Gulf of Mars: Rover finds evidence of 'vacation-style' beaches on Mars

• READ MORE:  Scientists make discovery on Mars that could reveal alien life

By XANTHA LEATHAM DEPUTY SCIENCE EDITOR

It might not be the most obvious place for a holiday.

But Mars was once home to sun-soaked, sandy beaches with gentle, lapping waves, according to a new study.

Recent data from the Zhurong Mars rover reveals the red planet might have boasted vast ancient oceans and sandy beaches, potentially supporting microbial life. This groundbreaking discovery, providing the clearest evidence yet, redefines our understanding of Mars as a once potentially habitable world.

Credit: SciTechDaily.com

Researchers have discovered evidence of a ‘vacation-style’ environment on the Red Planet, despite there being no visible liquid on the surface of Mars today.

An international team of scientists used data from China's Zhurong Mars rover to unearth hidden layers of rock underneath the planet’s surface that strongly suggest the presence of an ancient northern ocean.

The new research offers the clearest evidence yet that the planet once contained a significant body of water and a more habitable environment for life, the researchers said.

The Zhurong rover landed on Mars in 2021 in an area known as Utopia Planitia and sent back data on the geology of its surroundings in search of signs of ancient water or ice.

Unlike other rovers it came equipped with ground-penetrating radar which allowed it to explore the planet’s subsurface, using both low and high-frequency radar to penetrate the Martian soil and identify buried rock formations.

By studying the underground sedimentary deposits, scientists are now able to piece together a more complete picture of the planet’s history.

A hypothetical picture of Mars 3.6 billion years ago, when an ocean may have covered nearly half the planet. The blue areas show the depth of the ocean filled to the shoreline level of the ancient, now-gone sea, dubbed Deuteronilus. The orange star represents the landing site of the Chinese rover Zhurong. The yellow star is the site of NASA’s Perseverance rover, which landed a few months before Zhurong. 

Researchers have discovered evidence of a ‘vacation-style’ environment on the Red Planet, despite there being no visible liquid on the surface of Mars today

Credit: Robert Citron

The new research offers the clearest evidence yet that the planet once contained a significant body of water and a more habitable environment for life, the researchers said

When the team reviewed radar data, it revealed a similar layered structure to beaches on Earth.

They noticed formations called ‘foreshore’ deposits’ that slope downwards towards oceans and form when sediments are carried by tides and waves into a large body of water.

When the team compared the Martian data with radar images of coastal deposits on Earth, they found striking similarities.

The dip angles observed on Mars fell right within the range of those seen in coastal sedimentary deposits on Earth.

The discovery indicates that Mars was once a much wetter place than it is today, further supporting the hypothesis of a past ocean that covered a large portion of the northern pole of the planet, the researchers said.

The study also provides new information on the evolution of the Martian environment, suggesting that a life-friendly warm and wet period spanned potentially tens of millions of years.

Co-author Benjamin Cardenas, from Penn State University, said: ‘We’re finding places on Mars that used to look like ancient beaches and ancient river deltas.

‘We found evidence for wind, waves, no shortage of sand — a proper, vacation-style beach.’

The study also provides new information on the evolution of the Martian environment, suggesting that a life-friendly warm and wet period spanned potentially tens of millions of years

Professor Michael Manga, from the University of California, Berkeley, also contributed to the paper.

'The structures don't look like sand dunes,' he said. 'They don't look like an impact crater. They don't look like lava flows. That's when we started thinking about oceans.

'The orientation of these features are parallel to what the old shoreline would have been. They have both the right orientation and the right slope to support the idea that there was an ocean for a long period of time to accumulate the sand-like beach.'

The findings were published in the Proceedings of the National Academy of Sciences journal.

{ https://www.dailymail.co.uk/ }

24-02-2025 om 23:57 geschreven door peter  

Reliëf van Thoetmosis II in het tempelcomplex van Karnak

(CC0 – wiki)

Het betreft het lang verloren gegane graf van Thoetmosis II, waarvan men denkt dat het de laatste onontdekte koninklijke begraafplaats van de 18de dynastie is.

Archeologen hebben het graf van Thoetmosis II gevonden, de vierde farao van de 18de dynastie en echtgenoot van de beroemde koningin Hatsjepsoet. Deze ontdekking is baanbrekend: het is namelijk het eerste faraograf dat sinds de legendarische vondst van Toetanchamon door Howard Carter in 1922 is blootgelegd.

Graf
Het graf werd opgegraven door een Brits-Egyptisch team. De indrukwekkende grandeur van de begraafplaats was onmiddellijk zichtbaar, met een majestueuze trap en een imposante afdalende gang die de koninklijke betekenis van het graf onthulden. “Een deel van het plafond was nog intact”, herinnert onderzoeker Piers Litherland zich. “Het was blauw geschilderd, met gele sterren erop. Dergelijke blauwgeschilderde plafonds met gele sterren komen alleen voor in koningsgraven.”

Meer over Thoetmosis II
Thoetmosis II besteeg de troon rond 1493 v.Chr. Zijn regering was relatief bescheiden in vergelijking met die van zijn voorgangers en opvolgers. Als zoon van Thoetmosis I en zijn tweede vrouw Mutnofret, verstevigde hij zijn macht door met zijn halfzus, Hatsjepsoet, te trouwen. Zijn heerschappij werd gekenmerkt door kleine militaire expedities en het onderdrukken van onrust in Nubië en de Sinaï, maar bracht weinig grote overwinningen voort. Zijn leven eindigde vroeg, rond 1479 v.Chr., waarbij hij zijn jonge zoon Thoetmosis III (geboren uit zijn minder belangrijke vrouw Iset) en dochter Neferure met Hatsjepsoet achterliet.

Het betreden van de grafkamer was allesbehalve makkelijk. Het team kroop door een smalle gang van 10 meter en wrikte zich door een opening van slechts 40 x 40 centimeter breed voordat ze de binnenkamer bereikten. Daar werden ze verwelkomd door een opvallend blauw plafond, versierd met scènes uit de Amduat, een oude funerale tekst die alleen voor koningen was bedoeld – het ultieme bewijs dat ze de rustplaats van een farao hadden gevonden.

Artefacten uit de tombe, waaronder fragmenten van albasten kruiken met de namen van Thoetmosis II en Hatsjepsoet

Ministerie van Toerisme en Oudheden

Voorwerpen
Het onomstotelijke bewijs dat ze op het graf van Thoetmosis II waren gestuit, kwam in de vorm van scherven van een albasten pot met zowel zijn naam als die van Hatsjepsoet erop, de eerste voorwerpen die ooit aan zijn begrafenis konden worden gekoppeld. De onderzoekers vermoeden dat het graf ongeveer zes jaar na de begrafenis mogelijk is overstroomd, wat tot het verplaatsen van de inhoud zou hebben geleid. De onderzoekers denken een mogelijke locatie voor dit tweede graf te hebben gevonden, waar wellicht nog onaangeroerde schatten te ontdekken zijn.

Mysterie
“Deze ontdekking ontrafelt een groot mysterie uit het Oude Egypte: het biedt de oplossing voor de eeuwenoude puzzel over de locatie van koninklijke graven uit de vroege 18de Dynastie”, zegt Litherland. “Het graf van deze voorouder van Toetanchamon was nooit gevonden, omdat men altijd dacht dat het aan de andere kant van de berg, dichtbij de Vallei der Koningen, lag. In eerste instantie dachten we misschien een graf van een koninklijke vrouw te hebben ontdekt, maar de brede trap en de grote deur wezen op iets veel belangrijkers. Het was enorm opwindend om te ontdekken dat de grafkamer versierd was met scènes uit de Amduat, een religieuze tekst die alleen voor koningen is bestemd – de eerste aanwijzing dat we een koningsgraf hadden gevonden.”

Toegewijd werk
Deze ontdekking is het resultaat van meer dan 12 jaar toegewijd werk van Litherland en zijn team. Eerder hebben hun inspanningen al geleid tot de opgraving van 54 graven in de westelijke Thebaanse bergen van Luxor en de identificatie van meer dan 30 koninklijke vrouwen en hofvrouwen. Maar deze nieuwe ontdekking spant toch wel de kroon. “Dit is het eerste koninklijke graf sinds de baanbrekende ontdekking van koning Toetanchamons tombe in 1922”, benadrukt de Egyptische minister van Toerisme en Oudheden, Sherif Fathy. “Een bijzonder moment voor de egyptologie en een belangrijke stap in ons begrip van het gezamenlijke verleden van de mensheid.”

Dood
De omstandigheden rond de dood van Thoetmosis II blijven in nevelen gehuld. Het wordt echter algemeen aangenomen dat hij niet door een gewelddadige daad of ongeluk om het leven kwam, maar waarschijnlijk door ziekte of natuurlijke oorzaken. Zijn korte regering en aanwijzingen over zijn zwakke gezondheid suggereren dat hij mogelijk leed aan een langdurige aandoening die zijn energie had uitgeput.

Onderzoek van zijn gemummificeerde resten toont aan dat zijn lichaam verzwakt was door ziekte. Sommige wetenschappers speculeren dat hij mogelijk leed aan een chronische huidaandoening, een infectieziekte of zelfs een erfelijke aandoening, mogelijk veroorzaakt door generaties van koninklijke huwelijken binnen de familie. Wat de precieze oorzaak van zijn vroege dood rond 1479 v.Chr. was, blijft echter een raadsel.

Na de dood van Thoetmosis II fungeerde Hatsjepsoet aanvankelijk als regent voor haar jonge stiefzoon, maar al snel greep ze zelf de macht en verklaarde haar goddelijke recht om te heersen. Veel wetenschappers denken dat ze de regering van haar overleden man als teleurstellend beschouwde, wat haar motiveerde om een veel indrukwekkender erfgoed te creëren. Als een van de krachtigste vrouwelijke farao’s uit de geschiedenis richtte ze zich op monumentale bouwwerken, waarvan haar majestueuze graftempel in Deir el-Bahari de meest iconische is.

Bronmateriaal

• "Discovery of Thutmose II’s tomb" - Egypt Museum
• Afbeelding bovenaan dit artikel: Egypt Museum

{ https://scientias.nl/nieuws/geschiedenis/ }

24-02-2025 om 20:44 geschreven door peter  

The journey to Mars will subject astronauts to extended periods of exposure to radiation during their months-long travel through space. While NASA’s Artemis 1 mission lasted only a matter of weeks, it provided valuable radiation exposure data that scientists can use to predict the radiation risks for future Mars crews. The measurements not only validated existing radiation prediction models but also revealed unexpected insights about the effectiveness of radiation shielding strategies too. 

Space radiation poses one of the most significant health risks for astronauts travelling beyond Earth’s magnetic field. Unlike the radiation from medical X-rays or nuclear sources on Earth, space radiation includes high-energy galactic cosmic rays and solar particle events that can penetrate traditional shielding materials. When these particles collide with human tissue, they can damage DNA, increase cancer risk and weaken the immune system. The effects are cumulative too, with longer missions like a journey to Mars significantly increasing exposure and health risks. 

The International Space Station crews receive radiation doses similar to nuclear power plant workers due to a little protection from Earth’s magnetosphere, but astronauts traveling to Mars would face much higher exposure levels during their multi-month journey. NASA estimates that a mission to Mars could expose astronauts to radiation levels that exceed current career exposure limits, making effective radiation shielding one of the key challenges for deep space exploration.

A paper recently published by a team led by Tony C Slaba from the Langley Research Centre at NASA, they use computer models and data from on-board detectors to assess the health risk to long term space flight. The data is taken from the International Space Station (ISS,) the Orion Spacecraft, the BioSentinel CubeSat and from receivers on the surface of Mars. Collectively this data enables a full mission profile to be modelled for a Martian journey. The data was captured during the time period of the Artemis-1 mission, just under one month in duration.

Space radiation comes in two primary forms that pose risks to astronauts and spacecraft. Solar Particle Events occur during solar storms, releasing intense bursts of energetic particles from the Sun, while Galactic Cosmic Rays represent a constant stream of highly penetrating radiation from deep space. The findings enabled the team to assess current models for accuracy. They found that predictions match actual measurements to within 10-25% for the International Space Station, 4% for deep space conditions, and 10% for the Martian surface. This level of precision gives confidence in the existing models and in planning radiation protection for future missions.

A cloud of cold charged gas around Earth, called the plasmasphere and seen here in purple, interacts with the particles in Earth’s radiation belts — shown in grey — to create an impenetrable barrier that blocks the fastest electrons from moving in closer to our planet. 

NASA/Goddard

They also found that, having assessed traditional shielding approaches, that they are largely ineffective against Galactic Cosmic Rays. In some cases, excessive shielding or inappropriate material choices can even amplify radiation exposure through secondary particle production. This occurs when the ‘original radiation’ creates a cascade of new particles on impact that can be more dangerous than the original radiation! They found that radiation levels vary substantially depending on location and the specific shielding configurations used! Quite the headache for engineers!

Radiation exposure is one of the greatest challenges in human space exploration. The study shows that our models for assessing radiation risk are reliable and that the ability to accurately assess those risks is crucial for protecting astronauts from serious health consequences. Having a good understanding of the risk directly influences how spacecraft are engineered, and plays a key role in mission planning for trips beyond Earth orbit. More work is needed now in the design of radiation protection systems if our space travellers are to be better protected from the long term risks posed by radiation.

Source : 

• Validated space radiation exposure predictions from earth to mars during Artemis-I

RELATED VIDEOS

{ https://www.universetoday.com/ }

24-02-2025 om 12:36 geschreven door peter  

Satellites often face a disappointing end: despite having fully working systems, they are often de-orbited after their propellant runs out. However, a breakthrough is on the cards with the launch of China’s Shijian-25 satellite which has been launched into orbit to test orbital refuelling operations. The plan; docking with satellite Beidou-3 G7 and transferring 142 kilograms of hydrazine to extend its life by 8 years! It’s success will mean China plans to develop a network of orbital refuelling stations!

Like cars on Earth, satellites need fuel to manoeuvre and for their constantly decaying orbits to be boosted. But unlike vehicles on the ground, when satellites run out of propellant, they become expensive space debris. This challenge has driven the development of orbital refuelling technology, which could extend satellite lifespans and transform space operations.

The International Space Station (ISS) offers one of the most well known examples of an orbiting ‘satellite’ and it too needs to deal with boosting its orbit. The problem is the drag imposed upon the structures by gas in our atmosphere. In the case of the ISS, docked supply craft are typically used to fire their engines to reposition ISS to the correct altitude. Without these periodic “orbital boosts,” the ISS would eventually lose altitude and reenter the atmosphere.

A significant milestone in autonomous refuelling came in 2007 with DARPA’s Orbital Express mission. This demonstration involved two spacecraft: the ASTRO servicing vehicle and a prototype modular satellite called NextSat. Over three months, they performed multiple autonomous fuel transfers and component replacements, proving that robotic spacecraft could conduct complex servicing operations without direct human control.

The technology continues to advance with China’s Shijian-25 satellite (launched on 6 January 2025) representing another step forward in orbital refuelling capabilities. The mission aims to demonstrate refuelling operations in geosynchronous orbit approximately 36,000 kilometres above Earth. This is particularly significant because geosynchronous orbits often host communications satellites that benefit from life extension.

The technical challenges of orbital refuelling are considerable though. Spacecraft must achieve extremely precise rendezvous and docking while travelling in excess of 28,000 kilometres per hour. The fuel transfer system must prevent leaks, which could be hazardous to both spacecraft and create hazardous debris. Adding to the challenge is that many satellites were never designed with refuelling in mind, lacking any form of standardised fuel ports or docking interfaces.

Looking ahead, several companies and space agencies are developing orbital refuelling systems. These range from dedicated “gas station” satellites to more versatile servicing vehicles that can perform repairs and upgrades alongside refuelling. As the technology advances, it could significantly change how we operate in space, making satellite operations more sustainable and cost-effective.

Source : 

• China successfully sent Shijian-25 satellite

{ https://www.universetoday.com/ }

24-02-2025 om 11:57 geschreven door peter  

This radiation reveals everything from star-forming gas clouds to the shapes of the galaxy’s spiral arms. Whereas visible light just gets caught up in all the interstellar dust at it tries to traverse the tens of thousands of light-years across the galaxy, 21cm radiation just sails right though.

But mapping the galaxy’s structure is just one part of the story. Astronomers can also learn about the Milky Way’s rotation by studying the redshift and blueshift of the 21cm radiation. When an object in space moves away from us, the wavelength of the light or radiation it emits gets stretched out, making it appear redder (redshift). Conversely, when an object moves toward us, the wavelength gets compressed, making it appear bluer (blueshift).

By analyzing the redshift and blueshift of the 21cm radiation from different parts of the galaxy, astronomers can determine how fast various regions of the Milky Way are rotating. This information helps them build a more comprehensive picture of our galaxy’s dynamics and motion.

The utility of 21cm radiation isn’t limited to the Milky Way alone. Astronomers can use these same techniques to study distant galaxies as well. By examining the neutral hydrogen gas clouds in far-off galaxies, they can estimate the masses of these galaxies. This is because the amount of 21cm radiation emitted is related to the number of hydrogen atoms present, which in turn gives clues about the galaxy’s overall mass.

21cm radiation is a powerful tool in the field of astronomy that allows astronomers to map the structure of our Milky Way galaxy, understand its rotation, and even estimate the masses of distant galaxies. This technique opens a window into the vast and complex universe, helping us unravel the mysteries of the cosmos with every new observation.

So next time you gaze up at the night sky, remember that there’s a whole lot more going on than meets the eye. Thanks to 21cm radiation, we’re able to peel back the layers of the Milky Way and explore the wonders of the universe in ways that were once unimaginable.

{ https://www.universetoday.com/ }

23-02-2025 om 22:13 geschreven door peter  

NASA astronomers have been continuing to monitor the trajectory of asteroid 2024 YR4. The initial calculations suggested a 1.3% probability of an Earth impact event, which temporarily increased to 3.1% as more data came in. However, and with a sigh of relief, recent analysis brings encouraging news: the Earth impact probability has decreased significantly to 0.28%, though calculations now show a 1% chance of lunar impact. Observations will continue with the James Webb Space Telescope so stay tuned. 

Asteroids are rocky, airless worlds that are remnants left over from the formation of our Solar System about 4.6 billion years ago. They range in size from tiny pebbles to massive bodies hundreds of kilometres across. Most asteroids are found in the asteroid belt between the orbits of Mars and Jupiter although some follow paths that bring them closer to Earth.  Occasionally, they can pose a threat to Earth, which is why astronomers and space agencies closely monitor their orbits and develop potential deflection techniques.

Asteroid Ryugu as seen by Japan’s Hayabusa 2 spacecraft, which returned a sample of the ancient asteroid to Earth in 2020.

Image Courtesy ISAS/JAXA

Asteroid 2024 YR4 is one such asteroid that has had gripped the nations media over recent weeks. It’s a near-Earth object that was discovered on 27 December 2024, by the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Chile. Initially, it had an estimated 1.3% chance of impact with Earth in 2032, making it one of the highest-risk asteroids ever recorded. However, further observations raised that risk!

Astronomers use systems like ATLAS to identify near-Earth objects (NEOs) that could pose a potential threat to our planet. It was developed by the University of Hawaii and funded by NASA and consists of a network of telescopes positioned around the world to provide continuous sky surveys. Its primary goal is to detect asteroids before a potential impact, allowing for timely warnings and mitigation efforts. Since its installation, ATLAS has successfully discovered thousands of asteroids, including hazardous ones just like 2024 YR4. 

Understanding the level of threat from asteroids like 2024 YR4 requires time, time and observations. Imagine a game of tennis and the ball is hit, sending it flying over the net. A photographer sat in the crowd grabs a snapshot of the ball as it flies over the net. The picture is a clear, sharp capture of a point in time however analysis of the image can only reveal the exact location of the ball and not its trajectory. It’s the same with asteroids, once they are discovered, a single observation will reveal where it is but a series of observations are required to understand where it’s going. Ok so this is a simplistic view but it shows how important continued observations are to asteroids like 2024 YR4.

Further observations of asteroid 2024 YR4, conducted during the night of 19-20 February have revealed encouraging results. NASA’s planetary defence team have reported that the probability of an Earth impact has decreased to 0.28%. Monitoring will of course continue to refine trajectory predictions, but current calculations indicate a slight increase in the possibility of lunar impact, now estimated at 1%. These percentages are of course tiny and pose no cause for alarm but 2024 YR4 will continue to be observed over the coming months, just to be sure.

Source : 

• Additional Observations Continue to Reduce Chance of Asteroid Impact in 2032

{ https://www.universetoday.com/ }

23-02-2025 om 22:07 geschreven door peter  

NASA engineers are pressing ahead with preparations for the Artemis II mission unless someone tells them otherwise. The ambitious flight will send four astronauts on a trajectory similar to Apollo 8’s historic lunar journey, with the crew traveling around the Moon in an Orion Capsule before returning to Earth. A crucial milestone in the mission preparations was reached as technicians completed the assembly of the Space Launch System’s twin solid rocket boosters inside the Vehicle Assembly Building. The stacking process began in late November 2024 and concluded on February 19th.

In a significant step forward for our return to the Moon, NASA engineers at Kennedy Space Center have finished assembling the massive solid rocket boosters that will power the Artemis II mission. The stacking operation, completed on 19 February 2025, marks a key milestone in preparation for the first crewed lunar mission since Apollo. As someone who never saw the Apollo Moon landings, I’m excited. 

The assembly process began on 20 November 2024, inside Kennedy’s amazing Vehicle Assembly Building (VAB), where generations of Moon rockets have been built. Using techniques that have been refined over decades of spaceflight experience, technicians employed one of the facility’s overhead cranes to carefully position each segment of the twin boosters.

These solid rocket boosters represent modern engineering at its best, being assembled on Mobile Launcher 1, a huge structure standing 380 feet tall – roughly the height of a 38-story building. This launch platform serves a number of different functions, acting as both the assembly base for the Space Launch System (SLS) rocket and Orion spacecraft, and the launch platform from which the mission will eventually depart for the Moon.

The completed boosters will form part of the most powerful rocket ever built by NASA, more powerful even than Saturn V that took Apollo astronauts to the Moon. When ignited, these twin rockets will generate millions of pounds of thrust, working in together with the SLS core stage to lift the Orion spacecraft and its four-person crew toward the Moon.

Artemis II represents a historic moment in space exploration as the first time humans will venture beyond low Earth orbit since 1972. The mission profile calls for a crew of four astronauts to journey around the Moon in the Orion spacecraft, testing critical systems and procedures before future missions attempt lunar landings.

The successful completion of booster stacking demonstrates the expertise of NASA’s engineering teams. Each segment had to be perfectly aligned and secured, with no room for error in a process that demands accuracy. The boosters will eventually help propel the spacecraft to speeds exceeding 17,000 miles per hour – fast enough to break free of Earth’s gravity and get to the Moon.

With this milestone achieved, NASA continues toward launch, carefully checking and testing each system to ensure the safety of the crew and the success of this ambitious mission to return humans to deep space.

Moon, here we come, once again. 

Source : 

• Artemis II Rocket Booster Stacking Complete

RELATED VIDEOS

{ https://www.universetoday.com/  }

21-02-2025 om 14:40 geschreven door peter  

Artist's impression of an asteroid or a comet.

Credit: Mark A. Garlick, space-art.co.uk, University of Warwick and University of Cambridge

How Big is YR4 and What Would an Impact Mean?

YR4 measures approximately 40 and 90 meters (130–300 feet) in diameter, comparable in height to the Leaning Tower of Pisa. While relatively small in cosmic terms, an asteroid of this size carries significant destructive potential. If it were to strike Earth, it could unleash the equivalent of 8 megatons of energy—over 500 times more powerful than the Hiroshima explosion. This would be sufficient to devastate a city, though not large enough to trigger a global catastrophe.

There is also a slim possibility that YR4 could collide with the Moon rather than Earth, though the most likely outcome remains a harmless flyby when it makes its closest approach in 2032.

Torino Scale and Emergency Observations

Due to its initial impact probability exceeding 1%, YR4 reached Level 3 on the Torino Impact Hazard Scale. This classification is reserved for objects that warrant further study but are expected to be downgraded as more data is gathered. Most asteroids initially placed at this level ultimately pose no risk once their orbits are better understood.

In response to the early uncertainty, an international team of scientists has been granted emergency access to the James Webb Space Telescope. This advanced observatory will provide highly detailed observations, helping to refine YR4’s projected trajectory. Over the coming months, astronomers expect to confirm that it poses no danger to Earth.

For now, there is no reason for concern. The history of asteroid tracking shows that initial impact probabilities tend to decrease with more precise data. Scientists continue to monitor YR4 closely, but all indications suggest that it will pass by Earth without incident.

As new observations come in, NASA and other space agencies will provide ongoing updates. Follow trusted sources for the latest information on asteroid 2024 YR4 and other near-Earth objects.

{ https://curiosmos.com/ }

20-02-2025 om 23:35 geschreven door peter  

Artist's illustration of an asteroid impacting the Atlantic ocean.

Depositphotos.

The James Webb Space Telescope (JWST) is set to observe the asteroid before it moves out of view, aiming to refine estimates of its size, trajectory, and composition. Once 2024 YR4 travels further into the solar system, gathering new data will become much more difficult.

What Happens If 2024 YR4 Hits Earth?

At an estimated 40 to 90 meters (130 to 300 feet) wide, this asteroid wouldn’t wipe out civilization, but it could cause catastrophic regional destruction.

If it were to strike a populated area, the energy released would be equivalent to 8 megatons of TNT, over 500 times more powerful than the Hiroshima bomb. Possible impact zones include South America, Africa, the Middle East, and South Asia, with major cities like Bogotá, Lagos, and Mumbai at risk.

However, experts have noted an unexpected best-case scenario: an impact on the Moon. If 2024 YR4 were to collide with the Moon instead of Earth, it would remove the risk entirely while providing an unprecedented opportunity for scientists to study an asteroid impact up close.

How Do We Stop an Incoming Asteroid?

Humanity is not defenseless against threats like 2024 YR4. The DART (Double Asteroid Redirection Test) mission, launched by NASA in 2022, successfully altered the trajectory of an asteroid by smashing a spacecraft into it. This marked the first real-world test of asteroid deflection.

Building on that success, the European Space Agency (ESA) launched Hera in October 2024. This follow-up mission is set to analyze the aftermath of DART’s impact, collecting crucial data to refine future planetary defense strategies and better prepare Earth for potential threats.

Meanwhile, nuclear-based asteroid deflection remains a last resort. Scientists at the Lawrence Livermore National Laboratory (LLNL) have simulated scenarios where nuclear devices could shatter an asteroid into smaller, non-lethal fragments. While controversial, this remains one of the most powerful backup options if an asteroid is detected too late for other interventions.

What Are the Odds of an Asteroid Impact?

Despite the headlines, Earth is not in immediate danger. Space agencies continuously track thousands of near-Earth objects, and NASA estimates that the chance of a “city-killer” asteroid hitting our planet is just 0.1% per year.

Even if an impact were to occur, there’s a 70% chance it would land in the ocean, with another 25% chance it would strike an unpopulated region.

That being said, 2024 YR4 is unique—it’s one of the few asteroids with an impact probability high enough to trigger early planetary defense discussions. If that probability increases further, we may witness history: the first-ever mission to deflect an asteroid outside of a test environment.

With eight years until its potential impact, scientists have time to improve tracking, refine predictions, and prepare defensive measures. NASA, ESA, and China will continue monitoring 2024 YR4, adjusting estimates as more data comes in.

For now, the takeaway is clear: Earth is watching, and if necessary, we are ready to act.

RELATED VIDEOS

{ https://curiosmos.com/ }

20-02-2025 om 23:23 geschreven door peter  

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  

{ https://www.universetoday.com/ }

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