ST/ Newly formed craters located on Mars

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Paradigm

31 min readSep 28, 2022

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Space biweekly vol.61, 14th September — 28th September

TL;DR

An international team of researchers with NASA’s InSight mission located four new craters created by impacts on the surface of Mars. Using data from a seismometer and visuals acquired from the Mars Reconnaissance Orbiter, the team successfully calculated and confirmed the impact locations. Researchers have now captured the dynamics of an impact on Mars.
Astronomers have developed a new technique to identify small planets hidden in protoplanetary disks.
Using data from the Gaia space telescope, a team has shown that large parts of the Milky Way’s outer disk vibrate. The ripples are caused by a dwarf galaxy, now seen in the constellation Sagittarius, that shook our galaxy as it passed by hundreds of millions of years ago.
Scientists propose a lost moon of Saturn, which they call Chrysalis, pulled on the planet until it ripped apart, forming rings and contributing to Saturn’s tilt.
Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have spotted signs of a ‘hot spot’ orbiting Sagittarius A*, the black hole at the centre of our galaxy. The finding helps us better understand the enigmatic and dynamic environment of our supermassive black hole.
Astronomers risk misinterpreting planetary signals in James Webb data if models to interpret the data don’t improve, a new study finds.
Astrophysicists show how and when specific particles form and offers clues to questions that have troubled scientists since the 1940s.
The search for extraterrestrial life just got more interesting as a team of scientists has discovered new evidence for a key building block for life in the subsurface ocean of Saturn’s moon Enceladus. New modeling indicates that Enceladus’s ocean should be relatively rich in dissolved phosphorus, an essential ingredient for life.
Astronomical observations from ground-based telescopes are sensitive to local atmospheric conditions. Anthropogenic climate change will negatively affect some of these conditions at observation sites around the globe.
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Analysts at Morgan Stanley and Goldman Sachs have predicted that economic activity in space will become a multi-trillion-dollar market in the coming decades. Morgan Stanley’s Space Team estimates that the roughly USD 350 billion global space industry could surge to over USD 1 trillion by 2040.

Source: Satellite Industry Association, Morgan Stanley Research, Thomson Reuters. *2040 estimates

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Newly formed craters on Mars located using seismic and acoustic wave data from InSight

by Raphael F. Garcia, Ingrid J. Daubar, Éric Beucler, Liliya V. Posiolova, Gareth S. Collins, Philippe Lognonné, Lucie Rolland, Zongbo Xu, et al in Nature Geoscience

An international team of researchers with NASA’s InSight mission located four new craters created by impacts on the surface of Mars. Using data from a seismometer and visuals acquired from the Mars Reconnaissance Orbiter, the team successfully calculated and confirmed the impact locations. This is the first time that researchers have been able to capture the dynamics of an impact on Mars.

“Meteoroids and other projectiles in space can change the atmosphere and surface of any planet through impact,” said University of Maryland Geology Associate Professor Nicholas Schmerr, a co-author of the paper. “We’ve seen this on Earth, where these objects can hurtle through the atmosphere, hit the ground and leave behind a crater. But before this, we’ve never been able to capture the dynamics of an impact on Mars, where there’s a much thinner atmosphere.”

Sketch of meteor impact phenomena and their recordings by InSight.

As space projectiles enter the planetary atmosphere and impact the ground, the projectiles trigger acoustic waves (sound waves that travel through fluid or gas) and seismic waves (waves that travel through a solid medium). Schmerr and his InSight colleagues used these waves, measured by the SEIS (Seismic Experiment for Interior Structure) instrument on InSight, to estimate the approximate locations of resulting impact sites, observing the unique physics that dictated the projectiles’ movements. The team then matched their approximations to visuals provided by high-resolution cameras, confirming the sites and accuracy of the team’s modeling.

These findings demonstrate how planetary seismology (the study of quakes and related events like volcanic eruptions) can be used to identify sources of seismic activity. According to Schmerr, this ability may help researchers measure how often new impacts occur in the inner solar system, where both Mars and Earth reside — an observation essential to understanding the population of near-Earth objects like asteroids or rock fragments that may pose a danger to Earth.

Additionally, using images to determine the precise location of these impacts makes their associated acoustic and seismic waves invaluable for studying the Martian atmosphere and interior. With a better understanding of marsquake locations, scientists will be able to gather essential information about the planet, such as the size and solidity of its core or its heating processes. Geophysicists like Schmerr anticipate that new advances in planetary seismology will allow them to better investigate underlying tectonic activities and other sources of seismic activity within Mars. The findings ultimately bring researchers another step closer to understanding planetary formation and evolution.

“Studying how impacts work on Mars is like opening a window into the fundamental processes of how terrestrial planets form,” Schmerr said. “All inner solar system planets share this commonality, including Earth.”

NASA’s InSight is a robotic lander designed to study the interior structure of Mars. Active since 2018, the lander is expected to continue the InSight mission until its ability to gather solar power is fully depleted.

Orbital motion near Sagittarius A*

by M. Wielgus, M. Moscibrodzka, J. Vos, Z. Gelles, I. Martí-Vidal, J. Farah, N. Marchili, C. Goddi, H. Messias in Astronomy & Astrophysics

Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have spotted signs of a ‘hot spot’ orbiting Sagittarius A*, the black hole at the centre of our galaxy. The finding helps us better understand the enigmatic and dynamic environment of our supermassive black hole.

“We think we’re looking at a hot bubble of gas zipping around Sagittarius A* on an orbit similar in size to that of the planet Mercury, but making a full loop in just around 70 minutes. This requires a mind blowing velocity of about 30% of the speed of light!” says Maciek Wielgus of the Max Planck Institute for Radio Astronomy in Bonn, Germany, who led the study.

The observations were made with ALMA in the Chilean Andes — a radio telescope co-owned by the European Southern Observatory (ESO) — during a campaign by the Event Horizon Telescope (EHT) Collaboration to image black holes. In April 2017 the EHT linked together eight existing radio telescopes worldwide, including ALMA, resulting in the recently released first ever image of Sagittarius A*. To calibrate the EHT data, Wielgus and his colleagues, who are members of the EHT Collaboration, used ALMA data recorded simultaneously with the EHT observations of Sagittarius A*. To the team’s surprise, there were more clues to the nature of the black hole hidden in the ALMA-only measurements.

By chance, some of the observations were done shortly after a burst or flare of X-ray energy was emitted from the centre of our galaxy, which was spotted by NASA’s Chandra Space Telescope. These kinds of flares, previously observed with X-ray and infrared telescopes, are thought to be associated with so-called ‘hot spots’, hot gas bubbles that orbit very fast and close to the black hole.

Full Stokes 229 GHz ALMA light curves of Sgr A* obtained on 2017 Apr. 6, 7, and 11.

“What is really new and interesting is that such flares were so far only clearly present in X-ray and infrared observations of Sagittarius A*. Here we see for the first time a very strong indication that orbiting hot spots are also present in radio observations,” says Wielgus, who is also affiliated with the Nicolaus Copernicus Astronomical Centre, Poland and the Black Hole Initiative at Harvard University, USA.
“Perhaps these hot spots detected at infrared wavelengths are a manifestation of the same physical phenomenon: as infrared-emitting hot spots cool down, they become visible at longer wavelengths, like the ones observed by ALMA and the EHT,” adds Jesse Vos, a PhD student at Radboud University, the Netherlands, who was also involved in this study.

The flares were long thought to originate from magnetic interactions in the very hot gas orbiting very close to Sagittarius A*, and the new findings support this idea. “Now we find strong evidence for a magnetic origin of these flares and our observations give us a clue about the geometry of the process. The new data are extremely helpful for building a theoretical interpretation of these events,” says co-author Monika Mocibrodzka from Radboud University.

ALMA allows astronomers to study polarised radio emission from Sagittarius A*, which can be used to unveil the black hole’s magnetic field. The team used these observations together with theoretical models to learn more about the formation of the hot spot and the environment it is embedded in, including the magnetic field around Sagittarius A*. Their research provides stronger constraints on the shape of this magnetic field than previous observations, helping astronomers uncover the nature of our black hole and its surroundings.

Polarimetric loops observed by ALMA at 229 GHz on 2017 Apr. 11.

The observations confirm some of the previous discoveries made by the GRAVITY instrument at ESO’s Very Large Telescope (VLT), which observes in the infrared. The data from GRAVITY and ALMA both suggest the flare originates in a clump of gas swirling around the black hole at about 30% of the speed of light in a clockwise direction in the sky, with the orbit of the hot spot being nearly face-on.

“In the future we should be able to track hot spots across frequencies using coordinated multiwavelength observations with both GRAVITY and ALMA — the success of such an endeavour would be a true milestone for our understanding of the physics of flares in the Galactic centre,” says Ivan Marti-Vidal of the University of València in Spain, co-author of the study.

The team is also hoping to be able to directly observe the orbiting gas clumps with the EHT, to probe ever closer to the black hole and learn more about it.

“Hopefully, one day, we will be comfortable saying that we ‘know’ what is going on in Sagittarius A*,” Wielgus concludes.

The disturbed outer Milky Way disc

by Paul J McMillan, Jonathan Petersson, Thor Tepper-Garcia, Joss Bland-Hawthorn, Teresa Antoja, Laurent Chemin, Francesca Figueras, Shourya Khanna, Georges Kordopatis, Pau Ramos, Merce Romero-Gómez, George Seabroke in Monthly Notices of the Royal Astronomical Society

Using data from the Gaia space telescope, a team led by researchers at Lund University in Sweden has shown that large parts of the Milky Way’s outer disk vibrate. The ripples are caused by a dwarf galaxy, now seen in the constellation Sagittarius, that shook our galaxy as it passed by hundreds of millions of years ago.

Our cosmic home, the Milky Way, contains between 100 and 400 billion stars. Astronomers believe that the galaxy was born 13.6 billion years ago, emerging from a rotating cloud of gas composed of hydrogen and helium. Over billions of years, the gas then collected in a rotating disk where the stars, such as our sun, were formed.

In a new study, the research team presents their findings about the stars in the outer regions of the galactic disk.

“We can see that these stars wobble and move up and down at different speeds. When the dwarf galaxy Sagittarius passed the Milky Way, it created wave motions in our galaxy, a little bit like when a stone is dropped into a pond,” Paul McMillan, the astronomy researcher at Lund Observatory who led the study, explains.

By using data from the European space telescope Gaia, the research team was able to study a much larger area of the Milky Way’s disk than was previously possible. By measuring how strong the ripples are in different parts of the disc, the researchers have begun to piece together a complex puzzle, providing clues about Sagittarius’ history and orbit around our home galaxy.

“At the moment, Sagittarius is slowly being torn apart, but 1–2 billion years ago it was significantly larger, probably around 20 percent of the mass of the Milky Way’s disk,” says Paul McMillan.

The researchers were surprised by how much of the Milky Way they could study using the data from Gaia. To date the telescope, which has been in operation since 2013, has measured the movement across the sky of approximately two billion stars and the movement towards or away from us of 33 million.

“With this new discovery, we can study the Milky Way in the same way that geologists draw conclusions about the structure of the Earth from the seismic waves that travel through it. This type of “galactic seismology” will teach us a lot about our home galaxy and its evolution,” Paul McMillan concludes.

Abundant phosphorus expected for possible life in Enceladus’s ocean

by Jihua Hao, Christopher R. Glein, Fang Huang, Nathan Yee, David C. Catling, Frank Postberg, Jon K. Hillier, Robert M. Hazen in Proceedings of the National Academy of Sciences

The search for extraterrestrial life just got more interesting as a team of scientists including Southwest Research Institute’s Dr. Christopher Glein has discovered new evidence for a key building block for life in the subsurface ocean of Saturn’s moon Enceladus. New modeling indicates that Enceladus’s ocean should be relatively rich in dissolved phosphorus, an essential ingredient for life.

“Enceladus is one of the prime targets in humanity’s search for life in our solar system,” said Glein, a leading expert in extraterrestrial oceanography. He is a co-author of a paper describing this research. “In the years since NASA’s Cassini spacecraft visited the Saturn system, we have been repeatedly blown away by the discoveries made possible by the collected data.”

The Cassini spacecraft discovered Enceladus’s subsurface liquid water and analyzed samples as plumes of ice grains and water vapor erupted into space from cracks in the moon’s icy surface.

“What we have learned is that the plume contains almost all the basic requirements of life as we know it,” Glein said. “While the bioessential element phosphorus has yet to be identified directly, our team discovered evidence for its availability in the ocean beneath the moon’s icy crust.”

Thermodynamically favored form of dissolved phosphorus as a function of pH and equilibrium oxidation state (as activity of dissolved hydrogen, or fugacity of hydrogen gas in bars) at 0 °C and 70 bars (1 bar for reference in dashed lines).

One of the most profound discoveries in planetary science over the past 25 years is that worlds with oceans beneath a surface layer of ice are common in our solar system. Such worlds include the icy satellites of the giant planets, such as Europa, Titan and Enceladus, as well as more distant bodies like Pluto. Worlds like Earth with surface oceans must reside within a narrow range of distances from their host stars to maintain the temperatures that support surface liquid water. Interior water ocean worlds, however, can occur over a much wider range of distances, greatly expanding the number of habitable worlds likely to exist across the galaxy.

“The quest for extraterrestrial habitability in the solar system has shifted focus, as we now look for the building blocks for life, including organic molecules, ammonia, sulfur-bearing compounds as well as the chemical energy needed to support life,” Glein said. “Phosphorus presents an interesting case because previous work suggested that it might be scarce in the ocean of Enceladus, which would dim the prospects for life.”

Predicted concentration of orthophosphate (mainly HPO42−) in Enceladus’s ocean depending on if (A) fluoride is sufficiently abundant or (B) there is insufficient fluoride in the ocean–seafloor system to affect the oceanic abundance of P. Variation of dissolved P is controlled by the solubility of the least soluble P-bearing minerals, which is largely affected by the variation of major cations.

Phosphorus in the form of phosphates is vital for all life on Earth. It is essential for the creation of DNA and RNA, energy-carrying molecules, cell membranes, bones and teeth in people and animals, and even the sea’s microbiome of plankton. Team members performed thermodynamic and kinetic modeling that simulates the geochemistry of phosphorus based on insights from Cassini about the ocean-seafloor system on Enceladus. In the course of their research, they developed the most detailed geochemical model to date of how seafloor minerals dissolve into Enceladus’s ocean and predicted that phosphate minerals would be unusually soluble there.

“The underlying geochemistry has an elegant simplicity that makes the presence of dissolved phosphorus inevitable, reaching levels close to or even higher than those in modern Earth seawater,” Glein said. “What this means for astrobiology is that we can be more confident than before that the ocean of Enceladus is habitable.”

According to Glein, the next step is clear: “We need to get back to Enceladus to see if a habitable ocean is actually inhabited.”

Geological diversity and microbiological potential of lakes on Mars

by Joseph R. Michalski, Timothy A. Goudge, Sean A. Crowe, Javier Cuadros, John F. Mustard, Sarah Stewart Johnson in Nature Astronomy

Lakes are bodies of water fed by rainfall, snowmelt, rivers and groundwater, through which, Earth is teeming with life. Lakes also contain critical geologic records of past climates. Though Mars is a frozen desert today, scientists have shown that Mars contains evidence of ancient lakes that existed billions of years ago, which could contain evidence for ancient life and climate conditions on the red planet. Through a meta-analysis of years of satellite data that shows evidence for lakes on Mars, Dr Joseph Michalski, a geologist in the Department of Earth Sciences, The University of Hong Kong (HKU) proposed that scientists might have dramatically underestimated the number of ancient Martian lakes that once existed. Michalski and the international team recently published their results, which describe a global analysis of ancient Martian lakes.

“We know of approximately 500 ancient lakes deposited on Mars, but nearly all the lakes we know about are larger than 100 km2,” explains Michalski. “But on Earth, 70% of the lakes are smaller than this size, occurring in cold environments where glaciers have retreated. These small-sized lakes are difficult to identify on Mars by satellite remote sensing, but many small lakes probably did exist. It is likely that at least 70% of Martian lakes have yet to be discovered.”

Scientists monitor these small lakes on Earth in order to understand climate change. The missing small lakes on Mars might also contain critical information about past climates.

Four categories of lakes identified on Mars.

The recent paper also reports that most known Martian lakes date to a period 3,500 to 4,000 million years ago, but each of the lakes might have lasted only a geologically short time (10,000 to 100,000 years) during this time span. This means that ancient Mars was probably mostly cold and dry as well, but it warmed episodically for short periods of time. Michalski adds, “Because of the lower gravity on Mars and the pervasive, fine-grained soil, lakes on Mars would have been very murky and might not have allowed light to penetrate very deeply, which could present a challenge to photosynthetic life, if it existed.”

Lakes contain water, nutrients and energy sources for possible microbial life, including light for photosynthesis. Therefore, lakes are the top targets for astrobiological exploration by Mars Rovers such as NASA’s Perseverance rover now on Mars. But Michalski warns, “Not all lakes are created equal. In other words, some Martian lakes would be more interesting for microbial life than others because some of the lakes were large, deep, long-lived and had a wide range of environments such as hydrothermal systems that could have been conducive to the formation of simple life.” From this point of view, it might make sense to target large, ancient, environmentally diverse lakes for future exploration.

Schematic diagram of geobiological considerations in a Martian lake.

“Earth is host to many environments that can serve as analogs to other planets. From the harsh terrain of Svalbard to the depths of Mono Lake — we can determine how to design tools for detecting life elsewhere right here at home. Most of those tools are aimed at detecting the remains and residues of microbial life,” said Dr David BAKER, an ecologist at HKU School of Biological Sciences who is well-informed about the Earth’s microbial systems in lakes.

Loss of a satellite could explain Saturn’s obliquity and young rings

by Jack Wisdom, Rola Dbouk, Burkhard Militzer, William B. Hubbard, Francis Nimmo, Brynna G. Downey, Richard G. French in Science

Swirling around the planet’s equator, the rings of Saturn are a dead giveaway that the planet is spinning at a tilt. The belted giant rotates at a 26.7-degree angle relative to the plane in which it orbits the sun. Astronomers have long suspected that this tilt comes from gravitational interactions with its neighbor Neptune, as Saturn’s tilt precesses, like a spinning top, at nearly the same rate as the orbit of Neptune.

But a new modeling study by astronomers at MIT and elsewhere has found that, while the two planets may have once been in sync, Saturn has since escaped Neptune’s pull. What was responsible for this planetary realignment? The team has one meticulously tested hypothesis: a missing moon.

In a study, the team proposes that Saturn, which today hosts 83 moons, once harbored at least one more, an extra satellite that they name Chrysalis. Together with its siblings, the researchers suggest, Chrysalis orbited Saturn for several billion years, pulling and tugging on the planet in a way that kept its tilt, or “obliquity,” in resonance with Neptune. But around 160 million years ago, the team estimates, Chrysalis became unstable and came too close to its planet in a grazing encounter that pulled the satellite apart. The loss of the moon was enough to remove Saturn from Neptune’s grasp and leave it with the present-day tilt.

What’s more, the researchers surmise, while most of Chrysalis’ shattered body may have made impact with Saturn, a fraction of its fragments could have remained suspended in orbit, eventually breaking into small icy chunks to form the planet’s signature rings. The missing satellite, therefore, could explain two longstanding mysteries: Saturn’s present-day tilt and the age of its rings, which were previously estimated to be about 100 million years old — much younger than the planet itself.

“Just like a butterfly’s chrysalis, this satellite was long dormant and suddenly became active, and the rings emerged,” says Jack Wisdom, professor of planetary sciences at MIT and lead author of the new study.

The study’s co-authors include Rola Dbouk at MIT, Burkhard Militzer of the University of California at Berkeley, William Hubbard at the University of Arizona, Francis Nimmo and Brynna Downey of the University of California at Santa Cruz, and Richard French of Wellesley College.

Saturn’s normalized angular momentum as a function of rotation period.

In the early 2000s, scientists put forward the idea that Saturn’s tilted axis is a result of the planet being trapped in a resonance, or gravitational association, with Neptune. But observations taken by NASA’s Cassini spacecraft, which orbited Saturn from 2004 to 2017, put a new twist on the problem. Scientists found that Titan, Saturn’s largest satellite, was migrating away from Saturn at a faster clip than expected, at a rate of about 11 centimeters per year. Titan’s fast migration, and its gravitational pull, led scientists to conclude that the moon was likely responsible for tilting and keeping Saturn in resonance with Neptune. But this explanation hinges on one major unknown: Saturn’s moment of inertia, which is how mass is distributed in the planet’s interior. Saturn’s tilt could behave differently, depending on whether matter is more concentrated at its core or toward the surface.

“To make progress on the problem, we had to determine the moment of inertia of Saturn,” Wisdom says.

In their new study, Wisdom and his colleagues looked to pin down Saturn’s moment of inertia using some of the last observations taken by Cassini in its “Grand Finale,” a phase of the mission during which the spacecraft made an extremely close approach to precisely map the gravitational field around the entire planet. The gravitational field can be used to determine the distribution of mass in the planet. Wisdom and his colleagues modeled the interior of Saturn and identified a distribution of mass that matched the gravitational field that Cassini observed. Surprisingly, they found that this newly identified moment of inertia placed Saturn close to, but just outside the resonance with Neptune. The planets may have once been in sync, but are no longer.

“Then we went hunting for ways of getting Saturn out of Neptune’s resonance,” Wisdom says.

Eccentricity of Chrysalis as a function of its semimajor axis, in an example simulation.

The team first carried out simulations to evolve the orbital dynamics of Saturn and its moons backward in time, to see whether any natural instabilities among the existing satellites could have influenced the planet’s tilt. This search came up empty. So, the researchers reexamined the mathematical equations that describe a planet’s precession, which is how a planet’s axis of rotation changes over time. One term in this equation has contributions from all the satellites. The team reasoned that if one satellite were removed from this sum, it could affect the planet’s precession.

The question was, how massive would that satellite have to be, and what dynamics would it have to undergo to take Saturn out of Neptune’s resonance? Wisdom and his colleagues ran simulations to determine the properties of a satellite, such as its mass and orbital radius, and the orbital dynamics that would be required to knock Saturn out of the resonance. They conclude that Saturn’s present tilt is the result of the resonance with Neptune and that the loss of the satellite, Chrysalis, which was about the size of Iapetus, Saturn’s third-largest moon, allowed it to escape the resonance.

Sometime between 200 and 100 million years ago, Chrysalis entered a chaotic orbital zone, experienced a number of close encounters with Iapetus and Titan, and eventually came too close to Saturn, in a grazing encounter that ripped the satellite to bits, leaving a small fraction to circle the planet as a debris-strewn ring. The loss of Chrysalis, they found, explains Saturn’s precession, and its present-day tilt, as well as the late formation of its rings.

“It’s a pretty good story, but like any other result, it will have to be examined by others,” Wisdom says. “But it seems that this lost satellite was just a chrysalis, waiting to have its instability.”

The impending opacity challenge in exoplanet atmospheric characterization

by Prajwal Niraula, Julien de Wit, Iouli E. Gordon, Robert J. Hargreaves, Clara Sousa-Silva, Roman V. Kochanov in Nature Astronomy

NASA’s James Webb Space Telescope is revealing the universe with spectacular, unprecedented clarity. The observatory’s ultrasharp infrared vision has cut through the cosmic dust to illuminate some of the earliest structures in the universe, along with previously obscured stellar nurseries and spinning galaxies lying hundreds of millions of light years away.

In addition to seeing farther into the universe than ever before, Webb will capture the most comprehensive view of objects in our own galaxy — namely, some of the 5,000 planets that have been discovered in the Milky Way. Astronomers are harnessing the telescope’s light-parsing precision to decode the atmospheres surrounding some of these nearby worlds. The properties of their atmospheres could give clues to how a planet formed and whether it harbors signs of life. But a new MIT study suggests that the tools astronomers typically use to decode light-based signals may not be good enough to accurately interpret the new telescope’s data. Specifically, opacity models — the tools that model how light interacts with matter as a function of the matter’s properties — may need significant retuning in order to match the precision of Webb’s data, the researchers say.

If these models are not refined? The researchers predict that properties of planetary atmospheres, such as their temperature, pressure, and elemental composition, could be off by an order of magnitude.

“There is a scientifically significant difference between a compound like water being present at 5 percent versus 25 percent, which current models cannot differentiate,” says study co-leader Julien de Wit, assistant professor in MIT’s Department of Earth, Atmospheric, and Planetary Sciences (EAPS).
“Currently, the model we use to decrypt spectral information is not up to par with the precision and quality of data we have from the James Webb telescope,” adds EAPS graduate student Prajwal Niraula. “We need to up our game and tackle together the opacity problem.”

Co-authors include spectroscopy experts Iouli Gordon, Robert Hargreaves, Clara Sousa-Silva, and Roman Kochanov of the Harvard-Smithsonian Center for Astrophysics.

Ensemble of opacity-model perturbations at the level of an opacity cross-section.

Opacity is a measure of how easily photons pass through a material. Photons of certain wavelengths can pass straight through a material, be absorbed, or be reflected back out depending on whether and how they interact with certain molecules within a material. This interaction also depends on a material’s temperature and pressure. An opacity model works on the basis of various assumptions of how light interacts with matter. Astronomers use opacity models to derive certain properties of a material, given the spectrum of light that the material emits. In the context of explanets, an opacity model can decode the type and abundance of chemicals in a planet’s atmosphere, based on the light from the planet that a telescope captures.

De Wit says that the current state-of-the-art opacity model, which he likens to a classical language translation tool, has done a decent job of decoding spectral data taken by instruments such as those on the Hubble Space Telescope.

“So far, this Rosetta Stone has been doing OK,” de Wit says. “But now that we’re going to the next level with Webb’s precision, our translation process will prevent us from catching important subtleties, such as those making the difference between a planet being habitable or not.”

Transmission-spectrum fit quality unaffected by opacity-model perturbations.

He and his colleagues make this point in their study, in which they put the most commonly used opacity model to the test. The team looked to see what atmospheric properties the model would derive if it were tweaked to assume certain limitations in our understanding of how light and matter interact. The researchers created eight such “perturbed” models. They then fed each model, including the real version, “synthetic spectra” — patterns of light that were simulated by the group and similar to the precision that the James Webb telescope would see.

They found that, based on the same light spectra, each perturbed model produced wide-ranging predictions for the properties of a planet’s atmosphere. Based on their analysis, the team concludes that, if existing opacity models are applied to light spectra taken by the Webb telescope, they will hit an “accuracy wall.” That is, they won’t be sensitive enough to tell whether a planet has an atmospheric temperature of 300 Kelvin or 600 Kelvin, or whether a certain gas takes up 5 percent or 25 percent of an atmospheric layer.

“That difference matters in order for us to constrain planetary formation mechanisms and reliably identify biosignatures,” Niraula says.

The team also found that every model also produced a “good fit” with the data, meaning, even though a perturbed model produced a chemical composition that the researchers knew to be incorrect, it also generated a light spectrum from that chemical composition that was close enough to, or “fit” with the original spectrum.

“We found that there are enough parameters to tweak, even with a wrong model, to still get a good fit, meaning you wouldn’t know that your model is wrong and what it’s telling you is wrong,” de Wit explains.

He and his colleagues raise some ideas for how to improve existing opacity models, including the need for more laboratory measurements and theoretical calculations to refine the models’ assumptions of how light and various molecules interact, as well as collaborations across disciplines, and in particular, between astronomy and spectroscopy.

“There is so much that could be done if we knew perfectly how light and matter interact,” Niraula says. “We know that well enough around the Earth’s conditions, but as soon as we move to different types of atmospheres, things change, and that’s a lot of data, with increasing quality, that we risk misinterpreting.”

ALMA Detection of Dust Trapping around Lagrangian Points in the LkCa 15 Disk

by Feng Long, Sean M. Andrews, Shangjia Zhang, Chunhua Qi, Myriam Benisty, Stefano Facchini, Andrea Isella, David J. Wilner, Jaehan Bae, Jane Huang, Ryan A. Loomis, Karin I. Öberg, Zhaohuan Zhu in The Astrophysical Journal Letters

Astronomers agree that planets are born in protoplanetary disks — rings of dust and gas that surround young, newborn stars. While hundreds of these disks have been spotted throughout the universe, observations of actual planetary birth and formation have proved difficult within these environments.

Now, astronomers at the Center for Astrophysics | Harvard & Smithsonian have developed a new way to detect these elusive newborn planets — and with it, “smoking gun” evidence of a small Neptune or Saturn-like planet lurking in a disk.

“Directly detecting young planets is very challenging and has so far only been successful in one or two cases,” says Feng Long, a postdoctoral fellow at the Center for Astrophysics who led the new study. “The planets are always too faint for us to see because they’re embedded in thick layers of gas and dust.”

Left and middle: continuum emission images of the LkCa 15 disk at 1.3 and 0.88 mm, respectively, with identical beam size of 50 mas, shown in the bottom left corner of each panel. An asinh color stretch is applied to highlight the faint emission. Right: azimuthally averaged radial intensity profiles in brightness temperature. The three prominent dust rings are marked by the dashed vertical lines. The spectral index profile between the two bands is indicated by the dotted line (y-axis labels on the right side). The Gaussian profile in the bottom right corner shows the FWHM of the synthesized beam.

Scientists instead must hunt for clues to infer a planet is developing beneath the dust.

“In the past few years, we’ve seen many structures pop up on disks that we think are caused by a planet’s presence, but it could be caused by something else, too” Long says. “We need new techniques to look at and support that a planet is there.”

For her study, Long decided to re-examine a protoplanetary disk known as LkCa 15. Located 518 light years away, the disk sits in the Taurus constellation on the sky. Scientists previously reported evidence for planet formation in the disk using observations with the ALMA Observatory. Long dove into new high-resolution ALMA data on LkCa 15, obtained primarily in 2019, and discovered two faint features that had not previously been detected. About 42 astronomical units out from the star — or 42 times the distance Earth is from the Sun — Long discovered a dusty ring with two separate and bright bunches of material orbiting within it. The material took the shape of a small clump and a larger arc, and were separated by 120 degrees. Long examined the scenario with computer models to figure out what was causing the buildup of material and learned that their size and locations matched the model for the presence of a planet.

“This arc and clump are separated by about 120 degrees,” she says. “That degree of separation doesn’t just happen — it’s important mathematically.”

Top panels: residual images after subtracting the frank model, shown in signal-to-noise ratio. The images are convolved with the same circular beam of 50 mas, with noise levels of 4.4 and 15.5μJy beam−1 at B6 and B7, respectively. The three ellipses indicate the derived ring locations. Bottom left: the zoom-in comparison of the two residual images for the relative locations of the two excess emission features, with B7 residuals shown in contours at 4 and 6σ. Bottom right: the B42 azimuthal intensity profiles from the data (top) and residual images (bottom). The vertical dashed line marks the peak location of the clump identified in the B6 data at 32° and the shaded region is a rough estimate of the arc extension from 115°–195°.

Long points to positions in space known as Lagrange points, where two bodies in motion — such as a star and orbiting planet — produce enhanced regions of attraction around them where matter may accumulate.

“We’re seeing that this material is not just floating around freely, it’s stable and has a preference where it wants to be located based on physics and the objects involved,” Long explains.

In this case, the arc and clump of material Long detected are located at the L4 and L5 Lagrange points. Hidden 60 degrees between them is a small planet causing the accumulation of dust at points L4 and L5. The results show the planet is roughly the size of Neptune or Saturn, and around one to three million years old. (That’s relatively young when it comes to planets.) Directly imaging the small, newborn planet may not be possible any time soon due to technology constraints, but Long believes further ALMA observations of LkCa 15 can provide additional evidence supporting her planetary discovery. She also hopes her new approach for detecting planets — with material preferentially accumulating at Lagrange points — will be utilized in the future by astronomers.

“I do hope this method can be widely adopted in the future,” she says. “The only caveat is that this requires very deep data as the signal is weak.”

Ion and Electron Acceleration in Fully Kinetic Plasma Turbulence

by Luca Comisso, Lorenzo Sironi in The Astrophysical Journal Letters

For decades, scientists have been trying to solve a vexing problem about the weather in outer space: At unpredictable times, high-energy particles bombard the earth and objects outside the earth’s atmosphere with radiation that can endanger the lives of astronauts and destroy satellites’ electronic equipment. These flare-ups can even trigger showers of radiation strong enough to reach passengers in airplanes flying over the North Pole. Despite scientists’ best efforts, a clear pattern of how and when flare-ups will occur has remained enduringly difficult to identify.

In a paper, authors Luca Comisso and Lorenzo Sironi of Columbia’s Department of Astronomy and the Astrophysics Laboratory, have for the first time used supercomputers to simulate when and how high-energy particles are born in turbulent environments like that on the atmosphere of the sun. This new research paves the way for more accurate predictions of when dangerous bursts of these particles will occur.

“This exciting new research will allow us to better predict the origin of solar energetic particles and improve forecasting models of space weather events, a key goal of NASA and other space agencies and governments around the globe,” Comisso said. Within the next couple of years, he added, NASA’s Parker Solar Probe, the closest spacecraft to the sun, may be able to validate the paper’s findings by directly observing the predicted distribution of high-energy particles that are generated in the sun’s outer atmosphere.

(a) Volume rendering of the current density ∣ J ∣ at t = 1.25 l/vA from the fiducial simulation (β0 = 0.08). (b) Zoomed-in subdomain with five x–y slices at different z showing the current density Jz , along with selected magnetic field lines illustrating the presence of magnetic flux ropes. (c) One-dimensional k⊥ energy spectra of magnetic (blue) and velocity (red) fluctuations at t = 1.25 l/vA . Different spectral slopes are provided for reference.

In their paper, Comisso and Sironi demonstrate that magnetic fields in the outer atmosphere of the sun can accelerate ions and electrons up to velocities close to the speed of light. The sun and other stars’ outer atmosphere consist of particles in a plasma state, a highly turbulent state distinct from liquid, gas, and solid states. Scientists have long believed that the sun’s plasma generates high-energy particles. But particles in plasma move so erratically and unpredictably that they have until now not been able to fully demonstrate how and when this occurs.

Using supercomputers at Columbia, NASA, and the National Energy Research Scientific Computing Center, Comisso and Sironi created computer simulations that show the exact movements of electrons and ions in the sun’s plasma. These simulations mimic the atmospheric conditions on the sun, and provide the most extensive data gathered to-date on how and when high-energy particles will form.

The research provides answers to questions that scientists have been investigating for at least 70 years: In 1949, the physicist Enrico Fermi began to investigate magnetic fields in outer space as a potential source of the high-energy particles (which he called cosmic rays) that were observed entering the earth’s atmosphere. Since then, scientists have suspected that the sun’s plasma is a major source of these particles, but definitively proving it has been difficult.

(a) Kinetic energy evolution for five representative ions (shades of blue) and five representative electrons (shades of red) that end up in the power-law range of the nonthermal tail. (b) PDFs of ∣Jp ∣/Jrms experienced by high-energy ions (blue triangles) and high-energy electrons (red circles) at their tinj and by all our tracked particles at t = 1.25 l/vA (black diamonds). (c) Distribution of ions (left) and electrons (right) with respect to Wtot and W∥/Wtot, at the end of the β0 = 0.08 simulation (t = 8 l/vA ). (d) Median of the conditional PDFs at given Wtot for ions (left) and electrons (right) at t = 8 l/vA from simulations with different β0.

Comisso and Sironi’s research, which was conducted with support from NASA and the National Science Foundation, has implications far beyond our own solar system. The vast majority of the observable matter in the universe is in a plasma state. Understanding how some of the particles that constitute plasma can be accelerated to high-energy levels is an important new research area since energetic particles are routinely observed not just around the sun but also in other environments across the universe, including the surroundings of black holes and neutron stars.

While Comisso and Sironi’s new paper focuses on the sun, further simulations could be run in other contexts to understand how and when distant stars, black holes, and other entities in the universe will generate their own bursts of energy.

“Our results center on the sun but can also be seen as a starting point to better understanding how high-energy particles are produced in more distant stars and around black holes,” Comisso said. “We’ve only scratched the surface of what supercomputer simulations can tell us about how these particles are born across the universe.”

Impact of climate change on site characteristics of eight major astronomical observatories using high-resolution global climate projections until 2050

by C. Haslebacher, M.-E. Demory, B.-O. Demory, M. Sarazin, P. L. Vidale in Astronomy & Astrophysics

The quality of ground-based astronomical observations delicately depends on the clarity of the atmosphere above the location from which they are made. Sites for telescopes are therefore very carefully selected. They are often high above sea level, so that less atmosphere stands between them and their targets. Many telescopes are also built in deserts, as clouds and even water vapour hinder a clear view of the night sky.

A team of researchers led by the University of Bern and the National Centre of Competence in Research (NCCR) PlanetS shows in a study how one of the major challenges of our time — anthropogenic climate change — now even affects our view of the cosmos.

“Even though telescopes usually have a lifetime of several decades, site selection processes only consider the atmospheric conditions over a short timeframe. Usually over the past five years — too short to capture long-term trends, let alone future changes caused by global warming,” Caroline Haslebacher, lead author of the study and researcher at the NCCR PlanetS at the University of Bern, points out. The team of researchers from the University of Bern and the NCCR PlanetS, ETH Zurich, the European Southern Observatory (ESO) as well as the University of Reading in the UK therefore took it upon themselves to show the long-term perspective.

Example of model performance assessment.

Their analysis of future climate trends, based on high resolution global climate models, shows that major astronomical observatories from Hawaii to the Canary Islands, Chile, Mexico, South Africa and Australia will likely experience an increase in temperature and atmospheric water content by 2050. This, in turn, could mean a loss in observing time as well as a loss of quality in the observations.

“Nowadays, astronomical observatories are designed to work under the current site conditions and only have a few possibilities for adaptation. Potential consequences of the climatic conditions for telescopes therefore include a higher risk of condensation due to an increased dew point or malfunctioning cooling systems, which can lead to more air turbulence in the telescope dome,” Haslebacher says.

The fact that the effects of climate change on observatories had not been taken into account before was not an oversight, as study co-author Marie-Estelle Demory says, but was not least due to the state of the art: “This is the first time that such a study has been possible. Thanks to the higher resolution of the global climate models developed through the Horizon 2020 PRIMAVERA project, we were able to examine the conditions at various locations of the globe with great fidelity — something that we were unable to do with conventional models. These models are valuable tools for the work we do at the Wyss Academy,” says the senior scientist at the University of Bern and member of the Wyss Academy for Nature.

“This now allows us to say with certainty that anthropogenic climate change must be taken into account in the site selection for next-generation telescopes, and in the construction and maintenance of astronomical facilities,” says Haslebacher.

The quality of ground-based astronomical observations delicately depends on the clarity of the atmosphere above the location from which they are made. Sites for telescopes are therefore very carefully selected. They are often high above sea level, so that less atmosphere stands between them and their targets. Many telescopes are also built in deserts, as clouds and even water vapour hinder a clear view of the night sky.