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The Earth and Moon have been locked in a gravitational dance for billions of years. Each day, as the Earth turns, the Moon tugs upon the oceans of the world, causing the rise and fall of tides. As a result, the Earth’s day gets a little bit longer, and the Moon gets a little more distant. The effect is small, but over geologic time it adds up. About 620 million years ago, a day on Earth was only 22 hours long, and the Moon was at least 10,000 km closer than it is now.

Evidence for this evolving dance in the geological record only goes back about two billion years. Beyond that, the Earth was so very different that there simply isn’t enough evidence to gather. So, instead, we must rely on computational models and our understanding of dynamics. We know that when the Earth formed, it had no large moon. Then, about 4.4 billion years ago, a Mars-sized protoplanet named Theia collided with our world to create the Earth-Moon system. What’s interesting is that most of the computer simulations for this collision generate a Moon that is much closer to the Earth than we’d expect. Early Earth didn’t have vast oceans, so there were no water tides to drive the Moon to a larger orbit. So how did the Moon get to its present distance?

The potential structure of a lava planet. Credit: Farhat, et al

A new study argues that back then the Earth did have tides, but they were made of lava, not water. Just after the Great Collision, Earth would have been covered in an ocean of hot lava. With the Moon so near, the lava would have experienced strong tides. Since lava is much denser than water, the effects of the tide would have been much greater. The Earth’s rotation would have slowed down much faster, and the Moon would quickly become more distant. Based on their simulations, the authors argue that the Moon’s distance would have increased by 25 Earth-radii in just 10,000 to 100,000 years. This would explain how the Moon moved towards its present distance range rather quickly.

The idea of tides on an ocean world also has implications for planets around other stars. Planets that form very close to their sun would be extremely hot, and many of them could have lava oceans for a billion years or more. Simulations of such worlds show that lava tides would accelerate the spin dynamics of such a world and could cause them to become tidally locked on a million-year timescale instead of a billion-year timescale. If this model is correct, it would have a significant impact on potentially habitable worlds. Most exoplanets orbit red dwarf stars, since red dwarfs make up about 75% of the stars in our galaxy. The habitable zone of red dwarfs is very close to the star, meaning that many of them would have begun as lava worlds. This would mean most potentially habitable worlds would have one side always facing the sun, while the other side is forever in the cold. Life on these worlds would be very different from what we see on Earth.

Reference: Farhat, Mohammad, et al. “Tides on Lava Worlds: Application to Close-in Exoplanets and the Early Earth-Moon System.” arXiv preprint arXiv:2412.07285 (2024).

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Currently, 5,788 exoplanets have been confirmed in 4,326 star systems, while thousands more candidates await confirmation. So far, the vast majority of these planets have been gas giants (3,826) or Super-Earths (1,735), while only 210 have been “Earth-like” – meaning rocky planets similar in size and mass to Earth. What’s more, the majority of these planets have been discovered orbiting within M-type (red dwarf) star systems, while only a few have been found orbiting Sun-like stars. Nevertheless, no Earth-like planets orbiting within a Sun-like star’s habitable zone (HZ) have been discovered so far.

This is largely due to the limitations of existing observatories, which have been unable to resolve Earth-sized planets with longer orbital periods (200 to 500 days). This is where next-generation instruments like the ESA’s PLAnetary Transits and Oscillations of stars (PLATO) mission come into play. This mission, scheduled to launch in 2026, will spend four years surveying up to one million stars for signs of planetary transits caused by rocky exoplanets. In a recent study, an international team of scientists considered what PLATO would likely see based on what it would see if observing the Solar System itself.

The study was led by Andreas F. Krenn, a PhD student at the Space Research Institute at the Austrian Academy of Sciences. He was joined by researchers from the Observatoire Astronomique de l’Université de Genève, Aix Marseille University, the Columbia Astrophysics Laboratory, the Leibniz Institute for Astrophysics Potsdam (AIP), the Institute of Astronomy at KU Leuven, the National Center for Atmospheric Research, and the Kanzelhöhe Observatory for Solar and Environmental Research at the University of Graz. The paper that describes their research recently appeared in the journal Astronomy & Astrophysics.

As they note in their study, an Earth-like planet orbiting within the HZ of a G-type star would be a prime target to search for biosignatures. These include oxygen gas, carbon dioxide, methane, ammonia, and water vapor in the atmosphere, as well as indications of photosynthesis taking place on the surface – i.e., the vegetation red edge (VRE). This has been very difficult for telescopes as Earth-like planets are more likely to orbit closer to Sun-like stars, making it difficult to obtain data on their atmospheres using either Direct Imaging or transmission spectra.

This latter technique involves the Transit Photometry (or the Transit Method), where astronomers measure the light curve of distant stars for periodic dips in brightness. These are often the result of exoplanets passing in front of the star (i.e., transiting) relative to the observer. To date, the vast majority of exoplanets – more than 4,300, or 74.5% – have been confirmed using this method. When the conditions are right, astronomers sometimes observe light as it passes through the exoplanet’s atmosphere, which is then studied using spectrometers to determine its chemical composition.

But as Krenn told Universe Today via email, this has been a significant challenge for astronomers:

“The main difficulty is the small signals that such planets generate. For example, the radial velocity amplitude of the Earth is roughly 0.1 m/s. This is about the speed of a giant Galapagos tortoise. That means that if a distant observer would like to see the Sun’s motion around the common center of mass of the Earth-Sun system, they would need to see the Sun move at the speed of a giant Galapagos tortoise from light years away.

“Similarly, the relative amount emitted by the Sun that is blocked by the Earth when a distant observer observes the Earth transiting across the solar disk is 84 parts per million, which is 0.0084%. So a distant observer would need to see the light of that star being dimmed by 0.0084% in order to detect Earth.”

Moreover, Krenn added that existing spectrographs have not been precise enough to measure such small signals. Whereas exoplanet-hunting missions like the ESA’s CHaracterising ExOPlanets Satellite (CHEOPS) have managed to obtain spectra from transiting exoplanets, several transit events were needed to achieve this precision. This isn’t easy when dealing with planets like Earth with longer orbital periods that fit into the 200- to 500-day range. Lastly, instrumental effects and stellar variability can be orders of magnitude larger than a planetary signal.

This is expected to change considerably with the ESA’s next-generation PLAnetary Transits and Oscillations of stars (PLATO) space telescope. This mission will rely on a multi-telescope approach involving 26 cameras, including 24 “normal” cameras organized in 4 groups and 2 “fast” cameras for bright stars. These instruments will continuously observe the same area of the sky for at least two years to detect transit signals by Earth-like planets around solar analogs. Said Krenn:

“PLATO’s photometric instrument will be precise enough to detect the transit of an Earth-like planet orbiting a solar-like star using a single transit event. Supported by its stellar variability program and ground-based follow-up campaign, we will hopefully be able to correctly account for the influences of noise sources. In short, PLATO will utilize the interdisciplinary of exoplanet science on a whole new level. It will combine high-precision photometry, up-to-date data analysis tools, a dedicated stellar variability program, and its own ground-based follow-up campaign.

“Experts from all of these fields will work together to try and make the detection of these tiny planetary signals possible. Additionally, PLATO will also utilize a special observing strategy that allows it to observe thousands of stars a the same time and produce 2 years of almost continuous photometric data for each of them.”

ESA’s trifecta of dedicated exoplanet missions – Cheops, Plato, and Ariel – will also be complemented by the James Webb Space Telescope mission Credit: ESA

To assess what PLATO might see when observing thousands of Sun-like stars for Earth analogs, the team modeled the impact of short-term solar variability using the Sun as a proxy. This consisted of using data obtained by the Helioseismic and Magnetic Imager (HMI) aboard NASA’s Solar Dynamics Observatory, which has been observing the Sun continuously since 2010. Using 88 consecutive days of HMI observations, they injected Earth-like transit signals and noise models into the data and simulated PLATO observations for five scenarios and five stellar magnitudes.

Their results showed that transit signals can be reliability detected with a high signal-to-noise ratio for bright targets, but still very likely for faint ones. They further found that the PLATO mission has a good shot at precisely and accurately measuring the size of Earth-like planets, one of its chief objectives. As Krenn explained, these findings could help inform the PLATO mission and assist in finding the signals of Earth analogs amid all the noise, though much work needs to be done to ensure all sources of noise are accounted for:

“In our analysis, we focused only on the effects of short-term variability, which we know is only one of many noise sources that will affect PLATO observations. We have seen that even correctly accounting for this single type of noise can be challenging. The final analysis of PLATO data will need to combine a variety of complex noise models simultaneously to correctly account for all of the different noise sources. I think our research has shown that we need to have an in-depth understanding of individual noise sources but, at the same time, also need to learn how to best combine all of the individual models.”

Other next-generation instruments, such as the James Webb Space Telescope (JWST), the Atmospheric Remote-sensing Infrared Exoplanet Large-survey (ARIEL) telescope, and the Nancy Grace Roman Space Telescope will also allow for the discovery and characterization of countless exoplanets using the Direct Imaging Method. Along with upcoming ground-based observatories, these missions will rely on advanced optics, coronographs, and spectrometers to locate more Earth analogs and analyze their atmospheres and surfaces for evidence of life. Soon enough, astronomers will do away with terms like “potentially habitable” and be able to say with confidence that an exoplanet is “habitable” (and perhaps even “inhabited”!)

Further Reading: Astronomy & Astrophysics

The post Could the ESA’s PLATO Mission Find Earth 2.0? appeared first on Universe Today.

Most galaxies are thought to play host to black holes. At the center of Centaurus A, a galaxy 12 million light years away, a jet is being fired out into space. Images that have been captured by NASA’s Chandra X-ray observatory show that the high energy particles have struck a nearby object creating a shockwave. The target is thought to be a giant star, maybe even a binary system, where the collision and turbulence has increased density in the region.

A black hole is an object and a region of space! At the centre is the singularity, a single point object where density is infinite and all the laws of physics seem to fail us. Surrounding the singularity is a region of space where the velocity needed to escape the singularity’s gravitational pull is in excess of the speed of light. The boundary between the region of space dominated by the singularity and dare I say ‘normal space’ is known as the event horizon. Collectively we call this phenomenon a black hole. 

3D rendering of a rapidly spinning black hole’s accretion disk and a resulting black hole-powered jet. Credit: Ore Gottlieb et al. (2024)

Black holes at the centre of galaxies are usually supermassive, often millions to billions of times more massive than the Sun. They exert an immense pull of gravity which has an impact on the motion of stars and gas within their host galaxy. Matter getting drawn toward a black hole by its immense gravitational pull forms into an accretion disk surrounding the black hole. Here the gravitational force is high and so it heats the incoming material. The material falling in to the black hole gets heated to extreme temperatures generating strong electromagnetic fields. The fields can accelerate the particles outward forming into the familiar jet structure. 

A simulation of a galaxy’s ‘heart and lungs’ at work is pictured inset on an artist’s impression of bi-polar jets of gas originating from a supermassive black hole at the centre of a galaxy. Credit ESA/Hubble, L. Calçada (ESO) / C Richards/MD Smith/University of Kent Licence type Attribution (CC BY 4.0)

Our own Milky Way galaxy has a black hole at the centre as does the galaxy Centaurus A. At a distance of 12 million light years, it’s relatively in our back yard! A team of astronomers have turned NASA’s Chandra X-Ray observatory on Centaurus A and found the jet of its black hole striking an unidentified object. The team of astronomers discovered that parts of the jet are moving at speeds close to the speed of light. They also detected the region where it seemed to be striking something, appearing as a bright source of X-rays in the image, known as C4. 

This is Centaurus A, the nearest galaxy with an active nucleus. The active nucleus is where a supermassive black hole resides. One of the questions in astrophysics is how SMBHs grow so large, and the JWST should help answer that question. Image Credit: By ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)

At a distance of 12 million light years, it’s too far away for the object to be seen but the team theorise that it’s either a massive star or one with a companion star. It’s thought that the X-rays are caused by a collision between the particles in the jet and the stellar wind from the star. The impact from the collision can be the generation of turbulence which leads to an increase in the density of gas in the jet, driving the X-ray emissions that have been detected. 

In the deepest image from Chandra, at the C4 source there appeared a strange V-shaped structure. The shape is not fully understood but analysis revealed the arms of the ‘V’ are at least 700 light years long! The results were published in the Astrophysical Journal by lead author David Bogensberger from the University of Michigan and a team of US astronomers. 

Source : Black Hole Jet Stumbles Into Something in the Dark

The post Zap! A Black Hole Scores a Direct Hit With its Jet appeared first on Universe Today.

Do we have a planetary bias when it comes to understanding where life can perpetuate? It’s only natural that we do. After all, we’re on one.

However, planets may not be necessary for life, and a pair of scientists from Scotland and the USA are inviting us to reconsider the notion.

We focus on planets as habitats for life because they meet the conditions necessary for life to survive. Liquid water, the right temperature and pressure to keep it in a liquid state, and protection from harmful radiation are the primary requirements for photosynthetic life. But what if other environments, even ones maintained by organisms themselves, can also provide these necessities?

In new research published in the journal Astrobiology, researchers point out that ecosystems could generate and sustain the conditions necessary for their own survival without requiring a planet. The paper is titled “Self-Sustaining Living Habitats in Extraterrestrial Environments.” The authors are Robin Wordsworth, Professor of Earth and Planetary Sciences at Harvard, and Charles Cockell, Professor of Astrobiology in the School of Physics and Astronomy at the University of Edinburgh.

“Standard definitions of habitability assume that life requires the presence of planetary gravity wells to stabilize liquid water and regulate surface temperature,” they write. “Here the consequences of relaxing this assumption are evaluated.”

Wordsworth and Cockell write that biologically generated barriers and structures can mimic the planetary conditions that enable life without the planet. They can let light in for photosynthesis while blocking UV light. They can also prevent volatile loss while in a vacuum and maintain the temperature and pressure range required for water to remain in a liquid state.

“Biologically generated barriers capable of transmitting visible radiation, blocking ultraviolet, and sustaining temperature gradients of 25-100 K and pressure differences of 10 kPa against the vacuum of space can allow habitable conditions between 1 and 5 astronomical units in the Solar System,” they write.

“To understand the constraints on life beyond Earth, we can start by reviewing why our home planet is a good habitat for life in the first place,” write the authors.

The Earth is our only example of a biosphere, but it’s possible that extraterrestrial life could create its own self-sustaining habitat. Image Credit: ESA/Meteosat

Earth does more than just provide liquid water and protection from radiation. It’s an entire system with layers of interacting complexity. The planet’s surface is exposed to an easily accessible source of energy from the Sun that drives the whole biosphere. The elements we think of as essential for life are available, though sometimes limited: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorous, and Sulfur. They cycle through the biosphere via volcanism and plate tectonics and become available again. Earth is also oxidizing in the atmosphere and on the surface and reducing in other regions like sediments and the deep subsurface. This allows for “the exploitation of redox gradients for metabolic purposes,” the authors explain.

Those conditions don’t exist elsewhere. Astrobiology targets the solar system’s frozen moons because of their warm, salty oceans. But do they have nutrient cycles?

Low-mass objects in the outer Solar System have ample surface area, but the Sun’s energy is weak. They’re unlikely to be able to hold onto their atmospheres, so the correct pressure and temperature for liquid water are out of reach. They’re also unprotected from UV radiation and cosmic rays.

“To persist beyond Earth,” the authors write, “any living organism must modify or adapt to its environment enough to surmount these challenges.”

The authors write that biological materials here on Earth can already do that. It’s plausible that ecosystems could develop the conditions for their own survival, and if photosynthetic life can do it in the vacuum of space, then so could we. It would be a major benefit for human space exploration.

It starts with water, and when it comes to liquid water, scientists refer to its triple point. A triple point is a thermodynamic reference point that explains phase transitions and how water behaves under different pressures and temperatures. “The minimum pressure required to sustain liquid water is the triple point: 611.6 Pa at 0?C (273 K),” the researchers explain. That number rises to a few kPa between 15 to 25 Celsius.

Cyanobacteria can grow with air headspace pressures of 10 kPa so long as the light, temperature and pH are in the right ranges. The question is, do any living things that we know of generate walls that can maintain 10kPa?

“Internal pressure differences of order 10 kPa are easily maintained by biological materials and in fact common in macroscopic organisms on Earth,” the authors write. “The blood pressure increase from the head to the feet of a 1.5-m tall human is around 15 kPa.” Seaweed can also sustain internal float nodule pressures of 15-25 kPa by releasing CO2 from photosynthesis.

Ascophyllum nodosum grows egg-shaped air bladders that sustain internal pressure. Image Credit: By Dozens at en.wikipedia, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=10867583

Temperature is the next consideration when it comes to liquid water. Earth maintains its temperature through the atmospheric greenhouse effect. But small rocky bodies, for example, are unlikely to replicate this. “Hence, a biologically generated habitat must achieve the same effect via solid-state physics,” write the authors.

Incoming energy and outgoing energy need to be balanced, and some organisms on Earth have evolved to maintain this balance. “Saharan silver ants, for example, have evolved the ability to enhance both their surface near-infrared reflectivity and their thermal emissivity, allowing them to survive in ambient temperatures above the range of all other known arthropods,” Wordsworth and Cockell write. It allows them to survive by foraging in the heat of the day when predators must stay out of the Sun.

Saharan Silver Ants devouring a camel tick. Image Credit: By Bjørn Christian Tørrissen – Own work by uploader, http://bjornfree.com/galleries.html, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=17131784

Humans have made silica aerogels with extremely low density and thermal conductivity. While there are no direct biological equivalents, the authors write that “many organisms do exist in nature that produce complex silica structures.”

In fact, some diatoms can produce silica structures by manipulating silica particles smaller than those used in our manufacturing processes. Aerogels manufactured from organic materials have similar characteristics to artificial ones. “Given this, it is plausible that highly insulating materials could be produced artificially from biogenic feedstocks or even directly by living organisms,” the authors write.

This figure from the research shows two different geometries for aerogel-type habitats: (a) a spherically symmetric geometry and (b) a Sun-facing geometry. Blue color represents translucent solid-state greenhouse material of thickness a few cm, while grey represents a thicker layer of opaque, thermally insulating material. Image Credit: Wordsworth and Cockell, 2024

The authors calculated that these types of structures could maintain the right temperature and pressure to maintain liquid water.

“As can be seen, maintaining internal temperature at 288 K is possible for a wide range of orbital distances,” they explain. “This calculation assumes a free-floating habitat, but similar considerations apply to habitats on the surface of an asteroid, moon or planet.”

This figure shows how passive solid-state warming can enable habitability beyond Earth. It shows the thermal conductivity of a solid-state greenhouse layer vs. orbital distance, given a habitat interior temperature of 288 K. Red and blue curves show cases assuming spherically symmetric and Sun-facing geometry, respectively. The green shaded area indicates typical thermal conductivities for translucent silica and organic aerogels reported in other research. Image Credit: Wordsworth and Cockell, 2024.

Volatile loss is another problem. A habitat that can’t hold onto its atmosphere can’t maintain the temperature and pressure necessary for liquid water. “All materials have some permeability to atoms and small molecules, and over long timescales, the vacuum of space represents an essentially permanent sink for volatile species,” the authors explain.

This can be solved by the same barriers that maintain pressure and temperature. “Inhibition of volatile escape would be most easily achieved by the same part of the habitat wall responsible for maintaining the pressure differential necessary to stabilize liquid water,” write the authors.

The authors also consider the effects of UV radiation. Radiation can be deadly, but there are examples of life here on Earth that have evolved to figure it out. “However, it is easily blocked by compounds such as amorphous silica and reduced iron, which attenuate UV in silicified biofilms and stromatolites today without blocking the visible radiation needed for photosynthesis,” they write.

The availability of solar energy for photosynthesis likely isn’t much of a barrier in many parts of the Solar System. The authors point out that Arctic algae grows in extremely weak light under the ice.

Some type of nutrient cycle would be required, just like on Earth. “Long-term, an additional consideration is the ability of a closed-loop ecosystem to process waste products such as recalcitrant organic matter and to sustain internal redox gradients,” explain the authors. The extreme heat in Earth’s interior gets it done, but without those extremes, “a fully closed-loop ecosystem in space would require some internal compartmentalization to establish chemical gradients and specialist biota capable of breaking down recalcitrant waste products,” they write.

In their paper, the authors cover other factors like cell size and the factors that limit the size of unicellular organisms and larger, more complex organisms. They conclude that fully autonomous living habitats can’t be ruled out. “Nonetheless, a fully autonomous system capable of regeneration and growth is apparently not prohibited by any physical or chemical constraints and is therefore interesting to consider a little further,” they write.

It’s possible as long as the system can regenerate its walls. The authors point out that existing photosynthetic life can already produce amorphous silica and organic polymers. These materials could serve as walls and at least show that there’s a pathway where organisms could evolve to create habitat walls. “A more autonomous living habitat would be able to grow its own wall material, just as plant cells regenerate their own walls on the micrometre scale,” they explain.

We tend to think that if life exists elsewhere, it follows the same evolutionary pathway as it did here on Earth, but that may not be true. “Because the evolution of life elsewhere may have followed very different pathways from on Earth, living habitats could also exist outside traditional habitable environments around other stars, where they would have unusual but potentially detectable biosignatures,” the authors write.

The authors ask, “Could the kind of biological structures we discuss here evolve naturally, without intelligent intervention?” They argue that non-sentient life can sustain all of the conditions necessary to survive in extraterrestrial environments.

“Life on Earth has not yet done this, although it has certainly adapted to an increasingly wide range of environmental conditions over time,” they conclude. “Investigating the plausibility of different evolutionary pathways for life under alternative planetary boundary conditions will be an interesting topic for future research.”

The post Does Life Really Need Planets? Maybe Not appeared first on Universe Today.

We know that interstellar objects occasionally visit our solar system. So far, we have only discovered two interstellar objects (ISOs), but that’s mainly because we can only distinguish them from solar system bodies by their orbital motion, and that takes a series of observations over time. The two we have discovered, ?Oumuamua and Borisov, were only noticed because they had highly unusual orbits that moved through the inner solar system. But when sky survey telescopes such as the Vera Rubin Observatory come online, we will likely find new interstellar objects all the time. It’s estimated that several ISOs enter the solar system every year, and there could be hundreds of them passing by at any given time. But that raises an interesting question about how these objects arrive. Do they enter our solar system randomly from all directions, or do they appear in clusters a few at a time?

That is the question addressed in a new paper on the *arXiv*. It looks at how streams of interstellar bodies might escape a solar system and how they would then move through the Milky Way. While it is always possible for a random asteroid or comet to have a random flyby near a large planet that tosses it out of a system, most interstellar bodies would occur during the tumultuous early period of a star system when it is cleared of debris. In our solar system this process created the Oort cloud surrounding the Sun, which likely occurred in other systems. So star systems likely create bursts of ISOs, which then stream through the Milky Way until they encounter another star system.

Simulated streams of ISOs in the Milky Way. Credit: Forbes, et al

To study all this, the team started with simulated bursts and then modeled how the resulting streams would evolve. Based on the distribution and typical ages of stars in our region of the Milky Way, they could then simulate streams that might intersect the Sun’s path through the galaxy. They found that the Sun likely intersects with streams regularly, which would give us plenty of interstellar visitors. They also found that just as Earth experiences meteor showers as it passes through the remnant debris streams of comets, the Sun would experience bursts of interstellar objects as it passes through a stream. With the abilities of Rubin and other observatories, we should be able to identify ISOs that are “siblings,” having originated from the same star system. Over time, this could give us a better idea of the composition and diversity of planetary systems. We may even be able to pinpoint the origin of sibling ISOs to a particular star.

One final interesting aspect of these interstellar streams is their overall appearance. Several of the authors of this work are from Aotearoa New Zealand, and they noticed that the simulated patterns have a braided appearance similar to the braided rivers such as Rakaia on the South Island. So they named these interstellar streams he awa whiria, which means the braiding rivers in te reo M?ori, as an homage to that region and its people. It’s a nice reminder of our humanity and the connection between the world around us and the sky above.

Reference: Forbes, John C., et al. “He awa whiria: the tidal streams of interstellar objects.” arXiv preprint arXiv:2411.14577 (2024).

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The orbits of the planets around the Sun have been the source for many a scientific debate. Their current orbital properties are well understood but the planetary orbits have evolved and changed since the formation of the Solar System. Planetary migrations have been the most prominent idea of recent decades suggesting that planetary interactions caused the young planets to migrate inwards or outwards from their original positions. Now a new theory suggests 2-50 Jupiter mass object passing through the Solar System could be the cause. 

The evolution of the orbits of the planets is a complex process. Initially the planets formed out of a rotating disk of gas and dust around the young hot Sun. The phenomenon of the conservation of angular momentum caused the material to form a plane leading to orbits that were circular and in the same plane. 

The latest view of Saturn from NASA’s Hubble Space Telescope captures exquisite details of the ring system — which looks like a phonograph record with grooves that represent detailed structure within the rings — and atmospheric details that once could only be captured by spacecraft visiting the distant world. Hubble’s Wide Field Camera 3 observed Saturn on June 20, 2019, as the planet made its closest approach to Earth, at about 845 million miles away. This image is the second in a yearly series of snapshots taken as part of the Outer Planets Atmospheres Legacy (OPAL) project. OPAL is helping scientists understand the atmospheric dynamics and evolution of our solar system’s gas giant planets. In Saturn’s case, astronomers will be able to track shifting weather patterns and other changes to identify trends. Credits: NASA, ESA, A. Simon (GSFC), M.H. Wong (University of California, Berkeley) and the OPAL Team

As the planets grew, interactions within the protoplanetary disk led to orbital migrations with planets moving inwards or outwards. There were gravitational interactions too that led to significant changes in the eccentricity and inclination, sometimes causing protoplanets to be ejected out of the solar system. Tidal forces from the Sun could also have altered the orbits. 

While protoplanet ejections are thought to have been fairly common as the Solar System was forming, on occasions celestial objects visited us. These objects seem to have been rare and provide a valuable insight into distant planetary systems. Oumuamua, was discovered in 2017 and was the first confirmed interstellar visitor. It exhibited an elongated shape and unusual acceleration, probably caused by outgassing or other non-gravitational forces. A paper recently published has suggested such an interstellar visitor could have driven changes in the orbits of our planetary cousins. 

An artist’s depiction of the interstellar comet ‘Oumuamua, as it warmed up in its approach to the sun and outgassed hydrogen (white mist), which slightly altered its orbit. The comet, which is most likely pancake-shaped, is the first known object other than dust grains to visit our solar system from another star. (Image credit: NASA, ESA and Joseph Olmsted and Frank Summers of STScI)

The paper was authored by a team of scientists led by Garett Brown University of Toronto. They explore the nature of the eccentricity of the gas giants suggesting it is unlikely the current theories can explain observations. Instead they demonstrate that an object with between 2 to 50 times the mass of Jupiter passing through the Solar System was a more likely cause. Their paper explains that an object passing through with a perihelion distance (closest distance from Sun) of less than 20 astronomical units and a hyperbolic excess velocity less than 6km/s-1 could explain observations.  

Their calculations suggest there is a 1 in 100 chance that an interstellar visitor could produce the orbits we see today, chances that are far better than other theories. Using simulations and approximate values for the properties of the visitor, the team conclude that the theory is the most plausible to date. 

Source : A substellar flyby that shaped the orbits of the giant planets

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Propulsion technologies are the key to exploring the outer solar system, and many organizations have been working on novel ones. One with a long track record is the Ad Astra Rocket Company, which has been developing its Variable Specific Impulse Magnetoplasma Rocket (VASIMR) system for decades. However, this type of electric propulsion system requires a lot of energy, so the company has opted for a unique tie-up for a power plant that could solve that problem – a nuclear reactor. Ad Astra has recently entered into a strategic alliance with the Space Nuclear Power Corporation, or SpaceNukes, responsible for developing the Kilopower reactor, a 1kW nuclear reactor for use in space missions.

There are plenty of synergies to justify such a tie-up between the companies, but let’s look at each of their technologies, in turn, to understand why. VASIMR, the propulsion system Ad Astra has been working on for more than 20 years, is a magnetoplasma rocket, a type of electric propulsion system. Ion drives are the most commonly known form of electric propulsion and are known for being exceptionally fuel efficient. They aren’t powerful enough to lift a craft out of a planet’s gravity well, but once in space with little gravitational pull, they shine at long bursts of slow acceleration that translate into massive speeds when engaged for long enough.

The problem is they need lots of power to do so. They must ionize their fuel, which requires a significant amount of energy, and that energy is hard to come by when not connected to a power grid. Current solutions utilize either solar panels, which would require a massive area to provide enough power to something like VASIMR, or a radioisotope thermal generator (RTG), which has been in common use for years to power the systems of different spacecraft, including Voyager and Perseverance, but isn’t capable of providing enough power for a viable electric propulsion system. 

Fraser describes how ion engines, a type of electric propulsion system, work.

Enter another form of nuclear energy—the traditional kind. SpaceNukes has been working on its Kilopower reactor in various guises for more than 10 years and has proven a functional system at 1kW of power on a ground-based system back in 2018. It’s now working with the US Space Force under a project named JETSON to develop a 12kW design that could be used in a flight demonstration.

VASIMR scales well with larger power outputs – on the order of 100kW or more could significantly increase the rocket’s efficiency. The only viable option for such power in space is nuclear reactors, so the tie-up between the two companies seems apt. However, there is still a long way to go before a 100kW system would be flight tested – the press release announcing the company’s memorandum of understanding says they hope to have a flight demonstration done “by the end of the decades” and to commercialize the technology “in the 2030s”. 

If they manage to pull that timeline off—and that is still a big if—a combined VASIMR and Kilopower-driven spacecraft would achieve the dream of Nuclear Electric Propulsion that excites many space propulsion enthusiasts. It could cut down the round-trip travel times to Mars from over a year to a few months and allow for more and better missions to the outer solar system, including interesting moons like Enceladus and Titan. 

Fraser describes KRUSTY, one of the experiments leading up to the Kilopower reactor.

Given both companies’ track records of slow and steady improvement, it seems likely that eventually t, the technologies will see the light of day and enable a revolution in space propulsion. They have to keep pushing – like the engines they hope to fly someday.

Learn More:
Space Nuclear Power Corporation – Ad Astra Rocket Company and The Space Nuclear Power Corporation Forge Strategic Alliance to Pioneer High-Power Nuclear Electric Propulsion
UT – New Nuclear Rocket Design to Send Missions to Mars in Just 45 Days
UT – What Future Propulsion Technologies Should NASA Invest In?
UT – Exploring the Universe with Nuclear Power

Lead Image:
Rendering of VASIMR in flight around Mars.
Credit – Ad Astra Rocket Company

The post A Commercial Tie-Up Bring High-Energy Nuclear Electric Propulsion Closer to Reality appeared first on Universe Today.

Dyson spheres and rings have always held a special fascination for me. The concept is simple, build a great big structure either as a sphere or ring to harness the energy from a star. Dyson rings are far more simple and feasible to construct and in a recent paper, a team of scientists explore how we might detect them by analysing the light from distant stars. The team suggests they might be able to detect Dyson rings around pulsars using their new technique.

Like their spherical cousins, Dyson rings remain for now, a popular idea in science fiction yet they are starting to appear more and more in scientific debates. The concept of the ring is similar to the sphere, a megastructure designed to encircle a star, harnessing its energy on a gargantuan scale. It might consist of a series of satellites or even habitats in a circular orbit with solar collectors and unlike the spheres, require far less resources to build. The concept of the sphere was first proposed by physicist and mathematician Freeman Dyson in 1960. Such structures might be detectable and reveal the existence of intelligent civilisations. 

A Type II civilization is one that can directly harvest the energy of its star using a Dyson Sphere or something similar. Credit: Fraser Cain (with Midjourney)

It’s fascinating to think about civilisations building such constructions. Our own civilisation currently consumes around 15,000 terawatts per hour and that number is only going to increase as our population grows and we become even more reliant on technology. To endeavour to quantify the energy usage from the level of technological capability, the Kardashev scale was developed. On this scale, we are currently at Type I which means our power usage is  4 × 1019 erg s?1 (4 terawatts) If a civilisation requires 4 × 1033 erg s?1 (400 trillion terawatts) then it is considered to be type II and it is these civilisations that may be capable and indeed it may be necessary to build Dyson structures. 

To create either a solid sphere or even a sphere with orbiting satellites would require phenomenal amounts of material. A sphere which had a radius of 1 astronomical unit (the average distance between Earth and the Sun) would require more material than exists in the entire Solar System. It is far more likely that civilisations would create ring structures. Rings of this nature around a star would be able to harness significant amounts of energy but a ring around a pulsar would, if the pulse beam of the star could be tracked, be able to capture even more energy, of the order of 10 thousand trillion terawatts.

There are Dyson rings and spheres and this, an illustration of a Dyson swarm. Could this or a variation of it be what we’re detecting around KIC? Not likely, but a fun thought experiment. Credit: Wikipedia

In the paper written by Ogetay Kayali from Michigan Technological University and team, they propose further exploration of pulsar light curves to see if features that could reveal their presence have been missed. The features the team suggest arise from effects of the pulsar beam striking the ring structure. The beams travel at superluminal speeds which could result in multiple images of the pulsar spot on the Dyson ring appearing simultaneously. This may be visible in light curve analysis. A similar effect is seen when dust rings are illuminated with pulsar radiation.

Source : Search for Dyson Rings Around Pulsars: Unexpected Light Curves 

The post New Technique for Spotting Dyson Rings Unveiled. appeared first on Universe Today.

Sometimes in astronomy, a simple question has a difficult answer. One such question is this: what is the mass of our galaxy?

On Earth, we usually determine the mass of an object by placing it on a scale or balance. The weight of an object in Earth’s gravitational field lets us determine the mass. But we can’t put the Milky Way on a scale. Another difficulty with massing our galaxy is that there are two types of mass. There is the mass of dark matter that makes up most of the Milky Way’s mass, and there is all the regular matter like stars, planets, and us, which is known as baryonic matter.

We have several approaches to determining the total galactic mass, which usually involves measuring the speed of things such as stars, globular clusters, or nearby galaxies. Each of these approaches have strengths and weaknesses, though they all give a total value of a trillion solar masses, give or take a few hundred billion. All of these methods, however, only tell us the total mass. They say nothing about how much of the galaxy is baryonic mass. While baryonic mass is only a fraction of the total, it is what gives us all sorts of cool things like star formation, planetary systems, and digital watches.

Calculating the baryonic mass of our galaxy is even more difficult because you have to count up all the mass of regular stuff without counting dark matter. That’s relatively easy to do for things like stars and dense molecular clouds, but it’s much more challenging for things such as diffuse interstellar clouds. This is particularly true for the halo of stars and gas surrounding the Milky Way. No matter how much stuff we see at the fringes of our galaxy, there may be even more lurking about we haven’t seen. Which is why a new study looks at high-velocity clouds (HVCs) in the halo.

Most of the baryonic matter we have accounted for moves around the galaxy at the same rate. It’s easier to track things if you have an idea about how they move. But high-velocity clouds are different. They are interstellar clouds of hydrogen that can speed through the galactic halo at up to 500 km/s, and they often travel in directions very different from the galactic plane. Some astronomers have argued that HVCs might comprise a good portion of baryonic matter in the halo. So the team looked at data from the Galactic All Sky Survey (GASS) to determine whether this is true.

An image of the total GASS dataset. Credit: S. Janowiecki

The GASS survey was made by the Parkes radio telescope in Australia and captured radio emissions from neutral hydrogen gas seen in the Southern Hemisphere. Since HVCs are mostly made of neutral hydrogen, they are contained in the GASS data. But GASS only tells us the direction and relative motion of these clouds, so the team had to estimate their distance. They did this by comparing the motion of the HVCs relative to the motion of the Magellanic clouds. Also, since GASS only observed portions of the southern sky, the authors used Bayesian statistics to calculate the distribution of HVCs within the entire galaxy.

Previous observations of high-velocity clouds within the galactic disk of the Milky Way show that HVCs comprise a fraction of a percent of baryonic matter there. A simple extrapolation to the halo would suggest that up to 10% of halo baryonic mass could be due to HVCs. But this new work estimates the true value is closer to 0.1%, meaning that they comprise an insignificant fraction of baryonic mass in our galaxy’s halo. But the authors stress that their calculations are based on their assumptions of cloud distances, which could be wrong. Further radio surveys would be needed to pin down the HVC distances to obtain a better value.

Reference: Tahir, Noraiz, Martín López-Corredoira, and Francesco De Paolis. “The baryonic mass estimates of the Milky Way halo in the form of high-velocity clouds.” New Astronomy 115 (2025): 102328.

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The anthropic principle states that the fundamental parameters of the Universe such as the strength of the fundamental forces, have been finely tuned to support life. Whether this is true or not or whether it is even worthy of scientific investigation has been hotly debated. A new paper proposes some ways that this may now be tested and perhaps brings the topic under scientific scrutiny for the first time.

The idea of the anthropic principle was first suggested by physicist Brandon Carter in 1973. The proposal by Carter was tabled at a conference to mark the 500th anniversary of the birth of Nicolaus Copernicus. The principle attempts to rationalise the apparent ‘fine tuning’ of various universal parameters that support a cosmos where observers like humans can exist. If the parameters are slightly different, life may not have evolved.

Nicolaus Copernicus portrait from Town Hall in Torun (Thorn), 1580. Credit: frombork.art.pl

There are two versions; the Weak Anthropic Principle which postulates we observe the universe as being compatible with our very existence because, the argument goes, we wouldn’t be here to observe it if not! Then there is the Strong Anthropic Principle which goes much further stating simply that the universe must have parameters that make life possible. 

Science of philosophy? Either way, for a theory to be of any use, it must be possible to test it. Until now it’s been thought the anthropic principle was beyond the possibility of being tested. The paper, published in the Journal of Cosmology and Astroparticle Physics was authored by Nemanja Kaloper from the University of California and Alexander Westphal from the Deutsches Elektronen-Synchrotron. They propose for the first time, a way that the principle can be experimentally tested.

The AP proposes that if the universe is to develop as a place that our carbon based life can evolve, it must have begun with a very specific set of parameters. The gravitational constant, Planck’s constant and the electron charge are such parameters that, if they had been different at the beginning of time, the universe would have been very different, very different indeed. 

Kaloper and Westphal identify the initial parameters implied by the anthropic principle and are able to model how the universe would have evolved. It would then be possible to compare the result to the cosmos observed today. Any variance between the model and the observed universe would provide a measure of the validity of the principle. 

A computer model of the large-scale structure of the universe using the Illustris simulator. This image depicts the dark matter and gas involved in forming galaxies and galaxy clusters, as well as the filaments connecting them. Image Credit: Illustris TNG

There are a number of predictions the team say can be used as a measure including the cosmic inflation and the nature of dark matter. Perhaps frustratingly close now to proving, in some way, the validity of the principle yet we are still a few more years away from being able to acquire all the necessary evidence. Until then, the anthropic principle remains a very interesting curiosity and one that, since the publication of this latest paper, does at least deserve our attention. 

Source : Falsifying anthropics

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As a species, we’ve come to the awareness that we’re a minuscule part of a vast Universe defined by galaxy superclusters and the large-scale structure of the Universe. Driven by a healthy intellectual curiosity, we’re examining our surroundings and facing the question posed by Nature: how did everything get this way?

We only have incremental answers to that huge, almost infinitely-faceted question. And the incremental answers are unearthed by our better instruments, including space telescopes, which get better and more capable as time passes.

Enter the James Webb Space Telescope.

One of the reasons NASA and their partners built and launched the James Webb Space Telescope is to study the history of galaxy formation and to understand how they evolved into what we see today. That involves observing galaxies, galaxy clusters, galaxy superclusters, and the complex network of sheets, voids, and filaments that comprise the large-scale structure of the Universe. It also involves observing proto-clusters, the early stage of a galaxy cluster. They’re like building blocks for the cosmic web, which collapse and merge to form clusters and superclusters.

The Spiderweb protocluster is an ancient and well-studied object in the early Universe. More than 100 individual galaxies are forming a cluster at redshift z = 2.16, meaning it took more than 10 billion years for its light to reach us.

“We are observing the build-up of one the largest structures in the Universe, a city of galaxies in construction.”

Jose M. Pérez-Martínez, Instituto de Astrofísica de Canarias

Protoclusters are one key to understanding the Universe, and in two new papers, researchers present the results of the JWST’s observations of the Spiderweb protocluster. Among other things, the results show that gravity doesn’t play as large a role as thought in the formation of a cluster.

The difficulty in observing the Spiderweb is that it’s obscured by a healthy amount of cosmic dust. The dust blocks visible light but allows infrared light through. Since the JWST is an enormously powerful infrared telescope, its gaze has revealed things previously hidden from astronomers.

“We are observing the build-up of one the largest structures in the Universe, a city of galaxies in construction,” explained Jose M. Pérez-Martínez of the Instituto de Astrofísica de Canarias and the Universidad de La Laguna in Spain. “We know that most galaxies in local galaxy clusters (the biggest metropolises of the Universe) are old and not very active, whereas in this work we are looking at these objects during their adolescence. As this city in construction grows, their physical properties will also be affected. Now, Webb is giving us new insights into the build-up of such structures for the first time.”

The JWST can observe hydrogen gas more thoroughly than other telescopes. Astronomers often observe hydrogen-alpha (h-alpha) emissions to probe galaxies. h-alpha emissions are a specific type of light emitted when electrons transition between energy levels. However, there’s another type of infrared hydrogen emission called Paschen-beta emissions (Pa-beta) that the JWST can observe. It’s emitted by different electron transitions in hydrogen and is a valuable tracer of the star formation rate (SFR) in galaxies. While the JWST isn’t specifically designed to single out these emissions, it can observe the infrared wavelengths that include the Pa-beta line.

The two new papers based on the JWST observations are:

• JWST/NIRCam Pa-beta Narrowband Imaging Reveals Ordinary Dust Extinction for H? Emitters within the Spiderweb Protocluster at z = 2.16
• JWST/NIRCam Narrowband Survey of Pa-beta Emitters in the Spiderweb Protocluster at z = 2.16

These observations revealed the presence of new, previously undetected galaxies in the protocluster that were obscured by dust.

Using the NASA/ESA/CSA James Webb Space Telescope, an international team of astronomers has found new galaxies in the Spiderweb protocluster. They found that gravitational interactions in these dense regions are not as important as previously thought. This annotated image shows the galaxy distribution in the Spiderweb protocluster as seen by Webb’s NIRCam (Near-InfraRed Camera). The galaxies are annotated by white circles, and the collection of gravitationally-bound galaxies is identified in the centre of the image. A selection of these galaxies are featured as individual close-ups at the bottom of the image. Image Credit: ESA/Webb, NASA & CSA, H. Dannerbauer

“As expected, we found new galaxy cluster members, but we were surprised to find more than expected,” explained Rhythm Shimakawa of Waseda University in Japan. “We found that previously-known galaxy members (similar to the typical star-forming galaxies like our Milky Way galaxy) are not as obscured or dust-filled as previously expected, which also came as a surprise.”

The characteristics of the dust show that gravitational interactions aren’t playing as large a role as thought. If there were gravity-driven mergers, the dust production would be higher as mergers trigger rapid SFRs. However, these observations show that the dust is being produced smoothly rather than abruptly.

“This can be explained by the fact that the growth of these typical galaxies is not triggered primarily by galaxy interactions or mergers that induce star-formation,” added Helmut Dannerbauer of the Instituto de Astrofísica de Canarias in Spain. “We now figure this can instead be explained by star formation that is fueled through gas accumulating at different locations all across the object’s large-scale structure.”

“These results support the scenario for which dust production within the main galaxy population of this protocluster is driven by secular star formation activities fueled by smooth gas accretion across its large-scale structure,” the authors write in the first paper. “This downplays the role of gravitational interactions in boosting star formation and dust production within the Spiderweb protocluster, in contrast with observations in higher redshift and less evolved protocluster cores.”

“We find no correlation between the dustiness of our sample of HAEs and their distribution in phase space (spectroscopic sample) or as a function of the projected clustercentric radius or local density,” the authors of the first paper explain. If gravity-driven mergers were behind the star and dust formation, it would be clumpy.

The second paper’s original goal was to make a deep-line survey aimed at Pa-beta emitters (PBEs). It used a unique narrow-band filter on the NIRCam that’s less sensitive to dust extinction. They ended up detecting new member candidates in the Spiderweb Protocluster. Interestingly, not all of the h? emitters are also Pa-beta emitters.

The researchers narrowed their Pa-beta emitters down to 41 sources. Only 17 of those are also confirmed as h? emitters. “The remaining 24 objects are considered to be unconfirmed candidates associated with the Spiderweb protocluster,” the authors write. “These PBE candidates are still at risk of foreground or background emitters other than PBEs; therefore, further follow-up studies are needed to establish that they are protocluster members.”

Finding more members of the Spiderweb protocluster and finding that gravity isn’t as important as thought is just a beginning. These are incremental answers on our path to understanding how the Universe evolved into what we see today. Science is a journey, and as is so often the case on the journey, more observations are the next step.

“Follow-up confirmations and characterizations of the PBE candidates will provide a better understanding of the total star formation rate in the Spiderweb protocluster, the environmental dependence of galaxy formation, and a transition process from a protocluster to a bona fide cluster of galaxies,” the authors of the second paper write in their conclusion.

The researchers intend to follow up this work with more spectroscopic observations form the JWST. Those observations should provide additional confirmation of the Spiderweb’s new members.

The post Webb Sees a Supercluster of Galaxies Coming Together appeared first on Universe Today.

The term quasar comes from quasi-stellar objects, a name that reflected our uncertainty about their nature. The first quasars were discovered solely because of their radio emissions, with no corresponding visual objects. This is surprising since quasars blaze with the light of trillions of stars.

In recent observations, the Hubble examined a historical quasar named 3C 273, the first quasar to be linked with a visual object.

Maarten Schmidt was the California Institute of Technology astronomer who first connected the radio emissions from 3C 273 with a visual object back in 1963. At the time, it looked just like a star through the powerful telescopes available, though its light was red-shifted. Schmidt’s discovery showed us the true nature of these extraordinary objects, and now we know of about one million quasars.

A quasar is an extremely luminous active galactic nucleus (AGN) powered by a supermassive black hole (SMBH) at the center of a galaxy. Accretion disks of gas form around SMBHs, and the swirling gas heats up and releases electromagnetic energy. Only a small percentage of galaxies have quasars and their luminosities can be thousands of times greater than a galaxy like the Milky Way.

3C 273 is about 2.5 billion light-years away and is the most distant object visible in a backyard telescope. Recently, Hubble captured its best view of the quasar, revealing previously unseen details in its vicinity.

The quasar’s blinding light makes its surroundings difficult to discern. However, astronomers figured out a way to use Hubble’s Space Telescope Imaging Spectrograph (STIS) instrument to make coronagraphic observations of the region. The coronograph allowed astronomers to look eight times closer to the black hole than ever before.

The researchers found a new core jet, a core blob, and other smaller blobs. Their results are in a research letter titled “3C 273 Host Galaxy with Hubble Space Telescope Coronagraphy.” It’s published in the journal Astronomy and Astrophysics, and the lead author is Bin Ren, who also happens to be associated with the California Institute of Technology.

Hubble’s STIS coronagraph allowed astronomers to get a clearer look at the region surrounding the quasar 3C 273. Image Credit: NASA, ESA, Bin Ren (Université Côte d’Azur/CNRS)

By blocking out the quasar’s blinding glare, Hubble was able to better examine its surroundings. The astronomers found weird filaments, lobes, and a mysterious L-shaped structure. These are all probably the results of the SMBH devouring small galaxies.

“We have detected a more symmetric core component, CC, for the host galaxy of 3C 273, in addition to confirming the existing large-scale asymmetric components IC and OC that were previously identified in HST/ACS coronagraphy from Martel et al. (2003),” the authors explain in their research letter.

These four images from the research show some of the detail uncovered by the new coronagraphic observations. (a) contains original data. (b) is the isophote model. (c) and (d) are isophote-removed data. (An isophote is a curve on an illuminated surface that connects points of equal brightness.) CC is a newly identified symmetric Core Component, IJ is the Inner Jet, CJ is the newly observed Core Jet, CB is the Core Blob, JC is the Jet Component, and b1, b2 and b3 are newly observed blobs. The filament in panel d is also newly observed. Image Credit: NASA, ESA, Bin Ren (Université Côte d’Azur/CNRS)

“With the STIS coronagraphic observations, we also identify a core blob (CB) component, as well as other point-sourcelike objects, after removing isophotes from the host galaxy,” the authors continue. “The nature of the newly identified components, as well as the point source-like objects, would require observations from other telescopes for further study.”

There are also filamentary structures to the northeast, east, and west of the galactic nucleus. They extend as far as 10 kiloparsecs (32,600 light-years) from the nucleus. The authors explain that they’re similar to structures observed in other galaxies, where they’re thought to be multiphase gas that’s condensing out of the intergalactic medium. This gas could be fuelling AGN feedback. AGN feedback is a self-regulating process that links the energy released by the AGN to the surrounding gaseous medium.

Previous observations of the same quasar 22 years ago allowed the authors to compare images and constrain some properties of the previously observed Inner Jet, which is 300,000 light-years long. “We witness a potential trend that the motion is faster when it is further out,” they write.

This figure from the research shows 200 different randomly sampled components of the jet as grey lines. As the figure shows, the jets move faster the further they are from the source. Image Credit: NASA, ESA, Bin Ren (Université Côte d’Azur/CNRS)

This fascinating object begs for more observations to better understand what’s happening. The authors explain that we need methods and telescopes with better inner working angles (IWA) to do that. Both the Hubble and the JWST can do it. “With smaller IWAs for both telescopes, we can both confirm the existence of closest-in components and constrain their physical properties from multi-band imaging. In high-energy observations, we can better characterize such structures,” the authors explain.

“With the fine spatial structures and jet motion, Hubble bridged a gap between the small-scale radio interferometry and large-scale optical imaging observations, and thus we can take an observational step towards a more complete understanding of quasar host morphology. Our previous view was very limited, but Hubble is allowing us to understand the complicated quasar morphology and galactic interactions in detail,” said lead author Ren.

“In the future, looking further at 3C 273 in infrared light with the James Webb Space Telescope might give us more clues,” said Ren.

The post Hubble Gets its Best Look At the First Quasar appeared first on Universe Today.

Lots of things out in the Universe can cause a supernova, from the gravitational collapse of a massive star, to the collision of white dwarfs. But most of the supernovae we observe are in other galaxies, too distant for us to see the details of the process. So, instead, we categorize supernovae by observed characteristics such as the light curves of how they brighten and fade and the types of elements identified in their spectra. While this gives us some idea of the underlying cause, there are still things we don’t entirely understand. This is particularly true for one particular kind of supernova known as Type Ia.

You have likely heard of Type Ia supernovae because they are central to our understanding of cosmology. They have an important characteristic of having a uniform maximum brightness. This means we can observe their apparent brightness, compare it to their actual brightness, and calculate their distance. For this reason, they are often referred to as standard candles, and they were the first way we learned that the Universe is not just expanding; it’s accelerating under the influence of dark energy.

From the spectra of these supernovae, we can see that the initial brightness is powered by the radioactive decay of nickel-56, while much of the later brightness comes from the decay of cobalt-56. We also see the presence of ionized silicon near peak brightness, which no other type of supernova has. This tells us that Type Ia supernova are not caused by the core collapse of a star, but rather some kind of thermal runaway effect.

Single progenitor of a Type Ia Supernova. Credit: NASA, ESA and A. Feild (STScI)

The most popular model for Type Ia supernovae is that they are caused by the collapse of a white dwarf. When a white dwarf is part of a close binary with an aging red giant, the white dwarf can capture some of the companion’s outer layer. Over time, the white dwarf captures enough mass that it crosses the Chandresekhar limit, which triggers the supernova. Since the Chandrasekhar limit is always at 1.4 solar masses, this would explain why Type Ia supernovae always have the same maximum brightness.

But as we’ve observed ever more supernovae, we’ve learned that Type Ia supernovae don’t always have the same maximum brightness. There are some that are particularly brighter, with weaker silicon lines in their spectra and stronger iron lines. There are some that are much dimmer than usual, with strong titanium absorption lines. This doesn’t prevent their use as standard candles since we can identify them by the spectra and adjust our brightness calculations accordingly, but it does suggest that the single progenitor model is incomplete.

Illustration of colliding white dwarf stars. Credit: European Southern Observatory

One possibility is that some Type Ia supernovae are caused by white dwarf collisions. Given the calculated number of binary white dwarf systems, collisions can’t account for all supernovae of this type, but stellar collisions are known to occur, and they wouldn’t be bound by the Chandresekhar limit, thus allowing for supernovae that are brighter or dimmer than usual. It’s also possible that some Type Ia supernovae are caused by accretion from a close companion, but the resulting supernova doesn’t destroy the white dwarf, which could explain the dimmer subtypes of these supernovae.

Right now, there are lots of possibilities, and we simply don’t have enough data to pinpoint causes. But the good news is that with new observatories and sky surveys such as Rubin Observatory coming online soon, we will gather a wealth of observational data, particularly from supernovae that occur within our own galaxy. This will provide us with the information we need to finally solve this longstanding astronomical problem.

Reference: Ruiter, Ashley J., and Ivo R. Seitenzahl. “Type Ia supernova progenitors: a contemporary view of a long-standing puzzle.” arXiv preprint arXiv:2412.01766 (2024).

The post Do We Really Know What Becomes a Type Ia Supernova? appeared first on Universe Today.

A spacecraft that can provide the propulsion necessary to reach other planets while also being reproducible, relatively light, and inexpensive would be a great boon to larger missions in the inner solar system. Micocosm, Inc., based in Hawthorne, California, proposed just such a system via a NASA Small Business Innovation Research (SBIR) grant. Its Hummingbird spacecraft would have provided a platform to visit nearby planets and asteroids and a payload to do some basic scouting of them.

Large space missions are expensive, so using a much less expensive spacecraft to collect preliminary data on the mission target could potentially help save money on the larger mission’s final design. That is the role that Hummingbird would play. It is designed essentially as a propulsion system, with slots for radiation-hardened CubeSat components as well as a larger exchangeable payload, such as a telescope.

The key component of the Hummingbird is its propulsion system. It uses a rocket engine that runs on hydrazine fuel. More importantly, it holds a lot of that fuel. A fully assembled system is expected to weigh 25 kg “Dry”—meaning without propellant installed—whereas a fully fueled “Wet” system would weigh an estimated 80 kg. 

Travelling to a Lagrange Point is one of the things Hummingbird could do – Fraser explains why this points in space are important.

That would give Hummingbird plenty of “oomph” – enough to bring its orbital speed up to an estimated 3.5 km/s delta-V, which is required for getting to hard-to-reach objects like some near-Earth asteroids. However, it could also reach other, larger places, like Mars or even Venus, the various Lagrange points, or even Mars’ moons.

When it got there, the prototype of Hummingbird described in a paper presented back in 2013 would take images of its target world using an Exelis telescope. The manufacturer of this telescope has since been bought by Harris Systems, which was then rolled into L3Harris Technologies, the owner of Aerojet Rocketdyne. However, the authors stress that the payload itself was interchangeable and could be tailored to the mission that it was meant to scout.

The Hummingbird bus was also the fuel tank, and it had additional slots for CubeSat components. These components could be used for further data collection or data analysis. However, the paper doesn’t necessarily mention how Hummingbird would handle standard CubeSat operations, like attitude control or communications back to a ground station.

A CubeSat has already made its way to Mars – as described in the JPL video.
Credit – NASA Jet Propulsion Laboratory YouTube Channel

Those could likely have been worked out in future iterations. Additionally, the final design was published before the dramatically reduced cost of getting to orbit, which is now available – the authors don’t even mention a “Falcon” as a potential launch service. A lot has changed in the space industry in the last 11 years. Still, the idea behind Hummingbird, an inexpensive, adaptable platform for preliminary scouting missions to interesting places in the inner solar system, has yet to see its day in the Sun – the project did not appear to receive a Phase II SBIR grant, which could have continued its development. But maybe, someday, it or a similar system will see the light of interplanetary space.

Learn More:
C. Taylor et al – Hummingbird: Versatile Interplanetary Mission Architecture
UT – What Happened to those CubeSats that were Launched with Artemis I?
UT – A CubeSat Mission to Phobos Could Map Staging Bases for a Mars Landing
UT – We Could SCATTER CubeSats Around Uranus To Track How It Changes

Lead Image:
Computer-generated mockup of the Hummingbird spacecraft
Credit – C. Taylor et al.

The post A Cheap Satellite with Large Fuel Tank Could Scout For Interplanetary Missions appeared first on Universe Today.

Don’t let the bright Moon deter you from seeing the one of the best meteor showers of the year.

One of the best meteor showers of 2024 closes out the year this coming weekend. If skies are clear, watch for the Geminid meteors, peaking on the night of Friday into Saturday, December 13-14th.

The Geminids in 2024

To be sure, the Geminids have a few strikes against them this year. Not only is it cold outside, but the Moon is near Full, 98% illuminated waxing gibbous at the shower’s max. But don’t despair: the shower hits its maximum at 3:00 Universal Time (UT) on December 14th (10:00 PM EST on the 13th) with a max Zenithal Hourly Rate of 120 meteors per hour. This means the shower will favor western Europe and North America, a plus. The radiant in Gemini near the bright star Castor (Alpha Geminorum) also means that the shower starts to be active in the late evening before local midnight.

The Geminid radiant, looking east on the evening of December 13th. Credit: Stellarium.

The source of the Geminids is none other than prolific ‘rock-comet’ 3200 Phaethon. Clearly, something intriguing is going on with this object. On a short 1.4 year orbit, 3200 Phaethon seems to blur the line between asteroid and semi-dormant comet nucleus. Japan wants to send its DESTINY+ mission to 3200 Phaethon in 2028 to get a closer look.

A radio animation of 3200 Phaethon. Credit: Arecibo/NASA/NSF

The Geminids have put on a show since 1862, though they seem to have really taken off in recent decades, surpassing the August Perseids as the best annual meteor shower of the year.

Fighting the Moon

The key to seeing any meteor shower at its best is to find dark skies and a clear, unobstructed horizon. The December Moon sits just a constellation away in Taurus at the shower’s peak… but keep in mind, the shower is also active on the evenings prior to and after the 14th. I plan to select my observing site with this in mind, and block the Moon behind a hill or tree. Early morning predawn observing will put the Moon lower to the horizon.

A sequence of Geminid meteors from 2014. Credit: Mary McIntyre.

There’s a reason the Moon is currently so high in the sky: not only is the Moon near the December Solstice and occupying the slot that the Sun will hold in June, but we’re headed towards a once every 18.6-year Major Lunar Standstill of the Moon in 2025.

A Geminid meteor all-sky camera view. Credit: Eliot Herman.

Observing and contributing to meteor shower science is as easy as watching, recording what you’re seeing at a designated interval, and reporting that count to the International Meteor Organization (IMO). Keep in mind, several other meteor showers are still active in mid-December, including the November Taurid fireballs and the Ursids, peaking on December 22nd. For imaging, I like to simply automate the process, and set a wide-field DSLR camera running on a tripod with an intervalometer to take timed exposure shots and see what turns up later in post processing. Aim the camera off to one side of the radiant by about 45 to 90 degrees to catch the Geminid meteors in profile.

Don’t miss the 2024 Geminids, as a fine way to round out sky-watching in 2024.

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The standard theory of cosmology is based upon four things: the structure of space and time, matter, dark matter, and dark energy. Of these, dark energy is the one we currently understand the least. Within the standard model, dark energy is part of the structure of space and time as described by general relativity. It is uniform throughout the cosmos and expressed as a parameter known as the cosmological constant. But initial observations from the Dark Energy Spectroscopic Instrument (DESI) suggest the rate of comic expansion may vary over time. If further observations reinforce this, it could open up cosmological models to alternatives to general relativity known as modified gravity.

In a recent paper on the arXiv, the authors look at one version of modified gravity known as Horndeski’s theory. The theory is based upon a generalization of general relativity. Einstein’s original theory was based upon the principle of equivalence, from which he derived a generalized description of spacetime through what is known as a metric tensor. From this, you can derive the equations of motion for objects in a gravitation field, just as Newton’s laws lead to equations of motion for objects under physical and gravitational forces.

General relativity is the simplest model with a metric tensor. Horndeski’s theory is the most general model with a metric tensor and allows for the presence of a uniform scalar field. There are special cases of Horndeski’s theory, such as the Brans-Dicke model and the model of quintessence. Both of these models have been used to describe dark energy in a more general way, as well as dark matter in some cases. While observations of gravitational waves, galactic clustering and cosmic expansion constrain these models to some degree, they don’t entirely rule them out. So far, our data on dark energy isn’t rich enough to distinguish between alternatives.

Comparison between standard model and modified gravity. Credit: Chudaykin and Kunz

This latest work looks at the DESI results in the context of Horndeski models, specifically looking at how it might address the time-evolution of cosmic expansion suggested by the DESI data. It found that if the time evolution is taken to be correct, then a modified gravity is a better fit than the standard model. The study goes on to show that Horndeski models only work where the time evolution of the scalar field correlates to the proposed time evolution of dark matter. This rules out some Horndeski models that have been used to explain dark matter.

Overall, the authors argue that the DESI observations make Horndeski’s theory a viable alternative to general relativity. That is, if the data holds up. The Dark Energy Spectroscopic Instrument is still in its early stages, and we don’t yet know what the final results will be. But it is clear that Einstein’s seat on the theoretical throne isn’t entirely assured, and Horndeski’s theory might just be the one to steal the crown.

Reference: Chudaykin, Anton, and Martin Kunz. “Modified gravity interpretation of the evolving dark energy in light of DESI data.” arXiv preprint arXiv:2407.02558 (2024).

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The nature of dark matter has been a hotly debated topic for decades. If it’s a heavy, slow moving particle then it’s just possible that neutrinos may be emitted during interactions with normal matter. A new paper proposes that Jupiter may be the place to watch this happen. It has enough gravity to capture dark matter particles which may be detectable using a water Cherenkov detector. The researchers suggest using a water Cherenkov detector to watch for excess neutrinos coming from the direction of Jupiter with energies between 100 MeV and 5 GeV.

Jupiter is the largest planet in the solar system, large enough to swallow up all the planets and have a little room to spare. It’s composed mainly of hydrogen and helium and  is devoid of a solid surface. Of all the planets, Jupiter has a powerful magnetic field and a strong gravitational field. It’s gravitational field is so powerful that, over the years, it has attracted, and even destroyed comets like Shoemaker-Levy 9 back in 1994. Of all the features visible in the planet’s atmosphere, the giant storm known as the Great Red Spot is by far the most prominent. 

Image of Jupiter taken by NASA’s James Webb Space Telescope’s NIRCam (Near-Infrared Camera) in July 2022 displays striking features of the largest planet in the solar system in infrared light, with brightness indicating high altitudes. One of these features is a jet stream within the large bright band just above Jupiter’s equator, which was the focus of this study. (Credit: NASA, ESA, CSA, STScI, R. Hueso (University of the Basque Country), I. de Pater (University of California, Berkeley), T. Fouchet (Observatory of Paris), L. Fletcher (University of Leicester), M. Wong (University of California, Berkeley), J. DePasquale (STScI))

Planets in the solar system would, until now, be the last place to go hunting for dark matter. This mysterious stuff is invisible to all normal detection methods but is thought to make up 27% of the universe, outweighing visible matter at 5% (the majority of remainder made up of dark energy.) As its name suggests, dark matter doesn’t emit, absorb or reflect light making it hard to observe. It’s existence has been inferred from the gravitational effects on galaxies, galaxy clusters and the largest scale structures of the universe. Despite its prominence in the universe, the nature of it remains largely unknown. 

Researchers are making progress mapping dark matter, but they don’t know what it is. This is a 3D density map of dark matter in the local universe, with the Milky Way marked by an X. Dots are galaxies, and the arrows indicate the directions of motion derived from the reconstructed gravitational potential of dark matter. Image Credit: Hong et al., doi: 10.3847/1538-4357/abf040.

Dark matter is measured in GeV because this is a standard method in high energy physics to express the mass of particles. Until recently attempts to detect dark matter have relied upon experiments where dark matter is scattered with electrons, protons or neutrons in a detector. The interactions cause energy transfers which then reveal he presence of dark matter. 

A view of the Large Underground Xenon (LUX) dark matter detector. Shown are photomultiplier tubes that can ferret out single photons of light. Signals from these photons told physicists that they had not yet found Weakly Interacting Massive Particles (WIMPs) Credit: Matthew Kapust / South Dakota Science and Technology Authority

In a paper by Sandra Robles from Kings College London and Stephan Meighen-Berger from the University of Melbourne, they propose and calculate the level of annihilating dark matter neutrinos within Jupiter and whether they could be detected using existing neutrino observatories. The team also propose a way to use of water Cherenkov detectors which are designed to detect high-energy particles such as neutrinos or cosmic rays. This is achieved by capturing Cherenkov radiation emitted while they travel through water. To give context to the process, the radiation is optical and occurs when a charged particle moves through a medium like water producing a faint flash of blue light. 

The team suggest Jupiter is an ideal location to hunt for dark matter using Cherenkov radiation detectors. It’s low core temperature and significant gravitational attraction will mean it could capture dark matter and retain it.  The presence of neutrinos in the direction of Jupiter reveals the capture and annihilation of dark matter. A similar technique is used by observing the Sun. 

Source : Extending the Dark Matter Reach of Water Cherenkov Detectors using Jupiter

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Through the Artemis Program, NASA hopes to lay the foundations for a program of “sustained lunar exploration and development.” This will include regular missions to the surface, the creation of infrastructure and habitats, and a long-term human presence. To facilitate this, NASA is teaming up with industry and international partners to develop Human Landing Systems (HLS) that can transport crews to and from the lunar surface and landers that can deliver payloads of equipment, vehicles, and supplies to the lunar surface.

In a recent statement, NASA indicated that it intends to award Blue Origin and SpaceX additional work under their existing contracts to develop landers that will deliver equipment and infrastructure to the lunar surface. NASA also plans to assign demonstration missions to these companies, in addition to design certification reviews, which will validate their concepts. This decision builds on NASA’s earlier request, made in 2023, that the two companies develop cargo versions of their HLS concepts, which are currently in development for the Artemis III, Artemis IV, and Artemis V missions.

Stephen D. Creech, the Assistant Deputy Associate Administrator (Technical) for the Moon to Mars Program Office, explained in the NASA statement:

“NASA is planning for both crewed missions and future services missions to the Moon beyond Artemis V. The Artemis campaign is a collaborative effort with international and industry partners. Having two lunar lander providers with different approaches for crew and cargo landing capability provides mission flexibility while ensuring a regular cadence of Moon landings for continued discovery and scientific opportunity.”

In previous statements issued in April and September of this year, NASA has emphasized the need for vehicles that can accommodate heavy payload deliveries – between 2,000 and 6,000 kg (4,400 and 13,000 pounds) to the Moon to accommodate the Artemis missions. Per the latest, NASA indicates that it plans for at least two heavy payload missions that will deliver elements of the Artemis Base Camp to the Moon. These large cargo landers must have the capacity and capability of landing approximately 12 to 15 metric tons (13 to 16.5 U.S. tons) of heavy cargo on the lunar surface.

The two missions will see SpaceX using a cargo lander version of their Starship to deliver the Habitable Mobility Platform (HMP) – a pressurized rover currently being developed by the Japan Aerospace Exploration Agency (JAXA) – no earlier than 2032 in support of Artemis VII and later missions. Meanwhile, the agency expects Blue Origin to deliver the Lunar Surface Habitat (LSH) element using its Blue Moon lander no earlier than 2033. Said Dr. Lisa Watson-Morgan, program manager for NASA’s Human Landing System:

“Based on current design and development progress for both crew and cargo landers and the Artemis mission schedules for the crew lander versions, NASA assigned a pressurized rover mission for SpaceX and a lunar habitat delivery for Blue Origin. These large cargo lander demonstration missions aim to optimize our NASA and industry technical expertise, resources, and funding as we prepare for the future of deep space exploration.”

SpaceX and Blue Origin will continue to develop their cargo lander concepts and prepare for demonstration missions as part of their NextSTEP Appendix H (Option B) and NextSTEP Appendix P contracts (respectively). NASA plans to issue an initial request for both proposals by early 2025.

Further Reading: NASA

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Telescopes in space have a huge advantage over those on the ground: they can see the universe more clearly. The Earth’s atmosphere, weather conditions, and low-flying satellites don’t obscure their view. But space telescopes have a disadvantage too. They can’t be repaired, at least not since NASA’s Space Shuttle program ended in 2011.

But next-generation telescopes are being planned with robotic servicing missions in mind. And not just in low earth orbit, where the Hubble Space Telescope received repairs and upgrades five times during its lifespan from space shuttle crews. Today’s engineers are preparing for ways to repair telescopes in deep space, including at the Sun-Earth Lagrange point L2.

L2 is the current home of the James Webb Space Telescope (JWST) and ESA’s Gaia mission. In this position, the Earth is kept between the Sun and the telescopes, giving them pristine conditions for observing the universe.

“While neither Gaia nor JWST were explicitly designed to be serviceable, next-generation space telescopes now in development include serviceability in their baseline designs,” write the authors of a new paper from a team at the Grainger College of Engineering, University of Illinois Urbana-Champaign.

Service spacecraft could attach themselves to derelict telescopes, bringing extra fuel, working reaction wheels, or even repairing damaged mirrors and other key components.

But it isn’t an easy task.

Artist’s illustration showing the location of the Sun-Earth Lagrange Points. Credit: NASA

The University of Illinois team, including Professor Siegfried Eggl and Ruthvik Bommena, used Gaia and JWST as test subjects to design a feasible service mission.

“Gaia is like a rotating cylinder with a solar panel. It is encapsulated, so it hasn’t been damaged, but after a decade out there it’s running low on fuel,” said Eggl in a press release. “Ruthvik Bommena designed a novel concept to add a sort of spider-looking attachment that can extend its life without impeding its data collection. Gaia will be decommissioned soon, so there isn’t enough time to reach it, but the James Webb might still be a possibility because it will be operating for several more years and they may decide to prolong its mission.”

JWST’s exposed mirrors have already been struck by micrometeorites multiple times, affecting the quality of its observations.

“We’re trying to stay a step ahead so there is a plan to replace broken mirrors, for example. If we don’t, it’s like buying an expensive sports car, then like throwing it away when it runs out of gas,” says Eggl.

One of the most significant barriers to long-distance servicing missions is designing a trajectory for rendezvous with the target.

“A spacecraft sent to repair or refuel a telescope needs to brake when it reaches it,” Bommena said. “Using the thrusters to slow down would be like pointing a blowtorch at the telescope. You don’t want to do that to a delicate structure like a telescopic mirror. How do we get there without torching the whole thing?”

In addition, the team is working to optimize both fuel efficiency and cost for such a mission.

As Professor Robyn Wollands, another author on the paper explains, “getting there is doable because of some hidden highways in our solar system. We have a trajectory that is optimal for the size of spacecraft needed to repair the JWST,” she said.

These ‘hidden highway’s are geometrically optimal paths that take advantage of orbital mechanics to make rendezvous safe and cost-efficient. The team have developed a new way to calculate and evaluate these optimal paths.

“After we create a map of initial solutions, we use optimal control theory to generate optimal end-to-end trajectories,” said PhD student Alex Pascarella. “Optimal control allows us to find trajectories that depart near Earth, and rendezvous with our space telescope in the least amount of time. The initial sampling of the solution space is fundamental—optimal control problems are notoriously difficult to solve, so we need a decent initial guess to work with.

“The novelty is in how we brought together two separate approaches to trajectory design: dynamical systems theory and optimal control theory,” Pascarella added.

With teams like this one laying the groundwork, the lifespan of space telescopes might be extended long past their original best-before date, and that’s good news for astrophysicists and space programs worldwide.

Learn More:

Alex Pascarella, Ruthvik Bommena, Siegfried Eggl, Robyn Woollands, “Mission design for space telescope servicing at Sun–Earth L2.” Acta Astronautica.

“A mission design for servicing telescopes in space.” EurekAlert.

The post Space Telescopes Could See a Second Life With a Servicing Mission appeared first on Universe Today.

Most people will think of a dry arid landscape when they think of Mars. When seen from orbit, dry river channels and lake-beds can be seen along with mineral deposits thought to be the created in the presence of liquid water. A team of researches now suggest that liquid carbon dioxide could also explain the features seen. On Earth, a process known as carbon sequestration liquefies CO2 which is buried underground. There are a number of mechanisms that could explain the liquid CO2 underground the researchers suggest.

Mars is often referred to as the ‘red planet’ due to its visual appearance. It’s the fourth planet from the Sun and has been a real focus for exploration and research for decades. The red colour is caused by iron oxide (rust) on its surface which can often be lifted up into the atmosphere by the Martian winds giving stunning pink skies. It’s just over half the size of the Earth, has a thin atmosphere mostly made of carbon dioxide and a surface composed of deserts and volcanoes like Olympus Mons. One of the key focusses of the exploration on Mars has been to establish whether the conditions are suitable for life, have been suitable in the past or whether liquid water exists on the surface. 

A full-disk view of Mars, courtesy of VMC. Credit: ESA

The presence of dry riverbeds and lake beds points to a surface that had liquid flowing long ago. Quite what that liquid is has been the cause for debate. Observations of minerals from orbit and from more direct analysis on the surface, suggest that the liquid was just water. However a team of researchers have published a paper in Nature Geoscience that suggests otherwise. They explain that water is only one of two possible liquids that could have existed on ancient Mars. The other is liquid carbon dioxide or CO2. Given the atmospheric conditions it may have been more likely and easier for CO2 in the atmosphere to condense into a liquid than for surface ice to melt into water. 

A topographic image of an area of anceint riverbeds on Mars. Created with data from the High-Resolution Stereo Camera on the Mars Express Orbiter. Image Credit: ESA/DLR/FU Berlin http://www.esa.int/spaceinimages/ESA_Multimedia/Copyright_Notice_Images

It has been the general consensus that the minerals point to liquid water. The paper suggests that processes like carbon sequestration, liquid CO2 buried underground can alter the composition of minerals even faster than water can. Lead author Michael Hecht, research scientist at MIT’s Haystack Observatory said “Understanding how sufficient liquid water was able to flow on early Mars to explain the morphology and mineralogy we see today is probably the greatest unsettled question of Mars science. There is likely no one right answer, and we are merely suggesting another possible piece of the puzzle.”

Image of the Martian atmosphere and surface obtained by the Viking 1 orbiter in June 1976. (Credit: NASA/Viking 1)

The paper explores our current understanding of the Martian atmosphere and combine it with the carbon sequestration research to conclude that the processes do support the evidence and mineralogy seen on Mars. They note however that this proposal does not suggest all Martian surface liquid was CO2 but rather there could have been a combination of the two.

They explain that liquid CO2 on the surface of Mars could exist as a stable surface liquid, as melted CO2 under CO2 ice or in subsurface reservoirs. Which actually took place would have dependent entirely on the distribution of CO2 at the time and the surface conditions too. The paper acknowledges that further testing is required under more realistic Martian conditions to test whether the same processes still occur. 

Source : Liquid on Mars was not necessarily all water

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