Category: 7. Science

Human eyes are masterpieces of biological engineering, but once damaged, they cannot rebuild themselves. Golden apple snails, by contrast, routinely replace an entire camera-type eye within a month.

In a new study, molecular and cellular biologist Alice Accorsi and colleagues at the University of California, Davis, show that snail and human eyes share both anatomical architecture and many of the genes that guide development.

By pairing those insights with new CRISPR-Cas9 genome-editing tools, the team has created a tractable system for probing the genetic logic of whole-eye regeneration. This knowledge could ultimately inform therapies for people who lose vision through injury or disease.

Invasion becomes inspiration

Pomacea canaliculata, native to South America but now invasive across the tropics, breeds fast, thrives in captivity, and possesses large, lens-bearing eyes mounted on stalks.

“Apple snails are resilient, their generation time is very short, and they have a lot of babies,” Accorsi said.

Those practical advantages overcome many of the hurdles that have deterred previous attempts to use gastropods in regenerative biology.

“When I started reading about this, I was asking myself, why isn’t anybody already using snails to study regeneration? I think it’s because we just hadn’t found the perfect snail to study – until now,” she explained.

Unlike planarians, which can regrow primordial light-sensing spots, or salamanders, which regenerate a functional retina but not an entire globe, the apple snail rebuilds every element of a complex camera-type eye. These include the transparent cornea, refractive lens, layered retina, and optic nerve.

That layout mirrors the vertebrate eye and sets the stage for meaningful cross-species comparisons.

Snail eyes mirror ours

Accorsi’s group combined high-resolution histology with transcriptome sequencing to map the similarities.

“We did a lot of work to show that many genes that participate in human eye development are also present in the snail,” she noted.

Canonical regulators such as the pax6, sox2, otx, and six gene families appear in the mollusc’s genome and activate during eye formation. Once regeneration is complete, “the morphology and gene expression of the new eye is pretty much identical to the original one.”

From the moment an eye stalk is amputated, the snail initiates replacement through coordinated phases. Wound closure seals the cut within 24 hours. Proliferating undifferentiated cells then invade the site, and by about day 15 the nascent organ shows recognizable lens fibers, retinal layers, and a reconnecting optic nerve.

Although fully formed, the tissue continues to mature for several more weeks. RNA profiling captured this transition: roughly 9,000 genes change expression early, but 1,175 remain different after 28 days, suggesting late-stage remodeling.

Editing snail genes for answers

To test gene function directly, the researchers established CRISPR-Cas9 mutagenesis in apple snail embryos.

“The idea is that we mutate specific genes and then see what effect it has on the animal,” Accorsi said.

As proof of principle, they knocked out pax6. Hatchlings carrying two inactive copies lacked eyes altogether. This demonstrates that, as in vertebrates and flies, pax6 is indispensable for initial eye assembly in snails.

The lab can now deploy the same strategy to explore whether pax6 or other regulators are also critical during regrowth in adults.

Rebuilding eyes from scratch

Imaging shows that regeneration begins with a burst of cell migration and proliferation near the stump. Accorsi hypothesizes that some of those cells originate from a reserve of stem-like cells at the base of the eye stalk. Others may derive from the surrounding epidermis or even blood-borne hemocytes.

Unraveling their lineage, and what signals tell them to adopt lens versus retina fates, will be a next challenge. With CRISPR, the team can tag cells or block signals to observe how regeneration stalls or progresses.

Behavioral tests are also on the agenda. “We still don’t have conclusive evidence that they can see images, but anatomically, they have all the components that are needed to form an image,” Accorsi said.

Designing assays that reveal light-guided behavior – perhaps tracking movement toward shaded refuges – will confirm functional recovery. These tests will also set benchmarks for comparing successful and failed genetic manipulations.

From snails to human sight

Humans carry the same developmental genes, but in mammals they’re mostly silenced after embryogenesis ends. Identifying reactivation signals may reveal molecular switches to coax human eye tissues into self-repair.

“If we find a set of genes that are important for eye regeneration, and these genes are also present in vertebrates, in theory we could activate them to enable eye regeneration in humans,” Accorsi remarked.

That long-term vision will require bridging vast evolutionary and physiological gaps, yet the new model provides a rare example of full organ restoration in a complex eye.

Because the apple snail’s genetics, life cycle, and regenerative capacity are now accessible, it offers a powerful research model. It promises to illuminate not only ophthalmology but also broader questions of stem-cell plasticity, immune modulation, and scar-free healing.

A pest becomes a pioneer

Accorsi’s project also illustrates how curiosity-driven exploration can expand the experimental repertoire of biomedicine.

A problem that seems intractable in standard lab rodents may yield to an unexpected organism with the right combination of traits.

As Accorsi’s lab continues to map the genetic circuitry of eye regrowth – and perhaps inspire other groups to adopt the apple snail – what began as an invasive pest could become a luminous guide to restoring sight.

The study is published in the journal Nature Communications.

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Mars is a world marked by dramatic landscapes and few regions showcase this better than Acheron Fossae, a spectacular network of deep cracks and valleys that slice through the red planet’s surface like ancient scars. Recent images from the European Space Agency’s Mars Express spacecraft reveal the western edge of this fascinating geological formation, offering new insights into Mars’s violent past and changing climate.

Image of Mars captured by the Hubble Space Telescope between April 27 and May 6, 1999, when Mars was 87 million kilometres from Earth (Credit : NASA/ESA)

Acheron Fossae is an extensive system of deep, fault like cracks (known as fossae), with alternating chunks of raised and lowered ground, a pattern geologists call “horst and graben.” Picture a broken chocolate bar where some pieces have been pushed up while others have dropped down, creating a jagged landscape of ridges and valleys that can be hundreds of kilometers long and several kilometers deep.

These features weren’t created overnight. Likely dating back over 3.7 billion years to when Mars was most geologically active, such a pattern was created as hot material rose upwards beneath the martian crust. As molten rock pushed upward from deep within Mars, it stretched and cracked the planet’s surface creating the deep valleys we see today.

Image of Acheron Fossae in Tharsis region on Mars (Credit : NASA)

What makes Acheron Fossae particularly intriguing isn’t just how it formed, but how it continues to change. The valley floors are relatively smooth, marked by gently weaving lines reminiscent of a flowing river. Rather than water, these valleys have been filled by a slow, viscous flow of ice rich rock, a lot like the rock glaciers we see here on Earth.

These Martian rock glaciers act like geological time capsules, preserving evidence of the Martian climatic history. Rock glaciers are very sensitive to changes in climate, and so act as good markers for how a planet’s environment has changed over time. Here, they indicate that this region of Mars has experienced alternating periods of cool and warm, freeze and thaw.

The key to understanding these climate swings lies in Mars’s unstable tilt. Unlike Earth, which maintains a relatively steady tilt thanks to the Moon’s stabilising influence, Mars wobbles dramatically over time. Mars’s tilt has swung between 15 and 45 degrees in the last 10 million years, while Earth’s has varied between 22 and 24.5 degrees.

These variations, known as the Milankovitch cycles, create alternating ice ages and warm periods on Mars. During extreme tilts, ice can creep near to the planet’s equator before shrinking back to its poles during warmer periods.

The images also reveal how erosion has transformed the landscape over millions of years. To the right of the main fossae, the deep cracks transition into flat, dark lowland plains, with a strip of raised mounds and rocky hills in between. These are the remains of what was once a continuous rock layer that has been slowly worn away by flows of ice and rock over time, leaving behind rounded hills called knobs and flat topped plateaus called mesas.

This erosion process creates a distinctive transition visible in the topographical data, from the deep red and yellow tones of higher ground gradually melting into light and darker blues indicating lower elevations. It’s like watching a mountain range slowly dissolve into a plain over geological time.

Illustration of ESA’s Mars Express spacecraft (Credit : NASA/JPL)

These remarkable insights come courtesy of ESA’s Mars Express spacecraft, which has been capturing and exploring Mars’s landscapes since 2003. Using its High Resolution Stereo Camera, the orbiter has mapped the planet’s surface in unprecedented detail, colour, and three dimensions for over two decades.

As we continue studying Mars, features like Acheron Fossae serve as natural laboratories for understanding planetary geology and climate evolution. They remind us that planets are dynamic systems, constantly changing over geological time scales. For future Mars missions, both robotic and human, understanding these processes will be crucial for navigation, resource utilisation, and safe exploration of our planetary neighbour.

Source : When Martian Ground Falls Apart

Researchers at the University of California, Irvine and Japan’s Okayama and Toho universities conducted a first-of-its-kind study to understand how chitons, mollusks that feed on algae growing on seashore rocks, develop such hard, wear-resistant and magnetic teeth, and what they learned is inspiring new ways to produce advanced materials for a variety of applications. The results are published today in Science.

In its study, the team unveiled the process by which chiton-specific, iron-binding proteins called RTMP1 are transported into newly forming teeth through nanoscopic tubules called microvilli. Where and when the proteins are deposited is precisely controlled, ensuring that the creatures develop a hard, strong and tough dental architecture that enables them to perform the repetitive abrasive motions on which their lives depend.

“Chiton teeth, which consist of both magnetite nanorods and organic material, are not only harder and stiffer than human tooth enamel, but also harder than high-carbon steels, stainless steel, and even zirconium oxide and aluminum oxide – advanced engineered ceramics made at high temperatures,” said co-author David Kisailus, UC Irvine professor of materials science and engineering. “Chiton grow new teeth every few days that are superior to materials used in industrial cutting tools, grinding media, dental implants, surgical implants and protective coatings, yet they are made at room temperature and with nanoscale precision. We can learn a lot from these biological designs and processes.”

There are more than 900 different chiton species worldwide, mostly dwelling within intertidal coastal regions. They can be found in places like Crystal Cove and Laguna Beach near the UC Irvine campus, but Kisailus said the ones investigated in this study are much larger and live in Northwest coastal areas of the United States and off the coast of Hokkaido, Japan. The research team learned that the RTMP1 proteins exist in chitons at disparate locations around the world, which suggests “some convergent biological design in controlling iron oxide deposition,” according to Kisailus.

He said that when he and his collaborators began, they were not aware of how and when these iron-binding proteins were conveyed into the chiton teeth. But by using a combination of advanced materials and molecular biological analyses, they discovered that these specialized proteins that were initially found within tissues surrounding immature, nonmineralized teeth were directed through nanostructured tubules into each tooth.

Once inside, the proteins bind to preassembled scaffolds of chitin nanofibers, the structural biopolymer that controls the architecture of the magnetite nanorods in the teeth. Concurrently, iron stored in ferritin, another protein found in the tissue outside the teeth, is released into each tooth, where it binds to the RTMP1, leading to the precise deposition of nanoscale iron oxide, which continues to grow during the tooth maturation into highly aligned magnetite nanorods that ultimately yield the ultrahard teeth.

Kisailus said this project has improved humanity’s understanding of cellular iron metabolism while providing insight into the synthesis of next-generation advanced materials.

“The fact that these organisms form new sets of teeth every few days not only enables us to study the mechanisms of precise, nanoscale mineral formation within the teeth, but also presents us with new opportunities toward the spatially and temporally controlled synthesis of other materials for a broad range of applications, such as batteries, fuel cell catalysts and semiconductors,” he said. “This includes new approaches toward additive manufacturing – 3D printing – and synthesis methods that are far more environmentally friendly and sustainable.”

Setting this study apart, according to Kisailus, was the blending of state-of-the-art materials science techniques, including ultra-high-resolution electron microscopy, X-ray analysis and spectroscopy, with biological methods such as immunofluorescence, gene expression tracking and RNA interference to reveal the full molecular choreography of chiton tooth formation.

“By combining biological and materials science approaches through wonderful, global efforts, we’ve uncovered how one of the hardest and strongest biological materials on Earth is built from the ground up,” Kisailus said.

His collaborators on this project were Michiko Nemoto, Koki Okada, Haruka Akamine, Yuki Odagaki, Yuka Narahara, Kiori Obuse, Hisao Moriya and Akira Satoh of Okayama University and Kenji Okoshi of Toho University.

Reference: Nemoto M, Okada K, Akamine H, et al. Radular teeth matrix protein 1 directs iron oxide deposition in chiton teeth. Science. 2025;389(6760):637-643. doi: 10.1126/science.adu0043

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“Then, at some point, they split apart,” says Taylor. “That can be from spinning up fast, or getting hit. That exposes ices and makes them become dark comets.” The process would also spin such objects to high speeds, which happens to be a characteristic shared by many dark comets – they spin as fast as once every six minutes, compared to once an hour, like other asteroids of a similar size.

Two kinds of dark comet

The discovery of more dark comets in December 2024 has also hinted that these objects might come in two forms: outer dark comets, which are around 100m-1km (330-3,300ft) in size and originate near Jupiter, and smaller, inner dark comets 10-20m (30-60ft) in size that have a circular orbit, similar to Earth’s. That suggests that the inner dark comets may be asteroids that have broken apart, exposing their ice, while the existence of more distant dark comets might be explained by another process – perhaps they are dying comets in the twilight of their lives.

“We’re seeing them while they’re about to run out of gas – the last absolute gasps of cometary activity,” says Kareta. “We’re seeing what is a very brief phase in some of these objects’ lifetimes.”

If dark comets are asteroids that contain ice, that might help solve the mystery of how water arrived on Earth. A popular theory is that water got here via asteroids or comets that crashed into our planet early during the history of the Solar System. Dark comets are a promising candidate for this scenario. “If there are lots of objects near Earth that we didn’t know were hydrated, then it’s possible they contributed,” says Seligman.

New research has uncovered compelling evidence that water from a comet is strikingly similar to that found in Earth’s oceans, offering fresh support for the idea that comets may have played a crucial role in delivering water—and possibly some of the molecular ingredients for life—to our planet.

Using the powerful Atacama Large Millimeter/submillimeter Array (ALMA), an international team of scientists, led by Martin Cordiner of NASA’s Goddard Space Flight Center, mapped the distribution of both ordinary water (H2O) and “heavy” water (HDO, which contains the heavier isotope, deuterium) in the coma (the cloud of gas surrounding the nucleus) of the Halley-type comet 12P/Pons-Brooks during its approach to the Sun. This marks the first time such detailed spatial mapping of these two forms of water has been achieved in a comet.

The ALMA observations were then combined with data on water and other gases, observed using NASA’s Infrared Telescope Facility (IRTF), to form a more complete picture of the comet. By combining the complementary capabilities of these two telescopes, the researchers were able  to measure more accurately the ratio of deuterium to hydrogen (D/H) in the comet’s water, a chemical fingerprint that helps scientists trace the origins and history of water throughout the Solar System. Remarkably, the D/H ratio of water in 12P/Pons-Brooks was found to be virtually indistinguishable from that of Earth’s oceans. The measurement, (1.71±0.44)×10−4, is the lowest such ratio ever measured in a Halley-type comet, and is at the lower end of values previously observed in other comets.

“Comets like this are frozen relics left over from the birth of our Solar System 4.5 billion years ago,” said Cordiner. “Since Earth is believed to have formed from materials lacking water, comet impacts have long been suggested as a source of Earth’s water. Our new results provide the strongest evidence yet that at least some Halley-type comets carried water with the same isotopic signature as that found on Earth, supporting the idea that comets could have helped make our planet habitable.”

Halley-type comets are a class of comet with intermediate orbital periods (between 20 to 200 years), and visit the inner Solar System only rarely, The study’s findings are significant because previous measurements in other comets often showed water with a D/H ratio different from Earth’s, leaving the cometary origin of Earth’s water in doubt. This new measurement suggests that some comets—particularly those like 12P/Pons-Brooks—could indeed have delivered water, and possibly other life-essential elements, to a young Earth.

The research also confirms the origin of the observed gases, providing a more accurate picture of the comet’s true composition. “By mapping both H2O and HDO in the comet’s coma, we can tell if these gases are coming from the frozen ices within the solid body of the nucleus, rather than forming from chemistry or other processes in the gas coma,” said NASA’s Stefanie Milam, a co-author of the study.

The observations were only possible thanks to ALMA’s exceptional sensitivity and unique imaging capabilities, which allowed the team to detect the faint signature of heavy water emanating from the innermost regions of the coma—something that has never before been mapped in a comet.

About NRAO

The National Radio Astronomy Observatory (NRAO) is a facility of the U.S. National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

About ALMA

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Southern Observatory (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

NASA has issued an alert about two massive asteroids set to make close approaches to Earth on Friday, August 8, 2025. While there’s no risk of impact, their impressive size, high velocity, and same-day flybys have sparked interest among scientists and space enthusiasts worldwide.

Asteroid (2025 OJ1) — Bigger Than a 30-Story Building

The first asteroid, designated (2025 OJ1), measures around 300 feet (91 meters) in diameter—roughly the height of a 30-story skyscraper. According to NASA’s Near-Earth Object tracking system, it will pass at a distance of 3.2 million miles (5.15 million km) from Earth—about 13 times farther than the Moon.

Despite the safe distance, astronomers are keen to observe its high-speed journey through near-Earth space. Powerful telescopes will capture its brief appearance, providing valuable data on asteroid composition, orbit, and movement.

Asteroid (2019 CO1) — The Size of a Jumbo Jet

Sharing the spotlight on the same day is (2019 CO1), an asteroid about 200 feet (61 meters) wide—similar in size to a large commercial airplane. It will pass Earth at 4.24 million miles (6.82 million km), making it slightly farther than (2025 OJ1) but still considered a close approach in astronomical terms.

Its smaller size doesn’t make it less interesting—its speed and orbital path are closely monitored, adding to the day’s rare double flyby excitement.

NASA Confirms Zero Threat

NASA has reassured the public that neither asteroid poses any danger to Earth. Advanced tracking confirms both will safely pass without entering our atmosphere or causing any disruption. Close approaches like these happen regularly and are part of the solar system’s natural activity.

Why Near-Earth Objects Matter

Near-Earth Objects (NEOs) are comets or asteroids with orbits bringing them near our planet. While most pass harmlessly, some could pose a threat in the distant future. That’s why agencies like NASA continuously monitor their paths—early detection can be crucial for planetary defense, allowing time for mitigation or deflection efforts if needed.You can follow NASA’s updates on these events via:
NASA’s Near-Earth Object Web Portal
Social media posts from the Planetary Defense Coordination Office
Live streams during notable flybys
Amateur astronomer networks also share real-time observation tips during such events.

The twin flybys of (2025 OJ1) and (2019 CO1) on August 8 serve as a reminder of the fast-moving and unpredictable environment of near-Earth space. Thanks to NASA’s technology and vigilance, Earth remains well-protected from potential asteroid threats—reinforcing the importance of continued investment in planetary defense as humanity’s eyes turn to the skies.