Category: 7. Science

We present a comprehensive analysis of the HL Tau dust disk by modeling its intensity profiles across six wavelengths (0.45 to 7.9 mm) with a resolution of 0.05 arcsec (∼7 au).

Using a Markov Chain Monte Carlo (MCMC) approach, we constrain key dust properties including temperature, surface density, maximum grain size, composition, filling factor, and size distribution. The full fitting, with all parameters free, shows a preference for organics-rich dust with a low filling factor in the outer region (r≳40 au), where the spectral index is ∼3.7, but amorphous-carbon-rich dust also reasonably reproduces the observed intensity profiles.

Considering the scattering polarization observed at 0.87 mm, compact, amorphous-carbon-rich dust is unlikely, and moderately porous dust is favored. Beyond 40 au, the maximum dust size is likely ∼100 μm if dust is compact or amorphous-carbon rich.

However, if the dust is moderately porous and organics-rich, both the predicted dust surface density and dust size can be sufficiently large for the pebble accretion rate to reach ∼10M_⊕ Myr⁻¹ in most regions, suggesting that pebble accretion could be a key mechanism for forming planets in the disk.

In contrast, if the dust is amorphous-carbon-rich, forming a giant planet core via pebble accretion is unlikely due to the combined effects of low dust surface density and small dust size required to match the observed emission, suggesting other mechanisms, such as disk fragmentation due to gravitational instability, may be responsible for planet formation in the HL Tau disk.

Takahiro Ueda, Sean M. Andrews, Carlos Carrasco-González, Osmar M. Guerra-Alvarado, Satoshi Okuzumi, Ryo Tazaki, Akimasa Kataoka

Comments: 20 pages, 11 figures, accepted for publication in ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2507.14443 [astro-ph.EP] (or arXiv:2507.14443v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2507.14443
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Submission history
From: Takahiro Ueda
[v1] Sat, 19 Jul 2025 02:39:16 UTC (10,856 KB)
https://arxiv.org/abs/2507.14443
Astrobiology, Astrochemistry,

On the slopes of Martian mountains and craters clings what appears to be flowing honey, coated in dust and frozen in time. In reality, these features are incredibly slow-moving glaciers, and their contents were once thought to be mostly rock enveloped in some ice.

Work over the last 20 years has demonstrated that at least some of these glaciers are mostly pure ice with only a thin cover of rock and dust, but according to a new paper published in Icarus, glaciers all over the planet actually contain more than 80% water ice, a significant finding. Ultimately, this means that Mars’s glacial ice deposits are nearly pure across the globe, providing a clearer understanding of Mars’ climate history and a possible resource for future utilization.

The paper was led by Yuval Steinberg, a recent graduate of the Weizmann Institute of Science, based in Israel. The two coauthors, Oded Aharonson and Isaac Smith, are senior scientists at the Planetary Science Institute, based in Tucson, with faculty appointments at the Weizmann Institute of Science and York University, respectively.

“This study highlights how NASA programs are advancing science not just within the United States, but also reaching students around the world,” Aharonson said.

The five sites that the team investigated for glacier purity. The fact that these disparate sites contained a similarly high ice-to-rock ratio implies that Mars experienced either one widespread glaciation or multiple glaciations that had similar properties, according to the team. Credit: Steinberg et. al.

Peering under the dust-covered veil

While reading up on past research, the team quickly realized that when it comes to analyzing debris-covered glaciers, it’s the Wild West.

“Different techniques had been applied by researchers to various sites, and the results could not be easily compared,” said Smith. “One of the sites in our study had never been studied, and at two of the five sites we used, only partial analysis had been completed previously.”

So, the team decided to standardize how these debris-covered glaciers are analyzed. They specifically measured their dielectric property (a measure of how quickly radar waves move through a material) and their loss tangent (a measure of how quickly energy dissipates from the radar wave into a material). From these, researchers can infer the ratio of rock to ice within a glacier. This cannot be done from visual observation of the glaciers that have dust and rock-covered surfaces.

They also identified another area on Mars where SHARAD, short for the SHAllow RADar instrument onboard the Mars Reconnaissance Orbiter, could also do these analyses. This gave them a total of five sites spread across the red planet, enabling global comparison.

They were surprised to find that all glaciers, even in opposite hemispheres, have nearly the same properties.

“This is important because it tells us that the formation and preservation mechanisms are probably the same everywhere,” Smith said. “From that, we can conclude that Mars experienced either one widespread glaciation or multiple glaciations that had similar properties. And, by bringing together these sites and techniques for the first time, we were able to unify our understanding of these types of glaciers.”

Knowing the minimum purity of these glaciers benefits scientific understanding of the processes that form and preserve them. Additionally, it helps when planning for future human exploration of Mars, when using local resources, such as water, becomes mission-critical.

Next, the team will seek out additional glaciers to add their global comparison and solidify their understanding of these dust-covered mysteries.

THE PLANETARY SCIENCE INSTITUTE

The Planetary Science Institute is a private, nonprofit 501(c)(3) corporation dedicated to Solar System exploration. It is headquartered in Tucson, Arizona, where it was founded in 1972.

PSI scientists are involved in numerous NASA and international missions, the study of Mars and other planets, the Moon, asteroids, comets, interplanetary dust, impact physics, the origin of the Solar System, extra-solar planet formation, dynamics, the rise of life, and other areas of research. They conduct fieldwork on all continents around the world. They are also actively involved in science education and public outreach through school programs, children’s books, popular science books and art.

PSI scientists are based in over 30 states, the District of Columbia and several international locations.

Physical properties of subsurface water ice deposits in Mars’s Mid-Latitudes from the shallow radar, Icarus (open access)

Astrobiology,

Summer nights are great for watching the sky. The best meteor shower of the year has started, most of the world will get to see a lunar eclipse soon, and even if you live in a city with light pollution, you can still catch the International Space Station (ISS) as it passes overhead.

Humans have lived in the ISS for almost a quarter of a century, and it is still going strong. It goes around the planet every 93 minutes, in a peculiar orbit; it has an inclination of 51.6 degrees to Earth’s equator, which means it is not passing over the same place over and over again. Well, not immediately.

The ISS does 15.5 orbits every 24 hours, covering a lot of Earth, but it is not bright enough to be seen during the day. At night it is easier to spot after dusk or before dawn, when it is still dark here on Earth, but 400 kilometers (250 miles) up, the station’s solar panels are still catching sunlight and reflecting it back to us. Sometimes there are periods where you can watch the ISS just once a month, and others where you can try multiple times a week.

When to see the ISS in the US

Right now, if you are in Los Angeles, you are in the latter category. It will be visible twice tonight, at 8:43 pm PT, and then at 10:17, and then tomorrow, at 9:29 pm. On July 27 and 28, it will repeat a similar pattern, just shifted by a few minutes. This won’t be a California exclusive, however. Wherever you are in the US, you will get the chance to see it multiple times this week. In New York, you have tonight and tomorrow at 10:11 pm and tomorrow at 9:22 pm to catch it, then again on July 28 and 30.

How to find the ISS from wherever you are on Earth

There are multiple official trackers to let you know where and when to look. The one linked here gives a prediction of direction and brightness. There is also a NASA official tracking app that comes with notifications for when the ISS is above your head.

ⓘ IFLScience is not responsible for content shared from external sites.

How to see the ISS 

You do not need binoculars or telescopes; the ISS is bright enough to be seen with the naked eye. It might be the length of an American football field (including the end zones), hundreds of kilometers up in the sky, but it is pretty reflective, making it an easy spot. Also, it moves! And not like an airplane does, or a satellite. It will be larger than you are probably expecting, will look quite clearly white, and will be moving fast across the sky in a smooth line at a steady pace. If it’s above you, you can’t miss it. 

And if the weather is not good right now for clear skies, don’t worry. The good thing about the ISS is that it comes around again and again.

Warning: This is a grisly one. Around 850,000 years ago, a small child belonging to a now extinct human species was decapitated and processed for food, according to new archaeological finds in northern Spain.

The specimen, a tiny vertebra, belonged to a two- to four-year-old member of the archaic human species known as Homo antecessor, which was recently excavated from the Gran Dolina site in Sierra de Atapuerca, Spain. This species of human lived in Western Europe during the Lower Palaeolithic era, around 1.2 million to 800,000 years ago. Some have argued that this species may have represented the common ancestor of Neanderthals and Homo sapiens.

The vertebra showed evidence of precision cutting, while other bones found at the site exhibited marks characteristic of defleshing and intentional fracturing. These are typical indicators of meat being removed for food and are common on animal bones eaten by these early humans.

“This case is particularly striking, not only because of the child’s age, but also due to the precision of the cut marks,” Dr Palmira Saladié, IPHES-CERCA researcher and co-director of the Gran Dolina excavation alongside Dr Andreu Ollé, explained in a statement. “The vertebra presents clear incisions at key anatomical points for disarticulating the head. It is direct evidence that the child was processed like any other prey.” 

Although this is a pretty unpalatable find, it is not the first time such behavior has been identified at this site. Nearly thirty years ago, the same archaeological level revealed the first known case of human cannibalism in the world.

“What we are documenting now is the continuity of that behaviour: the treatment of the dead was not exceptional, but repeated,” said Saladié.

The new evidence, which was excavated in July this year, adds to our belief that these humans exploited one another as a food source and possibly as a form of territorial control. In addition to the child’s vertebrae, archaeologists also recovered a hyena latrine with over 1,300 coprolites (fossilized poop) that were plopped on the level just above where the human remains were found. Such overlaying evidence helps archaeologists reconstruct who or what occupied the cave at different times, and as a result, get a better understanding of the history of interspecies competition in this environment.

The archaeologists believe there is likely more to be discovered at the site, especially in relation to human bones.

“Every year we uncover new evidence that forces us to rethink how they lived, how they died, and how the dead were treated nearly a million years ago,” Saladié concluded. 

Each cell in our bodies carries about two meters of DNA in its nucleus, packed into a tiny volume of just a few hundred cubic micrometers—about a millionth of a milliliter. The cell manages this by winding the strings of DNA around protein spools. The protein-DNA complexes are called nucleosomes, and they ensure that DNA is safely stored.

But this packaging into nucleosomes also poses a challenge: important cellular machinery must still access the genetic code to keep cells healthy and prevent diseases like cancer.

One of the most important proteins in our cells is p53, the “genome’s guardian.” It helps control cell growth, triggers repair of damaged DNA, and can even order faulty cells to self-destruct.

In many cancers, p53 is disabled or hijacked, so understanding how p53 works is vital for developing cancer therapies. But there’s a problem: most of the DNA sequences that p53 targets are buried inside nucleosomes, making them difficult to reach. Scientists have long wondered how p53 can reach those “hidden” sequences to do its job, as well as how other proteins that interact with p53 manage to find it in this maze of chromatin.

A new layer of control revealed

Now, researchers led by Nicolas Thomä, who holds the Paternot Chair in Cancer Research at EPFL, have found that nucleosomes act as a gatekeeper for p53’s molecular partners. By studying how p53 interacts with different cofactors while attached to nucleosomal DNA, the team has revealed a new layer of control over this critical protein’s activity.

The researchers used a combination of cutting-edge techniques, including cryo-electron microscopy (cryo-EM), biochemical assays, and genome-wide mapping. Using these tools, they reconstructed how p53 binds to its DNA targets when those targets are wrapped up in nucleosomes.

They then tested whether two important “cofactor” proteins could still reach p53 when it is bound to nucleosomal DNA: USP7, which helps stabilize p53, and the viral E6-E6AP complex, which helps degrade p53.

They found that p53 can still bind to DNA even when it is wrapped in nucleosomes, especially at the edges where DNA enters or exits the spool. But more surprisingly, the researchers discovered that USP7 could interact with p53 even while bound to the nucleosome, forming a stable complex that they could observe in detail using cryo-EM.

In contrast, E6-E6AP couldn’t access p53 when it was attached to nucleosomal DNA. This means that the structure of chromatin itself selectively allows or blocks certain proteins from reaching p53, adding an extra level of regulation beyond simple genetic sequences or protein-protein interactions.

The work shows that the physical structure of DNA and its packaging in the nucleus actively influences molecular interactions. By revealing how nucleosomes can “gatekeep” access to p53, the research opens new possibilities in cancer research that could inform future therapies that aim to restore or control p53 function in disease.

Other contributors

• Friedrich Miescher Institute for Biomedical Research
• University of Basel

Reference

Deyasini Chakraborty, Colby R. Sandate, Luke Isbel, Georg Kempf, Joscha Weiss, Simone Cavadini, Lukas Kater, Jan Seebacher, Zuzanna Kozicka, Lisa Stoos, Ralph S. Grand, Dirk Schübeler, Alicia K. Michael, Nicolas H. Thomä. Nucleosomes specify cofactor access to p53. Molecular Cell, 25 July 2025.

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A new study by researchers at the Hospital del Mar Research Institute and Yale University suggests that the origins of several brain-related disorders may be found in the earliest stages of fetal brain development. The findings, published in Nature Communications, show that many genes associated with neuropsychiatric and neurodegenerative diseases are active in neural stem cells, well before birth.

The research focused on nearly 3,000 genes linked to conditions such as autism, bipolar disorder, depression, schizophrenia and neurodegenerative diseases including Alzheimer’s and Parkinson’s. Using a combination of human and mouse data, alongside in vitro cellular models, the team simulated how genetic disruptions might affect the development of the fetal brain.

Simulating genetic disruptions in neural stem cells

Neural stem cells give rise to all the cell types of the brain, including neurons and their support cells. The study explored how gene alterations influence these progenitor cells during different stages of development. Researchers modelled regulatory networks for each relevant cell type and assessed how activating or silencing disease-linked genes affected their behaviour.

This approach allowed the team to identify when and where specific genes are most active, providing a clearer picture of how early genetic alterations may lead to brain structure and function changes later in life. Disorders ranging from cortical malformations, such as microcephaly and hydrocephaly, to anorexia, depression and schizophrenia were included in the analysis.

“Scientists usually study the genes of mental illnesses in adults, but in this work we discovered that many of these genes already act during the early stages of fetal brain formation, and that their alterations can affect brain development and promote mental disorders later on”.

Dr. Nicola Micali.

Cortical malformations

These refer to structural abnormalities in the cerebral cortex, the brain’s outer layer, which can lead to neurological and developmental disorders.

Broader implications for understanding disease mechanisms

The study suggests that disruptions to gene function in neural stem cells could contribute to a wide range of conditions affecting the cerebral cortex. It also highlights specific developmental windows when these genes are especially influential, which could be critical for identifying periods of heightened vulnerability or therapeutic opportunity.

The findings may contribute to future efforts in understanding how early brain development impacts mental and neurological health. They also lay the groundwork for more targeted studies into gene function during neurodevelopment, potentially informing future gene-based treatment approaches.

Reference: Mato-Blanco X, Kim SK, Jourdon A, et al. Early developmental origins of cortical disorders modeled in human neural stem cells. Nat Commun. 2025;16(1). doi: 10.1038/s41467-025-61316-w

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It’s been more than a year since the Ingenuity helicopter broke one of its blades, ending its experimental stint on Mars. On the heels of this wildly successful NASA mission, a defense contractor has introduced a new design concept to succeed the iconic Mars chopper—one that would release multiple vehicles to spread across the Martian landscape at the same time, like a coordinated swim team diving into the water.

Virginia-based AeroVironment (AV), in partnership with NASA’s Jet Propulsion Laboratory (JPL), recently revealed its Skyfall mission concept, a next-generation Mars helicopter designed to pave the way for a future human landing on the neighboring world. Skyfall would deploy six small choppers, similar to NASA’s Ingenuity, to the Red Planet using a single entry capsule, with each helicopter landing independently on the Martian surface. The mission is aiming for a launch date in 2028, according to AV.

The landing carrier would drop the six helicopters midway through its descent through the planet’s atmosphere, eliminating the need for a landing platform. Following their release from the carrier, each helicopter would land on the Martian surface under its own power. Each helicopter would quickly get to work, exploring different parts of the planet and investigating potential landing sites for a future human mission.

Operating independently, each chopper will collect high-resolution images of the surface and radar data from beneath the surface to search for potential resources on Mars. “With six helicopters, Skyfall offers a low-cost solution that multiplies the range we would cover, the data we would collect, and the scientific research we would conduct–making humanity’s first footprints on Mars meaningfully closer,” William Pomerantz, head of Space Ventures at AV, said in a statement.

Ingenuity was the first helicopter to fly on another planet, paving the way for a fleet of successors that can explore the Martian surface from above. The o.g. Mars helicopter arrived on the planet in February 2021, tucked inside the belly of NASA’s Perseverance rover. Shortly afterwards, the 19-inch-tall (48-centimeter), 4-pound (1.8-kilogram) helicopter became the first powered aircraft to lift off from the surface of another planet. Although it was originally intended to perform just five test flights, Ingenuity kept on going, performing 72 flights and flying 14 times farther than planned for a total flight time of two hours.

Things came crashing down for Ingenuity last year after the helicopter broke its blades while landing for the 72nd time, officially ending its mission in January 2024. Its mission more than exceeded expectations, delivering precious data on a new method of exploring the surface of another planet and opening up a new gateway for missions to Mars and elsewhere. Whatever chopper comes next will have some pretty big shoes to fill, so maybe sending six helicopters to Mars is the appropriate follow-up.