Researchers from France, China, the UK, and Greece revealed that the Petralona cranium is at least 286,000 years old, placing it firmly in the Middle Pleistocene era.
Category: 7. Science
-
Ancient Greek skull rewrites human evolutionary timeline
Ancient Greek skull rewrites human evolutionary timeline | The Jerusalem Post The reconstructed skull of a man who died 12,000 years ago in what is now Vietnam. (photo credit: C.M. Stimpson) ByJOANIE MARGULIES -
Europe’s largest recorded earthquake mystery finally solved in recent study
Researchers have finally unraveled the mystery behind Europe’s largest earthquake that struck Lisbon in 1755, killing tens of thousands in deadly calamity.
Researchers from the University of Lisbon in the recent study have found a piece of tectonic plate sinking in an area of the Atlantic Ocean under the Iberian Peninsula.
According to the findings, the piece was responsible for an 8.6 magnitude megaquake which was earlier considered an unknown seismic phenomenon.
The phenomenon called “lithosphere delamination” is responsible for causing such unprecedented seismic calamities. Earlier, this phenomenon had been observed on continents.
The study utilized sophisticated mapping techniques on a vast dataset from hundreds of land and ocean-bottom seismometers to construct a detailed model of the Earth’s structure down to 800km deep.
Beneath the Horseshoe Abyssal Plain, a region between the African and Eurasian plates, the researchers found a high velocity anomaly that is considered to be a sign of dense, sinking material.
The research also found that a portion of the oceanic plate is peeling away and sinking into the mantle. Due to which, there are deep faults but no obvious signs on the surface.
This process explains the genesis of massive historical quakes in the region.
Co-author of the study, Dr. Chiara Civiero from the University of Trieste stated, “This discovery opens up new avenues for understanding the evolution of the very early stages of oceanic subduction with important implications for plate tectonics.”
“If even areas without obvious surface faults, such as Horseshoe Abyssal Plain, can be subject to strong earthquakes, there is a need to revise seismic hazard models to include deep processes and structures that cannot be mapped using traditional methods.”
Continue Reading
-
Effects of population density on immunity and reproduction in bean beetles Callosobruchus maculatus
Noordwijk, A. J. & van de Jong, G. Acquisition and allocation of resources : their influence on variation in life history tactics. Am. Nat. 128, 137–142 (1986).
Stearns, S. C. Trade-offs in life-history evolution. Funct. Ecol. 3, 259–268 (1989).
Roff, D. A. Life History Evolution. (2002).
J Emlen, D. Environmental control of Horn length dimorphism in the beetle onthophagus acuminatus (Coleoptera: Scarabaeida). Proc. R Soc. Lond. B Biol. Sci. 256, 131–136 (1994).
Google Scholar
Moczek, A. P. & Emlen, D. J. Male Horn dimorphism in the scarab beetle, Onthophagus taurus: do alternative reproductive tactics favour alternative phenotypes? Anim. Behav. 59, 459–466 (2000).
Google Scholar
Braendle, C., Friebe, I., Caillaud, M. C. & Stern, D. L. Genetic variation for an aphid wing polyphenism is genetically linked to a naturally occurring wing polymorphism. Proc. R Soc. B Biol. Sci. 272, 657–664 (2005).
Yamane, T., Okada, K., Nakayama, S. & Miyatake, T. Dispersal and ejaculatory strategies associated with exaggeration of weapon in an armed beetle. Proc. R Soc. B Biol. Sci. 277, 1705–1710 (2010).
Smallegange, I. M., Deere, J. A. & Coulson, T. Correlative changes in life-history variables in response to environmental change in a model organism. Am. Nat. 183, 784–797 (2014).
Google Scholar
Katsuki, M. & Lewis, Z. A trade-off between pre- and post-copulatory sexual selection in a bean beetle. Behav. Ecol. Sociobiol. 69, 1597–1602 (2015).
Johnson, T. L., Symonds, M. R. E. & Elgar, M. A. Anticipatory flexibility: larval population density in moths determines male investment in antennae, wings and testes. Proc. R. Soc. B Biol. Sci. 284, (2017).
Peterson, M. L., Doak, D. F. & Morris, W. F. Both life-history plasticity and local adaptation will shape range-wide responses to climate warming in the tundra plant Silene acaulis. Glob Change Biol. 24, 1614–1625 (2018).
Google Scholar
Snell-Rood, E. C. & Moczek, A. P. Insulin signaling as a mechanism underlying developmental plasticity: the role of FOXO in a nutritional polyphenism. PLoS One 7.4, e34857 (2012).
Brommer, J. E. The evolution of fitness in life-history theory. Biol. Rev. 75, 377–404 (2000).
Google Scholar
Freitak, D., Wheat, C. W., Heckel, D. G. & Vogel, H. Immune system responses and fitness costs associated with consumption of bacteria in larvae of trichoplusia Ni. BMC Biol. 5, 56 (2007).
Google Scholar
Hanson, M. A., Lemaitre, B. & Unckless, R. L. Dynamic evolution of antimicrobial peptides underscores Trade-Offs between immunity and ecological fitness. Front Immunol 10, 2620 (2019).
Hosken, D. J. Sex and death: microevolutionary trade-offs between reproductive and immune investment in Dung flies. Curr. Biol. 11, 379–380 (2001).
Iglesias-Carrasco, M., Head, M. L., Jennions, M. D. & Cabido, C. Condition-dependent trade-offs between sexual traits, body condition and immunity: the effect of novel habitats. BMC Evol. Biol. 16, 1–10 (2016).
Leman, J. C. et al. Lovesick: immunological costs of mating to male sagebrush crickets. J. Evol. Biol. 22, 163–171 (2009).
Google Scholar
Fuxa, J. R. & Tanada, Y. Epizootiology of Insect Diseases (Wiley, 1991).
Wilson, K. & Cotter, S. Density-Dependent Prophylaxis in Insects. in Phenotypic Plasticity of Insects (eds. Whitman, D. & Ananthakrishnan, T.)Science Publishers, (2009). https://doi.org/10.1201/b10201-7
Møller, A. P. Parasites and sexual selection: current status of the Hamilton and Zuk hypothesis. J. Evol. Biol. 3, 319–328 (1990).
Dewsbury, D. A. The Darwin-Bateman paradigm in historical Context1. Integr. Comp. Biol. 45, 831–837 (2005).
Google Scholar
Janicke, T., Häderer, I. K., Lajeunesse, M. J. & Anthes, N. Darwinian sex roles confirmed across the animal Kingdom. Sci. Adv. 2, e1500983 (2016).
Google Scholar
Sheldon, B. C. & Verhulst, S. Ecological immunology: costly parasite defences and trade-offs in evolutionary ecology. Trends Ecol. Evol. 11, 317–321 (1996).
Google Scholar
Zuk, M. & McKean, K. A. Sex differences in parasite infections: patterns and processes. Int. J. Parasitol. 26, 1009–1024 (1996).
Google Scholar
Rolff, J. Bateman’s principle and immunity. Proc. R Soc. B Biol. Sci. 269, 867–872 (2002).
Marmaras, V. J., Charalambidis, N. D. & Zervas, C. G. Immune response in insects: the role of phenoloxidase in defense reactions in relation to melanization and sclerotization. Arch. Insect Biochem. Physiol. 31, 119–133 (1996).
Google Scholar
Gillespie, J. P., Kanost, M. R. & Trenczek, T. Biological mediators of insect immunity. Annu. Rev. Entomol. 42, 611–643 (1997).
Google Scholar
Kanost, M. R. & Gorman, M. J. Phenoloxidases in insect immunity. Insect Immunol. 1, 69–96 (2008).
Schmid-Hempel, P. Evolutionary ecology of insect immune defenses. Annu. Rev. Entomol. 50, 529–551 (2005).
Google Scholar
Roers, A., Hiller, B. & Hornung, V. Recognition of endogenous nucleic acids by the innate immune system. Immunity 44, 739–754 (2016).
Google Scholar
Kelly, C. D., Stoehr, A. M., Nunn, C., Smyth, K. N. & Prokop, Z. M. Sexual dimorphism in immunity across animals: a meta-analysis. Ecol. Lett. 21, 1885–1894 (2018).
Google Scholar
McAfee, A., Chapman, A., Pettis, J. S., Foster, L. J. & Tarpy, D. R. Trade-offs between sperm viability and immune protein expression in honey bee queens (Apis mellifera). Commun. Biol. 4, 1–11 (2021).
Gascoigne, S. J. L., Nalukwago, U., Barbosa, F. & D. I. & Larval density, sex, and allocation hierarchy affect life history trait covariances in a bean beetle. Am. Nat. 199, 291–301 (2022).
Google Scholar
Nokelainen, O., Lindstedt, C. & Mappes, J. Environment-mediated morph‐linked immune and life‐history responses in the aposematic wood tiger moth. J. Anim. Ecol. 82, 653–662 (2013).
Google Scholar
Silva, F. W. et al. Two’s a crowd: phenotypic adjustments and prophylaxis in Anticarsia gemmatalis larvae are triggered by the presence of conspecifics. PloS One. 8, e61582 (2013).
Google Scholar
Bailey, N. W., Gray, B. & Zuk, M. Does immunity vary with population density in wild populations of Mormon crickets? Evol. Ecol. Res. 10, 599–610 (2008).
Wilson, K. et al. Coping with crowds: density-dependent disease resistance in desert locusts. Proc. Natl. Acad. Sci. 99, 5471–5475 (2002).
Google Scholar
Kelly, C. D. & L’Heureux, V. Effect of rearing density on female investment in reproduction and melanotic encapsulation response in the sand cricket (Gryllus firmus) (Orthoptera: Gryllidae). Biol. J. Linn. Soc. 144, blae023 (2024).
Kelly, C. D., L’Heureux, V., Wey, T. W. & Réale, D. Effect of rearing density on the expression of fitness-related traits in male sand field crickets (Gryllus firmus). Evol. Ecol. 37, 835–846 (2023).
Rolff, J. & Siva-Jothy, M. T. Copulation corrupts immunity: a mechanism for a cost of mating in insects. Proc. Natl. Acad. Sci. 99, 9916–9918 (2002).
Google Scholar
Avila, F. W., Sirot, L. K., LaFlamme, B. A., Rubinstein, C. D. & Wolfner, M. F. Insect seminal fluid proteins: identification and function. Annu. Rev. Entomol. 56, 21–40 (2011).
Google Scholar
Immonen, E., Sayadi, A., Bayram, H. & Arnqvist, G. Mating changes sexually dimorphic gene expression in the seed beetle Callosobruchus maculatus. Genome Biol. Evol. 9, 677–699 (2017).
Google Scholar
Zera, A. J. The endocrine regulation of wing polymorphism in insects: state of the art, recent surprises, and future directions1. Integr. Comp. Biol. 43, 607–616 (2003).
Google Scholar
Wilson, K. Evolution of clutch size in insects. II. A test of static optimality models using the beetle Callosobruchus maculatus (Coleoptera: Bruchidae). J. Evol. Biol. 7, 365–386 (1994).
Vamosi, S. M. Interactive effects of larval host and competition on adult fitness: an experimental test with seed beetles (Coleoptera: Bruchidae). Funct. Ecol. 19, 859–864 (2005).
Beck, C. W. & Blumer, L. S. A handbook on bean beetles, Callosobruchus maculatus. Caryologia 24, 157–166 (2011).
Utida, S. Density dependent polymorphism in the adult of Callosobruchus maculatus (Coleoptera, Bruchidae). J. Stored Prod. Res. 8, 111–125 (1972).
Dougherty, L. R. et al. Sexual conflict and correlated evolution between male persistence and female resistance traits in the seed beetle Callosobruchus maculatus. Proc. R. Soc. B Biol. Sci. 284, (2017).
Rasband, W. S. ImageJ. (1997).
Microsystems, L. Leica application Suite version 2.0. (2010).
Peterson, R. A. Finding optimal normalizing transformations via bestNormalize. (2021).
SAS Institute Inc. JMP®. (1989).
Continue Reading
-
Nocturnal Spiders Use Trapped Fireflies as Glowing Bait to Attract Additional Prey, Study Confirms
Sheet-web spiders Psechrus clavis have been known to use their body color and webs as visual cues to deceptively lure and immediately consume insects. However, they do not immediately consume trapped male fireflies Diaphanes lampyroides; instead, the spiders retain them in their webs while the fireflies continue to emit their bioluminescent signal for up to an hour. According to a team of researchers from Tunghai University, the University of New South Wales, the University of Technology Sydney and the National Museum of Natural Science in Taichung, Taiwan, this observation raises the question: can the spiders exploit prey signals to attract additional prey, thereby enhancing their foraging success?
Sheet web spider with fireflies caught in web. Image credit: Tunghai University Spider.
Tunghai University researcher I-Min Tso and colleagues have observed Psechrus clavis spiders capturing fireflies in their webs and leaving them there while they emitted bioluminescent light for up to an hour.
They even observed the spiders going to check on the captured fireflies from time to time.
Intrigued by this unusual behavior, the study authors set up an experiment to test whether this was a strategy used by the spiders to increase their hunting success.
In the experiment, they placed LEDs that resembled fireflies, in real sheet spider webs and left other webs clear as controls.
They found three times the amount of prey was attracted to webs with the LEDs compared to the control webs.
This increased to ten times more prey when they only looked at fireflies being captured.
The findings confirm that captured fireflies left as bait increase the hunting success rate of the spiders.
The researchers also noticed that the majority of captured fireflies were male, who were likely mistaking the glow for potential mates.
“Our findings highlight a previously undocumented interaction where firefly signals, intended for sexual communication, are also beneficial to spiders,” Dr. Tso said.
“This study sheds new light on the ways that nocturnal sit-and-wait predators can rise to the challenges of attracting prey and provides a unique perspective on the complexity of predator-prey interactions.”
“This behavior could have developed in sheet web spiders to avoid costly investment in their own bioluminescence like other sit-and-wait predators, such as anglerfish.”
“Instead, the spiders are able to outsource prey attraction to their prey’s own signals.
Video footage captured by the scientists in their experiment shows sheet web spiders employing different strategies when interacting with different prey species.
Spiders would immediately consume any moths captured in their webs but would not immediately consume fireflies they captured.
“Handling prey in different ways suggests that the spider can use some kind of cue to distinguish between the prey species they capture and determine an appropriate response,” Dr. Tso said.
“We speculate that it is probably the bioluminescent signals of the fireflies that are used to identify fireflies enabling spiders to adjust their prey handling behavior accordingly.”
The study was published in the Journal of Animal Ecology.
_____
Ho Yin Yip et al. Prey bioluminescence-mediated visual luring in a sit and wait predator. Journal of Animal Ecology, published online August 27, 2025; doi: 10.1111/1365-2656.70102
Continue Reading
-
33 hungry SpaceX Raptors from below photo of the day for Sept. 1, 2025
Since its founding in 2002, SpaceX has worked to revolutionize the spaceflight industry, mainly through developing reusable rockets that can land and fly again. This includes the company’s Falcon 9 rocket, which has become the workhorse of global launches, ferrying cargo and astronauts to the International Space Station under contracts with NASA, among many other tasks.
But beyond the Falcon 9, SpaceX has been developing its Starship megarocket, which is designed to carry massive payloads and large crews on deep-space missions to the moon, Mars and beyond.
What is it?
In a recent post on X, SpaceX founder and CEO Elon Musk shared a photo taken from beneath the Starship spacecraft that was being prepped to launch on the vehicle’s 10th test flight. (That flight occurred on Aug. 26, and it went well.)
The photo shows the 33 Raptor engines of Super Heavy, Starship’s first stage, arranged in a dense circular pattern. Musk added in a separate post: “33 engines, each more than twice the power of all 4 engines on a 747.”
Where is it?
This photograph was taken at SpaceX’s Starbase site in South Texas, near Boca Chica, where the Starship system is built and tested.
A photo taken underneath Super Heavy, the first stage of SpaceX’s Starship megarocket, showing its many Raptor engines. (Image credit: Elon Musk via X.) Why is it amazing?
Packing 33 engines into a single stage presents some intense engineering challenges. Each Raptor engine must fire in perfect synchronization, maintaining stability during launch while withstanding extreme forces and vibrations.
As if this weren’t ambitious enough, Musk added the following in a thread on his original post: “Starship V4 will have 42 engines when 3 more Raptors are added to a significantly longer ship. That will fly in 2027.” With more engines providing additional thrust, systems like Starship can carry heavier payloads, making deep-space travel more achievable.
Want to learn more?
You can read more about SpaceX’s mission and its Starship system.
Continue Reading
-
Shrews Shrink and Regrow Brains, Offering Clues for Human Diseases
Summary: Scientists used non-invasive MRI to study shrews that seasonally shrink and regrow their brains, uncovering water loss as the key driver of this rare phenomenon. Despite losing about nine percent of their brain volume in winter, shrew brain cells remain alive, with aquaporin-4 proteins playing a key role in regulating water movement.
This discovery parallels mechanisms seen in human brain diseases, where brain volume loss typically leads to irreversible damage. Researchers hope studying how shrews regrow their brains could inspire novel approaches to treating neurodegenerative disorders.
Key Facts:
- Brain Shrinkage: Shrews lose about 9% of brain volume in winter without cell death.
- Water Balance: Aquaporin-4 proteins move water out of cells, preventing damage.
- Human Link: Mechanisms resemble Alzheimer’s and Parkinson’s, offering potential medical insights.
Source: Max Planck Institute
Common shrews are one of only a handful of mammals known to flexibly shrink and regrow their brains. This rare seasonal cycle, known as Dehnel’s phenomenon, has puzzled scientists for decades.
How can a brain lose volume and regrow months later without sustaining permanent damage?
A study using non-invasive MRI has scanned the brains of shrews undergoing shrinkage, identifying a key molecule involved in the phenomenon: water.
“Our shrews lost nine percent of their brains during shrinkage, but the cells did not die,” says first author Dr. Cecilia Baldoni, a postdoctoral researcher from the Max Planck Institute of Animal Behavior in Germany. “The cells lost water.”
Normally, brain cells that lose water become damaged and ultimately die, but in shrews, the opposite happened.
“The cells remained alive and even increased in number,” says Baldoni.
This finding solves a mystery—and opens up potential pathways for the treatment of human brain disease.
“We see that brain shrinkage in shrews matches closely what happens in patients suffering from Alzheimer’s, Parkinson’s, and other brain diseases,” says Associate Prof. John Nieland, an expert in human brain disease at Aalborg University, Denmark.
The study also shows that a specific protein known for regulating water—aquaporin 4—was likely involved in moving water out of the brain cells of shrews. “We see this same protein present in higher quantities in the diseased brains of humans, too,” says Nieland.
That the shrunken brains of shrews share characteristics with diseased human brains makes the case that these miniature mammals, with their ability to reverse brain loss, could also offer clues for medical treatments.
“The next step is to learn how shrews regrow their brains so that we might find ways to teach human brains to do the same,” Nieland adds.
Peering inside a shrinking brain
Dehnel’s phenomenon, or reversible brain shrinkage, is rare among animals. Up until now, it is known only in European moles, stoats and weasels, and some species of shrews. Among these, common shrews are the most studied. When undergoing Dehnel’s, their brains become smaller from summer to late winter, then regrow in spring.
Scientists call this reversible resizing “brain plasticity,” and it is thought to help shrews conserve energy when food is scarce.
“These tiny mammals, which are no bigger than your thumb, have to eat every few hours, whether it’s in summer when there’s lots to eat or in winter when there’s very little,” says Dina Dechmann, a group leader at the Max Planck Institute of Animal Behavior who has studied Dehnel’s phenomenon for over 13 years.
The researchers used high-resolution MRI to scan the brains of wild common shrews caught in Germany in summer and then recaptured in winter. The medical imaging technique allowed the scientists to non-invasively see inside the brains of living animals over seasons.
“In this way, we could track how the brains of individuals changed as they experienced shrinkage from summer to winter,” says senior author Prof. Dominik von Elverfeldt from the Faculty of Medicine at the University of Freiburg, Germany, who led the imaging.
They also compared these scans to microscopic examination of brain tissue in summer and winter to determine the number of cells at each stage.
How shrews pull off Dehnel’s
Overall, the brains of shrews in the study lost around nine percent volume in winter, which the team observed to be due to the movement of water out of brain cells. But when the team zoomed in on different brain regions, they noticed that not all areas shrank equally.
This uneven effect could explain Dehnel’s phenomenon’s great ecological paradox: how do animals survive with smaller brains?
“Shrews still need to find food, escape predators, and go about their daily lives all winter, which they manage to do with a smaller brain,” says Baldoni.
By human standards, says Nieland, “it’s astonishing what these shrews accomplish with brain loss of almost ten percent. We commonly see Alzheimer’s patients suffering from the same percentage brain reduction, and the loss of function in these patients is tremendous.”
The study’s neuroimaging results point to a potential answer. Most brain regions shrank in winter and exhibited consistent shifts in water balance characterized by less water inside the cells and more water surrounding them. However, the neocortex and cerebellum deviated from this general pattern, keeping a more stable balance of water inside and outside their cells.
“These regions are responsible for cognitive skills such as memory as well as motor control,” says Baldoni.
“The shrews seem to be adjusting their brains for winter like we might adjust heating in a house, keeping the essential rooms heated while dropping power in areas where we can afford to reduce operations.”
For the ecologists, the study explains the mechanism behind a rare seasonal strategy and raises new questions.
“Now that we understand the physiology better, we are keen to link this to the behavioral consequences of Dehnel’s phenomenon,” says Baldoni.
“How does having a smaller brain affect behavior? Can shrews solve the same navigational and coordination challenges in winter as they can in summer?”
Potential path to medical treatment?
For the neurologists, the story of what shrews can offer human medicine has just begun. Many brain diseases—Multiple Sclerosis, Parkinson’s disease, Amyotrophic Lateral Sclerosis (ALS), and Alzheimer’s disease—involve brain volume decline due to water loss. But for humans, this loss progresses in only one direction.
“So far, there is no treatment for any brain disease that can prevent or reverse this loss of brain volume,” says Nieland.
“We have now discovered, in shrews, an animal that is getting human-like symptoms of brain disease, but has biological tools not only to stop this process, but to reverse it too.”
The next step for the team is to study the second phase of Dehnel’s—the brain’s regrowth from winter to summer. By doing so, they hope to unlock clues for treating brain diseases.
Adds Nieland: “The idea that we might have a model animal that can help us learn how to treat diseases that are currently incurable is the most exciting thing I can think of.”
About this neuroscience and neuroplasticity research news
Author: Carla Avolio
Source: Max Planck Institute
Contact: Carla Avolio – Max Planck Institute
Image: The image is credited to Neuroscience NewsOriginal Research: Open access.
“Programmed seasonal brain shrinkage in the common shrew via water loss without cell death” by Cecilia Baldoni et al. Current Biology
Abstract
Programmed seasonal brain shrinkage in the common shrew via water loss without cell death
Brain plasticity, the brain’s inherent ability to adapt its structure and function, is crucial for responding to environmental challenges but is usually not linked to a significant change in size.
A striking exception to this is Dehnel’s phenomenon, where seasonal reversible brain-size reduction occurs in some small mammals to decrease metabolic demands during resource-scarce winter months.
Despite these volumetric changes being well documented, the specific microstructural alterations that facilitate this adaptation remain poorly understood.
Our study employed diffusion microstructure imaging (DMI) to explore these changes in common shrews, revealing significant alterations in water diffusion properties such as increased mean diffusivity and decreased fractional anisotropy, leading to decreased water content inside brain cells during winter.
These findings confirm that brain-size reduction correlates with a decrease in cell size, as our data indicate no reduction in cell numbers, showcasing a reorganization of brain tissue that supports survival without compromising brain function.
These findings extend our understanding of neuronal resilience and may inform future research on regenerative mechanisms, particularly during the spring regrowth phase, offering potential strategies relevant to neurodegenerative disease.
Continue Reading
-
Blood Moon total lunar eclipse: How to see it in the UK – BBC
- Blood Moon total lunar eclipse: How to see it in the UK BBC
- How to See the Total Lunar Eclipse and Blood Moon on September 7 WIRED
- Don’t miss it: Total lunar eclipse to darken Israel’s skies September 7 Ynetnews
- Chandra Grahan 2025 Next Week: Date, Timings, Where To Watch This Rare Blood Moon Times Now
- The full ‘Corn Moon’ rises this week on Sept 7 Dunya News
Continue Reading
-
Silane-Methane Competition in Sub-Neptune Atmospheres As A Diagnostic Of Metallicity And Magma Oceans
Envelope composition in the H–He–C–N–O–Si chemical system of TOI-421b (𝑅MEB = 1.65𝑅⊕, 𝑅𝑃 = 2.64𝑅⊕, 𝑀𝑃 = 6.7𝑀⊕, 𝑇MEB = 3000 K) as a function of H mass fraction. Elemental budgets, reactions, gas solubility laws, and real gas equations are described in Sect. 2. MEB partial pressures of the considered gases for (a) 1× solar metallicity and 100% mantle melt (IW–6.2 to IW–5.7), (b) 100× solar metallicity and 100% mantle melt (IW–5.5 to IW–5.2), (c) 1× solar metallicity and 1% mantle melt (IW–3.4 to IW–3.1), and (d) 100× solar metallicity and 1% mantle melt (IW–2.3 to IW–1.6). Full range of MEB partial pressures is shown in Fig. A2. The corresponding partitioning of volatile elements in magma and real gas fugacity coefficients are given in Fig. B1 and Fig. B2, respectively. — astro-ph.EP
The James Webb Space Telescope is characterising the atmospheres of sub-Neptunes. The presence of magma oceans on sub-Neptunes is expected to strongly alter the chemistry of their envelopes (100 bar-100 kbar) and atmospheres (1 mbar-100 bar).
At the magma ocean-envelope boundary (MEB, >10 kbar), gas properties deviate from ideality, yet the effects of real gas behaviour on chemical equilibria remain underexplored.
Here, we compute equilibrium between magma-gas and gas-gas reactions using real gas equations of state in the H-He-C-N-O-Si system for TOI-421 b, a canonical hot sub-Neptune potentially hosting a magma ocean. We find that H and N are the most soluble in magma, followed by He and C.
We fit real gas equations of state to experimental data on SiH4, and show that, for a fully molten mantle, SiH4 dominates at the MEB under accreted gas metallicity of 1× solar, but is supplanted by CH4 at 100× solar. Lower mantle melt fractions lower both magma-derived Si abundances in the envelope and the solubility of H and He in magma, yielding H2– and He-rich envelopes.
Projecting equilibrium chemistry through the atmosphere (1 mbar-100 bar), we find that condensation of β-quartz ‘clouds’ depletes Si-bearing gases, although SiH4 remains abundant at solar metallicity. SiH4/CH4 ratios increase with mantle melt fraction and decrease with metallicity. These effects also deplete H2 via CH4 and SiH4 formation and the dissolution of H2 into magma.
The competition between SiH4 and CH4 presents a diagnostic of metallicity and magma oceans. The corollary is that H2– and He-rich, SiH4– and CH4-poor (<5%) atmospheres may indicate a limited role or absence of magma oceans on sub-Neptunes.
Kaustubh Hakim, Dan J. Bower, Fabian Seidler, Paolo A. Sossi
Comments: 15 pages, 13 figures, submitted
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2508.19235 [astro-ph.EP] (or arXiv:2508.19235v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2508.19235
Focus to learn more
Submission history
From: Kaustubh Hakim
[v1] Tue, 26 Aug 2025 17:55:13 UTC (643 KB)
https://arxiv.org/abs/2508.19235Astrobiology
Continue Reading
-
Offworld Biology: Astronaut Zena Cardman Prepares Liver Tissue Research – astrobiology.com
- Offworld Biology: Astronaut Zena Cardman Prepares Liver Tissue Research astrobiology.com
- Bone and Brain Research Fine-Tuning Long-Term Astronaut Health NASA (.gov)
- ISS Crew Studies Bone Loss and Brain Adaptation to Safeguard Astronaut Health Gadgets 360
- NASA studies microgravitys impact on astronaut vision, brain pressure The News International
- ISS crew explores bone loss, brain adaptation, and spacesuit safety madhyamamonline.com
Continue Reading
-
Curiosity Rover ChemCam Views A Rock Shaped By Eons of Wind And Water – astrobiology.com
- Curiosity Rover ChemCam Views A Rock Shaped By Eons of Wind And Water astrobiology.com
- JPL Rover Images Reveal Ancient Water Activity on Mars Pasadena Now
- Did NASA just discover billion-year-old coral on Mars? futura-sciences.com
- A strange coral-shaped rock spotted on Mars intrigues scientists 3DVF
Continue Reading