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Wednesday, 23 June 2021

Quantitative Evidence Links Psychological Stress to Graying Hair


Legend has it that Marie Antoinette’s hair turned gray overnight just before her beheading in 1791.

Though the legend is inaccurate—hair that has already grown out of the follicle does not change color—a new study from researchers at Columbia University Vagelos College of Physicians and Surgeons is the first to offer quantitative evidence linking psychological stress to graying hair in people.

And while it may seem intuitive that stress can accelerate graying, the researchers were surprised to discover that hair color can be restored when stress is eliminated, a finding that contrasts with a recent study in mice that suggested that stressed-induced gray hairs are permanent.

The study, published June 22 in eLife, has broader significance than confirming age-old speculation about the effects of stress on hair color, says the study’s senior author Martin Picard, PhD, associate professor of behavioral medicine (in psychiatry and neurology) at Columbia University Vagelos College of Physicians and Surgeons. 

“Understanding the mechanisms that allow ‘old’ gray hairs to return to their ‘young’ pigmented states could yield new clues about the malleability of human aging in general and how it is influenced by stress,” Picard says.

“Our data add to a growing body of evidence demonstrating that human aging is not a linear, fixed biological process but may, at least in part, be halted or even temporarily reversed.”

Studying hair as an avenue to investigate aging

“Just as the rings in a tree trunk hold information about past decades in the life of a tree, our hair contains information about our biological history,” Picard says. “When hairs are still under the skin as follicles, they are subject to the influence of stress hormones and other things happening in our mind and body. Once hairs grow out of the scalp, they harden and permanently crystallize these exposures into a stable form.”

Though people have long believed that psychological stress can accelerate gray hair, scientists have debated the connection due to the lack of sensitive methods that can precisely correlate times of stress with hair pigmentation at a single-follicle level.

Splitting hairs to document hair pigmentation

Ayelet Rosenberg, first author on the study and a student in Picard’s laboratory, developed a new method for capturing highly detailed images of tiny slices of human hairs to quantify the extent of pigment loss (graying) in each of those slices. Each slice, about 1/20th of a millimeter wide, represents about an hour of hair growth.

“If you use your eyes to look at a hair, it will seem like it’s the same color throughout unless there is a major transition,” Picard says. “Under a high-resolution scanner, you see small, subtle variations in color, and that’s what we’re measuring.”

The researchers analyzed individual hairs from 14 volunteers. The results were compared with each volunteer’s stress diary, in which individuals were asked to review their calendars and rate each week’s level of stress.

The investigators immediately noticed that some gray hairs naturally regain their original color, which had never been quantitatively documented, Picard says.

When hairs were aligned with stress diaries by Shannon Rausser, second author on the paper and a student in Picard’s laboratory, striking associations between stress and hair graying were revealed and, in some cases, a reversal of graying with the lifting of stress.

“There was one individual who went on vacation, and five hairs on that person’s head reverted back to dark during the vacation, synchronized in time,” Picard says.

Blame the mind-mitochondria connection

To better understand how stress causes gray hair, the researchers also measured levels of thousands of proteins in the hairs and how protein levels changed over the length of each hair.

Changes in 300 proteins occurred when hair color changed, and the researchers developed a mathematical model that suggests stress-induced changes in mitochondria may explain how stress turns hair gray.

“We often hear that the mitochondria are the powerhouses of the cell, but that’s not the only role they play,” Picard says. “Mitochondria are actually like little antennas inside the cell that respond to a number of different signals, including psychological stress.”

The mitochondria connection between stress and hair color differs from that discovered in a recent study of mice, which found that stress-induced graying was caused by an irreversible loss of stem cells in the hair follicle.

“Our data show that graying is reversible in people, which implicates a different mechanism,”  says co-author Ralf Paus, PhD, professor of dermatology at the University of Miami Miller School of Medicine. “Mice have very different hair follicle biology, and this may be an instance where findings in mice don’t translate well to people.”

Hair re-pigmentation only possible for some

Reducing stress in your life is a good goal, but it won’t necessarily turn your hair to a normal color.

“Based on our mathematical modeling, we think hair needs to reach a threshold before it turns gray,” Picard says. “In middle age, when the hair is near that threshold because of biological age and other factors, stress will push it over the threshold and it transitions to gray.

“But we don’t think that reducing stress in a 70-year-old who’s been gray for years will darken their hair or increasing stress in a 10-year-old will be enough to tip their hair over the gray threshold.”

Reference: 

Rosenberg AM, Rausser S, Ren J, et al. Quantitative mapping of human hair greying and reversal in relation to life stress. eLife. 2021;10:e67437. doi: 10.7554/eLife.67437


Is dark matter real, or have we misunderstood gravity?


For many years now, astronomers and physicists have been in a conflict. Is the mysterious dark matter that we observe deep in the Universe real, or is what we see the result of subtle deviations from the laws of gravity as we know them? In 2016, Dutch physicist Erik Verlinde proposed a theory of the second kind: emergent gravity. New research, published in Astronomy & Astrophysics this week, pushes the limits of dark matter observations to the unknown outer regions of galaxies, and in doing so re-evaluates several dark matter models and alternative theories of gravity. Measurements of the gravity of 259,000 isolated galaxies show a very close relation between the contributions of dark matter and those of ordinary matter, as predicted in Verlinde's theory of emergent gravity and an alternative model called Modified Newtonian Dynamics. However, the results also appear to agree with a computer simulation of the Universe that assumes that dark matter is 'real stuff'.

The new research was carried out by an international team of astronomers, led by Margot Brouwer (RUG and UvA). Further important roles were played by Kyle Oman (RUG and Durham University) and Edwin Valentijn (RUG). In 2016, Brouwer also performed a first test of Verlinde's ideas; this time, Verlinde himself also joined the research team.

Matter or gravity?

So far, dark matter has never been observed directly—hence the name. What astronomers observe in the night sky are the consequences of matter that is potentially present: bending of starlight, stars that move faster than expected, and even effects on the motion of entire galaxies. Without a doubt all of these effects are caused by gravity, but the question is: are we truly observing additional gravity, caused by invisible matter, or are the laws of gravity themselves the thing that we haven't fully understood yet?

To answer this question, the new research uses a similar method to the one used in the original test in 2016. Brouwer and her colleagues make use of an ongoing series of photographic measurements that started ten years ago: the KiloDegree Survey (KiDS), performed using ESO's VLT Survey Telescope in Chili. In these observations one measures how starlight from far away galaxies is bent by gravity on its way to our telescopes. Whereas in 2016 the measurements of such 'lens effects' only covered an area of about 180 square degrees on the night sky, in the mean time this has been extended to about 1000 square degrees—allowing the researchers to measure the distribution of gravity in around a million different galaxies.

Comparative testing

Brouwer and her colleagues selected over 259,000 isolated galaxies, for which they were able to measure the so-called 'Radial Acceleration Relation' (RAR). This RAR compares the amount of gravity expected based on the visible matter in the galaxy, to the amount of gravity that is actually present—in other words: the result shows how much 'extra' gravity there is, in addition to that due to normal matter. Until now, the amount of extra gravity had only been determined in the outer regions of galaxies by observing the motions of stars, and in a region about five times larger by measuring the rotational velocity of cold gas. Using the lensing effects of gravity, the researchers were now able to determine the RAR at gravitational strengths which were one hundred times smaller, allowing them to penetrate much deeper into the regions far outside the individual galaxies.

This made it possible to measure the extra gravity extremely precisely—but is this gravity the result of invisible dark matter, or do we need to improve our understanding of gravity itself? Author Kyle Oman indicates that the assumption of 'real stuff' at least partially appears to work: "In our research, we compare the measurements to four different theoretical models: two that assume the existence of dark matter and form the base of computer simulations of our universe, and two that modify the laws of gravity—Erik Verlinde's model of emergent gravity and the so-called 'Modified Newtonian Dynamics' or MOND. One of the two dark matter simulations, MICE, makes predictions that match our measurements very nicely. It came as a surprise to us that the other simulation, BAHAMAS, led to very different predictions. That the predictions of the two models differed at all was already surprising, since the models are so similar. But moreover, we would have expected that if a difference would show up, BAHAMAS was going to perform best. BAHAMAS is a much more detailed model than MICE, approaching our current understanding of how galaxies form in a universe with dark matter much closer. Still, MICE performs better if we compare its predictions to our measurements. In the future, based on our findings, we want to further investigate what causes the differences between the simulations."

Young and old galaxies

Thus it seems that, at least one dark matter model does appear to work. However, the alternative models of gravity also predict the measured RAR. A standoff, it seems—so how do we find out which model is correct? Margot Brouwer, who led the research team, continues: "Based on our tests, our original conclusion was that the two alternative gravity models and MICE matched the observations reasonably well. However, the most exciting part was yet to come: because we had access to over 259,000 galaxies, we could divide them into several types—relatively young, blue spiral galaxies versus relatively old, red elliptical galaxies." Those two types of galaxies come about in very different ways: red elliptical galaxies form when different galaxies interact, for example when two blue spiral galaxies pass by each other closely, or even collide. As a result, the expectation within the particle theory of dark matter is that the ratio between regular and dark matter in the different types of galaxies can vary. Models such as Verlinde's theory and MOND on the other hand do not make use of dark matter particles, and therefore predict a fixed ratio between the expected and measured gravity in the two types of galaxies—that is, independent of their type. Brouwer: "We discovered that the RARs for the two types of galaxies differed significantly. That would be a strong hint towards the existence of dark matter as a particle."

However, there is a caveat: gas. Many galaxies are probably surrounded by a diffuse cloud of hot gas, which is very difficult to observe. If it were the case that there is hardly any gas around young blue spiral galaxies, but that old red elliptical galaxies live in a large cloud of gas—of roughly the same mass as the stars themselves—then that could explain the difference in the RAR between the two types. To reach a final judgement on the measured difference, one would therefore also need to measure the amounts of diffuse gas—and this is exactly what is not possible using the KiDS telescopes. Other measurements have been done for a small group of around one hundred galaxies, and these measurements indeed found more gas around elliptical galaxies, but it is still unclear how representative those measurements are for the 259,000 galaxies that were studied in the current research.

Dark matter for the win?

If it turns out that extra gas cannot explain the difference between the two types of galaxies, then the results of the measurements are easier to understand in terms of dark matter particles than in terms of alternative models of gravity. But even then, the matter is not settled yet. While the measured differences are hard to explain using MOND, Erik Verlinde still sees a way out for his own model. Verlinde: "My current model only applies to static, isolated, spherical galaxies, so it cannot be expected to distinguish the different types of galaxies. I view these results as a challenge and inspiration to develop an asymmetric, dynamical version of my theory, in which galaxies with a different shape and history can have a different amount of 'apparent dark matter'."

Therefore, even after the new measurements, the dispute between dark matter and alternative gravity theories is not settled yet. Still, the new results are a major step forward: if the measured difference in gravity between the two types of galaxies is correct, then the ultimate model, whichever one that is, will have to be precise enough to explain this difference. This means in particular that many existing models can be discarded, which considerably thins out the landscape of possible explanations. On top of that, the new research shows that systematic measurements of the hot gas around galaxies are necessary. Edwin Valentijn formulates is as follows: "As observational astronomers, we have reached the point where we are able to measure the extra gravity around galaxies more precisely than we can measure the amount of visible matter. The counterintuitive conclusion is that we must first measure the presence of ordinary matter in the form of hot gas around galaxies, before future telescopes such as Euclid can finally solve the mystery of dark matter."

Reference: 

Margot M. Brouwer et al, The weak lensing radial acceleration relation: Constraining modified gravity and cold dark matter theories with KiDS-1000, Astronomy & Astrophysics (2021). DOI: 10.1051/0004-6361/202040108


Tuesday, 22 June 2021

An enormous ‘mega comet’ is flying into our solar system


From mysterious interstellar objects like the 'Oumuamua, to several not-so-unique space rocks—a plethora of heavenly objects constantly visit our celestial backyard that is the solar system. While many of them are missed by residents of Earth due to their sheer number and the vast distance in between, some notable bodies still manage to catch our eye from time to time.

Now, one such remarkable object has been spotted lurking at the edge of our solar system, only this one appears to be a comet that’s much larger than the typical comets we have grown accustomed to!

Described as a ‘mega-comet’, this visitor is estimated to be anywhere between 100 and 370 kilometres wide. In fact, this very size also puts it closer to the small draft planet territory.

Astronomers identified this object through the findings of the Dark Energy Survey, which captured astronomical data between the years 2014 and 2018. The mega-comet has since been designated the title 2014 UN271.

While the object itself is strange, its orbit is even stranger. Analysis reveals that one end of this mega-comet’s orbit is close to our Sun, while the other end stretches all the way up to the Oort Cloud—the circumstellar disk of dust and gas which is considered to be the most distant region of our solar system.

Due to such a ginormous distance between the two end-points, the object takes a whopping 6,12,190 years to complete one full orbit!

At present, the 2014 UN271 is located about 22 astronomical units (AU) away from the Sun, with one AU being equivalent to the distance between the Earth and our host star. In the last seven years, it has covered the distance of one AU every year.

As per the estimates made by citizen scientists, this comet will reach as close as 10.9 AU of the Sun by 2031. Therefore, at its closest, it will approach Saturn’s orbit before taking a u-turn and returning to the outer edges of the solar system.

As its closest point will still be so far away, it will be impossible to see catch a glimpse of this mega-comet from Earth without the use of a telescope. Even with a telescope, it is only likely to be as bright as Pluto's largest moon Charon in the night sky.

Source: Link

Physicists create platform to achieve ultra-strong photon-to-magnon coupling


A team of scientists from NUST MISIS and MIPT have developed and tested a new platform for realization of the ultra-strong photon-to-magnon coupling. The proposed system is on-chip and is based on thin-film hetero-structures with superconducting, ferromagnetic and insulating layers. This discovery solves a problem that has been on the agenda of research teams from different countries for the last 10 years, and opens new opportunities in implementing quantum technologies. The study was published in the highly ranked journal Science Advances.

The last decade has seen significant progress in the development of artificial quantum systems. Scientists are exploring different platforms, each with its own advantages and disadvantages. The next critical step for advancing quantum industry requires an efficient method of information exchange between platform hybrid systems that could benefit from distinct platforms. For example, hybrid systems based on collective spin excitations, or magnons, are being developed. In such systems, magnons must interact with photons, standing electromagnetic waves trapped in a resonator. The main limiting factor for developing such systems is the fundamentally weak interaction between photons and magnons. They are of different sizes, and follow different dispersion laws. This size difference of a hundred times or more considerably complicates the interaction.

Scientists from MIPT, together with their colleagues, managed to create a system with what is called the ultra-strong photon-to-magnon coupling.

Vasily Stolyarov, deputy head of the MIPT Laboratory of Topological Quantum Phenomena in Superconducting Systems, commented, "We created two subsystems. In one, being a sandwich from superconductor/insulator/superconductor thin films, photons are slowed down, their phase velocity is reduced. In another one, which is also a sandwich from superconductor/ ferromagnetic/ superconductor thin films, superconducting proximity at both interfaces enhances the collective spin eigen-frequencies. The ultra strong photon-to-magnon coupling is achieved thanks to the suppressed photon phase velocity in the electromagnetic subsystem."

Igor Golovchanskiy, leading researcher, senior researcher at the MIPT Laboratory of Topological Quantum Phenomena in Superconducting Systems, head of the NUST MISIS Laboratory of Cryogenic Electronic Systems, explained, "Photons interact very weakly with magnons. We managed to create a system in which these two types of excitations interact very strongly. With the help of superconductors, we have significantly reduced the electromagnetic resonator. This resulted in a hundred times reduction of the phase velocity of photons, and their interaction with magnons increased by several times."

This discovery will accelerate the implementation of hybrid quantum systems, as well as open up new possibilities in superconducting spintronics and magnonics.

Reference: 

Igor A. Golovchanskiy et al, Ultrastrong photon-to-magnon coupling in multilayered heterostructures involving superconducting coherence via ferromagnetic layers, Science Advances (2021). DOI: 10.1126/sciadv.abe8638


Rocket Lab to design two orbital spacecraft for NASA to study Mars


A NASA-funded smallsat mission to Mars that lost its ride last year may get new life through a partnership with Rocket Lab.

Rocket Lab announced June 15 it won a contract from the Space Sciences Laboratory (SSL) of the University of California Berkeley to begin design work on a new version of the Escape and Plasma Acceleration and Dynamics Explorers (EscaPADE) mission to Mars. The two EscaPADE spacecraft will go into orbit around Mars to study the interaction of the solar wind with the planet’s atmosphere.

EscaPADE was one of three missions selected by NASA in 2019 as part of its Small Innovative Missions for Planetary Exploration (SIMPLEx) program of smallsat planetary missions. The original plan for EscaPADE was to launch as a secondary payload on the Psyche mission to the main-belt asteroid of the same name in 2022. EscaPADE would have been dropped off when Psyche made a flyby of Mars on its way to the asteroid.

However, a switch in launch vehicles for Psyche, from SpaceX’s Falcon 9 to Falcon Heavy, changed the trajectory parameters of the mission. At a preliminary design review for EscaPADE in August 2020, the agency determined that change made it “no longer viable to manifest EscaPADE as part of the Psyche mission.”

NASA delayed a review of EscaPADE, known as Key Decision Point C, to the middle of this year as it looked for a new ride. Earlier this year, there were rumors in the planetary science community that Rocket Lab would be involved in some way in a revised EscaPADE mission. Agency officials said at recent meetings that a review of EscaPADE was scheduled for this summer but offered few other updates about the mission.

The announcement suggests a broader overhaul for the mission than just a change in launch services. The EscaPADE spacecraft were originally described as spacecraft 60 by 70 by 90 centimeters in size, weighing no more than 90 kilograms each.

According to the Rocket Lab announcement, the EscaPADE spacecraft, named Blue and Gold, will be based on Rocket Lab’s Photon satellite bus. The Curie engine, used on Photon and the kick stage for its Electron rocket, will insert the spacecraft into orbit around Mars.

“This is a hugely promising mission that will deliver big science in a small package,” Peter Beck, chief executive of Rocket Lab, said in a statement. “Our Photon spacecraft for EscaPADE will demonstrate a more cost-effective approach to planetary exploration that will increase the science community’s access to our solar system for the better.”

The statement did not disclose the terms of the deal, and the original version of Rocket Lab’s press release even omitted with whom the contract was with, leading to erroneous reports that the contract was directly from NASA. Company spokesperson Morgan Bailey declined to disclose the value of the contract, but said it was “a phased contract beginning with design and progressing to a manufacturing stage” following agency reviews in June and July.

SSL did not respond to a request for comment on the contract. Missions under NASA’s SIMPLEx program have a cost cap of $55 million.

Also unclear are the launch arrangements for EscaPADE. Rocket Lab’s release said that the spacecraft will launch on a “NASA-provided commercial launch vehicle” in 2024. There are no NASA Mars missions scheduled for launch in 2024, meaning that EscaPADE would either need to find another mission with a compatible trajectory or have NASA procure a dedicated, and significantly more expensive, launch.

Source: Link

How the Brain's Memory Center Also Help Guide Decisions


Scientists have long known the brain's hippocampus is crucial for long-term memory. Now a new Northwestern Medicine study has found the hippocampus also plays a role in short-term memory and helps guide decision-making.

The findings shed light on how the hippocampus contributes to memory and exploration, potentially leading to therapies that restore hippocampal function, which is impacted in memory-related aging and neurodegenerative diseases such as dementia, the study authors said.

In the study, scientists monitored participants' brain activity and tracked their eye movements while looking at different complex pictures. The scientists discovered that as we visually scan our environment and absorb new information, our hippocampus becomes activated, using short-term memory to better process new visual information to help us rapidly reevaluate situations.

How our memory helps us scan new environments

Imagine walking down the street and noticing an awkwardly parked car on your neighbor's lawn. Maybe you quickly dismiss it and move on. But when you see an ambulance and fire truck approaching your location, you connect the dots and look back to see the scene of an accident. By using short-term memory to guide where you look, the hippocampus allows you to reexamine the car and form a lasting memory of the accident.

"At any given moment, your brain rapidly initiates eye movements that you are typically unaware of," said corresponding author James Kragel, a postdoctoral research fellow at Northwestern University Feinberg School of Medicine. "Our findings suggest the hippocampus uses memory to inform where your eyes look, thereby priming the visual system to learn and reevaluate our environment on the fly.

"If you didn't look back and see the crash, you might not encode that important information, but in using short-term memory retrieval, you can tie those clues together and remember details that cue bigger memories. It all comes down to building connections among these disparate elements that allow you to remember them later in a much easier way."

The study was published June 18 in the journal Science Advances.

"These findings emphasize that although hippocampal-dependent memory is typically considered a thing of the past, in fact, it operates in the moment to optimize our behavior and decision-making," said senior study author Joel Voss, associate professor of medical social sciences, neurology, and psychiatry and behavioral sciences at Feinberg. "This is key to understanding hippocampal function and developing effective treatments for memory disorders."

"It is as if you are using your memory to plan for what to expect, and then when it mismatches with what is actually unfolding, your hippocampus gets activated to reevaluate and update your current perception of what is going on," Kragel said.

Tracking eye movements to learn more about memory

The study was conducted on patients with epilepsy who were undergoing neurosurgical monitoring at Northwestern Memorial Hospital to localize the source of their seizures. They had electrodes implanted in their brains to map seizure-related brain activity. During their stay in the epilepsy-monitoring unit, participants performed a memory task in which they studied lists of complex scenes with multiple people and objects (e.g. someone sitting at a park bench with food on the table, things happening in the background) followed by a memory test.

During the test, the participants indicated whether a presented scene was old or new. Throughout the task, the authors simultaneously recorded eye movements and neural activity to link hippocampal activity to memory-guided behaviors.

When studying a scene for the first time, participants often returned their gaze to a location they had just viewed hundreds of milliseconds prior. These "revisitation" eye movements enhanced spatiotemporal memory for scenes (remembering where an object was located or the sequence in which something happened). Brain recordings revealed the brain networks involved in generating these "revisitations," as hippocampal activity shifted just before their execution. Increases in brain activity followed revisitations, which Kragel believes may form a lasting memory of the scene and its elements.

"This shows that the hippocampal contribution to memory unfolds over just hundreds of milliseconds during ongoing behavior, which is surprising given that the timecourse of its involvement, typically seen in long-term memory retrieval, is usually thought to be days to years," Voss said.

Reference: 

Kragel JE, Schuele S, VanHaerents S, Rosenow JM, Voss JL. Rapid coordination of effective learning by the human hippocampus. Sci Adv. 2021;7(25):eabf7144. doi: 10.1126/sciadv.abf7144


Hubble Space Telescope Has Been Offline for a Week as NASA Fails to Fix It for the Third Time


NASA is working to save its prized space telescope, Hubble, after a mysterious computer issue took it offline last week.

Hubble launched into space in 1990 and immediately began capturing the universe in revolutionary detail. The Earth-orbiting observatory has imaged the births and deaths of stars, discovered new moons around Pluto, and tracked two interstellar objects as they zipped through our solar system. It has allowed astronomers to calculate the age and expansion of the universe. It has spotted galaxies more than 13.4 billion light-years away, thereby capturing light from the universe's early years.

But the telescope's payload computer suddenly stopped working on June 13. That computer, built in the 1980s, is like Hubble's brain - it controls and monitors all the science instruments on the spacecraft. So NASA engineers rushed to analyze data from the telescope to pinpoint the problem.

They still haven't figured out why the computer halted. NASA tried, and failed, to restart it on June 14. Initial data indicated that the issue could stem from a computer-memory module that was degrading, so the Hubble team tried switching to one of three backup modules onboard the telescope. But the command to start up the new module didn't work. On Thursday, the Hubble team tried again to bring both the current module and the backup online. Both attempts failed.

So now the Hubble operations team "will be running tests and collecting more information on the system to further isolate the problem," NASA said in an update on Friday.

In the meantime, Hubble's science instruments are in a hibernation-like "safe mode." They're all in good health, NASA said on Friday, as is the telescope itself.

Hubble has a second payload computer that it should be able to switch to if NASA can't restore the current one.

Hubble has seen many fixes and upgrades in its 30 years

This isn't the first time Hubble has glitched or needed an upgrade - not even the first time this year. In March, a software error sent the observatory into safe mode. But within a week, NASA had fixed the problem and gotten the telescope back online.

Hubble is the first telescope designed for in-orbit servicing. Astronauts have visited the observatory to fix problems or replace old parts on five occasions.

The last such Hubble-servicing mission, in 2009, repaired two failing instruments and gave the telescope a new computer, new batteries, new insulation, a new camera, and a spectrograph.

By replacing or upgrading aging parts in this way, astronauts have given Hubble new capabilities throughout its life. That's why the telescope is still conducting groundbreaking science 30 years after its launch. It's unlikely, however, that NASA would send astronauts to address the current problem because the backup computer should be able to fix it.

NASA also plans to launch a more sophisticated space telescope into orbit in November. The new observatory, called the James Webb Space Telescope, will have a field of view about 15 times larger than Hubble's.

Even though JWST is not intended to be a Hubble replacement, the legacy space telescope can't go on forever. During the 2009 mission, astronauts also installed a device that can push Hubble into Earth's atmosphere when it comes time to decommission the telescope. As it falls towards Earth, friction will heat the observatory until it burns up. It's unclear when that might be necessary.

Source: Link

'Pack ice' tectonics reveal Venus' geological secrets


A new analysis of Venus' surface shows evidence of tectonic motion in the form of crustal blocks that have jostled against each other like broken chunks of pack ice. The movement of these blocks could indicate that Venus is still geologically active and give scientists insight into both exoplanet tectonics and the earliest tectonic activity on Earth.

"We've identified a previously unrecognized pattern of tectonic deformation on Venus, one that is driven by interior motion just like on Earth," says Paul Byrne, associate professor of planetary science at North Carolina State University and lead and co-corresponding author of the work. "Although different from the tectonics we currently see on Earth, it is still evidence of interior motion being expressed at the planet's surface."

The finding is important because Venus has long been assumed to have an immobile solid outer shell, or lithosphere, just like Mars or Earth's moon. In contrast, Earth's lithosphere is broken into tectonic plates, which slide against, apart from, and underneath each other on top of a hot, weaker mantle layer.

Byrne and an international group of researchers used radar images from NASA's Magellan mission to map the surface of Venus. In examining the extensive Venusian lowlands that make up most of the planet surface, they saw areas where large blocks of the lithosphere seem to have moved: pulling apart, pushing together, rotating and sliding past each other like broken pack ice over a frozen lake.

The team created a computer model of this deformation, and found that sluggish motion of the planet's interior can account for the style of tectonics seen at the surface.

"These observations tell us that interior motion is driving surface deformation on Venus, in a similar way to what happens on Earth," Byrne says. "Plate tectonics on Earth are driven by convection in the mantle. The mantle is hot or cold in different places, it moves, and some of that motion transfers to Earth's surface in the form of plate movement.

"A variation on that theme seems to be playing out on Venus as well. It's not plate tectonics like on Earth—there aren't huge mountain ranges being created here, or giant subduction systems—but it is evidence of deformation due to interior mantle flow, which hasn't been demonstrated on a global scale before."

The deformation associated with these crustal blocks could also indicate that Venus is still geologically active.

"We know that much of Venus has been volcanically resurfaced over time, so some parts of the planet might be really young, geologically speaking," Byrne says. "But several of the jostling blocks have formed in and deformed these young lava plains, which means that the lithosphere fragmented after those plains were laid down. This gives us reason to think that some of these blocks may have moved geologically very recently—perhaps even up to today."

The researchers are optimistic that Venus' newly recognized "pack ice" pattern could offer clues to understanding tectonic deformation on planets outside of our solar system, as well as on a much younger Earth.

"The thickness of a planet's lithosphere depends mainly upon how hot it is, both in the interior and on the surface," Byrne says. "Heat flow from the young Earth's interior was up to three times greater than it is now, so its lithosphere may have been similar to what we see on Venus today: not thick enough to form plates that subduct, but thick enough to have fragmented into blocks that pushed, pulled, and jostled."

NASA and the European Space Agency recently approved three new spacecraft missions to Venus that will acquire observations of the planet's surface at much higher resolution than Magellan. "It's great to see renewed interest in the exploration of Venus, and I'm particularly excited that these missions will be able to test our key finding that the planet's lowlands have fragmented into jostling crustal blocks," Byrne says.

The work appears in Proceedings of the National Academy of Sciences.

Sean Solomon of Columbia University is co-corresponding author. Richard Ghail of the University of London, Surrey; A. M. Celâl Sengör of Istanbul Technical University; Peter James of Baylor University; and Christian Klimczak of the University of Georgia also contributed to the work.

Reference: 

Paul K. Byrne el al., "A globally fragmented and mobile lithosphere on Venus," PNAS (2021). www.pnas.org/cgi/doi/10.1073/pnas.2025919118