physics before the hot Big Bang, including evidence that primordial fluctuations were scale invariant. Recent work has developed a "cosmological bootstrap" approach to derive correlation functions by imposing physical consistency conditions rather than directly computing time integrals. This approach reveals differential equations whose solutions encode particle production during inflation and emerge time evolution, providing a new perspective on cosmology without time.
La historia de la vida en la Tierra y en otras plataformas planetarios potenciales portadoras de vida están profundamente ligadas a la historia del Universo. Puesto que la vida, tal como la conocemos, se basa en elementos químicos forjados en estrellas pesadas moribundas, el Universo tiene que ser lo suficientemente antiguo para que las estrellas se formaran y evolucionaran. La teoría cosmológica actual indica que el Universo es de 13,7 ± 0,13 mil millones de años y que las primeras estrellas se formaron cientos de millones de años después del Big Bang. En este trabajo, se argumenta que podemos dividir la historia cosmológica en cuatro edades, desde el Big Bang a la vida inteligente.
The document summarizes key evidence that supports the Big Bang theory of the origin and evolution of the universe. It describes how the Big Bang resulted in the rapid expansion and cooling of the early universe from an incredibly dense and hot state approximately 13.7 billion years ago. It explains how elements like hydrogen, helium, and lithium were formed during nucleosynthesis in the first moments after the Big Bang, and how their cosmic abundances match predictions. It also discusses the cosmic microwave background radiation and redshifts of distant galaxies as further evidence for the Big Bang.
The document summarizes the Rare Earth Hypothesis, which argues that the emergence of complex life on Earth required an improbable combination of astrophysical and geophysical events. It outlines various finely tuned parameters needed for a planet to support life, including properties of the star, planet, atmosphere, water, and biochemistry. The probability of these factors aligning on a planet is estimated to be as low as 1 in 1024, suggesting that complex life is uniquely rare in the universe.
Similar to A Giant Impact Origin for the First Subduction on Earth (20)
Compositions of iron-meteorite parent bodies constrainthe structure of the pr...Sérgio Sacani
Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System,and they preserve information about conditions and planet-forming processes in thesolar nebula. In this study, we include comprehensive elemental compositions andfractional-crystallization modeling for iron meteorites from the cores of five differenti-ated asteroids from the inner Solar System. Together with previous results of metalliccores from the outer Solar System, we conclude that asteroidal cores from the outerSolar System have smaller sizes, elevated siderophile-element abundances, and simplercrystallization processes than those from the inner Solar System. These differences arerelated to the formation locations of the parent asteroids because the solar protoplane-tary disk varied in redox conditions, elemental distributions, and dynamics at differentheliocentric distances. Using highly siderophile-element data from iron meteorites, wereconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across theprotoplanetary disk within the first million years of Solar-System history. CAIs, the firstsolids to condense in the Solar System, formed close to the Sun. They were, however,concentrated within the outer disk and depleted within the inner disk. Future modelsof the structure and evolution of the protoplanetary disk should account for this dis-tribution pattern of CAIs.
Signatures of wave erosion in Titan’s coastsSérgio Sacani
The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it isunclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theo-retical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion,but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titanremain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively dis-cern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combinelandscape evolution models with measurements of shoreline shape on Earth to characterize how differentcoastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that theshorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded bywaves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates atfetch lengths of tens of kilometers.
SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole⋆Sérgio Sacani
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
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(
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−
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)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
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Ca-rich population. Although such an object is too red for any low-
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cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
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) with
Λ
CDM. Therefore unlike low-
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Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
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truly diverge from their low-
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counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...Sérgio Sacani
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...Sérgio Sacani
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDSSérgio Sacani
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
Anti-Universe And Emergent Gravity and the Dark UniverseSérgio Sacani
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional ‘dark’ gravitational force describing the ‘elastic’ response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton’s constant and the Hubble acceleration scale a0 = cH0, and provide evidence for the fact that this additional ‘dark gravity force’ explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
PPT on Sustainable Land Management presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
PPT on Alternate Wetting and Drying presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
Sexuality - Issues, Attitude and Behaviour - Applied Social Psychology - Psyc...PsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
CLASS 12th CHEMISTRY SOLID STATE ppt (Animated)eitps1506
Description:
Dive into the fascinating realm of solid-state physics with our meticulously crafted online PowerPoint presentation. This immersive educational resource offers a comprehensive exploration of the fundamental concepts, theories, and applications within the realm of solid-state physics.
From crystalline structures to semiconductor devices, this presentation delves into the intricate principles governing the behavior of solids, providing clear explanations and illustrative examples to enhance understanding. Whether you're a student delving into the subject for the first time or a seasoned researcher seeking to deepen your knowledge, our presentation offers valuable insights and in-depth analyses to cater to various levels of expertise.
Key topics covered include:
Crystal Structures: Unravel the mysteries of crystalline arrangements and their significance in determining material properties.
Band Theory: Explore the electronic band structure of solids and understand how it influences their conductive properties.
Semiconductor Physics: Delve into the behavior of semiconductors, including doping, carrier transport, and device applications.
Magnetic Properties: Investigate the magnetic behavior of solids, including ferromagnetism, antiferromagnetism, and ferrimagnetism.
Optical Properties: Examine the interaction of light with solids, including absorption, reflection, and transmission phenomena.
With visually engaging slides, informative content, and interactive elements, our online PowerPoint presentation serves as a valuable resource for students, educators, and enthusiasts alike, facilitating a deeper understanding of the captivating world of solid-state physics. Explore the intricacies of solid-state materials and unlock the secrets behind their remarkable properties with our comprehensive presentation.
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
Microbial interaction
Microorganisms interacts with each other and can be physically associated with another organisms in a variety of ways.
One organism can be located on the surface of another organism as an ectobiont or located within another organism as endobiont.
Microbial interaction may be positive such as mutualism, proto-cooperation, commensalism or may be negative such as parasitism, predation or competition
Types of microbial interaction
Positive interaction: mutualism, proto-cooperation, commensalism
Negative interaction: Ammensalism (antagonism), parasitism, predation, competition
I. Mutualism:
It is defined as the relationship in which each organism in interaction gets benefits from association. It is an obligatory relationship in which mutualist and host are metabolically dependent on each other.
Mutualistic relationship is very specific where one member of association cannot be replaced by another species.
Mutualism require close physical contact between interacting organisms.
Relationship of mutualism allows organisms to exist in habitat that could not occupied by either species alone.
Mutualistic relationship between organisms allows them to act as a single organism.
Examples of mutualism:
i. Lichens:
Lichens are excellent example of mutualism.
They are the association of specific fungi and certain genus of algae. In lichen, fungal partner is called mycobiont and algal partner is called
II. Syntrophism:
It is an association in which the growth of one organism either depends on or improved by the substrate provided by another organism.
In syntrophism both organism in association gets benefits.
Compound A
Utilized by population 1
Compound B
Utilized by population 2
Compound C
utilized by both Population 1+2
Products
In this theoretical example of syntrophism, population 1 is able to utilize and metabolize compound A, forming compound B but cannot metabolize beyond compound B without co-operation of population 2. Population 2is unable to utilize compound A but it can metabolize compound B forming compound C. Then both population 1 and 2 are able to carry out metabolic reaction which leads to formation of end product that neither population could produce alone.
Examples of syntrophism:
i. Methanogenic ecosystem in sludge digester
Methane produced by methanogenic bacteria depends upon interspecies hydrogen transfer by other fermentative bacteria.
Anaerobic fermentative bacteria generate CO2 and H2 utilizing carbohydrates which is then utilized by methanogenic bacteria (Methanobacter) to produce methane.
ii. Lactobacillus arobinosus and Enterococcus faecalis:
In the minimal media, Lactobacillus arobinosus and Enterococcus faecalis are able to grow together but not alone.
The synergistic relationship between E. faecalis and L. arobinosus occurs in which E. faecalis require folic acid
2. O’Neill et al., 2017), which may coincide with the period of magma ocean solidification. Recently, plume‐
induced subduction has been increasingly proposed as a viable mechanism for subduction initiation in the
early Earth (Baes et al., 2021). Nevertheless, it is unclear how to generate strong mantle plumes in a vigorous
convecting Hadean mantle (Korenaga, 2008).
The MGI is typically thought violent enough to melt a substantial portion or even the entire mantle, especially in
scenarios involving high energy and high angular momentum (Lock & Stewart, 2017; Nakajima & Steven-
son, 2015). Using two different giant impact computational methods with improved equations of state (Stewart
et al., 2020) and at high (Deng et al., 2019) and ultra‐high (Kegerreis et al., 2022) resolution, our recent work
(Yuan et al., 2023) demonstrates that the lower half of Earth's mantle would have remained mostly solid after a
canonical MGI. It also suggests that large intact domains of Theia's likely Fe‐rich mantle are candidates of the two
seismically‐observed large low‐shear velocity provinces (LLSVPs). Furthermore, the concomitant core formation
process during the MGI may substantially heat the core to raise the temperatures at the core‐mantle boundary
(CMB) (Canup, 2004; Deng et al., 2019). This unique thermochemical structure, featuring a solid lower mantle
and a hotter CMB resulting from the MGI, provides ideal conditions for the formation of strong mantle plumes, a
scenario less likely when the mantle and core are in equilibrium. Accretion scenarios built from only smaller‐scale
impacts dissipate more of their gravitational potential energy in the mantle and yield a more stable initial thermal
structure. Here, we test the hypothesis that such strong mantle plumes can be developed in the early Hadean,
weakening the lithosphere and eventually causing subduction initiation (Figure 1). We model this scenario using
2‐D and 3‐D whole‐mantle thermo‐chemical‐mechanical models with a visco‐elasto‐plastic rock rheology.
2. Geodynamic Models
We compute whole‐mantle convection models in 2D and 3D Cartesian geometries using Underworld2, an open‐
source, particle‐in‐cell, finite element code (Mansour et al., 2020; Moresi et al., 2007).
2.1. Governing Equations and Material Description
The computations solve the conservation equations of mass, momentum, and energy:
∇ · u = 0 (1)
∇ · σ′ ∇P + ρgẑ = 0 (2)
ρcp (
∂T
∂t
+ u · ∇T) ∇ · k∇T H = 0. (3)
Figure 1. A schematic illustration of the path from the Moon‐forming giant impact (MGI) to plume‐induced subduction in the
early Hadean. A canonical MGI (a) leads to a two‐layered mantle structure with a mostly solid lower mantle and an elevated
core‐mantle boundary temperature (b) (Deng et al., 2019; Yuan et al., 2023). After solidification of the upper magma ocean
within several million years (Hamano et al., 2013; Nikolaou et al., 2019), we assume a proto‐lithosphere gradually formed
over 50–100 million years (c), which was then destabilized and segmented by a mantle plume from an large low‐shear
velocity province made of the Theia mantle remnant (Yuan et al., 2023) (d).
Geophysical Research Letters 10.1029/2023GL106723
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3. where u is velocity, σ′ is deviatoric stress, P is pressure, T is temperature, ρ is density, g is gravitational accel-
eration, ẑ is the vertical unit vector, cp is heat capacity, k is thermal conductivity and H is heat production.
An incompressible Maxwell‐rheological model is adopted to reflect viscoelastic behavior:
ε̇ij =
1
2Ke
σ̇ij +
1
2η
σij (4)
where ε̇ij is the strain rate tensor, σ̇ij is the stress rate tensor, Ke is the shear modulus for elasticity, and η is the
viscosity. Non‐Newtonian and temperature‐dependent rheology is specified by:
η(T,ε̇) = η0e
( E
nRT
E
nRT0
)
(
ε̇
ε̇0
)
1 n
n
(5)
where E is the activation energy, R is the gas constant, and n is the exponent for shear thinning in dislocation
creep. Material yielding is included by imposing an upper limit on the stress, thus the effective viscosity becomes
ηeff = min(η(T,ε̇),
τy
ε̇II
) (6)
where τy is the yield stress and ε̇II is the second invariant of the strain rate tensor. The effective viscosity is
restricted to the range between 1018
and 1024
Pa s. The yield stress follows the Drucker–Prager yielding criteria
with an upper cut‐off:
τy = min C + μyp,τy0) (7)
where τy is the yield stress, C and μy are cohesion and friction coefficient, p is pressure, and τy0 is the maximum
yield stress.
Similar to previous studies (Li & Gurnis, 2022), weakening processes are approximated by reducing the yield
stress with plastic strain, following a two‐stage process: prior to a strain saturation, C and μy linearly decrease as
follows:
C = (τyf C0) min(
εP
εP0
,1) + C0 (8)
μy = μy0 μy0 min(
εP
εP0
,1) (9)
where the variables are the accumulated plastic strain εP, the reference plastic strain εP0 that determines the rate of
weakening (thus, the inverse of εP0 is the weakening rate), minimum yield stress τyf, initial cohesion C0, and initial
friction coefficient μy0.
Three materials are present within the model domain: a 30‐km‐thick mafic crust on top that can metamorphose to
eclogite at depth (Hacker et al., 2003), LLSVP material, and background mantle.
2.2. Model Setup in 2D
Most 2D models have a domain that is 5,780 × 2,890 km with 256 × 128 linear, quadrilateral elements, with 30
Lagrangian particles in each element. We have verified the validity of 2D results with a higher‐resolution grid of
512 × 256 elements, and in longer aspect ratio of 14,450 × 2,890 km with 640 × 128 elements. A free‐slip
boundary condition is applied to all model domain boundaries. The temperature at the upper boundary is
maintained at 273 K, and the bottom boundary is fixed at a varying temperature (5273 K down to 3273 K). The
lithosphere's maximum yield strength in 2D is set between 80 and 180 MPa. As seismic observations require that
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4. LLSVPs have a distinct bulk modulus (Tan & Gurnis, 2005), we use a depth‐dependent density profile within the
LLSVP. The values of physical parameters are listed in Table S1 of Supporting Information S1.
2.3. Model Setup in 3D
Three‐dimensional plume‐induced subduction computations are used to verify the 2D results and consist of a
Cartesian domain 2,890 km deep, 2,000 × 2,000 km horizontally. We use a resolution of 128 × 80 × 80 elements
with a uniform grid spacing in each coordinate direction. Each element initially has 30 material points randomly
located in each element. Free slip conditions are applied to all the boundaries. Maximum yield stresses of lith-
osphere between 60 and 100 MPa were tested in 3D.
3. Results
Following the MGI, a surface magma ocean extending to a certain depth is expected. Tracking magma ocean
solidification is beyond the scope of this study, but it is generally accepted that the solidification process would be
mostly complete within several million years (Hamano et al., 2013; Nikolaou et al., 2019). For simplicity, our
models begin 50 Myr after the magma ocean solidification; the initial state is derived from a 2D thermo-
mechanical model with a proto‐lithosphere defined by a half‐space cooling model with a prescribed age of 50 Ma.
Most model runs include an intrinsically dense layer of Theia mantle materials above the CMB. Current estimates
of the present‐day CMB temperature that account for a lower boundary layer range from ∼3473 to 4573 K
(Deschamps & Cobden, 2022), but because of Earth's secular cooling, the Hadean CMB temperature should have
been higher. Moreover, a hot CMB is anticipated after the MGI due to the deposition of Theia's iron core, as
shown in previous MGI simulations (Canup, 2004). Consequently, for most cases we used a higher CMB tem-
perature (5273 K) and a boundary‐layer contrast of 1273 K between the CMB and the initial LLSVP temperature.
Such high CMB temperature may lead to partial or complete melting in the boundary layer, but temperature
should drop quickly below the solidus of likely lower mantle compositions above the CMB. A thin partial melting
zone within the mantle does not substantially alter the dynamics, since the fully molten core sets the lower free
slip boundary condition in all cases. Furthermore, we note that similar or higher CMB temperatures were used in
previous convection simulations (Nakagawa & Tackley, 2010), and we confirm our results with lower CMB
temperatures (4273 and 3773 K). We mostly used a 80 MPa yield strength for the proto‐lithosphere (Rudi
et al., 2022).
Model runs with this initial configuration consistently show that a mantle plume nucleates atop the LLSVP‐like
thermochemical pile, ascends through the mantle, ruptures the lithosphere, and initiates subduction after ∼120
Myr (Figure 2). In detail, typical model evolution can be divided into several stages. First, the initial layer of
intrinsically dense material (Figure 2a) at the CMB concentrates into discrete piles due to a combination of strong
CMB heating and its depth‐dependent density (Tan & Gurnis, 2005). Meanwhile, the lithosphere grows thicker
due to inefficient cooling while in a stagnant‐lid convection, although the mode of magmatism may affect a
planet's tectonic regime (Lourenço et al., 2018). At 99 Myr, a strong mantle plume develops from the top of the
central pile (Figure 2b). This plume quickly rises to the upper mantle, becoming narrower due to the viscosity
decrease in the transition zone. As the plume approaches the surface, the lithosphere is locally weakened through
yielding above the plume and, at 109 Myr, the persistent localized thinning leads to plume penetration through the
lithosphere, forming a high‐temperature, low‐viscosity wedge structure (Figure 2c). Meanwhile, the proximal
lithosphere thickens around the plume head, resulting in two lithospheric‐scale shear bands on each side
(Figure 2c). The plume then starts to spread near the surface, overcoming the yield strength of the surrounding
lithosphere segments and forming shear zones along the subducting plate boundary that promote self‐sustaining
and retreating subduction at 123 Myr (Figure 2d).
Our reference case above shows that strong plumes can arise from the LLSVPs and initiate subduction when the
lithosphere's strength is less than 100 MPa, a threshold yield stress consistent with previous geodynamic studies
(Moresi & Solomatov, 1998; Van Heck & Tackley, 2008). Here, we aim to explore the maximum lithosphere
strength that the MGI‐caused mantle plumes can breach to initiate subduction and assess the influence of LLSVPs
on this capability (Figure 3). Initially, we increase the lithosphere yield strength from 80 to 100 MPa and find that
it becomes more challenging to induce subduction; subduction only occurs on one side of the plume head
(Figure 3a). When the lithosphere yield stress is further increased to 150 MPa, plumes from LLSVPs do not
penetrate through the lithosphere to induce subduction but instead spread at the base of the lithosphere
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5. (Figure 3b). Next, for the same calculation after removing LLSVPs materials, we find that strong plumes rising
from the CMB can initiate subduction, as shown in Figure 3c for a case with a yield stress of 150 MPa, and in
another case with a yield stress of 180 MPa (Figure 3d).
As studied in previous research on plume‐induced subduction, temperature, size, and buoyancy of plumes play a
major role in subduction initiation. Therefore, we systematically explore the influence of CMB temperature,
which significantly affects all these factors in models where plumes are self‐consistently generated. We lower the
CMB temperature to 4773 K (Figure 3e) and 3773 K (Figure 3f), and find an increase in the time delay for plume‐
induced subduction initiation (Figures 3i and 3j) due to the lower buoyancy of the plumes. Nonetheless, sub-
duction still occurs as long as CMB temperature is ≥3773 K. When CMB temperature is 3273 K, no subduction is
initiated (Figures 3g and 3k). However, if we assume that LLSVP materials are enriched in heat‐producing el-
ements for the same calculation (Citron et al., 2020), the results indicate that plumes rising from hotter LLSVPs
can still generate subduction (Figures 3h and 3l).
Figure 2. Temporal evolution for the temperature (left column) and viscosity (right column) fields of the reference case showing a LLSVP‐sourced plume inducing
subduction initiation. (a) Initial set up of the model; (b) Plume rising from the LLSVP; (c) Plume penetrates the lithosphere; (d) Slab retreat and melting of crust. The
yellow contours in temperature field marks the boundary of different materials including crust, lithosphere, molten materials, and large low‐shear velocity province
materials.
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6. Computations with different rheologies, compositions, lithosphere thicknesses, and model geometries showed
that these factors have a second‐order influence on outcomes compared to the maximum yield strength and CMB
temperature. Cases with different rheologies show that a smaller viscosity of the LLSVPs (Figures S1a in
Supporting Information S1), a larger reference viscosity (Figures S1b in Supporting Information S1), and a more
strongly temperature‐dependent viscosity (Figures S1c in Supporting Information S1) do not significantly alter
the plume‐induced subduction process, except for the onset time (77–320 Myr)—in general, higher mantle
viscosity leads to later plume‐induced subduction initiation. We considered cases with lower (Figures S1d in
Supporting Information S1) and higher (Figures S1e in Supporting Information S1) LLSVP density than the
reference case, as in our earlier work (Yuan and Li, 2022a, 2022b), as well as a more compressible (more depth‐
dependent density) LLSVP case (Figures S1f in Supporting Information S1). We find the overall dynamics of
these computations closely resemble those of the reference case. Different ages of the lithosphere from 25 to 100
Myr (Figures S2a–S2c in Supporting Information S1) and different weakening rates (Figures S2d and S2e in
Supporting Information S1) were also considered, and their results remain similar to the reference case. Models
with higher resolution and periodic boundary conditions (Figure S2f in Supporting Information S1), and a
different aspect ratio (5:1) (Figure S3 in Supporting Information S1) do not significantly differ in the results.
We further test our model using 3D whole‐mantle thermomechanical models, as plume‐induced subduction
necessitates a three‐dimensional perspective. As in the 2D geometry, we observe that strong mantle plumes can be
generated from the top of an LLSVP‐like pile (Figures 4a and 4b). As the plume rises and pierces the lithosphere
(Figure 4c), it spreads over broken lithosphere segments in a circular area, pushing them downward into the
mantle by overcoming their yield strength. As the plume continues to spread, the surface shear zones extend
deeper along the subducting plate boundary, which facilitates subduction and retreat of the circular subduction
zone (Figure 4d). The evolution resembles previous 3D models of plume‐initiated subduction in which the plume
Figure 3. Snapshots of viscosity and temperature field of eight representative cases with varying lithosphere yield stress (τy0) and core‐mantle boundary (CMB)
temperatures (T_cmb). Each panel from (a–h) represents a different calculation, with panels (i–l) corresponding to the viscosity field for cases in panels (e–h). In panels
(a–b), the lithosphere yield strength is 100, 150, 150, and 180 MPa, respectively. Note there are no large low‐shear velocity province (LLSVP) materials in panels (c–d).
For panels (e–g), the CMB temperature is 4773 K (e), 3773 K (f), 3273 K (g). Panel (h) has the same parameters as panel (g) except that the LLSVP materials
(Radi_LLSVP) are enriched in heat‐producing elements.
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7. was imposed (Gerya et al., 2015). In another 3D case, we find that a slightly higher yield strength for the lith-
osphere (80 MPa) does not significantly influence the results (Figure S4 in Supporting Information S1), but
subduction is not initiated if the lithosphere strength is 100 MPa as shown in another case (Figure S5 in Sup-
porting Information S1). However, if we simply remove LLSVP materials, plumes rising from the CMB can still
cause subduction initiation (Figure S6 in Supporting Information S1), similar to what we identified in our 2D
models. In the next 3D case, we lower the CMB temperature to 3773 K, the plume does not penetrate the lith-
osphere or initiate subduction (Figure S7 in Supporting Information S1). Thus, the systematic trends we identified
in 2D computations—that a higher CMB temperature is crucial in plume‐induced subduction when the litho-
sphere strength is not very strong—remain unchanged in 3D, though the threshold values may differ due to effect
of geometry, plume size and morphology.
4. Discussion and Conclusion
Hadean detrital zircons and anomalies in isotope ratios derived from short‐lived radioactive decay systems
support the notion that subduction operated in the Hadean (Hyung & Jacobsen, 2020; Valley et al., 2002; Watson
& Harrison, 2005). Lithospheric dripping, suggested as an alternative mechanism in early Earth tectonics, may
arise from plume‐lid interaction (Fischer & Gerya, 2016) or high magmatic intrusion/extrusion ratios (Lourenço
et al., 2020). However, lithospheric dripping represents non‐plate‐tectonic subduction, and a recent experimental
study (Hastie et al., 2023) lends support to subduction over the dripping mechanism for the formation of Earth's
earliest continental crust. Their results indicate that the absence of garnet in the lower crust would complicate the
initiation of the gravitational instability typically necessary for crustal drips and delamination, though not
necessarily in grain‐damage scenarios. Other studies suggest an early surface ocean could thermally weaken the
Figure 4. Temporal evolution for the viscosity (upper row) and compositional (lower row) field of the 3D reference case showing LLSVP‐sourced plume‐induced
subduction initiation. (a–) Model snapshots at 0 Myr (a), 104 Myr (b), 108 Myr (c), and 111 Myr (d), respectively.
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8. lithosphere, aiding subduction initiation (Korenaga, 2007). Yet, advanced models on crack formation and ser-
pentinization effects leading to subduction are still lacking. Plume‐induced subduction presents an appealing
mechanism for the earliest subduction initiation, as it does not necessitate pre‐existing weak zones or other
external forces (Baes et al., 2021). It also holds the potential to trigger plate tectonics (Gerya et al., 2015), but
developing such strong mantle plumes in an expected hot Hadean Earth is difficult. Our computations show that
there is a path to developing such plumes, and it is closely linked to the presumed MGI, which happened <150 Ma
before the oldest dated terrestrial zircons. Following the earliest subduction, the proto‐lithosphere can usually be
recycled globally, depending on lithosphere strength and plume‐slab interactions, with subsequent periods of
sluggish lid convection where the subducting slab periodically tears off, similar to the tectonic mode inferred for
early Earth (Foley, 2020).
The present model builds on results of high‐resolution MGI simulations that yield an end‐state with a largely solid
lower mantle (Yuan et al., 2023) and an expected increase in CMB temperature due to the gravitational deposition
of Theia's core during the agglomeration process (Asphaug, 2014). Although the exact CMB temperature increase
varies in different MGI models, it should be higher than that resulting from the core‐formation process during
previous smaller impacts (Nimmo, 2022). Pebble accretion may also increase CMB temperatures, while recent
studies suggest this mechanism is so efficient that it could melt the entire mantle (e.g., Johansen et al., 2023),
leaving no solid mantle to produce strong mantle plumes. Our results show that the unique context caused by the
MGI can give rise to strong mantle plumes capable of inducing subduction even when the maximum lithosphere
yield strength is >150 MPa, which is noticeably higher than inversions based on present‐day plate tectonics (Rudi
et al., 2022). In addition, our recent work suggests parts of Theia's iron‐rich mantle may persist over time and form
the seismically‐observed LLSVPs (Yuan et al., 2023). Here, we assess the influence of dense LLSVPs on sub-
duction initiation. Our results suggest that plumes rising from the CMB, rather than from LLSVPs, are more
capable of generating subduction and allow the mechanism to operate under a stronger lithosphere. In addition,
the timing of subduction due to the presence of LLSVPs is shown to be slightly later compared to the case where
plumes rise from the CMB, consistent with an earlier study (Kreielkamp et al., 2022). Nevertheless, our results
suggest that plumes rising from LLSVPs are still able to generate subduction to match the Hadean zircon records
as long as the CMB temperature is ≥3773 K. As the CMB temperature further decreases over time, plumes may
not be strong enough to induce new subduction (Figure 3e). However, if LLSVP materials are enriched in heat‐
producing elements, LLSVP‐sourced plumes may continue to trigger transient episodes of subduction (Figures 3h
and 3l). The enrichment of heat‐producing elements in LLSVPs can be created by Earth's internal differentiation
process (Citron et al., 2020). If LLSVPs are made of Theia's mantle (Yuan et al., 2023), they are likely also
enriched in heat‐producing elements, given that the canonical MGI suggests Theia resembles Mars, which has
been estimated to have higher heat‐producing elements than Earth (Table S2 in Supporting Information S1). Thus,
exploring the potential link between ancient plume‐induced subduction sites and the location of LLSVPs may
provide a powerful means to reconstruct global plate motions beyond 200 Ma.
Earth's unique convective regime, mobile‐lid plate tectonics, is distinctly absent on its twin planet, Venus. This is
true even though there are potential sites of subduction, at least on modern Venus, thought to be plume‐induced,
which do not apparently mature into full mobile‐lid tectonics. This may be due to the high surface temperature of
Venus, which allows rapid healing of damage along shear zones (Bercovici & Ricard, 2014) and arrests the
formation of continuous plate boundaries (Davaille et al., 2017). Alternatively, it may be harder to convert Venus
crust to eclogite, hindering development of planetary‐scale subduction (Chen et al., 2022). In addition to the
various ongoing differences between the two planets, another significant distinction may be the initial conditions.
The absence of a moon and a core‐generated dynamo suggest that Venus never experienced late Moon‐forming
giant impacts, based on planetary accretion models (Jacobson et al., 2017). Our proposed link between the MGI
and subduction initiation on Earth thus implies that the conditions for nucleation of early subduction on Earth may
have been absent on Venus. Given that a planet's tectonic development is history‐dependent (O’Neill et al., 2016),
the early giant impact events may play a crucial role in shaping their divergent evolutionary paths.
Data Availability Statement
The geodynamic code used in this work is available in Mansour et al. (2020). The model data on which this article
is based are available at figshare (Yuan, 2024). The code used to make the figures can be accessed at Tian
et al. (2023) and Ahrens et al. (2005).
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Acknowledgments
We appreciate the constructive comments
by Bradford Foley and an anonymous
reviewer, as well as the editor's efficient
handling of our study. Discussions with W.
Mao, M. Li. H. Deng, J. Kegerreis, Y.
Miyazaki, E. Asphaug are appreciated. Q.
Yuan acknowledges support from the O.K.
Earl Postdoctoral Fellowship at Caltech
and partial support by the NSF through
OCE‐2049086 and EAR‐2330810. We
acknowledge use of the Anvil
supercomputer at Purdue University
supported by the NSF ACCESS program
TG‐EAR160027. Some figures in this
study use the perceptually uniform color
map “batlow” (Crameri et al., 2020).
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