Could There Be Life On Jupiter’s Moons? (Planetary Science)

The search for life outside of Earth has taken many forms. Mars, our neighbouring world, looks like it was once habitable. Perhaps too Venus, despite its current hellish conditions. But in recent years, scientists’ gazes have been drawn elsewhere. What about the moons of Jupiter?

Three of Jupiter’s four largest moons are icy, and in 1998 NASA’s Galileo spacecraft detected tantalising hints of an ocean beneath one, Europa. Since then, further studies have detected signs of water plumes possibly erupting from this ocean.

The other two large icy moons, Ganymede and Callisto, are also thought to have oceans beneath their surfaces. Now, new questions are being asked: if there is water on these moons, could there be life? And could we look for it?

To help answer that question, the European Space Agency is planning to send a spacecraft to Jupiter in 2022, called the Jupiter Icy Moons Explorer (JUICE). Scheduled for arrival by 2029, it will perform multiple flybys of Europa and Callisto before entering orbit around Ganymede from 2032-2034 – the first spacecraft to orbit a moon other than Earth’s moon. During this time, it will return invaluable data back to Earth.

Before it even gets there, however, scientists are already busy studying these moons for signs of habitability, and preparing for the data that will be returned by the mission.

Trapped

The oceans under these moons are likely large, spanning the entire moons’ circumferences and extending tens of kilometres deep. But they are also trapped under tens of kilometres of ice, making studies of them very difficult.

One of our best approaches so far has been to look for the effects of salt in the oceans on their electrical conductivity by studying magnetic fields around the moons. But these studies ‘have mostly neglected all the other effects that generate magnetic fields,’ said Professor Joachim Saur, a planetary scientist from the University of Cologne, Germany, such as thin atmospheres around the moons. ‘It’s very important to disentangle the effects that really come from the ocean.’

Prof. Saur is the project coordinator on Exo-Oceans, which is hoping to answer this question. The project is using models and data from NASA’s Galileo spacecraft, which orbited in the Jovian system from 1995 to 2003, along with measurements from NASA’s Juno spacecraft currently at Jupiter and remote observations from telescopes like Hubble, to examine these oceans.

‘Our results will not overturn the idea of an ocean,’ on Europa and Ganymede said Prof. Saur, although he noted they might question one on Callisto. But it’s hoped they could give a better indication on things such as the thickness of the oceans, their salt content, and their distance from the icy sheets above.

All this has important implications for the habitability of the moons. To be able to support life, it’s thought the oceans need to be in contact with rock at the bottom in order for life to have a source of ‘food’, and currently only Europa is thought to meet that condition.

‘Europa is one of the best candidates for habitability because the liquid water is in direct contact with the silicate mantle,’ said Prof. Saur. ‘So there’s a possibility of the leaching out of minerals from the crust into the ocean. And the richer it is in chemical compounds, the better it is for the evolution of life.’

But there’s only so much that can be done before JUICE arrives. Once it does, its magnetometer instrument will provide useful measurements on the magnetic fields of the moons, giving us vital data on the oceans underneath. ‘This will allow us to separate all the different effects,’ said Prof. Saur.

‘Europa is one of the best candidates for habitability because the liquid water is in direct contact with the silicate mantle.’

— Prof. Joachim Saur, University of Cologne, Germany

Radiation

Another important factor regarding the habitability of the moons is how much radiation from Jupiter is hitting them. Jupiter produces a lot of damaging radiation, so much that it can harm spacecraft that get too close.

One way to study this is to observe aurorae on the moons, produced when charged particles from Jupiter hit magnetic fields around them. Europa, for example, has a constant aurora that can be observed in ultraviolet images from Hubble.

‘It relates to how the moon is exposed to this radiation because the charged particles from the radiation creates the aurora,’ said Dr Lorenz Roth, a planetary astronomer and physicist from the KTH Royal Institute of Technology in Stockholm, Sweden. ‘So it’s kind of a measurement for how much radiation is there.’

Dr Roth worked on the AuroraMHD project, which sought to use some of these auroral observations of Europa and Jupiter’s volcanically active moon Io to learn more about them. While the project was hampered by the Covid-19 pandemic, it did provide some useful data.

In particular, it helped confirm the existence of water plumes on Europa, and investigated how they interacted with its atmosphere. And it’s hoped that this work can be built upon, with JUICE, to further study the habitability of Jupiter’s icy moons.

‘The question of habitability and life always lingers in the background,’ said Dr Roth. ‘In all aspects, including size, the large Jupiter moons are like planets: they are similar to or bigger than Mercury, one has a magnetic field, they have atmospheres, they have oceans (and so on).

‘Europa is more promising (because its) water is very likely directly connected to the rocky material at the sea floor, which allows some reaction to take place.’

JUICE will be equipped with its own ultraviolet instrument that could study the aurorae of the moons in more detail, helping scientists work out how Jupiter’s radiation might impact their chances of life. ‘Once JUICE is in orbit, we’ll get a lot of information,’ said Dr Roth. ‘It can continuously measure the magnetic fields around the moons.’

In 2022, ESA will launch a spacecraft called JUICE to explore Jupiter’s moons, including Europa (left). Image credit – NASA, ESA, STScI, A. Simon (Goddard Space Flight Center), and M.H. Wong (University of California, Berkeley) and the OPAL team

Potential habitability

By itself, JUICE is not expected to tell us definitively if there is life on Jupiter’s moons. But its data, along with NASA’s Europa Clipper mission that will arrive in the Jovian system at a similar time to study Europa, could provide useful information on their potential habitability.

In the same way that initial missions to Mars assessed its habitability, before later missions – like NASA’s recently-landed Perseverance rover – were sent to look for life, so too might similar research take place for Jupiter’s moons.

‘While JUICE and the Europa Clipper have not even launched yet, there are already discussions about what could be next,’ said Prof. Saur, such as landers using drills to go into the ice and sample these oceans. ‘There is already work going on in parallel on what could be the next steps,’ he said.

The research in this article was funded by the EU.

Featured image: Europa, one of Jupiter’s large moons, is considered to be the best candidate for habitability because scientists think its sub-surface ocean is in contact with rock, meaning minerals can leach into the ocean and enrich it. Image credit – NASA/JPL


Provided by Horizon

Hubble Views a Galaxy with Faint Threads (Astronomy)

This unusual lenticular galaxy, which is between a spiral and elliptical shape, has lost almost all the gas and dust from its signature spiral arms, which used to orbit around its center. Known as NGC 1947, this galaxy was discovered almost 200 years ago by James Dunlop, a Scottish-born astronomer who later studied the sky from Australia. NGC 1947 can only be seen from the southern hemisphere, in the constellation Dorado (the Dolphinfish).

Residing around 40 million light-years away from Earth, this galaxy shows off its structure by backlighting its remaining faint gas and dust disk with millions of stars. In this picture, taken with the NASA/ESA Hubble Space Telescope, the faint remnants of the galaxy’s spiral arms can still be made out in the stretched thin threads of dark gas encircling it. Without most of its star-forming material, it is unlikely that many new stars will be born within NGC 1947, leaving this galaxy to continue fading with time.

Text credit: European Space Agency (ESA)
Image credit: ESA/Hubble & NASA, D. Rosario; Acknowledgment: L. Shatz


Provided by NASA

Researchers Identify Optimal Human Landing System Architectures to Land on the Moon (Planetary Science)

Researchers from Skoltech and the Massachusetts Institute of Technology have analyzed several dozen options to pick the best one in terms of performance and costs for the ‘last mile’ of a future mission to the Moon – actually delivering astronauts to the lunar surface and back up to the safety of the orbiting lunar station. The paper was published in the journal Acta Astronautica.

Ever since December 1972, when the crew of Apollo 17 left the lunar surface, humans have been eager to return to the Moon. In 2017, the US government launched the Artemis program, which intends to bring “the first woman and the next man” to the lunar south pole by 2024. The Artemis mission will use a new orbital platform, dubbed the Lunar Gateway, which is going to be a permanent space station from which reusable modules will bring astronauts back to the Moon. This new approach requires a reanalysis of the optimal landing approaches; the private companies contracted by NASA to design the reusable landing modules are conducting this research, but keeping their findings to themselves.

Skoltech M.Sc. student Kir Latyshev, Ph.D. student Nicola Garzaniti, Associate Professor Alessandro Golkar, and MIT’s Edward Crawley developed mathematical models to assess the most promising options for human landing systems for a future Artemis mission. For instance, the Apollo program used 2-stage architecture, when the Apollo Lunar Module, consisting of a descent and ascent modules, was able to carry two people to the lunar surface and back up, leaving the descent module behind.

The team assumed the Lunar Gateway is located in the L2 near rectilinear halo orbit, the currently preferred option that has the station orbiting the L2 Lagrange point in a way that makes it easier to land on the lunar south pole. They also modeled an expedition of four astronauts, who will spend around seven days on the Moon. The scientists considered both the optimal number of stages and the preferred propellants for the system. In total, they went through 39 variants of the future lunar human landing system, also modeling the cost for the most promising options.

The team went through a comprehensive approach for assessing alternative concepts of lunar human landers, looking at a broad number of options using architectural screening models. They first defined the key set of architectural decisions to be taken, such as number of stages and propellant type to be employed at each stage of the lander. They organized the information in mathematical models, and performed a comprehensive computational exploration of alternative system architectures coming from the combination of the different architectural decisions. Finally, they analyzed the resulting tradespace and identified preferred architectures for consideration by stakeholders concerned with the design of human lunar landers.

Their analysis showed that for expendable landing systems such as the ones used in the Apollo program, the 2-stage architecture is indeed the most advantageous as it has both lower total dry masses and propellant loads as well as lower launch costs per mission. However, for reusable vehicles planned for the Artemis program, 1-stage and 3-stage systems quickly become comparable in their advantages.

With all assumptions in the paper considered, the ‘ultimate’ winner for a number of short ‘sortie’-type lunar missions is the 1-stage reusable module running on liquid oxygen and liquid hydrogen (LOX/LH2). The authors note that this is a preliminary analysis, which does not take into account crew safety, probability of mission success as well as project management risks considerations – these will require more elaborate modeling at a later stage of the program.

Kir Latyshev notes that, for the Apollo program, NASA engineers did a similar analysis and chose the 2-stage lunar module. However, the overall architecture of lunar missions was different back then. It did not have an orbiting lunar station to keep the lunar module at between the missions, which meant that all ALM flights should be performed directly from Earth. It also meant using fully expendable lunar modules (a new vehicle for each mission), as opposed to reusable ones considered nowadays. Apart from that, without the lunar station, one of the current options – the 3-stage landing system – was not possible at all.

“Interestingly, our study finds that, even with the orbiting station, if fully expendable vehicles are considered, then the 2-stage (Apollo-like) landing system is still expected to have lower masses and, therefore, lower costs – which sort of reconfirms the Apollo decision. However, reusability changes that. Though 1-stage and 3-stage vehicles in this case are still heavier than the 2-stage one, they allow to reuse more of the ‘vehicle mass’ (approximately 70-100% compared to around 60% for the 2-stage option) over and over again, thus saving money on producing and delivering new vehicles to the orbiting station and making lunar missions potentially cheaper,” Latyshev says.

He adds that crew safety consideration is an important factor in designing human space systems which the authors did not account for in their study. “This safety factor can affect the results in either way. For example, multi-stage solutions might offer more safe return opportunities in case of emergency in the parking lunar orbit prior to descent to the surface than our ‘winner’, the 1-stage system: either the descent or ascent vehicle can be used for return in case of 3-stage and 2-stage systems as opposed to the single stage of the 1-stage system. At the same time, 2-stage and 3-stage systems are expected to be more complex and therefore to have more risks of breakdowns, as opposed to the simpler 1-stage solution. So there is a trade-off again,” Latyshev explains.

The team plans to expand the work in the future, with a comprehensive exploration of the system architecture of the entire exploration infrastructure required in future human spaceflight programs for lunar exploration.

Featured image: The ‘last mile’ of a future mission to the Moon © Pavel Odinev (Skoltech)


Reference: Kir Latyshev, Nicola Garzaniti, Edward Crawley, Alessandro Golkar, Lunar human landing system architecture tradespace modeling, Acta Astronautica, Volume 181, 2021, Pages 352-361, ISSN 0094-5765, https://doi.org/10.1016/j.actaastro.2021.01.015. (https://www.sciencedirect.com/science/article/pii/S0094576521000151)


Provided by Skoltech

What Happens In Your Brain When You ‘Lose Yourself’ in Fiction? (Neuroscience)

Study examines fans of ‘Game of Thrones’ characters

If you count yourself among those who lose themselves in the lives of fictional characters, scientists now have a better idea of how that happens.

Researchers found that the more immersed people tend to get into “becoming” a fictional character, the more they use the same part of the brain to think about the character as they do to think about themselves.

“When they think about a favorite fictional character, it appears similar in one part of the brain as when they are thinking about themselves,” said Timothy Broom, lead author of the study and doctoral student in psychology at The Ohio State University.

Timothy Broom © Ohio State News

The study was published online recently in the journal Social Cognitive and Affective Neuroscience.

The study involved scanning the brains of 19 self-described fans of the HBO series “Game of Thrones” while they thought about themselves, nine of their friends and nine characters from the series. (The characters were Bronn, Catelyn Stark, Cersei Lannister, Davos Seaworth, Jaime Lannister, Jon Snow, Petyr Baelish, Sandor Clegane and Ygritte.)

Participants reported which “Game of Thrones” character they felt closest to and liked the most.

“Game of Thrones” was a fantasy drama series lasting eight seasons and concerning political and military conflicts between ruling families on two fictional continents. It was ideal for this study, Broom said, because it attracted a devoted fan base and the large cast presented a variety of characters that people could become attached to.

One of the key findings involved participants in the study who scored highest on what is called “trait identification.” In a questionnaire they completed as part of the study, these participants agreed most strongly with statements like “I really get involved in the feelings of the characters in a novel.”

“People who are high in trait identification not only get absorbed into a story, they also are really absorbed into a particular character,” Broom said. “They report matching the thoughts of the character, they are thinking what the character is thinking, they are feeling what the character is feeling. They are inhabiting the role of that character.”

For the study, the participants’ brains were scanned in an fMRI machine while they evaluated themselves, friends and “Game of Thrones” characters. An fMRI indirectly measures activity in various parts of the brain through small changes in blood flow.

The researchers were particularly interested in what was happening in a part of the brain called the ventral medial prefrontal cortex (vMPFC), which shows increased activity when people think about themselves and, to a lesser extent, when thinking about close friends.

Dylan Wagner © Ohio State news

The process was simple. While in the fMRI, participants were shown a series of names – sometimes themselves, sometimes one of their nine friends, and other times one of the nine characters from “Game of Thrones.” Each name appeared above a trait, like lonely, sad, trustworthy or smart.

Participants simply said “yes” or “no” to whether the trait described the person while the researchers simultaneously measured activity in the vMPFC portion of their brains.

As expected, the vMPFC was most active when people were evaluating themselves, less active when they evaluated friends, and least active when they evaluated “Game of Thrones” characters.

But for those who were high in trait identification, the vMPFC was more active when they thought about the fictional characters than it was for participants who identified less with the characters. That brain area was especially active when they evaluated the character they felt closest to and liked the most.

The findings help explain how fiction can have such a big impact on some people, said Dylan Wanger, co-author of the study and assistant professor of psychology at Ohio State.

“For some people, fiction is a chance to take on new identities, to see worlds though others’ eyes and return from those experiences changed,” Wagner said.

“What previous studies have found is that when people experience stories as if they were one of the characters, a connection is made with that character, and the character becomes intwined with the self. In our study, we see evidence of that in their brains.”

Robert Chavez, an assistant professor of psychology at the University of Oregon and former postdoctoral researcher at Ohio State, was also a co-author.

Featured image: Could you see yourself as a Viking warrior that you read about in a book? © Ohio State news


Reference: Timothy W Broom, Robert S Chavez, Dylan D Wagner, Becoming the King in the North: identification with fictional characters is associated with greater self–other neural overlap, Social Cognitive and Affective Neuroscience, 2021;, nsab021, https://doi.org/10.1093/scan/nsab021


Provided by Ohio State news

Do β-Blockers Cause Depression? (Psychiatry)

Meta-analysis of potential psychiatric side effects

Drugs such as beta-adrenergic antagonists (beta blockers) have been linked to a range of adverse effects, including depression. But how reliable are these data, and which psychiatric side effects might indeed be caused by these drugs? These questions have been addressed by a team of researchers from Charité – Universitätsmedizin Berlin, whose comprehensive meta-analysis has been published in Hypertension*. While treatment with beta blockers was not found to be associated with an increased incidence of depression, some studies recorded higher levels of sleep disturbance.

Beta-adrenergic antagonists such as metoprolol or propranolol are among the drugs most commonly prescribed for the treatment of cardiovascular disease. Their effect is to slow the heart rate and reduce blood pressure, which is why they are used in patients with heart failure, arrhythmias, and high blood pressure. Beta blockers have repeatedly been linked to an increased risk of depression, but also other side effects such as anxiety, sleep disturbance and hallucinations; these links had not previously been explored in a systematic manner.

“We found no evidence to suggest a link between the use of beta blockers and depression,” says Prof. Dr. Reinhold Kreutz, Director of Charité’s Institute of Clinical Pharmacology and Toxicology. “The same also goes for most of the other psychiatric symptoms described in the studies included in our analysis.” Continuing his description of the meta-analysis conducted by his team – the first to study the full range of psychiatric side effects – he adds: “However, some patients developed sleep-related symptoms during treatment with beta blockers.” The researchers analyzed data from more than 53,000 persons. These were taken from 285 individual studies and involved 24 different beta blockers. Only data from double-blind, randomized, controlled trials were included in the analysis. The majority of these related to high blood pressure and had been conducted more than 20 years ago.

Despite being the most commonly reported psychiatric side effect, depression did not occur more frequently during treatment with beta blockers than during treatment with a placebo. Prof. Kreutz, currently President of the European Society of Hypertension, explains: “Patients with a history of cardiovascular problems such as heart attack or stroke are per se prone to develop mental health complications. This means that, while we found no causal link for this problem with beta blockers, these patients should be anyway monitored in this regard in clinical practice.” Patients treated with beta blockers were no more likely to discontinue their medications due to depression than patients undergoing different treatments. However, drowsiness and fatigue were the most commonly reported reasons for discontinuing treatment. Among the other side effects studied – such as anxiety and loss of appetite, memory, or libido – only sleep disturbance and abnormal dreams were found to be linked with beta blockers.

Summing up the results of the research, Prof. Kreutz says: “Our results show that concerns regarding undesirable psychiatric effects, in particular depression, should not influence the decision-making process regarding the use of beta blockers. For the most part, beta blockers have a good psychiatric safety profile.” Therefore, concerns about psychological health should not affect the clinical use of beta-blockers.


Reference: Riemer TG et al. Do β-blockers cause depression? Systematic review and meta-analysis of psychiatric adverse events during β-blocker therapy. Hypertension (2021), doi: 10.1161/HYPERTENSIONAHA.120.16590.


Provided by Charité University, Berlin

3 Bacterial Strains Discovered On Space Station May Help Grow Plants on Mars (Planetary Science)

Swab samples of 8 surfaces aboard the International Space Station have led to the identifying of 4 strains of bacteria, 3 of which belong to a newly discovered novel species within the genus Methylobacterium. According to researchers, these new strains might be useful in helping future space missions grow food in extreme environments.

In order to withstand the rigors of space on deep-space missions, food grown outside of Earth needs a little extra help from bacteria. Now, a recent discovery aboard the International Space Station (ISS) has researchers may help create the ‘fuel’ to help plants withstand such stressful situations.

Publishing their findings to Frontiers in Microbiology, researchers working with NASA described the discovery and isolation of 4 strains of bacteria belonging to the family Methylobacteriaceae from different locations aboard the ISS across two consecutive flights.

While 1 strain was identified as Methylorubrum rhodesianum, the other 3 were previously undiscovered and belong to a novel species novel. The rod-shaped, motile bacteria were given the designations IF7SW-B2T, IIF1SW-B5, and IIF4SW-B5 with genetic analysis showing them to be closely related to  Methylobacterium indicum. Methylobacterium species are involved in nitrogen fixation, phosphate solubilization, abiotic stress tolerance, plant growth promotion and biocontrol activity against plant pathogens.

Potential for Mars missions

Now, in honor of the renowned Indian biodiversity scientist Dr Ajmal Khan, the researchers have proposed to call the novel species Methylobacterium ajmalii.

Commenting on the discovery, Dr Kasthuri Venkateswaran (Venkat) and Dr Nitin Kumar Singh of NASA’s Jet Propulsion Laboratory, (JPL), say that the strains might possess “biotechnologically useful genetic determinants” for the growing of crops in space.

However, further experimental biology is needed to prove that it is, indeed, a potential game-changer for space farming.

“To grow plants in extreme places where resources are minimal, isolation of novel microbes that help to promote plant growth under stressful conditions is essential,” they said.

Along with JPL, other researchers collaborating on this discovery are based at the University of Southern California, Los Angeles; Cornell University and the University of Hyderabad in India.

With NASA one day looking to take humans to the surface of Mars – and potentially beyond – the US National Research Council Decadal Survey recommends that the space agency use the ISS as a “test-bed for surveying microorganisms”, according to Venkat and Singh.

“Since our group possess expertise in cultivating microorganisms from extreme niches, we have been tasked by the NASA Space Biology Program to survey the ISS for the presence and persistence of the microorganisms,” they add.

“Needless to say, the ISS is a cleanly-maintained extreme environment. Crew safety is the number 1 priority and hence understanding human/plant pathogens are important, but beneficial microbes like this novel Methylobacterium ajmalii are also needed.”

Expanding the ISS lab

As part of an ongoing surveillance mission, 8 locations on the ISS are being monitored for bacterial growths and have been for the last 6 years. These sample areas include where the crew assembles or where experiments are conducted, such as the plant growth chamber.

While hundreds of bacterial samples from the ISS have been analyzed to date, approximately 1,000 samples have been collected from various other locations on the space station but are awaiting a trip back to Earth where they can be examined.

According to Venkat and Singh, the eventual goal is to bypass this lengthy process and potentially find new novel strains using molecular biology equipment developed and demonstrated for the ISS.

“Instead of bringing samples back to Earth for analyses, we need an integrated microbial monitoring system that collect, process, and analyze samples in space using molecular technologies,” Venkat and Singh said.

“This miniaturized ‘omics in space’ technology – a biosensor development – will help NASA and other space-faring nations achieve safe and sustainable space exploration for long periods of time.”

Featured image: Interior view from the International Space Station cupola. Image: NASA


Reference: Swati Bijlani, Nitin K. Singh, V. V. Ramprasad Eedara, Appa Rao Podile, Christopher E. Mason, Clay C. C. Wang and Kasthuri Venkateswaran, “Methylobacterium ajmalii sp. nov., Isolated From the International Space Station”, Front. Microbiol., 15 March 2021 | https://doi.org/10.3389/fmicb.2021.639396


Provided by Frontiers

UIC Researchers Discover Hidden Link Between Cellular Defense Systems (Medicine)

Researchers at the University of Illinois Chicago have discovered that heparanase, HPSE, a poorly understood protein, is a key regulator of cells’ innate defense mechanisms. 

Innate defense responses are programmed cellular mechanisms that are triggered by various danger signals, which have been conserved in many species throughout evolution. These systems can be set into action by pathogens, such as viruses, bacteria and parasites, as well as by environmental toxins and dysfunctional cells that can accumulate in the body over time. A more thorough understanding of the commonalities and connections between these processes has the potential to generate multi-target therapy against a variety of human diseases.

In a multi-institution team led by Alex Agelidis, a UIC MD/Ph.D. dual degree medical student, and Dr. Deepak Shukla, the UIC Marion Schenk Professor of Ophthalmology and UIC professor of microbiology and immunology at the College of Medicine, researchers used a systems approach to track shifts in important cellular building blocks in cells and mice genetically engineered to lack HPSE. 

In this collaborative multidisciplinary study, Agelidis and coauthors show for the first time that HPSE acts as a cellular crossroads between antiviral immunity, proliferative signals and cell death.  

“HPSE has been long known to drive late-stage inflammatory diseases yet it was once thought that this was primarily due to enzymatic activity of the protein breaking down heparan sulfate, a sugar molecule present in chains on the surface of virtually all cells,” Agelidis said.  

While a major focus of the study was on identifying mechanisms of pathogenesis of herpes simplex virus (HSV-1), their work has broad implications for the treatment of diseases involving dysregulation of HPSE, including cancer, atherosclerosis and autoimmune disorders. 

Their research findings were published in the February issue of the Journal of Clinical Investigation Insight: 10.1172/jci.insight.144255

Benjamin Turturice, Rahul Suryawanshi, Tejabhiram Yadavalli, James Hopkins, Lulia Koujah, Chandrashekhar Patil, Satvik Hadigal, Evan Kyzar, David Perkins and Patricia Finn at UIC, Dinesh Jaishankar at Northwestern University, Anaamika Campeau, Jacob Wozniak and David Gonzalez at University of California San Diego, Israel Vlodavsky at Rappaport Institute, Israel, and Jin-ping Li at the University of Uppsala, Sweden, are co-authors of the publication. 

This work was supported by National Institutes of Health grants R01EY024710, R01EY029426 and R01AI139768. 

Featured image: UIC medical and Ph.D. student Alex Agelid, left, and Dr. Deepak Shukla, UIC Marion Schenk Professor of Ophthalmology and UIC professor of microbiology and immunology at the College of Medicine. © UIC


Provided by UIC

There Might Be Many Planets With Water-rich Atmospheres (Planetary Science)

UChicago study finds way that hot, rocky planets in other systems could form and keep atmospheres

An atmosphere is what makes life on Earth’s surface possible, regulating our climate and sheltering us from damaging cosmic rays. But although telescopes have counted a growing number of rocky planets, scientists had thought most of their atmospheres long lost.

However, a new study by University of Chicago and Stanford University researchers suggests a mechanism whereby these planets could not only develop atmospheres full of water vapor, but keep them for long stretches. Published March 15 in the Astrophysical Journal Letters, the research expands our picture of planetary formation and could help direct the search for habitable worlds in other star systems.

“Our model is saying that these hot, rocky exoplanets should have a water-dominated atmosphere at some stage, and for some planets, it may be quite a long time,” said Asst. Prof. Edwin Kite, an expert in how planetary atmospheres evolve over time.

As telescopes document more and more exoplanets, scientists are trying to figure out what they might look like. Generally, telescopes can tell you about an exoplanet’s physical size, its proximity to its star and if you’re lucky, how much mass it has. To go much further, scientists have to extrapolate based on what we know about Earth and the other planets in our own solar system. But the most abundant planets don’t seem to be similar to the ones we see around us.

“What we already knew from the Kepler mission is that planets a little smaller than Neptune are really abundant, which was a surprise because there are none in our solar system,” Kite said. “We don’t know for sure what they are made of, but there’s strong evidence they are magma balls cloaked in a hydrogen atmosphere.”

There’s also a healthy number of smaller rocky planets that are similar, but without the hydrogen cloaks. So scientists surmised that many planets probably start out like those larger planets that have atmospheres made out of hydrogen, but lose their atmospheres when the nearby star ignites and blows away the hydrogen.

But lots of details remain to be filled out in those models. Kite and co-author Laura Schaefer of Stanford University began to explore some of the potential consequences of having a planet covered in oceans of melted rock.

“Liquid magma is actually quite runny,” Kite said, so it also turns over vigorously, just like oceans on Earth do. There’s a good chance these magma oceans are sucking hydrogen out of the atmosphere and reacting to form water. Some of that water escapes to the atmosphere, but much more gets slurped up into the magma.

Then, after the nearby star strips away the hydrogen atmosphere, the water gets pulled out into the atmosphere instead in the form of water vapor. Eventually, the planet is left with a water-dominated atmosphere.

This stage could persist on some planets for billions of years, Kite said.

There are several ways to test this hypothesis. The James Webb Space Telescope, the powerful successor to the Hubble Telescope, is scheduled to launch later this year; it will be able to conduct measurements of the composition of an exoplanet’s atmosphere. If it detects planets with water in their atmospheres, that would be one signal.

Another way to test is to look for indirect signs of atmospheres. Most of these planets are tidally locked; unlike Earth, they don’t spin as they move around their sun, so one side is always hot and the other cold.

A pair of UChicago alumni have suggested a way to use this phenomenon to check for an atmosphere. Scientists Laura Kreidberg, PhD’16, and Daniel Koll, PhD’16–now at the Max Planck Institute for Astronomy and MIT, respectively–pointed out that an atmosphere would moderate the temperature for the planet, so there wouldn’t be a sharp difference between the day sides and night sides. If a telescope can measure how strongly the day side glows, it should be able to tell whether there’s an atmosphere redistributing heat.

Featured image: A study suggests that exoplanets close to their stars may actually retain a thick atmosphere full of water. Above, an artist’s illustration of the exoplanet WASP-121b, which appears to have water in its atmosphere. © Engine House VFX, At-Bristol Science Centre, University of Exeter


Reference: “Water on hot rocky exoplanets.” Kite and Schaefer, Astrophysical Journal Letters, March 11, 2021.


Provided by University of Chicago

Whispers From The Dark Side: What Can Gravitational Waves Reveal About Dark Matter? (Astronomy)

Scientists of the PRISMA+ Cluster of Excellence analyze data from the gravitational wave observatory NANOGrav

The NANOGrav Collaboration recently captured the first signs of very low-frequency gravitational waves. Prof. Pedro Schwaller and Wolfram Ratzinger analyzed the data and, in particular, considered the possibility of whether this may point towards new physics beyond the Standard Model. In an article published in the journal SciPost Physics, they report that the signal is consistent with both a phase transition in the early universe and the presence of a field of extremely light axion-like particles (ALPs). The latter are considered as promising candidates for dark matter.

Gravitational waves open a window into the early universe. While the ubiquitous cosmic microwave background yields no clues about the first 300,000 years of our universe, they provide some glimpses of what happened during Big Bang. “It’s exactly this very early universe that is so exciting for particle physicists,” explains Pedro Schwaller, Professor of Theoretical Physics at the PRISMA+ Cluster of Excellence at Johannes Gutenberg University Mainz (JGU). “This is the time when the elementary particles like quarks and gluons are present, and then combine to form the building blocks of atomic nuclei.”

The special thing about the gravitational waves which the NANOGrav Collaboration has detected for the first time is that they have a very low frequency of 10-8 Hertz, which equates to approximately one oscillation per year. Due to their correspondingly large wavelength, in order to detect them any detector would also have to be equally large. As such a detector is not possible here on Earth, the astronomers at NANOGrav use distant pulsars and their light signals as huge detectors.

Wolfram Ratzinger outlines the motivation behind their work: “Even though so far the data only provides us with a first hint of the existence of low-frequency gravitational waves, it is still very exciting for us to work with them. This is because such waves could be produced by various processes that occurred in the early universe. We can now use the data we already have to decide, which of these come into consideration and which do not fit the data at all.”

As a result, the Mainz-based scientists decided to take a particularly close look at two scenarios that could have caused the observed gravitational waves: Phase transitions in the early universe and a dark matter field of extremely light axion-like particles (ALPs). Phase transitions such as these occur due to the falling temperature in the primordial soup after the Big Bang and result in massive turbulences – however, like dark matter they are not covered by the Standard Model.

Based on the data available, Pedro Schwaller and Wolfram Ratzinger interpret the results of their analysis with relative caution: “Perhaps slightly more probable is the early phase transition scenario.” On the other hand, the two physicists believe that the fact that they are able to work out certain possibilities based only on limited data proves the potential of their approach. “Our work is a first, but important development – it gives us a lot of confidence that with more precise data we can draw reliable conclusions about the message gravitational waves are sending us from the early universe.”

“Furthermore,” Pedro Schwaller concludes, “we can already begin to pin down certain characteristics of the scenarios and put constraints on them, in our case the strength of the phase transition and the mass of the axions.”

Featured image: Representative illustration of the Earth embedded in space-time which is deformed by the background gravitational waves and its effects on radio signals coming from observed pulsars ©: NANOGrav / T. Klein


Publication
W. Ratzinger, P. Schwaller, Whispers from the dark side: Confronting light new physics with NANOGrav data, SciPost Physics 10, 23 February 2021,
DOI:10.21468/SciPostPhys.10.2.047


Provided by Johannes Guntenberg University