Callisto has a different appearance than other suspected ocean moons like Europa and Saturn’s Enceladus. Europa clearly has a white, icy surface, although it has other brownish colours, too. Enceladus has an extremely bright, icy surface and has the highest albedo of any object in the Solar System. Callisto, on the other hand, has a dark, icy surface and is covered in craters.

However, the evidence for its ocean is unrelated to its surface appearance and any visible ice.

The main evidence supporting an ocean on Callisto comes from the moon’s magnetic field. Unlike Earth’s internally generated magnetic field, Callisto’s is induced. That means the field is created from Callisto’s interactions with Jupiter and its extremely powerful magnetic field. For Callisto to induce a magnetic field, it has to have a layer of conductive material.

The question is, is the layer an ocean or something else?

Different researchers have been trying to answer that question since Galileo gathered its data. One of the spacecraft’s instruments was a magnetometer, a type called a Dual-Technique Magnetometer (DTM). There are multiple types of magnetometers, and each one works differently. Galileo’s DTM provided redundancy and allowed for cross-checking, which increased the accuracy and reliability of its data. It was especially good at detecting the subtle magnetic fields of Jupiter’s moons, including Callisto. It also collected data continuously, which let scientists gain insights into how the magnetic fields of Jupiter and its moons varied over time due to different interactions.

In a 2017 paper, researchers pointed to the ionosphere as the primary cause of Callisto’s magnetic fields. “We find that induction within Callisto’s ionosphere is responsible for a significant part of the observed magnetic fields,” the authors wrote. “Ionospheric induction creates induced magnetic fields to some extent similar as expected from a subsurface water ocean.”

New research in AGU Advances based on Galileo data strengthens the idea that Callisto has a subsurface ocean and that it’s responsible for the moon’s magnetic field rather than its ionosphere. The paper is titled “Stronger Evidence of a Subsurface Ocean Within Callisto From a Multifrequency Investigation of Its Induced Magnetic Field.” The lead author is Corey Cochrane, a scientist at JPL who studies planetary interiors and geophysics. An important part of this research is that they considered data from multiple Galileo flybys (C03, C09, and C10).

“Although there is high certainty that the induced field measured at Europa is attributed to a global-scale subsurface ocean, there is still uncertainty around the possibility that the induced field measured at Callisto is evidence of an ocean,” Cochrane and his co-researchers write. “This uncertainty is due to the presence of a conductive ionosphere, which will also produce an induction signal in response to Jupiter’s strong time-varying magnetic field.”

In short, Callisto’s magnetic field could be caused by its ionosphere, an ocean, or a combination of both. The problem is that Callisto’s conductive ionosphere creates a magnetic field that can mask the presence of an ocean. To get to the truth, the authors used previously published simulations of the moon’s interactions combined with “both an inverse and an ensemble forward modeling method.” The authors write that this brings some clarity about the possible range of Callisto’s interior properties.

The researchers created a four-layer model of Callisto, including its ionosphere. “Among these models, we vary the thickness of the ice shell, the thickness of the ocean, and the conductivity,” the authors write. They also varied the seafloor depth and the ionosphere’s conductance.

The researchers concluded that the moon’s ionosphere alone cannot explain the magnetic field. Instead, it “more likely arises from the combination of a thick conductive ocean and an ionosphere rather than from an ionosphere alone.”

They also concluded that the ocean is tens of kilometres thick from the seafloor to the ice shell, and the ice shell could also be tens of kilometres thick. “As our results demonstrate, both the inverse and forward modelling approaches support the presence of an ocean when considering data acquired from flyby C10 alongside C03 and C09,” the researchers explain. “Our analysis, the first to simultaneously fit C03, C09, and C10 flyby data together, favours the presence of a thick and deep ocean within Callisto.”

The models also favour a thick ice shell “consistent with Callisto’s heavily cratered geology,” they explain.

Galileo wasn’t dedicated to studying Callisto, so there is a dearth of data in all research into its magnetic fields. “It is challenging to place tighter constraints on the properties of Callisto’s ocean because of the limited number of close Galileo flybys that produced reliable data and because of the uncertainty associated with the plasma interaction,” the authors write in their conclusion.

Better and more complete data is in the future, though. Both NASA’s Europa Clipper and the ESA’s JUICE mission will gather more data, some of it from very close to Callisto’s surface.

The Europa Clipper is scheduled to make nine flybys of Callisto. Seven will be within 1800 km of the surface, and four of those will be within 250 km. Its magnetometer will operate continuously during those flybys. The ESA’s JUICE mission is scheduled to perform 21 flybys of Callisto. All of them will be within 7000 km of the surface, and most will be below 1000 km.

Both the Europa Clipper and JUICE have instruments that Galileo didn’t have. Though Galileo came within about 1100 km of Callisto’s surface, it simply could not provide the same kind of data that these newer missions will. The Clipper and JUICE are scheduled to reach the Jovian system in 2030 and 2031, respectively.

As their data starts to arrive and reaches scientists, we will likely determine for sure if Callisto is yet another of the Solar System’s ocean moons.

• Press Release: Jupiter’s Moon Callisto Is Very Likely an Ocean World
• Research: Stronger Evidence of a Subsurface Ocean Within Callisto From a Multifrequency Investigation of Its Induced Magnetic Field

{ https://www.universetoday.com/ }

20-02-2025 om 22:09 geschreven door peter  

Sending crewed missions to Mars presents many challenges, including logistics and health hazards. In the past 20 years, the shortest distance between Earth and Mars was 55 million km (34 million miles), or roughly 142 times the distance between the Earth and the Moon. This was in 2003 and was the closest the two planets had been in over 50,000 years. Using conventional methods, it would take six to nine months to make a one-way transit, during which time astronauts will experience physiological changes caused by long-term exposure to microgravity.

These include muscle atrophy, loss of bone density, a weakened cardiovascular system, etc. Moreover, a return mission could last as long as three years, during which time astronauts would spend at least a year living and working in Martian gravity (36.5% that of Earth). There’s also the risk of elevated radiation exposure astronauts will experience during transits and while operating on the surface of Mars. However, there are also the potential health effects caused by exposure to Martian regolith. As Wang described to Universe Today via email:

“There are many potential toxic elements that astronauts could be exposed to on Mars. Most critically, there is an abundance of silica dust in addition to iron dust from basalt and nanophase iron, both of which are reactive to the lungs and can cause respiratory diseases. What makes dust on Mars more hazardous is that the average dust particle size on Mars is much smaller than the minimum size that the mucus in our lungs is able to expel, so they’re more likely to cause disease.”

During the Apollo Era, the Apollo astronauts reported how lunar regolith would stick to their spacesuits and adhere to all surfaces inside their spacecraft. Upon their return to Earth, they also reported physical symptoms like coughing, throat irritation, watery eyes, and blurred vision. In a 2005 NASA study, the reports of six of the Apollo astronauts were studied to assess the overall effects of lunar dust on EVA systems, which concluded that the most significant health risks included “vision obscuration” and “inhalation and irritation.”

“Silica directly causes silicosis, which is typically considered an occupational disease for workers that are exposed to silica (i.e., mining and construction),” said Wang. “Silicosis and exposure to toxic iron dust resemble coal worker’s pneumoconiosis, which is common in coal miners and is colloquially known as black lung disease.”

Beyond causing lung irritation and respiratory and vision problems, Martian dust is known for its toxic components. These include perchlorates, silica, iron oxides (rust), gypsum, and trace amounts of toxic metals like chromium, beryllium, arsenic, and cadmium – the abundance of which is not well understood. On Earth, the health effects of exposure to these metals have been studied extensively, which Wang and his team drew upon to assess the risk they pose to astronauts bound for Mars in the coming decades:

“It’s significantly more difficult to treat astronauts on Mars for diseases because the transit time is significantly longer than other previous missions to the ISS and the Moon. In this case, we need to be prepared for a wide array of health problems that astronauts can develop on their long-duration missions. In addition, [microgravity and radiation] negatively impact the human body, can make astronauts more susceptible to diseases, and complicate treatments. In particular, radiation exposure can cause lung disease, which can compound the effects that dust will have on astronauts’ lungs.”

In addition to food, water, and oxygen gas, the distance between Earth and Mars also complicates the delivery of crucial medical supplies, and astronauts cannot be rushed back to Earth for life-saving treatments either. According to Wang and his colleagues, this means that crewed missions will need to be as self-sufficient as possible when it comes to medical treatment as well. As with all major health hazards, they emphasize the need for prevention first, though they also identify some possible countermeasures to mitigate the risks:

“Limiting dust contamination of astronaut habitats and being able to filter out any dust that breaks through will be the most important countermeasure. Of course, some dust will be able to get through, especially when Martian dust storms make maintaining a clean environment more difficult. We’ve found studies that suggest vitamin C can help prevent diseases from chromium exposure and iodine can help prevent thyroid diseases from perchlorate.”

They also stressed that these and other potential countermeasures need to be taken with caution. As Wang indicated, taking too much vitamin C can increase the risk of kidney stones, which astronauts are already at risk for after spending extended periods in microgravity. In addition, an excess of idione can contribute to the same thyroid diseases that it is meant to treat in the first place. For years, space agencies have been actively developing technologies and strategies to mitigate the risks of lunar and Martian regolith.

Examples include special sprays, electron beams, and protective coatings, while multiple studies and experiments are investigating regolith to learn more about its transport mechanisms and behavior. As the Artemis Program unfolds and missions to Mars draw nearer, we are likely to see advances in pharmacology and medical treatments that address the hazards of space exploration as well.

Further Reading: 

• GeoHealth

{ https://www.universetoday.com/ }

20-02-2025 om 21:43 geschreven door peter  

Strange radio signals traced to outskirts of long-dead galaxy — and scientists aren't sure why

"Of the thousands of FRBs discovered to date, only about a hundred have been pinpointed to their host galaxies," Tarraneh Eftekhari, a co-author of both new studies and an astronomer at Northwestern University, told Live Science. "And those galaxies tend to have a lot of star formation, which means more stars are going supernova."

But then, Eftekhari and her colleagues zeroed in on a new repeating burst, combining 22 signals detected between February and November 2024 by the Canadian Hydrogen Intensity Mapping Experiment (CHIME), a radio telescope array in British Columbia. The results trace the bursts back to an unexpected culprit: the outskirts of an 11 billion-year-old dead galaxy that should have retired from star formation long ago. But that doesn't necessarily mean it's sparking back to life.

"This observation from a very dead galaxy tells us that there needs to be some other way for an FRB to be produced," Eftekhari said. "This discovery goes against the nicer picture we've had of FRBs so far."

A cosmic "outlier"

According to study co-author Vishwangi Shah, an astronomer at McGill University, FRBs also tend to occur near the centers of galaxies, making this burst from the galaxy's edge even more peculiar. "All of these surprises combined make this FRB an outlier among the larger population," Shah told Live Science.

The team has some ideas of what might be behind the burst. One possibility is that two old stars may have collided. The other is that a white dwarf — the shriveled remains of a dead star — may have collapsed on itself. Either way, the new discovery leaves much to be investigated about the nature of FRBs.

Within the coming months, more of CHIME's telescope array will come online, with the goal of adding hundreds of additional bursts to the FRB inventory, Eftekhari said. "We'll be able to zoom in on the environments of tons more of these events and trace them back to different types of galaxies," she added.

{ https://www.livescience.com/space }

19-02-2025 om 00:00 geschreven door peter  

Humanity may not be extraordinary but rather the natural evolutionary outcome for our planet and likely others, according to a new model for how intelligent life developed on Earth.

The model, which upends the decades-old "hard steps" theory that intelligent life was an incredibly improbable event, suggests that maybe it wasn't all that hard or improbable. A team of researchers at Penn State, who led the work, said the new interpretation of humanity's origin increases the probability of intelligent life elsewhere in the universe.

"This is a significant shift in how we think about the history of life," said Jennifer Macalady, professor of geosciences at Penn State and co-author on the paper, which was published Feb. 14 in the journal  Science Advances.

"It suggests that the evolution of complex life may be less about luck and more about the interplay between life and its environment, opening up exciting new avenues of research in our quest to understand our origins and our place in the universe."

• Panspermia – The Idea That Life Came From The Stars
• Does Tucker Carlson Have A Point About the Theory of Evolution?

The “Hard Steps” Model Disputed, and Maybe Refuted

Initially developed by theoretical physicist Brandon Carter in 1983, the "hard steps" model argues that our evolutionary origin was highly unlikely due to the time it took for humans to evolve on Earth relative to the total lifespan of the sun—and therefore the likelihood of finding human-like beings beyond Earth is extremely low.

AI-generated illustration of the so-called “primordial soup” out of which life on Earth evolved once the planet had warmed and the necessary chemicals were in the water and the atmosphere

(NASA/Public Domain).

In the new study, a team of researchers that included astrophysicists and geobiologists argued that Earth's environment was initially inhospitable to many forms of life, and that key evolutionary steps only became possible when the global environment reached a "permissive" state.

For example, complex animal life requires a certain level of oxygen in the atmosphere. So the oxygenation of Earth's atmosphere through photosynthesizing microbes and bacteria was a natural evolutionary step for the planet, which created a window of opportunity for more recent life forms to develop, explained Dan Mills, postdoctoral researcher at The University of Munich and lead author of the new paper.

"We're arguing that intelligent life may not require a series of lucky breaks to exist," said Mills, who worked in Macalady's astrobiology lab at Penn State as an undergraduate researcher.

"Humans didn't evolve 'early' or 'late' in Earth's history, but 'on time," when the conditions were in place. Perhaps it's only a matter of time, and maybe other planets are able to achieve these conditions more rapidly than Earth did, while other planets might take even longer."

The central prediction of the "hard steps" theory states that very few, if any, other civilizations exist throughout the universe. This is because steps such as the origin of life, the development of complex cells and the emergence of human intelligence are improbable based on Carter's interpretation of the sun's total lifespan being 10 billion years, and the Earth's age of around 5 billion years.

• Gaia: Recognizing Our Role on a Living Earth
• New Science Addresses a Noisy Problem with the Evolutionary Hypothesis

In the new study, the researchers proposed that the timing of human origins can be explained by the sequential opening of "windows of habitability" over Earth's history, driven by changes in nutrient availability, sea surface temperature, ocean salinity levels and the amount of oxygen in the atmosphere.

“This framework raises the possibility that biospheric evolution generally proceeds in a coarsely deterministic or predictable fashion, governed by long-term biospheric trends like increasing habitat diversity in response to unidirectional changes in Earth’s surface environment,” the study authors wrote in their Science Advances article. “Not only would these trends and processes apply to Earth through time, but their analogs may apply to other inhabited Earth-like worlds in the Universe.

Given all the interplaying factors, they said, the Earth has only recently become hospitable to humanity—it's simply the natural result of those conditions at work.

"We're taking the view that rather than base our predictions on the lifespan of the sun, we should use a geological time scale, because that's how long it takes for the atmosphere and landscape to change," said Jason Wright, professor of astronomy and astrophysics at Penn State and co-author on the paper. "These are normal timescales on the Earth. If life evolves with the planet, then it will evolve on a planetary time scale at a planetary pace."

AI-generated illustration of the so-called “primordial soup” out of which life on Earth evolved once the planet had warmed and the necessary chemicals were in the water and the atmosphere.

Moving Beyond Astrophysics

Wright explained that part of the reason that the "hard steps" model has prevailed for so long is that it originated from his own discipline of astrophysics, which is the default field used to understand the formation of planets and celestial systems.

The team's paper is a collaboration between physicists and geobiologists, each learning from each other's fields to develop a nuanced picture of how life evolves on a planet like Earth.

"This paper is the most generous act of interdisciplinary work," said Macalady, who also directs Penn State's Astrobiology Research Center. "Our fields were far apart, and we put them on the same page to get at this question of how we got here and are we alone? There was a gulf, and we built a bridge."

The researchers said they plan to test their alternative model, including questioning the unique status of the proposed evolutionary "hard steps." The recommended research projects are outlined in the current paper and include such work as searching the atmospheres of planets outside our solar system for biosignatures, like the presence of oxygen.

The team also proposed testing the requirements for proposed "hard steps" to determine how hard they actually are by studying uni- and multicellular forms of life under specific environmental conditions such as lower oxygen and temperature levels.

Beyond the proposed projects, the team suggested the research community should investigate whether innovations —such as the origin of life, oxygenic photosynthesis, eukaryotic cells, animal multicellularity and Homo sapiens—are truly singular events in Earth's history. Could similar innovations have evolved independently in the past, but evidence that they happened was lost due to extinction or other factors?

"This new perspective suggests that the emergence of intelligent life might not be such a long shot after all," Wright said. "Instead of a series of improbable events, evolution may be more of a predictable process, unfolding as global conditions allow. Our framework applies not only to Earth, but also other planets, increasing the possibility that life similar to ours could exist elsewhere."

• Top image: View from the International Space Station, looking down at a blue and fertile Earth where life has blossomed.

Source:

• NASA.
• This is an edited version of an article published by Penn State University entitled ‘Does planetary evolution favor human-like life? Study ups odds we're not alone.’

{ https://www.ancient-origins.net/science-space }

18-02-2025 om 23:13 geschreven door peter  

An artistic rendering of a black hole devouring a star.

Depositphotos.

3. Some Black Holes Are Invisible

While most black holes are detected by their interaction with nearby stars, some are completely invisible. These “rogue” black holes drift through space undetected, waiting to be discovered. Without a nearby light source or a disk of heated material, they remain nearly impossible to spot.

4. The Largest Ones Can Swallow Billions of Suns

Supermassive black holes sit at the heart of most galaxies, and some are truly colossal. The black hole in the center of the galaxy M87, for example, is over six billion times the mass of the Sun. These giants shape entire galaxies, controlling the flow of gas and star formation across vast distances.

5. They Can Merge and Send Shockwaves Through Space

When two black holes collide, they create ripples in space-time known as gravitational waves. These waves travel across the universe and can be detected by sensitive instruments on Earth. Each detection confirms Einstein’s theory of relativity and provides a glimpse into some of the most powerful events in existence.

6. Some May Be Wormholes

A few theories suggest that certain black holes might actually be tunnels through space-time. If true, falling into one could lead to another part of the universe or even a different dimension. However, without concrete evidence, this remains pure speculation.

7. They Can Trap Light But Also Shine Brightly

Even though light cannot escape from within a black hole, the material spiraling into it can produce some of the brightest emissions in the universe. When matter falls toward a black hole, it heats up to millions of degrees, creating powerful X-ray bursts and high-energy jets that shoot across space.

8. Some Are Born in Violent Explosions

Stellar-mass black holes form when massive stars collapse under their own weight in a supernova explosion. The outer layers of the star are blasted into space, while the core shrinks into a dense object with gravity so strong that not even light can escape.

9. The Laws of Physics Break Down Inside

What happens inside a black hole is one of the biggest mysteries in science. The core, known as the singularity, is a point where matter is crushed to infinite density. Current physics cannot explain what goes on in this region, making black holes the ultimate cosmic paradox.

10. The Universe Could Be Full of Mini Black Holes

Some scientists believe that tiny black holes formed in the early universe and may still exist today. Unlike their massive counterparts, these mini black holes could be as small as an atom but with the mass of a mountain. If proven, they could help us understand dark matter and the true nature of space itself.

Black holes continue to challenge our understanding of reality. As telescopes and technology improve, scientists are uncovering more secrets about these cosmic enigmas. One thing is certain—black holes are far stranger than we ever imagined!

RELATED VIDEOS

{ https://curiosmos.com/ }

18-02-2025 om 22:29 geschreven door peter  

It is believed that 4.4 billion years ago, a celestial body (Theia) slammed into Earth and produced the Moon.

Image Credit: NASA/JPL-Caltech

For one, we are the only rocky planet with a substantial moon. Mercury and Venus have none, while Mars lays claim to only two small, captured asteroids. The very existence of our large moon demands explanation.

Second, there’s spin. The Earth spins much faster than the other rocky planets, and the Moon orbits around us at a surprisingly swift pace. Something deep in our past must have provided all that energy, and a collision with another protoplanet explains it with ease.

Lastly, we have an unexpected piece of evidence from our human adventures to the Moon. The Apollo missions were more than pursuits of glory; they were scientific enterprises. Trained by expert geologists, the Apollo astronauts, beginning with Armstrong and Aldrin, where taught to search for and extract interesting findings.

What they returned to Earth revealed an enormous wealth of scientific knowledge of the Moon’s composition, because for the first time we were able to acquire large amounts of regolith – the generic term for the loose material that makes up the lunar surface – and return it to Earth for further study. All told, the six successful Apollo missions brought back 2,200 samples totaling almost 400 kilograms of material.

The regolith returned by the Apollo missions displayed a remarkable property: the lunar surface is oddly similar in constitution to the Earth’s crust, with similar ratios of elements. The only conclusion is that we must have a common origin.

So while we are never able to turn the clock back and witness the formation of the Earth and Moon, we can use the clues scattered around us to help us understand this cataclysmic event that took place over four billion years ago.

{ https://www.universetoday.com/ }

18-02-2025 om 21:35 geschreven door peter  

There’s a concept known as the “Galactic tide”. As our solar system moves through the galaxy, it is subjected to gravitational forces of other objects, like stars and black holes, that are closer or farther away from it. Like Earth’s Moon forces the water on the surface towards it due to its gravity, the galactic center, where most of the galaxy’s mass is, affects large objects in our solar system.

For the planets, this influence is drowned out by their gravitational bond to the Sun. But for Oort cloud objects, it plays a major role in determining their positioning. New long-period comets are formed when a nuance in the galactic tide either forces them into the inner solar system itself or causes them to collide with one another, sending one off on a trajectory toward the Sun.

Modeling this complex dynamic is hard, and the researchers, including lead author David Nesvorný, had to rely on a supercomputer at NASA to run their analytical model and compare it to previous simulations of the structure of the Oort cloud. They found something intriguing hiding in the data.

According to their model, the Oort cloud looks like a spiral disk about 15,000 au across, offset by the ecliptic by about 30 degrees. But more interestingly, it has two spiral arms that almost make it look like a galaxy.

These spiral arms, which are located nearly perpendicular to the galaxy’s center, resulting from the influence of the Galactic tide, are represented in the mathematical model by a phenomenon known as the Kozai-Lidov effect. In this quirk of celestial mechanics, large bodies are affected by “Kozai oscillations” that result from the gravitational influence of objects that are much farther away but, in the aggregate, still have an impact on the mechanics of a body.

The changes those oscillations make take a long time, but according to the researcher’s analysis, they almost solely determine the shape of the inner Oort cloud. The gravitational pull of the solar system’s planets or nearby passing stars doesn’t seem to have much effect.

According to the paper, taking a picture of this two-armed spiral will be exceedingly difficult. The authors suggest doing so would either require direct observation of a large number of objects in that space (which is unlikely in the near term) or separation of radiation from those objects that eliminates background and foreground sources so it could track the specific structure.

As of now, neither observational method has any resources dedicated to it. But, if we want to learn more about the home of any potential new comets and their impact on us, it wouldn’t be a bad idea to start planning how to look.

Learn More:

• Nesvorný et al – A Spiral Structure in the Inner Oort Cloud
• UT – The Oort Cloud Might be More Active Than We Thought
• UT – A Star Passed Through the Oort Cloud Less Than 500,000 Years Ago. It Wasn’t the Only One.
• UT – There Could Be Captured Planets in the Oort Cloud

Lead Image:

• Illustration of the Oort Cloud.
  Credit – NASA

{ https://www.universetoday.com/ }

18-02-2025 om 21:02 geschreven door peter  

Fast facts: What is the Habitable Zone?

The definition of “habitable zone” is the distance from a star at which liquid water could exist on orbiting planets’ surfaces. Habitable zones are also known as Goldilocks’ zones, where conditions might be just right – neither too hot nor too cold – for life.

When searching for possibly habitable exoplanets, it helps to start with worlds similar to our own. But what does “similar” mean? Many rocky planets have been detected in Earth’s size-range: a point in favor of possible life. Based on what we’ve observed in our own solar system, large, gaseous worlds like Jupiter seem far less likely to offer habitable conditions. But most of these Earth-sized worlds have been detected orbiting red-dwarf stars; Earth-sized planets in wide orbits around Sun-like stars are much harder to detect.

And, of course, when talking about habitable exoplanets, we’re really talking about their stars, the dominant force in any planetary system. Habitable zones potentially capable of hosting life-bearing planets are wider for hotter stars. Smaller, dimmer red dwarfs, the most common type in our Milky Way galaxy, have much tighter habitable zones as in the TRAPPIST-1 system. Planets in a red dwarf's comparatively narrow habitable zone, which is very close to the star, are exposed to extreme levels of X-ray and ultraviolet (UV) radiation, which can be up to hundreds of thousands of times more intense than what Earth receives from the Sun.

This infographic compares the characteristics of three classes of stars in our galaxy: Sunlike stars are classified as G stars; stars less massive and cooler than our Sun are K dwarfs; and even fainter and cooler stars are the reddish M dwarfs.

NASA, ESA and Z. Levy (STScI)

Where Are We Looking for Life, and Why?

An old joke offers an answer: Asked why, on a dark night, he was looking for his missing car keys beneath a street lamp, the man answered, "because the light's better." Life on other planets might be like nothing on Earth – it could be life as we don't know it. But it makes sense, at least at first, to search for something more familiar. Life as we know it should be easier to find. And "the light's better" in the habitable zone, or the area around a star where planetary surface temperatures could allow the pooling of water.

Other similarities to Earth come into sharper focus in the search for life. Many rocky planets have been detected in Earth’s size-range: a point in favor of possible life. Based on what we’ve observed in our own solar system, large, gaseous worlds like Jupiter seem far less likely to offer habitable conditions. But most of these Earth-sized worlds have been detected orbiting red-dwarf stars; Earth-sized planets in wide orbits around Sun-like stars are much harder to detect. Yet these red-dwarfs have a potentially deadly habit, especially in their younger years: Powerful flares tend to erupt with some frequency from their surfaces. These could sterilize closely orbiting planets where life had only begun to get a toehold. That’s a strike against possible life.

Because our Sun has nurtured life on Earth for nearly 4 billion years, conventional wisdom would suggest that stars like it would be prime candidates in the search for other potentially habitable worlds. G-type yellow stars like our Sun, however, are shorter-lived and less common in our galaxy.

The artist's conception shows a hypothetical planet with two moons orbiting in the habitable zone of a red dwarf star. More about stars ›

Stars slightly cooler and less luminous than our Sun — called orange dwarfs — are considered by some scientists as potentially better for advanced life. They can burn steadily for tens of billions of years. This opens up a vast timescape for biological evolution to pursue an infinity of experiments for yielding robust life forms. And, for every star like our Sun there are three times as many orange dwarfs in the Milky Way.

K dwarfs, are the true "Goldilocks stars," said Edward Guinan of Villanova University, Villanova, Pennsylvania. "K-dwarf stars are in the 'sweet spot,' with properties intermediate between the rarer, more luminous, but shorter-lived solar-type stars (G stars) and the more numerous red dwarf stars (M stars). The K stars, especially the warmer ones, have the best of all worlds. If you are looking for planets with habitability, the abundance of K stars pump up your chances of finding life."

Exoplanet temperature, size, star type: the galaxy offers up a menu of worlds that echo aspects of our own, yet at the same time are vastly different.

Traditional picture of the habitable zone – not too hot, not too cold.

NASA

{ https://www.nasa.gov/ }

17-02-2025 om 23:00 geschreven door peter  

Even if we restrict ourselves to the basic biochemistry that makes Earthly life possible, we have many more options than we naively thought. Hycean worlds, planets thought to be englobed by water surrounded by thick hydrogen atmospheres, once thought to be too toxic for any kind of life, might be even more suitable than terrestrial worlds.

What about tidally-locked planets around red dwarf stars, like our nearest neighbor Proxima b and the intriguing system of TRAPPIST-1? Conditions on those planets might be hellish, with one side facing the incessant glare of its star and the other locked in permanent night. Neither of those extremes seem suitable for life as we know it. But even those worlds can support temperate atmospheres if the conditions are just right. A delicate balancing act for sure, but a balancing act that every life-bearing planet must walk.

Our galaxy contains billions of dead stars, the white dwarves and neutron stars. We know of planets in those systems. Indeed, the first exoplanets were discovered around a pulsar. Sometimes those dead stars retain planets from their former lives; other times the planets assemble anew from the stellar wreckage. In either case, the stars, though dead, are still warm, providing a source of energy for any life that might find a home there. And considering the sheer longevity of those stars the incredibly long history of our galaxy, life has had many chances to appear – and sustain itself – in systems that are now dead.

Who needs planets, anyway? Methanogens could take advantage of the exotic, cold chemistry of molecular clouds, feasting on chemicals processed by millennia of distant high-energy starlight. It might even be possible for life to sustain itself in a free-floating biological system, with the gravity of its own mass holding on to an atmosphere. It’s a wild concept, but all the foundational functions of a free-floating habitat – scaffolding, energy capture and storge, semi-permeable membranes – are found on terrestrial life.

We should absolutely continue our current searches – after all, they’re not groundless. But before we invest in the next generation of super-telescopes, we should pause and reconsider our options. We should invest in research that pushes the edges of what life means and where it can exist, and we should explore pathways to identifying and observing those potential habitats. Only after we have extended research along these lines can we decide on a best-case strategy.

In other words, we should replace a goal, that of finding life like our own, with a vision of finding life wherever we can. Nature has surprised us many times in the past, and we shouldn’t let our biases and assumptions get in the way of our path of discovery.

The definition of “habitable zone” is the distance from a star at which liquid water could exist on orbiting planets’ surfaces. Habitable zones are also known as Goldilocks’ zones, where conditions might be just right – neither too hot nor too cold – for life.

{ https://www.universetoday.com/ }

17-02-2025 om 22:43 geschreven door peter  

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17-02-2025 om 22:13 geschreven door peter  

They began their study by working backward from the known properties of ‘Oumuamua.

When it was visible to Earth’s telescopes for just a few months in 2017, it showed an intensely variable brightness, changing from bright to dim every four hours. Astronomers interpreted this variability as an elongated, cigar-shaped object tumbling through space.

Two other things made ‘Oumuamua unique. First, it appeared to have a dry, rocky surface, akin to the asteroids known in our solar system. But it also changed its orbit in a way that could not purely be explained by the laws of gravity – something else made it change direction.

Redirections like this are sometimes seen in icy comets. As they approach the Sun, off-gassing released from the heated ice acts like a thruster, changing the comet’s trajectory.

Somehow, ‘Oumuamua displayed a mix of both comet-like and asteroid-like properties.

One plausible explanation, proposed in 2020, is that ‘Oumuamua-like objects are formed by tidal fragmentation. That’s when a ‘volatile-rich’ parent body (like a large comet) passes too close to its star at high speeds, shattering it into long, thin shards. The heating process in these extreme interactions causes the formation of an elongated rocky shell, but preserves an interior of subsurface ice. This unique combination, not seen in our own solar system, would explain ‘Oumuamua’s orbital maneuvers despite its rocky composition.

It also explains why we don’t tend to see them in our solar system, because “ejected planetesimals experienced tidal fragmentation at more than twice the rate of surviving planetesimals (3.1% versus 1.4%),” the authors write. In other words, if the orbital forces are strong enough for tidal fragmentation to happen, it also means they’re strong enough to kick the object out of the system entirely.

Interstellar space may therefore be full of dagger-shaped shards of rock and ice (an exaggeration, but a fun quote for dinner parties nonetheless).

The simplest star system that could cause this type of tidal fragmentation are those home to white dwarfs. These are the extremely dense, dead cores of old exploded stars. A white dwarf, encircled by a belt of distant comet-like objects, similar to the Sun’s Oort cloud, could spawn ‘Oumuamua clones with regular frequency.

But the process is enhanced in systems that host Jupiter-sized planets.

The exception is ‘Hot Jupiters’ that orbit close to their star. These are less likely to interact with objects subject to tidal fragmentation.

But Jupiter-sized planets distant from their host star are very effective at producing ‘Oumuamua clones, especially if they have eccentric orbits. But even here, it’s not a perfect match for the origin of ‘Oumuamua, because these interactions tend to produce shards that are not as elongated, and at a rate lower than what is expected for ‘Oumuamua-type objects.

The authors conclude that the planetary systems most likely to have spawned ‘Oumuamua are those with many planets, which are more “efficient at producing interstellar objects,” the authors say, though they propose a few other possibilities too.

So while there is now a strong, plausible explanation for the process that birthed ‘Oumuamua, the type of solar system that produced it is still very much an open question.

• Xi-Ling Zheng amd Ji-Lin Zhou, “Configuration of single giant planet systems generating ‘oumuamua-like interstellar asteroids.” Monthly Notices of the Royal Astronomical Society.

{ https://www.universetoday.com/ }

17-02-2025 om 21:45 geschreven door peter  

Scientists are baffled after discovering a mysterious radioactive 'blip' deep under the Pacific Ocean

• READ MORE: Scientists find structures under the ocean that 'shouldn't exist' 

By WILIAM HUNTER_

Scientists have been left baffled after discovering something vast and radioactive lurking in the depths of the Pacific Ocean.

While it might sound like the start of the next Godzilla movie, researchers say this 'blip' is a very real phenomenon.

An international team of scientists has found unexpectedly high levels of the rare radioactive isotope beryllium-10 in samples from the Pacific seabed.

And they believe it could have been caused by a blast of radiation from space more than 10 million years ago.

Beryllium-10 is an isotope - a variant of an element with a different number of neutrons in its atomic nuclei, formed when cosmic rays hit oxygen and nitrogen in the upper atmosphere.

After forming, this isotope falls to the ground in the rain and settles to the bottom of the seabed at a fairly constant rate.

However, when the researchers looked at samples of the seabed from 10 million years ago, they found that the levels of beryllium-10 were almost twice what they had expected.

Study author Dr Dominik Koll, from Helmholtz-Zentrum Dresden-Rossendorf, Germany, says: 'We had stumbled upon a previously undiscovered anomaly.'

Scientists have been baffled to find something vast and radioactive lurking beneath the Pacific Ocean. Although it sounds like the plot of the next Godzilla movie, the researchers say this anomaly is very real 

Researchers discovered an unexpectedly high amount of the rare radioactive isotope beryllium-10 from samples taken from the bottom of the Pacific Ocean. This compound is formed when cosmic rays hit oxygen and nitrogen in the atmosphere and falls to the ground in rain before sinking to the seabed 

In their study, published in Nature Communications, the researchers looked at the accumulation of Beryllium-10 in the seabed deep below the Pacific Ocean.

These unique samples were collected from several miles beneath the water and are made up of a mixture of iron and manganese called a ferromanganese crust.

Using a highly sensitive method called Accelerator Mass Spectrometry, the researchers were surprised to find an unexpected spike in beryllium-10 levels occurring about 10 million years ago.

To ensure this wasn't a fluke, Dr Koll and his colleagues looked at samples taken from elsewhere in the Pacific, but these samples all showed the same anomalous blip.

The researchers argue that there are two possible ways to explain this strange phenomenon: one earthly, and one extraterrestrial.

In one scenario, the unusual radioactive buildup could have been caused by the ocean circulation around the Antarctic suddenly and drastically changing 10 to 12 million years ago.

Dr Koll says: 'This could have caused beryllium-10 to be unevenly distributed across the Earth for a period of time due to the altered ocean currents.'

'As a result, beryllium-10 could have become particularly concentrated in the Pacific Ocean.' 

The levels of beryllium-10 should have been fairly consistant though time, but researchers found a significant spike in its abundance about 10 million years ago (illstrated) 

These samples (pictured left) came from a region of the northeast Pacific (shaded yellow) that currently sits by major ocean currents (red and blue lines). The researchers suggest that massive changes to  thes currents 10 million years ago could have built up more beryllium-10

What is beryllium-10?

Beryllium-10 is an isotope of beryllium which contains 10 neutrons in its nucleus.

This makes the atom unstable and radioactive, so it slowly decays into boron over millions of years.

Beryllium-10 has a half-life - the time needed for half of its atoms to decay - of 1.4 million years.

This means it can be used to date objects from more than 10 million years ago.  

In the more out-of-this-world theory, something might have happened in space which exposed the Earth to a sudden burst of radiation.

This could have been triggered by the after-effects of a near-Earth supernova, which would have bathed the planet in intense radiation.

Alternatively, the planet might have briefly lost its protective solar shield, known as the heliosphere, after passing through a dense interstellar cloud.

In either case, this would mean that beryllium-10 should be unusually common 10 million ago in oceans all around the world.

Dr Koll says: 'Only new measurements can indicate whether the beryllium anomaly was caused by changes in ocean currents or has astrophysical reason.

'That is why we plan to analyze more samples in the future and hope that other research groups will do the same.'

Discovering that this anomaly is present all around the world could be extremely valuable for scientists looking into the distant past.

Even though radioactive isotope dating is generally accurate, researchers still need common reference points in order to compare different sets of samples. 

Alternatively, the beryllium-10 could have been formed by the radioactive blast of supernova such as the one which left behind the Crab Nebula (pictured). This intense radiation would have led to more beryllium-10 forming all over the world 

For example, researchers studying more recent populations can often look for the spikes in C14 isotopes associated with nuclear weapons testing to help date organisms.

Dr Koll says: 'For periods spanning millions of years, such cosmogenic time markers do not yet exist.

'However, this beryllium anomaly has the potential to serve as such a marker.'

So, if this spike could be found all around the world, it would let researchers compare completely different archives by synching up to the same unexpected spike 10 million years ago.

{ https://www.dailymail.co.uk/ }

15-02-2025 om 22:32 geschreven door peter  

NASA And Japan Moon Landing Update

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15-02-2025 om 22:02 geschreven door peter  

The concept they used is called inertial morphing. In the case of SPLITTER, the robots “adjust inertia with changes in limb configurations and tether length,” according to lead author Yusuke Tanaka in an interview with TechXplore. The researchers turned to a technique called Model Predictive Control (MPC) to determine how each variable needs to be adjusted.

MPC is used in various industries and comes as advertised, with a model (i.e., a mathematical representation of the robots) and a prediction, which reflects what the software estimates will happen to the model next. With the model’s current state and expected next state, a controller can change the variables that affect the model’s state. Those changes will result in a stable flying path, allowing SPLITTER to soar through the skies, even without air. It also uses a physical phenomenon known as the Tennis Racket Theorem, which describes how an object can flip rotation around its intermediate axis while rotating around it. Most famously, this was demonstrated on the ISS with a t-handle. It looks chaotic, but the mathematics behind the motion are well-understood.

Implementing it in a tethered robotic system is another matter altogether, though. While SPLITTER is flying, it looks a lot like a bola used in ladder ball, except instead of round spheres on each end, it’s a robot body with four legs splayed out in different directions. The orientation of how those legs are spread out and the length of the tether connecting the two ends are the variables the MPC controls to stabilize its flight. SPLITTER can operate without heavy attitude control hardware, like reaction wheels or thrusters.

It also allows the system to perform other actions, like spelunking, where one robot is anchored firmly to the top of a cave system while the other rappels using the tether. Both robots only weigh about 10kg each on Earth, as well, which would make them even more agile on a world with smaller gravity like the Moon or an asteroid.

This isn’t the first robot system the RoMeLa lab designed for this purpose. They initially worked on a robot called the Spine-enhanced Climbing Autonomous Legged Exploration Robot) (SCALER), which had its limitations as they found the limbed climbing robot was too slow.

With SPLITTER, the research team thinks they have a better concept that can both traverse terrain faster and collect data that a robot tied to the ground would be unable to do. Unfortunately, for now, at least, SPLITTER is best described as a computer model, though some preliminary work has been done on the physics of MPC controlling a reaction wheel. Researchers at the lab intend to continue working on the concept, so maybe soon we’ll see a bola robot test jumping near Los Angeles.

Learn More:

• TechXplore – Modular robot design uses tethered jumping for planetary exploration
• Tanaka, Zhu, & Hong – Tethered Variable Inertial Attitude Control Mechanisms through a Modular Jumping Limbed Robot
• UT – Miniaturized Jumping Robots Could Study An Asteroid’s Gravity
• UT – A Jumping Robot Could Leap Over Enceladus’ Geysers

Lead Image:

• Depiction of one SPLITTER robot descending into a crater while the other anchors on the rim.
  Credit – Yusuke Tanaka, Alvin Zhu, & Dennis Hong

{ https://www.universetoday.com/  }

15-02-2025 om 16:00 geschreven door peter  

Large asteroids in the Main Asteroid Belt (MAB) are easier to study. Their large sizes mean they produce a bigger signal when observed, and astronomers can more easily determine their orbits. However, the MAB holds many smaller asteroids around 100-200 meters. There could be hundreds of millions of them. They’re big enough to devastate entire cities if they strike Earth, and they’re more difficult to track. The first step in determining their orbits is determining their distances, which is challenging and takes time.

Recent research submitted to The Astronomical Journal presents a new method of determining asteroid distances in much less time. It’s titled “Measuring the Distances to Asteroids from One Observatory in One Night with Upcoming All-Sky Telescopes” and is available at arxiv.org. The lead author is Maryann Fernandes from the Department of Electrical and Computer Engineering at Duke University.

The Vera Rubin Observatory (VRO) should see its first light in July 2025. One of its scientific objectives is to find more small objects in the Solar System, including asteroids, by scanning the entire visible southern sky every few nights. If it moves and reflects light, the VRO has a good chance of spotting it. However, it won’t automatically determine the distance to asteroids.

“When asteroids are measured with short observation time windows, the dominant uncertainty in orbit construction is due to distance uncertainty to the NEO,” the authors of the new paper write. They claim their method can shorten the time it takes to determine an asteroid’s distance to one night of observations. It’s based on a technique called topocentric parallax.

Topocentric parallax is based on the rotation of the Earth. In a 2022 paper by some of the same researchers, the authors wrote that “Topocentric parallax comes from the diversity of the observatory positions with respect to the center of the Earth in an inertial reference frame. Observations from multiple observatories or a single observatory can measure parallax because the Earth rotates.”

In the two years since that paper, the researchers have refined their method. The research expands on previous algorithms and tests the technique using both synthetic data and real-world observations.

“In this paper, we further develop and evaluate this technique to recover distances in as quickly as a single night,” the authors write in the new paper. “We first test the technique on synthetic data of 19 different asteroids ranging from ~ 0.05 AU to ~ 2.4 AU.”

The figure below shows the results of the test with synthetic data. Each asteroid was observed six times in one night, and two different equations were employed to process the data.

The researchers also tested their method by taking 15 observations of each asteroid over five nights (3 per night). In this test, Equation 1 performed poorly, while Equation 2 performed well.

Of course, the distance to the asteroid affected the accuracy of the measurements. The closer the object was, the more precise the measurement was. The paper notes that the method was able to recover distances “with uncertainties as low as the ~ 1.3% level for more nearby objects (about 0.3 AU or less) assuming typical astrometric uncertainties.”

After these tests with synthetic data, the team acquired their own single-night observations of two asteroids using a different algorithm. The real observations produced a less precise result, but it was still a meaningful improvement. The authors explain that they were able to recover distances “to the 3% level.”

So, what do all these tests, equations, and algorithms boil down to?

When we hear of an asteroid that could potentially strike Earth in a few years, people can wonder why the situation is so uncertain. Shouldn’t we know if an asteroid is heading straight for us? Trying to determine the orbit of these small rocks from tens of millions of km away is extremely difficult. An AU is almost 150 million km (93 million miles). 2024 YR, the latest asteroid of concern, is only 40 to 90 metres (130 to 300 ft) in diameter. Those numbers illustrate the problem.

If this method can improve the accuracy of our distance measurements and do it based on a single night of observations, that’s a big improvement.

The technique can be applied to data generated by the Vera Rubin Observatory and the Argus Array. According to the authors, “distances to NEOs on the scale of ~ 0.5 AU can be constrained to below the percent level within a single night.” As the study shows, the accuracy of those measurements from a single-site observatory depends heavily on the spacing between individual observations. If multiple observatories at different sites are used on the same night, the accuracy increases.

Though larger asteroids, like the one that wiped out the dinosaurs, tend to remain stable in the main asteroid belt, smaller asteroids are more easily perturbed and can become part of the NEO population. An impact from a smaller asteroid might not spell the end of civilization, but it can still be extremely destructive.

Anything humanity can do to understand the asteroid threat is wise. Many asteroids have struck Earth in the past, and it’s only a matter of time before another one comes our way. If we can see it coming in advance, we can try to do something about it.

Research: 

• Measuring the Distances to Asteroids from One Observatory in One Night with Upcoming All-Sky
  Telescopes

{ https://www.universetoday.com/  }

15-02-2025 om 15:39 geschreven door peter  

Scientists Uncover Possible Explanation for Bizarre ‘Atmospheric Ghosts’ Phenomenon

To be clear, we’re talking about the afterglow from transient luminous events, not the specters of dead people.

by Doris Elín Urrutia

 

Thomas Ashcraft

Four years ago, a green “ghost” appeared over a thunderstorm cloud in the Mediterranean Sea. To the delight of Spanish scientists, this ephemeral sighting finally offered a rare window into a little-known phenomenon playing out high in Earth’s skies.

When lightning strikes, it sometimes triggers the release of a violent optical emission at altitudes between 50 and 90 km above the thunderstorm cloud. These millisecond-long events, called transient luminous events (TLEs), are mysterious.

They can be shaped like jellyfish. These are known as sprites. Other TLE forms exist, boasting playful names like halos and elves. Just a few years ago, thrill seekers and citizen scientists discovered a new TLE, hovering above a sprite, called a ghost. While sprites appear red owing to the nitrogen in Earth’s atmosphere, and blue at more shallow altitudes due to higher atmospheric pressure, ghosts are green. They appear during and after the sprites, like fuzz on top of the jellyfish.

This puzzling afterglow was the subject of a new paper published in the journal Nature Communications on Tuesday.

Finding a Good Ghost

Researcher María Passas Varo led a team to use a special instrument called the Granada Sprite Spectrograph and Polarimeter (GRASSP), located outside Barcelona, to make a clear ghost sighting.

She and other atmospheric researchers were intrigued when, in the early half of 2019, storm chaser Hank Schyma noticed something new: in the wake of a sprite over the skies of Oklahoma, there was a greenish afterglow. He called the emerald-colored splotch a ghost, short for Green emissions from excited Oxygen in Sprite Tops. The idea behind the name was that, since oxygen is associated with the verdant tones of auroras, that the gas creates the ghosts.

Passas Varo, a telecommunications engineer, spectroscopist, and surveyor of atmospheric electricity based at the Astrophysics Institute of Andalucía in Spain, searched relentlessly for a new ghost. But finding one that GRASSP could glean a lot of data from was hard.

“We have analyzed more than 2,000 spectra, one by one, with the naked eye. We only found one good spectrum of a ghost. So, it is a lot of work. It is tedious,” she tells Inverse.

Then they finally found a science-worthy ghost, radiating from a thunderstorm cloud in the Mediterranean Sea on September 21, 2019. It was their best candidate for spectrographic analysis, in which the team peered into light from the ghost for clues about its composition.

They found a surprise. Oxygen was present, as they expected. But the team also found evidence of iron.

Iron is present in Earth’s upper atmosphere. It comes from the interplanetary dust particles that enter our atmosphere. But according to Passas Varo, it’s usually found at much higher altitudes.

Approximately one in every 100 sprites have ghosts. These events sometimes happen, but aren’t consistent. What makes a ghost appear could be a combination of different phenomena, and iron might provide a special clue.

A Need for Harmony

Cumulonimbus clouds are towers made of water droplets and ice crystals. These tiny particles journey along the updraft from the hot base of the cloud higher and higher until they reach the chilly top. Sometimes, they become larger molecules. If they bang against one another, they produce static electricity. These charged particles create lightning.

What goes down must be balanced in another form, and this need for harmony could be what causes the sprites and jets and all the other TLE oddities.

“When the lightning occurs, when the lightning strikes the ground, then an electric field appears above the cloud because you have to maintain, somehow, the balance of the electric field of the global electrical circuit,” Passas Varo tells Inverse. “Once you have this big discharge in the form of huge lightning downwards, then an electric field develops upwards. And this electric field develops a transient luminous event.”

One possible explanation for ghosts is that the sonic boom we know as thunder is, in one way or another, disrupting the iron from its usual altitude. Gravity waves on Earth, which are vertical, could also be playing a role in producing ghosts.

But what is clear is that a plethora of new observations are necessary. Passas Varo and the team have one good spectrum of a ghost but say it will take 99 more to get a clearer picture of what’s really happening.

{ https://www.inverse.com/ }

15-02-2025 om 00:00 geschreven door peter  

Scientists pinpoint exactly WHERE the 'city-destroying' asteroid could strike Earth in 2032

• READ MORE: Video shows 'city-killer' asteroid hitting Earth in 2032

By WILIAM HUNTER

The terrifying prediction that a 'city-destroying' asteroid is hurtling towards Earth has set alarm bells ringing at the world's space agencies.

Now, a NASA scientist has predicted exactly where the asteroid 2024 YR4 could strike.

David Rankin, an engineer with the NASA-funded Catalina Sky Survey Project, has sketched the 'risk corridor' according to the asteroid's current trajectory.

If 2024 YR4 really does hit Earth in 2032, it should fall somewhere in a narrow band stretching from northern South America across the Pacific to sub-Saharan Africa and into Asia.

Worryingly, this path extends over several densely populated regions including Chennai, India and Hainan Island, China.

Currently, NASA estimates that the asteroid has a one in 48, or 2.1 per cent, chance of colliding with the planet on December 22, 2032.

And with a diameter of up to 90 metres (300ft), or roughly the size of the Statue of Liberty, it could cause devastating damage to any populated area along the risk corridor.

If it were to strike, experts suggest it could unleash a blast equal to eight megatons of TNT - more than 500 times the size of the atomic bomb dropped on Hiroshima.

Scientists have predicted the exact path (shown in red) where the city-destroying asteroid 2024 YR4 could hit Earth. It should fall somewhere in a narrow band stretching from northern South America across the Pacific to sub-Saharan Africa and into Asia 

2024 YR4 was first detected in December last year but has quickly shot to the top of NASA's and the European Space Agency's (ESA) impact risk tables.

The asteroid is currently the only large asteroid with an impact probability greater than one per cent and has been awarded the rare rating of three on the Torino Scale, a scale for measuring the danger posed by asteroids.

The 'God of Chaos' asteroid 99942 Apophis is the only other object in the history of astronomy to be given a rating of three or higher on this scale.

While the odds of 2024 YR4 hitting Earth are still slim, Dr Rankin was able to use data about its orbit to predict where it might hit.

In the scenario where the asteroid does indeed collide with Earth, the 'risk corridor' threatens countries including India, Pakistan, Bangladesh, Ethiopia, Sudan, Nigeria, Venezuela, Colombia, and Ecuador.

Where it lands will also determine just how powerful the impact is, with regions at the end of the corridor more likely to receive a glancing blow. 

However, there currently isn't enough information to say where along this risk corridor the asteroid is most likely to hit.

Dr Rankin told Space.com: 'Size and are big players in possible damage, along with impact location.

NASA predicts that the asteroid 2024 YR4 currently has a one in 48, or 2.1 per cent, chance of hitting Earth on December 22, 2032 (stock image)

'It's hard to constrain size and composition with the current orbital situation, as it's outbound. Typically, the best way to constrain size is with radar observations and those are not possible right now.'

It is currently estimated that the blast would be similar in size to the Tunguska asteroid which detonated in an air-burst explosion in 1908.

While this blast hit an unpopulated area, the shockwave still flattened an estimated 80 million trees over 830 square miles (2,150 square kilometres) - more than twice the land area of New York.

At the higher end of estimates, scientists suggest this explosion could have been equivalent to 15 megatons of TNT.

A blast this powerful would topple residential buildings and cause fatalities up to 12 miles (18.9 km) in any direction from the epicentre.

In the coming months, NASA and ESA hope to use Earth's most powerful telescopes to further refine their predictions about the asteroid's orbit.

This includes a rare emergency decision to grant an international team of scientists the use of the James Webb Space Telescope (JWST) to study 2024 YR4.

This team will use the JWST's infrared sensors to measure the heat radiating from the asteroid to make a better prediction of its size and orbit.

With an estimated size of up to 90 metres (300 ft), or roughly the size of the Statue of Liberty, 2024 YR4 could hit Earth with a blast equal to eight megatons of TNT (artist's impression)

Asteroid 2024 YR4 is about the same size as the Tunguska asteroid, which caused the largest impact event in recorded history when it shot through Earth's atmosphere in 1908, flattening 830 square miles (2,150 square km) of forest (pictured)

Scientists will also have a good opportunity to learn more about the asteroid when it makes its first close pass of Earth in March at a distance of around 5 million miles (8 million kilometres).

The world's space agencies currently predict that the impact probability will drop towards zero as they learn more, but an impact cannot currently be ruled out.

A new simulation of the asteroid's path also presents a slim possibility that it could hit the moon instead of Earth.

Dr Rankin's calculations suggest that there is a one in 333 chance that 2024 YR4 will collide with the lunar surface, creating a brilliant but otherwise harmless explosion that could be seen from Earth with the naked eye. 

However, for the countries along this predicted risk corridor, these predictions raise the chilling possibility that they may face a devastating collision within the next eight years.

{ https://www.dailymail.co.uk/ }

14-02-2025 om 22:00 geschreven door peter  

It’s a familiar sight to see astronauts on board ISS on exercise equipment to minimise muscle and bone loss from weightlessness. A new study suggests that jumping workouts could help astronauts prevent cartilage damage during long missions to the Moon and Mars. They found that the knee cartilage in mice seems to grow stronger after jumping exercises, potentially counteracting the effects of low gravity on joint health. If effective in humans, this approach could be included in pre-flight routines or adapted for space missions.

In space, astronauts experience significant loss of bone and muscle mass due to microgravity. Without Earth’s gravitational pull, bones lose density, increasing fracture risk, while muscles, especially in the lower body and spine, weaken from reduced use. This deterioration can impair mobility when back on Earth and effect overall health. To combat this, astronauts follow rigorous exercise routines, including resistance and cardiovascular training, to maintain strength and bone integrity. 

The next obvious step as we reach out into the Solar System is the red planet Mars. Heading that far out into space will demand long periods of time in space since its a 9 month journey there. Permanent bases on the Moon too will test our physiology to its limits so managing the slow degradation is a big challenge to space agencies. A paper published by lead author Marco Chiaberge from the John Hopkins University has explored the knee joints of mice and how their cartilage grows thicker if they jump! They suggest astronauts should embed jumping activities into their exercise regiment. 

Cartilage cushions the joints between bones and decreases friction allowing for pain free movement. Unlike many other tissues in the body, cartilage does not regenerate as quickly so it is important to protect it. Prolonged periods of inactivity, even from bed rest but especially long duration space flight can accelerate the degradation. It’s also been shown that radiation from space can accelerate the effect too. 

To maintain a strong healthy body, astronauts spend a lot of time, up to 2 hours a day running on treadmills. This has previously shown to slow the breakdown of cartilage but the new study has shown that jumping based movements is particularly effective. 

(Credit: Merlin74/Shutterstock)

The team of researchers found that, over a nine week program of reduced movement, mice experienced a 14% reduction in cartilage thickness in joints. Other mice performed jumping movements three times a week and their cartilage was found to be show a 26% increase compared to a control group of mice. Compared to the group that had restricted movement, the jumping mice had 110% thicker cartilage. The study also showed that jumping activities increased bone strength too with the jumping mice having a 15% higher density than the control.

An interesting piece of research but further work is needed to see whether jumping would herald in the same benefits to humans but the study is promising. If so, then jumping exercises are likely to be a part of pre-flight and inflight exercise programs for astronauts. It is likely that for this to be a reality in the micro-gravitational environment, astronauts will be attached to strong elasticated material to simulate the pull of gravity. 

Source : 

• Jumping Workouts Could Help Astronauts on the Moon and Mars, Study in Mice Suggests.

{ https://www.universetoday.com/ }

14-02-2025 om 18:22 geschreven door peter  

via GIPHY

Earth has noctilucent clouds, too. They form in the upper atmosphere and are only visible during twilight when the atmosphere’s lower layers are in the shade and the upper atmosphere is sunlit. They form from water ice crystals between 76 to 85 km altitude and are the highest clouds in the atmosphere.

Mars’ noctilucent clouds are similar, but the main difference is that they contain carbon dioxide ice. They form at an altitude of around 60 to 80 km and are also classified as mesospheric clouds. On Mars, they occur in the Fall over the southern hemisphere. Only Mars’ high-altitude clouds containing carbon dioxide ice display iridescent colours.

This is the fourth year in succession that Curiosity has seen these noctilucent clouds. Its Mastcam instrument has different filters that let it see different wavelengths of light, and some of those filters are used to study the composition and particle size in clouds. It also has stereo vision, which helps scientists determine cloud height, shape, and the speed at which they’re moving. It can also observe the Sun through filters and determine how much sunlight the atmosphere is blocking. That tells scientists how much dust and ice is in the atmosphere and how it changes over time.

A November 2024 paper titled “Iridescence Reveals the Formation and Growth of Ice Aerosols in Martian Noctilucent Clouds” summarized Curiosity’s images and findings. The lead author is Mark Lemmon, an atmospheric scientist with the Space Science Institute in Boulder, Colorado.

“I’ll always remember the first time I saw those iridescent clouds and was sure at first it was some color artifact,” he said in a press release. “Now it’s become so predictable that we can plan our shots in advance; the clouds show up at exactly the same time of year.”

These clouds form only in early Martian fall and only in the southern hemisphere. Their iridescence is from uniform particle size, which indicates that the clouds had a brief evolution in a uniform environment. When clouds are both noctilucent and iridescent, they’re called nacreous clouds. It’s interesting to note that these colours would be easily seen by an astronaut on the Martian surface.

One of the mysteries behind these clouds concerns their location. They’re only seen in Mars’ southern hemisphere, and the Perseverance rover, which is in the Jezero Crater in the northern hemisphere, has never seen them. It seems pretty clear that they only form in certain locations, but the reasons why are unknown.

Lemmon says that gravity waves, which are atmospheric phenomena separate from astrophysical gravitational waves, could be responsible. They cool the atmosphere and could give rise to clouds of frozen CO2. “Carbon dioxide was not expected to be condensing into ice here, so something is cooling it to the point that it could happen. But Martian gravity waves are not fully understood, and we’re not entirely sure what is causing twilight clouds to form in one place but not another,” Lemmon said.

Scientists need more data to better understand these clouds. Curiosity wasn’t the only one to see them; the InSight lander did, too. But they could only see for a few hundred kilometres around their landing sites and their data is incomplete. “Orbiters capable of sunset and twilight times could constrain the cloud altitude,” Lemmon and his co-authors write in their paper.

There are unanswered questions about these clouds. Scientists would like to understand how quickly particles in these clouds evolve. They’d also like to know what the nature of the corona-forming layer is. A larger data sample could help answer these questions, as could more time-lapse imagery.

• Press Release: A Rainbow-colored “Feather” in the Martian Sky
• Press Release: NASA’s Curiosity Rover Captures Colorful Clouds Drifting Over Mars
• Published Research: Iridescence Reveals the Formation and Growth of Ice Aerosols in Martian Noctilucent Clouds

{ https://www.universetoday.com/ }

14-02-2025 om 18:01 geschreven door peter  

Alien life breakthrough as astronomers detect 'coherent' radio signal from distant planet

Astronomers have detected a 'coherent' radio signal from a distant planet, reigniting hope for the existence of extraterrestrial life.

The signal is thought to originate from a far-off, Earth-sized planet, suggesting it might possess a magnetic field similar to our own.

Scientists regularly monitor exoplanets and their potential to carry life. 85 new exoplanets were discovered outside our solar system, which could unlock secrets of the universe.

American astronomers have christened this rocky exoplanet 'YZ Ceti b,' asserting that it's a prime candidate for an Earth-like magnetic field, which could be crucial in humanity's quest for alien life.

The discovery has been hailed as significant for identifying a planet likely to have a magnetic field and offering a future technique to discover more such planets.

Using a radio telescope, the scientists detected a recurring radio signal from exoplanet YZ Ceti b, located approximately 70.5 trillion miles from Earth.

They speculate that these waves could be produced by interactions between the exoplanet's magnetic field and its host star, a small red dwarf named YZ Ceti.

This finding is essential for pinpointing a planet likely to have a magnetic field and establishing a foundation to discover similar planets in the future.

The researchers further suggested that this could mean witnessing the Northern Lights phenomenon - a result of interactions between magnetic fields and solar weather - on distant planets and stars could be possible.

Magnetic fields are vital in preventing a planet's atmospheric erosion caused by stellar emissions over time.

Drs. Sebastian Pineda and Jackie Villadsen have recently identified a repetitive radio signal from YC Ceti, a red dwarf star located 12 light years away. For context, one light year is nearly 5.88 trillion miles.

The Karl G. Jansky Very Large Array, a prominent radio telescope managed by the National Radio Astronomy Observatory under the US National Science Foundation, was the instrument that allowed them to gain deeper insights into the magnetic dynamics between distant stars and their planets.

This groundbreaking work, outlined in Nature Astronomy, was also funded by the independent federal agency, the National Science Foundation (NSF).

Joe Pesce from NSF, who works as the program director for the National Radio Astronomy Observatory, hails these discoveries as key in the ongoing quest to find life on other worlds, emphasizing, "The search for potentially habitable or life-bearing worlds in other solar systems depends in part on being able to determine if rocky, Earth-like exoplanets actually have magnetic fields."

Recent research marks a significant advancement in exoplanet studies, indicating that some rocky planets beyond our solar system may have magnetic fields. This discovery was achieved through a novel technique that could help identify more of these intriguing worlds.

Dr. Pineda of the University of Colorado, located on America's west coast, expressed the team's elation at detecting planetary radio emissions similar to those Earth emits: "We saw the initial burst, and it looked beautiful," he said enthusiastically.

Moments of scientific triumph followed as Pineda recounted: "When we saw it again, it was very indicative that, OK - maybe we really have something here."

Dr. Pineda noted that a sturdy magnetic field can be pivotal for a planet's ability to retain its atmosphere.

From the other side of the country, Assistant Professor Villadsen of Bucknell University remarked on the distinctiveness of their findings: "I witnessed something that no one has observed before."

Prior detections of exoplanetary magnetic fields were mainly limited to gas giants resembling Jupiter. However, unearthing Earth-sized counterparts calls for different, refined methods.

Since magnetic fields are inherently intangible, detecting their presence around distant planets poses a significant astronomical challenge that Assistant Prof Villadsen and her team are committed to addressing.

She explained their strategy: "We're looking for planets that are really close to their stars and are a similar size to Earth."

"These planets are way too close to their stars to be somewhere you could live, but because they are so close the planet is kind of ploughing through a bunch of stuff coming off the star."

"If the planet has a magnetic field and it ploughs through enough star stuff, it will cause the star to emit bright radio waves."

{ https://www.the-express.com/ }

14-02-2025 om 17:05 geschreven door peter