Mars, often called the Red Planet due to its distinctive rusty color from iron oxide on its surface, is Earth's neighboring planet and humanity's most likely next destination for exploration. It’s about half the size of Earth and takes nearly two years to complete one orbit around the Sun. Mars is home to the largest volcano in our solar system, Olympus Mons, as well as a massive canyon system called Valles Marineris. It continues to fascinate scientists who are searching for signs of past or present life while planning for the day humans pay a visit.

Mars, the red planet.

(Credit : Kevin Gill)

Scientists have made a groundbreaking discovery that may well bring that first human exploration a little closer. Researchers led by University of Mississippi planetary geologist Erica Luzzi have found strong evidence of water ice just beneath the Martian surface, a finding that could solve one of the biggest challenges facing future Mars missions. The research team discovered indications of water ice less than one meter below the surface in Mars' Amazonis Planitia region, located in the planet's middle latitudes.

Amazonis Planitia topography map.

(Credit : Martin Pauer)

Using high-resolution satellite images from HiRISE on board the Mars Reconnaissance Orbiter, the most powerful camera ever sent to another planet, they identified telltale signs including ice-exposing craters and polygonal terrain patterns that typically indicate near-surface ice. Amazonis Planitia region represents the "perfect compromise" for future missions, according to Luzzi. The middle latitudes receive enough sunlight to power equipment while remaining cold enough to preserve ice deposits. This makes the region an ideal candidate for humanity's first Mars landing site.

HiRISE camera of the Mars Reconnaissance Orbiter

(Credit : NASA)

Water ice isn't just about having something to drink, though that's certainly important, but for Mars explorers, water represents a lifeline that could mean the difference between mission success and failure. It can be broken down to provide oxygen for breathing and hydrogen for rocket fuel too, eliminating the need to transport the heavy resource from Earth.

"If we're going to send humans to Mars, you need H2O and not just for drinking, but for propellant and all manner of applications," Erica Luzzi, University of Mississippi.

This concept, called in situ resource utilization, is crucial for Mars missions because of the vast distances involved. While a resupply mission to the Moon takes about a week, reaching Mars requires months of travel time. Astronauts would need to be completely self-sufficient for extended periods.

Beyond supporting human missions, the ice discovery has exciting implications for astrobiology, the search for life beyond Earth. On our planet, ice can preserve biological markers from ancient life forms and even harbor living microorganisms in extreme environments. While the satellite evidence is compelling, scientists emphasize that physical confirmation is still needed. The next phase involves radar analysis to better understand the ice deposits' depth and distribution. Eventually, robotic missions or human explorers will need to drill samples to confirm whether the formations are pure water ice or contain other materials.

This research, published in the Journal of Geophysical Research: Planets, represents a crucial stepping stone toward establishing a human presence on Mars. While astronauts may still be years away from setting foot on the Red Planet, scientists now have a much clearer idea of where those historic first steps should be taken.

Source : 

• Researchers Take One Small Step Toward Planning Life on Mars

Within Earth's interior, the molten material that makes up the outer core flows around the inner core in the opposite direction of the Earth's rotation. This "dynamo" is believed to be responsible for generating Earth's magnetosphere, the intrinsic magnetic field that shields life on the surface from harmful radiation. But since the flow of molten material in Earth's core isn't perfectly stable, the magnetosphere ebbs and flows over time. Scientists also theorize that this field prevents Earth's atmosphere from being slowly stripped away by charged solar particles (solar wind), which is believed to have been the case with Mars.

As a result, Earth's magnetic field is theorized to be integral to Earth's habitability, though its role in maintaining the atmosphere remains an ongoing field of study. According to new research by a team of NASA scientists, changes in Earth's magnetic field over the past 540 million years are correlated to fluctuations of oxygen levels in our atmosphere. Their research suggests that processes in Earth's interior might be directly connected to changes in our atmosphere, which could have significant implications for our understanding of planetary habitability.

The study was led by Weijia Kuang, a geophysicist at the Geodesy and Geophysics Laboratory and Sellers Exoplanet Environments Collaboration (SEEC) at NASA’s Goddard Space Flight Center. She was joined by researchers from NASA Goddard's Planetary Environments Laboratory, the Department of Earth and Space Sciences/Astrobiology Program at the University of Washington, and the School of Earth and Environment at the University of Leeds. The paper describing their findings appeared on June 13th in Science Advances.

Artist's impression of Earth's interior structure.

Credit: Science Photo Library

Earth scientists have long known that the history of Earth's magnetic field is recorded by magnetized minerals in rocks. When magma rises to the surface and solidifies, the minerals retain indications of the magnetic field it formed in and how strong it was. As long as the minerals are not heated to the point that they become molten again, this magnetic record can remain intact indefinitely. Similarly, the chemical composition of rocks and minerals is dependent on the amount of oxygen in which they formed, allowing scientists to determine how oxygen levels rose and fell over time. As Kuang said in a NASA press release:

These two datasets are very similar. Earth is the only known planet that supports complex life. The correlations we’ve found could help us to understand how life evolves and how it’s connected to the interior processes of the planet.

Geophysicists and geochemists have compiled extensive records on both magnetism and oxygen levels, as recorded in ancient rocks. But according to the authors, there have been no detailed comparisons between these records before. When Kuang and his colleagues analyzed the two datasets, they found that fluctuations in Earth's magnetic field correlated with rising and falling levels of atmospheric oxygen since the Cambrian Explosion. This event, which occurred about 540 million years ago, is when complex life and practically all major animal phyla started to appear in the fossil record. Coauthor Benjamin Mills, a biogeochemist at the University of Leeds added:

This correlation raises the possibility that both the magnetic field strength and the atmospheric oxygen level are responding to a single underlying process, such as the movement of Earth’s continents.

The research team hopes to examine more datasets to test this correlation. This will include datasets that look back farther than the Cambrian Era, as well as those that catalog changes in other atmospheric components (like nitrogen) that are essential to life. These studies could reveal a vital connection between the interior dynamics of planets and habitability, which could also have implications for the search for life beyond Earth (astrobiology).

In what seemed to be a development that came from nowhere, there’s a new entrant into the reusable launch systems competition - Honda. The giant Japanese industrial conglomerate recently launched a prototype reusable rocket up to 300m and landed it safely back on Earth. So what does that mean for the reusable launch vehicle (RLV) industry and the future of inexpensive flights to orbit?

Competition is undoubtedly a good thing, and so far other companies have struggled to make their rockets reusable, one of the most important aspects of making access to space cheap. Blue Origin has done so with the booster for its New Shepard suborbital vehicle landing on a pad near its launch complex. LandSpace, a Chinese company, has successfully demonstrated the Zhuque-3 with a test hop similar to early RLV tests. But most notably, SpaceX has, at this point, successfully launched and landed hundreds of rockets over the course of the past few years, and are the only ones that have reached orbit with an RLV.

That sounds like a market that is ripe for disruption - and Honda certainly saw it that way. Their work with rockets goes back to 2021, but their work on many of the sub-components that go into rockets goes back much further than that. According to a press release, the transition from being a component supplier to being a rocket builder was “inspired by the dream of young Honda engineers.”

Those young engineers were probably (rightfully) thrilled when Honda’s first test launch took place on June 17th. During the test, a prototype rocket that was 6.3m tall and 85 cm in diameter, with a wet weight of 1312 kg, launched 271.4 m into the air and landed 37 cm from its nominal landing spot after a 56.6 second flight. Data was collected throughout the test to inform the next round of testing.

This step is the equivalent to the famous “Grasshopper” experiments that SpaceX completed back in 2013, where the rocket would launch, hover and return to the ground. It was a necessary step on the path to reusable rocketry, and Honda is now only the fourth company to ever complete this feat.

It has a competitive advantage over the other three companies though, in that it’s part of a much large industrial behemoth who makes everything from lawnmowers to motorcycles. Honda already employs tens of thousands of engineers, and has made some of the most reliable combustion related engines ever produced - just ask someone who owns a lawnmower with one of their engines. Compared to relative neophytes like SpaceX and Blue Origin, that industrial heft gives the company a much stronger financial footing from which to experiment.

Honda reusable rocket being prepped for launch.

Whether or not that is an advantage remains to be seen - SpaceX is famous for it’s work culture that is at least partly driven by fear of failure, which probably won’t be the case for the Honda engineers who could simply shuffle off to other parts of the organization if their rocketry experiments fail. But, given Japan’s increasing presence in the growing space industry, it was only a matter of time before a Japanese champion would join the fray of the new RLV industry. Honda is definitely one of the more capable of those potential entrants, but it remains to be seen what, if any impact their entrance will have on the industry at large. As the company moves to completion of a sub-orbital launch in 2029, more and more eyes will be turning toward it as potentially the greatest new competition in this space.

Learn More:

• Honda - Honda Conducts Successful Launch and Landing Test of Experimental Reusable Rocket
• UT - Reusable Chinese Rocket Soft-Lands in the Ocean in a New Test
• UT - Chinese Firm Successfully Tests a New Reusable Booster
• UT - Look out, Starship! China is Building a Massive Reusable Rocket!
• UT - After Awesome Launch, SpaceX's Starship Spins Out of Control

A team of astronomers has recently completed a long-range observation of a comet far from the Sun. This analysis proves that there’s lots going on, even in the icy depths of the solar system.

The targeted comet is C/2014 UN271 Bernardinelli-Bernstein. Comet UN271 is one of the largest Oort Cloud comets ever observed, measuring 140 kilometers across. It's currently at a distance of 16.5 Astronomical Units (AU) from the Sun, which makes it tough to observe with all but the largest telescopes. Astronomers have used the powerful Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to observe the comet, watching as jets of carbon monoxide gas are erupting from its nucleus. This is a surprising level of activity for a comet that's so far from the Sun.

ALMA telescopes on the Chajnantor Plateau.

Credit: ALMA/NSF/ESO

Comet UN271 was discovered in 2014 by astronomers Gary Bernstein and Pedro Bernardinelli. They noticed the faint fuzzball in archival images from the Dark Energy Survey, moving slowly as a +22nd magnitude smudge through the constellation Sculptor.

A Far Ranging Orbit

Almost immediately, astronomers knew Comet UN271 was something special, as its slow motion through the sky suggested it was far out in the solar system, and therefore quite large. After following the comet for a bit, astronomers realized it was 29 AU from the Sun at the time of discovery—about ¾ of the way to Pluto from the Sun—and had a nucleus about 120 kilometers (75 miles) across. For context, Halley’s Comet has a nucleus just 15 kilometers across. This puts Comet UN271 up there in terms of size, as the largest Oort Cloud comet seen to date.

The discovery image for Comet UN271 (annotated).

Credit: NOIRLab.

We’re fortunate to see Comet UN271 on its perihelion approach. In January 2031, the comet will pass 10.9 AU from the Sun, just outside the orbit of Saturn. On a 2.8-million-year orbit inbound, the comet will then head out of the solar system on a 4.6-million-year orbit outbound, for a far-off aphelion 55,000 AU from the Sun. That’s 87% of a light-year away, about a fifth of the way to Proxima Centauri, the nearest star.

The orbit of Comet UN271 through the solar system.

Credit: NASA/JPL Horizons.

The difference in orbit inbound versus outbound for the comet is due to its interaction with solar system planets while it's near the Sun. Any new comet entering the inner solar system stands about a 40% chance of having its orbit altered. Likely, Comet UN271 was knocked off its Oort Cloud perch by a stellar pass near the solar system that sent sunward, long ago.

Looking at a cold distant object like Comet UN271 really pushed the sensitivity and resolution of ALMA to its limits. The thermal signal received by ALMA will not only help to refine the comet’s size, but also help to chronicle the dust production rate seen.

"These measurements give us a look at how this enormous, icy world works," says Nathan Roth (NASA/GSFC) in a recent press release. "We're seeing explosive outgassing patterns that raise new questions about how this comet will evolve as it continues its journey towards the inner solar system."

False color images of Comet UN271, showing activity.

Credit: ALMA/NSF/ESO.

Not only was this a record-setting detection in terms of distance, but it also demonstrates that comets can still display activity, far from the Sun.

No missions are planned to give us a view of Comet UN271 up close. The European Space Agency does have a mission named Comet Interceptor in the works that would loiter in the inner solar system, ready to chase down the next big comet. Comet Interceptor is planned for launch in 2029.

The Hubble Space Telescope imaged Comet UN271 in January 2022. We should get good views of the comet from the James Webb Space Telescope leading up to perihelion if it's ever tasked to observe it. The Vera Rubin Observatory, which is set to reveal its very first images next week could provide amazing views of the comet as well in the years to come.

Hubble's view of Comet UN271 in 2022.

Credit: NASA/HST/STScI

And yes, a comet the size of UN271 would spell a bad day for Earth, though in this case, it isn’t coming anywhere near the inner solar system. UN271 is 12 times the size of the Chicxulub impactor (which was only about 10 kilometers across) that struck the Earth 66 million years ago, so it would definitely be an extinction-level event if something the size of UN271 ever came our way.

A size comparison for other known comets, versus UN271.

Credit: NASA/ESA/Zena Levy/STScI

Too bad Comet UN271 won’t visit the inner solar system... (just not too close!) It’s bigger than Hale-Bopp, and would provide an amazing show. For now, we’ll have to wait for the next Oort Cloud interloper to turn up. Still, the appearance of Comet UN271 shows us just what might be lurking out there, in the remote realms of the outer solar system.

For years, astronomers have been searching for a mysterious ninth planet lurking in the dark outer reaches of our Solar System. Now, a team of researchers have taken a completely different approach to this cosmic detective story, instead of looking for reflected sunlight, they're hunting for the planet's own heat signature.

The story begins with a puzzle in the outer Solar System. Scientists noticed that small icy bodies called Kuiper Belt Objects, which orbit far beyond Neptune, seem to be clustered together in unusual ways. Their orbits are aligned in patterns that shouldn't exist by chance alone. The leading and most tantalising explanation…. a massive, undiscovered planet (dubbed "Planet Nine”) is gravitationally shepherding these distant objects into their strange orbits.

Known objects in the Kuiper belt beyond the orbit of Neptune. Scale in Astronomical Units. Sun at centre, Jupiter, Saturn, Uranus and Neptune depicted as J, S, U and N

(Credit : Minor Planet Center)

If it exists, Planet Nine would be a true giant, roughly 5-10 times the mass of Earth, orbiting somewhere between 400-800 times farther from the Sun than our planet does. At such an enormous distance, it would be incredibly faint and nearly impossible to spot with traditional telescope searches that rely on detecting reflected sunlight.

This is where the new research gets ingenious. Led by Amos Chen from the National Tsing Hua University, the team realised that searching for Planet Nine's heat signature could be far more effective than looking for its reflected light. Here's why: when you double the distance from the Sun, reflected light becomes 16 times fainter (following what scientists call an inverse fourth-power relationship). But thermal radiation, the heat that all objects naturally emit, only becomes 4 times fainter when you double the distance.

Thermal image of Jupiter from JWST

(Credit : NASA/ESA)

The researchers turned to data from AKARI, a Japanese space telescope that conducted the most sensitive all-sky survey in far infrared light, the perfect wavelength range to detect the heat signature of a cold, distant planet. Unlike ground based telescopes that are hampered by Earth's atmosphere, AKARI could detect the faint thermal glow that Planet Nine should emit.

The team focused their search on a specific region of sky where computer simulations suggested Planet Nine was most likely to be found, based upon the orbital patterns of the Kuiper Belt Objects. They then faced the challenging task of distinguishing a slowly moving planet from the countless stars, galaxies, and cosmic debris that populate this region.

They had a rather elegant solution however, Planet Nine should appear stationary over the course of a single day but show detectable movement over months. By comparing AKARI observations taken at different times, they could identify objects with this specific type of motion while filtering out cosmic rays, background galaxies, and other false signals.

Illustration of JAXA's infrared astronomy satellite ASTRO-F "AKARI"

(Credit : JAXA)

After this meticulous analysis, the researchers identified two candidates. Both objects appear in the predicted location and emit the amount of infrared light that theory suggests Planet Nine should produce. While this doesn't constitute definitive proof, it represents the most promising lead in the search for our Solar System's hidden giant.

These discoveries mark an important milestone, but the journey isn't over. The candidates require follow up observations with more powerful telescopes to confirm whether they're truly moving in ways consistent with Planet Nine, or whether they're imposters, perhaps background galaxies or other astronomical objects.

If confirmed, the discovery of Planet Nine would revolutionise our understanding of how our Solar System formed and evolved. It would also demonstrate the power of thinking creatively about astronomical searches, sometimes the best way to find something isn't to look directly at it, but to feel its warmth instead!

Source : 

• A Far-Infrared Search for Planet Nine Using AKARI All-Sky Survey

The telescope's journey began in the early 1600s when Dutch spectacle maker Jan Lippershey discovered that combining lenses could magnify distant objects. Galileo Galilei quickly improved the designs and became the first to explore the heavens, revealing the Moon's craters, Jupiter’s moons and the rings of Saturn. Over the centuries, telescopes evolved from simple lens combinations to massive ground-based observatories with enormous mirrors, and eventually to space-based instruments like the Hubble Space Telescope that eliminated Earth's atmospheric interference. Today's cutting-edge telescopes, such as the James Webb Space Telescope, use advanced technology to look deeper into space than ever before.

The Hubble Space Telescope as seen from the departing Space Shuttle Atlantis, flying STS-125, HST Servicing Mission 4.

(Credit : NASA)

Among the astronomers who used these powerful instruments to revolutionize our view of the universe was Vera Rubin, whose groundbreaking observations in the 1970s would shake the very foundations of physics. Working with increasingly sophisticated telescopes, Rubin studied the rotation of spiral galaxies, expecting to confirm what seemed like basic physics: that stars farther from the center of a galaxy should orbit more slowly, just as outer planets in our Solar System move more leisurely than inner ones. Instead, her precise measurements revealed something utterly unexpected: stars at the edges of galaxies were moving far too fast, as if held in place by invisible matter that astronomers couldn't see. This discovery of what we now call dark matter didn't just add a new chapter to astronomy, it revealed that the vast majority of the universe consists of a mysterious, unseen substance that continues to puzzle us today.

Dark matter map for a patch of sky based on gravitational lensing analysis of a Kilo-Degree Survey

(Credit : Kilo-Degree Survey Collaboration)

Now, a new-generation telescope bearing Rubin's name is poised to continue her revolutionary work. Enter the Vera C. Rubin Observatory that has been under construction in Chile's Atacama Desert. It will conduct the most comprehensive survey of the night sky ever attempted, photographing the entire visible southern sky every few nights for ten years! This technological marvel, equipped with the world's largest digital camera containing 3.2 billion pixels, won't just search for the subtle effects of dark matter but will catalog billions of stars and galaxies, track dangerous asteroids, and monitor the universe's constant changes in real time. When it finally begins operations, the Rubin Observatory will generate more astronomical data in its first month than all previous telescopes combined have collected throughout history, that’s including my images too!

The telescope features an 8.4-meter primary mirror with a three-mirror design that provides an exceptionally wide 3.5-degree field of view, seven times the area of the full Moon. At its core is the Legacy Survey of Space and Time (LSST) Camera, the world's largest digital camera composed of 189 individual CCD sensors, weighing in at 3,200 kilograms and operating at -100°C to minimise electronic noise. Located at 2,647 meters elevation on Chile's Cerro Pachón, the observatory's design eliminates traditional mirror obstructions while delivering sharp images across its entire field of view. It can slew between targets in just five seconds and will operate using six optical filters, completing a full sky survey every three nights with 15-second exposures. Over its 10-year mission, it will catalog an estimated 20 billion galaxies and 17 billion stars.

Artist impression of the completed LSST

(Credit : LSST Press Office)

It's incredible that it's been just over 400 years since our first look at the universe through Galileo’s telescope. We are now about to perhaps hit another incredible milestone as the astronomical community eagerly awaits another historic moment! On 23rd June 2025 at 15:00 UTC, the Rubin Observatory will unveil its first spectacular images in what they're calling the "First Look" event. This event will be live-streamed via YouTube, allowing people worldwide to witness this exciting moment together. It represents more than just another technological achievement; it symbolises our relentless pursuit to understand the universe, carrying forward Vera Rubin's legacy of discovery into an age where the observatory that carries her name will give us a whole new view of the universe.

• Links to the live stream can be found on the Rubin Observatory website

Source : 

• Coming June 23, 2025: First Look at the cosmos with NSF–DOE Vera C. Rubin Observatory

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Imagine scanning the night sky for signs of alien technology using the same systems that hunt for exploding stars. This is exactly what researchers are now doing, transforming astronomical alert systems originally designed to catch supernovae into powerful tools for detecting potential technosignatures, the evidence of advanced civilisations beyond Earth.

The Crab Nebula is a supernova remnant in the constellation Taurus

(Credit : NASA/ESA)

Every night, the Zwicky Transient Facility (ZTF) generates up to 1 million alerts as it monitors the sky for changing objects. These alerts flow through nine different "alert brokers," which are sophisticated software systems that process and distribute information about anything that brightens, dims, or appears in the sky. The upcoming Legacy Survey of Space and Time (LSST) will increase this volume by an order of magnitude, creating an unprecedented flood of astronomical data.

While these systems were built to catch explosive events like supernovae and track asteroids, a new paper by researchers Eleanor Gallay, James Davenport, and Steve Croft demonstrates their untapped potential for SETI (Search for Extraterrestrial Intelligence). Their work shows how we can repurpose these astronomical systems to search for the subtle signatures that might indicate artificial structures or technologies around distant stars.

The Samuel Oschin Telescope, part of the Zwicky Transient Facility

The inspiration for this approach comes partly from "Boyajian's Star," otherwise known as "Tabby's Star" and with the official designator KIC 8462852, which puzzled astronomers with its mysterious dimming patterns. The researchers note that analysing nearby stars for similar behaviour over time was done in the case of Boyajian's Star, though natural explanations like dust clouds ultimately proved most likely. However, the study highlighted how unusual stellar behaviour could potentially indicate artificial megastructures like Dyson spheres, hypothetical constructs that advanced civilisations might build around their stars.

The new research takes this concept further, creating automated systems to identify "stellar dippers," stars that suddenly and dramatically dim without obvious natural causes. These objects are stars with a historically constant luminosity that drop suddenly in brightness for a reason unexplained by classical stellar variability or other astrophysical phenomena.

Artist's concept of an "uneven ring of dust" orbiting Tabby's Star

(Credit : NASA/JPL-Caltech)

The challenge is immense: filtering millions of nightly alerts to find the handful that might represent something genuinely anomalous. The researchers developed a two-stage approach. First, they use the alert broker's built-in filtering capabilities to narrow down candidates. Then they apply additional analysis using historical data to identify stars showing unprecedented dimming behaviour.

The team has deployed optical SETI techniques, such as planetary transit zone geometries and the SETI Ellipsoid. The SETI Ellipsoid is a particularly clever concept that identifies the zone in space where hypothetical alien observers would have seen Earth transit across the Sun, potentially prompting them to send signals in our direction.

The researchers are honest about current constraints. Though the SETI methods that alert brokers can execute are currently limited, they provide suggestions that may enhance future technosignature and anomaly searches in the era of the Vera C. Rubin Observatory. The existing systems weren't designed with SETI in mind, so some modifications and new approaches will be needed to fully realise their potential.

However, the foundation is solid. Alert brokers already possess sophisticated tools for identifying unusual astronomical events, and the researchers find some SETI projects are possible using features directly in the brokers. The Lasair alert broker, for instance, offers a "watchmap" feature that can monitor specific regions of sky for anomalous signals.

As the Vera C. Rubin Observatory comes online with LSST, the volume of astronomical alerts will increase dramatically. This creates both opportunities and challenges for technosignature research. More data means better chances of catching rare, anomalous events, but it also means developing even more sophisticated filtering techniques to avoid being overwhelmed.

Artist impression of the completed LSST

(Credit : LSST Project Office)

The researchers' work represents a sensible approach to SETI that uses existing infrastructure rather than requiring dedicated alien hunting telescopes. By utilising systems already scanning the entire visible sky every few nights, they're essentially getting a free ride on one of the most comprehensive surveillance networks ever pointed at the sky.

The team concludes that their initial results make clear the promising opportunity for future anomaly and technosignature searches using alert brokers on data from ZTF and the upcoming LSST. While we shouldn't expect to find alien megastructures next week, this research establishes the groundwork for a new generation of SETI that could operate continuously, scanning millions of stars for the signs that we are not alone in the universe.

Source : 

• Technosignature Searches with Real-time Alert Brokers

In the 1960s, scientists became acutely aware of a problem with the Universe's "mass budget." Based on the observed rotational curves of galaxies, they determined that about 85% of the Universe's mass was invisible, leading to the theory of Dark Matter. Scientists have also been aware for some time that much of the "normal" or baryonic matter (that which we can see) in the Universe was also unaccounted for. This has prompted multiple efforts to probe the Universe for this "missing" mass, using everything from X-ray emissions and ultraviolet observations of distant quasars to find hints of where it might be hiding.

In a new landmark study, astronomers at the Harvard & Smithsonian Center for Astrophysics (CfA) and Caltech announced the detection of the most distant fast radio burst (FRB) on record. Using this phenomenon as a guide, the team conducted the first detailed measurement of ordinary matter distribution across the cosmos. Their results show that more than three-quarters of the Universe's baryonic matter exists between galaxies (aka. the intergalactic medium) as hot, diffuse clouds of gas previously invisible to telescopes. This research helps resolve a longstanding mystery in cosmology and is a major step forward in understanding how matter interacts and behaves in the Universe.

The study was led by Liam Connor, a Canadian astrophysicist and radio astronomer with the CfA and the Cahill Center for Astronomy and Astrophysics at the California Institute of Technology. He was joined by colleagues from the CfA, Caltech's Owens Valley Radio Observatory, and the Observatories of the Carnegie Institution for Science. The paper that describes their findings, "A gas-rich cosmic web revealed by the partitioning of the missing baryons," recently appeared in Nature Astronomy.

Artist's impression of an extragalactic FRB.

Credit: ESO/M. Kornmesser

Fast Radio Bursts (FRBs) are bright explosions of radio waves that typically last for mere milliseconds, though events lasting a few seconds have been recorded. While the origin of these bursts is still subject to debate, the general consensus is that they are associated with compact objects (neutron stars and black holes). Recently, scientists demonstrated that FRBs from distant galaxies could be used to measure baryonic matter throughout the Universe. But until now, astronomers could not find the location of the most distant FRBs, which would allow them to explore the distribution of matter on cosmic scales.

"Baryons are pulled into galaxies by gravity, but supermassive black holes and exploding stars can blow them back out—like a cosmic thermostat cooling things down if the temperature gets too high," said Conner in a CfA press release. "Our results show this feedback must be efficient, blasting gas out of galaxies and into the IGM." As part of their research, a team analyzed 60 FRBs ranging in distance from 11.74 million light-years (FRB20200120E in the M81 galaxy) to the most distant FRB on record - FRB 20230521B, located ~9.1 billion light-years away. By measuring how much each FRB signal slowed as it passed through the intergalactic medium (IGM), Connor and his team could track the gas as it travelled to reach Earth. Said Conner:

The decades-old 'missing baryon problem' was never about whether the matter existed. It was always: Where is it? Now, thanks to FRBs, we know: three-quarters of it is floating between galaxies in the cosmic web." In other words, scientists now know the home address of the "missing" matter. FRBs act as cosmic flashlights. They shine through the fog of the intergalactic medium, and by precisely measuring how the light slows down, we can weigh that fog, even when it's too faint to see.

According to their results, approximately 76% of the Universe's baryonic matter lies in the IGM, about 15% is located in galaxy halos, and the remainder consists of stars, cold galactic gas, and other objects. These measurements align with predictions based on advanced cosmological simulations, confirming what was theoretical until now. Locating the missing matter in the Universe also has the potential to address other cosmological questions. These include how galaxies form, how matter coalesces in the Universe, and how light travels across vast cosmological distances. Vikram Ravi, an assistant professor of astronomy at Caltech and co-author on the paper, is also the co-Principal Investigator of Caltech's Deep Synoptic Array-110 (DSA-110):

It's a triumph of modern astronomy. We're beginning to see the Universe's structure and composition in a whole new light, thanks to FRBs. These brief flashes allow us to trace the otherwise invisible matter that fills the vast spaces between galaxies. We're entering a golden age. Next-generation radio telescopes like the DSA-2000 and the Canadian Hydrogen Observatory and Radio-transient Detector will detect thousands of FRBs, allowing us to map the cosmic web in incredible detail.

Further Reading: 

• CfA, 
• Nature

As NASA prepares for a return to the Moon through the Artemis program, one of the biggest health concerns for astronauts has been lunar dust. The fine, abrasive particles known as the regolith that coat the Moon's surface have long worried scientists, especially after Apollo astronauts experienced respiratory problems after their missions. However, groundbreaking research from the University of Technology Sydney has delivered surprisingly reassuring news: lunar dust is less harmful to human lung cells than previously feared, and significantly less toxic than common Earth based air pollution.

NASA’s Space Launch System rocket carrying the Orion spacecraft launches on the Artemis I flight test.

(Credit : Joel Kowsky)

The study, led by PhD candidate Michaela B. Smith, represents the most comprehensive analysis yet of how lunar dust affects human health. Smith investigated the impact of lunar dust simulants on human lung cells in the lab. She then compared the effects to those of airborne particulate matter collected from a busy street in Sydney.

The results were striking. While lunar dust can act as a physical irritant, it did not cause the severe cellular damage or inflammation seen from the urban Earth dust. Smith emphasises this crucial distinction “..between a physical irritant and a highly toxic substance".

Buzz Aldrin's bootprint in the lunar soil

(Credit : NASA)

The research focused on the tiniest particles, those measuring 2.5 micrometers or smaller which are small enough to bypass the body's natural defences and penetrate deep into the lungs. Using two different types of lung cells representing both upper and lower respiratory regions, the team discovered that Earth dust induced a greater inflammatory response and was more toxic to the cells than the lunar dust simulants.

This finding addresses concerns that arose from the Apollo missions, where astronauts experienced respiratory issues after fine dust that had clung to their spacesuits became airborne in the confined cabin and was subsequently inhaled, leading to respiratory issues, sneezing, and eye irritation.

The key difference lies in how the dust affects cells. The study suggests the primary mechanism of toxicity from lunar dust is mechanical damage caused by the particles' irregular shape and rough edges. Crucially, the lunar simulants did not cause significant damage through a process known as oxidative stress (damage caused by unstable molecules), a process often associated with fine particle toxicity.

"Any dust, if you inhale it, you'll sneeze, cough, and have some physical irritation. But it's not highly toxic like silica, where you end up with silicosis from being on a construction site for 10 years”

- Michaela B. Smith, lead author.

Despite these encouraging findings, NASA continues taking dust exposure seriously. The space agency has developed innovative engineering solutions, including ingenious suits that are attached to the outside of the rover, where the astronaut will climb in and out from inside, and the suit never goes inside, which prevents the dusty suit from ever contaminating the internal cabin environment.

This research provides crucial data for planning long term lunar missions and establishing permanent bases on the Moon, helping to ensure astronaut safety while reducing one significant health concern for humanity's next giant leap.

Source : 

• Lunar Dust Less Toxic Than City Pollution, Study Finds.

{ https://www.universetoday.com/ }

Hycean worlds are also called ocean worlds. They're planets covered in oceans that also have thick hydrogen atmospheres. There are no confirmed Hycean worlds—also called ocean worlds—but many candidates. Even though they're only candidates so far, researchers are curious about their habitability. New research examines the role tidal heating plays in their potential habitability.

If hycean planets do exist, they're likely common around red dwarfs (M dwarfs.) Red dwarfs are the most plentiful type of star in the galaxy, and Hycean worlds' thick hydrogen atmospheres might protect them from the devastating flaring behaviour of these small, long-lived stars. Hycean worlds may have larger habitable zones because of all their water, but their hydrogen atmospheres may contribute to the runaway greenhouse effect. When it comes to habitability, these hypothetical worlds are intriguing and mysterious.

In new research to appear in The Astrophysical Journal, the authors argue that for Hycean worlds close to their low-mass stars, tidal heating may be an important factor in determining their habitable zones. It's titled "Tides Tighten the Hycean Habitable Zone," and the lead author is Joseph Livesey. Livesey is from the Department of Astronomy and the Wisconsin Center for Origins Research, both at the University of Wisconsin-Madison.

When a new exoplanet is discovered, one of the first things scientists and the public want to know is if it's in the star's habitable zone. Researchers have made significant progress understanding the habitable zones for rocky planets. "Many studies have parameterized the habitable zone (HZ) for terrestrial exoplanets," the authors write. "The exact HZ boundaries can vary based on key characteristics such as stellar host type, planetary mass, atmospheric composition, and more."

But hycean worlds are much different than terrestrial worlds. They're sub-Neptunes with significant water layers and atmospheres dominated by hydrogen. They're oddballs, and determining if they are in habitable zones requires a different approach than with rocky planets.

In our Solar System, some of the gas giant moons have frozen shells with liquid oceans underneath. They're far too distant for the Sun to warm them. It's tidal flexing that maintains their liquid oceans. As moons like Europa and Enceladus orbit Jupiter and Saturn, the much-larger gas giants pull on the moons and they flex in response. That action creates heat. So, in effect, tidal flexing creates a habitable zone that's isolated from the Sun.

Since many hycean worlds are expected to orbit their stars closely, can tidal heating alter their habitable zones?

The researches say that the Hycean Habitable Zone (HHZ), when compared to the terrestrial habitable zone, may include smaller semi-major axes and could even extend to unbound planetary orbits. A near total absence of GHGs other than hydrogen along with a high albedo allows closer orbital proximity to the star, while internal heating from radiogenic sources, high pressures, a liquid water layer, and larger planet masses extend the HHZ outward.

Tidal heating creates another heat source aside from stellar radiation. Hycean worlds following moderately eccentric orbits experience tidal flexing and heating that shifts the HHZ outward. This creates a smaller HZ than previous estimates based on stellar heating.

Moderately eccentric orbits are common. Our Solar System has massive outer planets that have shifted the orbit of smaller planets into eccentricity. Many other solar systems are likely to have them too, meaning they're shifting smaller planets into eccentricity.

"These outer companions do occur in planetary systems around M dwarfs; the occurrence rate of giants in such systems has been found to be ∼ 10%, and the occurrence rate of planets in the range 10–100M⊕ is ∼ 20%," the authors write.

This figure shows The HHZ (blue shaded regions) and dark HHZ (red shaded regions) around a 0.12M⊙ star for a 7M⊕, 1.7R⊕ Hycean planet with tidal heating. The dark HHZ indicates a tidally-locked Hycean planet that can be habitable on its nightside. The low-opacity contours show the habitable zone locations without tidal heating, and the high-opacity contours show the habitable zone location where tidal heating is included. The dotted and dashed lines indicate the conservative and optimistic habitable zones for terrestrial planets.

Image Credit: Livesey et al. 2025. The Astrophysical Journal.

The above image shows how tidal heating shifts the HHZ around low-mass stars. However, most hycean candidates are orbiting more massive stars. The researchers found that the effect of tidal heating on the HHZ depends on the star's mass. They found that around more massive stars, the tidal heating effect isn't as pronounced.

This figure shows the HHZ and dark HHZ around stars of various mass for a 7M⊕, 1.7R⊕ Hycean planet. The orbital eccentricity for this planet is based on the Hycean candidate world K2-18 b, a planet known for evidence of potential biosignatures. The dotted line represents the stellar mass in the previous figure of 0.12 solar masses. "Clearly, the effect of tides on the extent of the habitable zone becomes negligible at high stellar masses," the researchers explain. Image Credit: Livesey et al. 2025.

The Astrophysical Journal.

This research shows that tidal flexing on ocean worlds shifts their habitable zones outward. The effect relies on a more massive companion planet that can introduce eccentricity into the hycean world's orbit.

"Hycean planets are likely to exhibit stronger tidal responses than a fiducial terrestrial world," the researchers explain. "We expect tides to have little effect on a lone planet at such small orbital radii. However, the presence of a large outer companion with moderate eccentricity will force an eccentricity cycle that periodically and indefinitely heats the interior of the planet in question, and push out the inner boundaries of the HHZ."

Though hycean worlds are only hypothetical at this point, their confirmation may not be too distant. Exoplanet scientists are intrigued by them because of their potential for habitability. Their extended atmospheres also make them desirable targets for atmospheric spectroscopy with telescopes like the JWST. K2-18b is a prime example of their potential. It's a candidate hycean world that repeatedly generated headlines when astronomers found evidence of water vapor, then carbon dioxide and methane, then the potential biosignature dimethyl sulfide in its atmosphere.

"A recent possible detection of dimethyl sulfide (DMS) in the atmosphere of the potential hycean exoplanet K2-18 b may indicate the presence of ocean-faring life; the only major source of DMS on Earth is phytoplankton," the authors write. They point out that on hycean worlds with deep oceans, the ocean tides generate a significant amount of heat that can be used by organisms. This sets them apart from Earth, where the tidal energy is dissipated. "We suggest, therefore, that strong tides on hycean planets could yield a significant power source for life and ultimately accelerate biological evolution," they explain.

If our Solar System seems stable, it's because our short lifespans make it seem that way. Earth revolves, night follows day, the Moon moves through light and shadow, and the Sun hangs in the sky. But in reality, everything is moving and influencing everything else, and the fine balance we observe can easily be disrupted. Could passing stars have disrupted Earth's orbit and ushered in dramatic climatic changes in our planet's past?

A stellar flyby is when another star passes close enough to our Solar System to cause some disruption. Our neighbourhood in the Milky Way is relatively sparsely populated, so stellar flybys are rarer than in other parts of the galaxy. But they still occur.

The most well-known one was probably Scholz's star. About 70,000 years ago, it passed through the Oort Cloud, our Solar System's outlying repository of long-period comets and icy planetesimals. It may have perturbed some comets from the Oort Cloud, but if it did, we won't know for a couple of million years. That's how long it would take for a comet to reach the inner Solar System.

Scholz's star illustrates the risk of stellar flybys. Scientists have wondered if these flybys have affected Earth's climate in the past by altering the planet's orbit. New research that will appear in The Astrophysical Journal examines stellar flybys to see if this is true. It's titled "No influence of passing stars on paleoclimate reconstructions over the past 56 million years." The authors are Richard Zeebe and David Hernandez. Zeebe is from the School of Ocean & Earth Science & Technology at the University of Hawaii, and Hernandez is from the Department of Astronomy at Yale University.

"Passing stars (also called stellar flybys) have notable effects on the solar system’s long-term dynamical evolution, injection of Oort cloud comets into the solar system, properties of trans-Neptunian objects, and more," the authors write. "Based on a simplified solar system model, ... it has recently been suggested that passing stars are also an important driver of paleoclimate before ∼50 Myr ago, including a climate event called the Paleocene-Eocene Thermal Maximum (PETM) (∼56 Myr ago)."

The PETM saw a 5–8 °C (9–14 °F) rise in global temperature and a massive influx of carbon into the atmosphere and oceans. It took 10,000 or 20,000 years for the temperature to rise and it lasted for about 100,000 or 200,000 years. Its effect on the biosphere was massive. Many marine organisms went extinct, tropical and sub-tropical regions extended toward the poles, and primates and other mammals appeared.

The Paleocene–Eocene Thermal Maximum was a prominent hyperthermal episode in Earth's climatic history. Its cause is unclear.

Image Credit: Svensen 2012. https://doi.org/10.1038/483413a

The cause is still debated, and there are several hypotheses. They include volcanic eruptions, comet impact, the release of methane clathrates, and orbital forcing. Researchers think that the giant planets play an important role during stellar flybys. When a roaming star passes by, the giant planets' gravitational fields can amplify the effect of the flyby and then alter the orbits of the smaller planets.

To find out if stellar flybys could be responsible for the PETM and other climatic changes, the researchers used a state of the art model of the Solar System and random stellar parameters in 400 simulations. The total number of stellar flybys was 1,800.

Other researchers who examined the same issue found that stellar flybys could've altered Earth's paleoclimate. [Kaib & Raymond (2024)] (https://iopscience.iop.org/article/10.3847/2041-8213/ad24fb) said, "Here we present simulations that include the Sun's nearby stellar population, and we find that close-passing field stars alter our entire planetary system's orbital evolution via their gravitational perturbations on the giant planets." They also wrote "Although it takes tens of Myr for the effects of stellar passages to significantly manifest themselves, the long-term orbital evolution of the Earth and the rest of the planets is linked to these stars."

However, Zeebe and Hernandez reached a different conclusion. "In contrast to Kaib and Raymond, we find no influence of passing stars on paleoclimate reconstructions over the past 56 Myr," they write.

This global map shows what Earth looked like 45 million years ago.

Image Credit: By Scotese, Christopher R.; Vérard, Christian; Burgener, Landon; Elling, Reece P.; Kocsis, Ádám T. - "Phanerozoic-scope supplementary material to "The Cretaceous World: Plate Tectonics, Paleogeography, and Paleoclimate (doi:10.1144/sp544-2024-28)" from the PALEOMAP project". doi:10.5281/zenodo.10659112 https://zenodo.org/records/10659112, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=155112444

One of the reasons for the different results is the completeness of the models used to understand the flybys. Some Solar System models, for example, excluded the Moon.

"Running accurate state-of-the-art solar system models that include all known secondary effects is computationally expensive," the authors write. "As a result, long-term studies on, e.g., Gyr-timescale tend to be based on simplified solar system models, or the outer planets alone."

By using a more complete Solar System model, Zeebe and Hernandez showed that stellar flybys are not likely behind Earth's dramatic paleoclimate shifts, like the PETM. They point out that the Moon has a stabilizing effect, and models that exclude it reach suspect conclusions.

"In contrast, using a state-of-the-art solar system model, including a lunar contribution and J2 (the Moon and Sun's quadrupole moment), and random stellar parameters, we find no influence of passing stars on paleoclimate reconstructions over the past 56 Myr," the authors explain. Even extremely close flybys seem to have no effect.

There have been many stellar flybys in the past and there'll be many more in the future. The orange dwarf Gliese 710 is expected to come within 0.1663 light-years or 10,520 astronomical units in about 1.29 million years. It has an 86% chance of passing through the Oort Cloud, and some researchers say it could trigger a swarm of comets into the inner Solar System. Could this flyby trigger a dramatic shift in Earth's climate?

There's a lot of uncertainty, and understanding the past and future of stellar flybys and how they might affect Earth's climate comes down to how detailed our scientific models are.

"Our results indicate that a complete physics model is essential to accurately study the effects of stellar flybys on Earth’s orbital evolution," the authors conclude.