It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Tuesday, April 25, 2023
Separating mining explosions from earthquakes in South Korea
South Korea is a relatively quiet country, seismically speaking, but a recent study identified more than 182,000 small seismic events--135,000 of which were related to mining explosions, according to a presentation at the Seismological Society of America (SSA)’s 2023 Annual Meeting.
After using machine learning techniques to detect tiny earthquakes in seven years’ worth of data collected by 421 seismic stations in the country, Jeong-Ung Woo of Stanford University and colleagues found distinct patterns in event times and locations that allowed them to identify which microseismic events were associated with mining operations. (Microseismicity usually refers to earthquakes of magnitude 2.0 and smaller.)
With relatively few natural earthquakes in South Korea, which is located in the middle of a tectonic plate, seismicity between 2016 and 2022 “was mostly occurring in the daytime, because the mining operations are usually occurring in the daytime,” Woo said.
Seismicity patterns also varied between summer and winter, due to how different sunrise and sunset times affected mining operations, Woo noted. The records showed a distinct drop off in seismic events on Sundays, when the mines are traditionally closed, and “even a little bit on Saturdays,” he added.
Natural seismicity doesn’t follow such regular timing, so microseismicity could be used as “very strong evidence to discriminate earthquakes and explosions without many physical techniques,” Woo said.
The researchers also compared their data with satellite images of mining locations, confirming that the seismic events identified as coming from mining blasts overlapped the location of operations.
There were unusual clusters of seismicity at the mining locations, between sunset and sunrise, that didn’t fit the timing of mining operations. “These could be considered mining-related events, or we need to figure out what else could be happening,” Woo said, such as whether mining blasts might be triggering natural seismicity in the area.
The microseismicity data could help seismologists pinpoint previously unidentified active faults or look more closely at earthquake aftershock sequences, he added.
Woo’s study of microseismicity in South Korea was inspired by a paper in the SSA open-access journal The Seismic Record, which showed how machine learning techniques could be used to identify hundreds of thousands of small earthquakes in Oklahoma and Kansas. Yongsoo Park, a former Ph.D. student at Stanford and now at Los Alamos National Laboratory, is a co-author of both studies.
South Korea experienced the largest earthquakes in its instrumental history in the past seven years: the magnitude 5.8 Gyeongju earthquake in 2016 and the magnitude 5.4 Pohang earthquake in 2017. The Pohang earthquake may have been triggered by water injected in rock layers at a geothermal plant. In the wake of the development of earthquake early-warning systems for these damaging and unexpected earthquakes, the country increased its number of seismic stations, creating the dense network that Woo and colleagues used in their study.
With the new microseismicity data, “it reveals previously unreported seismic swarms and activated faults in South Korea as well as capturing characteristic mining activities,” he said.
METHOD OF RESEARCH
Observational study
Research of National Field Scientific Observation and Research Station on Efficient Water Use of Oasis Agriculture shows it is possible to get bigger and sweeter tomatoes in Northwest China under changing climate under reduced nitrogen and water input
NANJING AGRICULTURAL UNIVERSITY THE ACADEMY OF SCIENCE
IMAGE: SCHEMATIC DIAGRAM OF THE INTEGRATED TOMATO PLANT AND FRUIT GROWTH AND FRUIT SUGAR METABOLISM (TGFS) MODELview more
CREDIT: HORTICULTURE RESEARCH
Process-based modelling is a powerful approach to deal with the complexity of biological systems of plants, their fruit, and the relationships between them. When simulating the response of fruit growth and quality to environmental factors and cultivation practices, the interactions between the mother plant and fruit need to be considered as a whole system. Here, we developed the integrative Tomato plant and fruit Growth and Fruit Sugar metabolism (TGFS) model by coupling equations describing the biophysical processes of leaf gas exchange, water transport, carbon allocation, organ growth and fruit sugar metabolism. The model also accounts for effects of soil nitrogen and atmospheric CO2 concentration on gaseous exchange of water and carbon by the leaf. With different nitrogen and water input values, TGFS performed well at simulating the dry mass of the tomato leaf, stem, root, and fruit, and the concentrations of soluble sugar and starch in fruit. TGFS simulations showed that increasing air temperature and CO2 concentration has positive effects on fruit growth, but not on sugar concentrations. Further model-based analyses of cultivation scenarios suggest that, in the context of climate change, decreasing N by 15%-25% and decreasing irrigation by 10%-20% relative to current levels, would increase tomato fresh weight by 27.8%-36.4% while increasing soluble sugar concentration by up to 10%. TGFS provides a promising tool to optimize N and water inputs for sustainable high-quality tomatoes.
Changes in the mature tomato fruit fresh weight (∆FW, %) and soluble sugar concentration (∆SSc, %) between 2021 and 2100 according to various possible sustainable scenarios using less nitrogen (N) and water (W) under future climate change
CREDIT
Horticulture Research
Reference
Authors
Huiping Zhou1,2, Shaozhong Kang1,2, Michel Génard3, Gilles Vercambre3, Jinliang Chen1,2*
Affiliations
1 Center for Agricultural Water Research in China, China Agricultural University, Beijing, 100083, China
2 National Field Scientific Observation and Research Station on Efficient Water Use of Oasis Agriculture in Wuwei of Gansu Province, Wuwei, 733009, China
3 INRAE, UR 1115 Plantes et Systèmes de Culture Horticoles, Avignon Cedex 9 F-84914, France
JOURNAL
Horticulture Research
University of Cincinnati research examines the impact of maternal stress during pregnancy on child’s health
First-of-its-kind research could provide key insight to fetal neurodevelopment
Prenatal maternal stress life events are associated with adverse neurodevelopmental outcomes in offspring. Biological mechanisms underlying these associations are largely unknown, but a chemical reaction in the body in which a small molecule known as a methyl group gets added to DNA, called DNA methylation, likely plays a role, according to researchers. These findings could provide new insights into how the fetal environment potentially influences not only neurodevelopment, but metabolism and immunologic functions as well.
More than 5,500 people took part in the study with that population broken down into 12 separate cohorts, according to Anna Ruehlmann, a postdoctoral fellow in the Department of Environmental and Public Health Sciences in the UC College of Medicine and lead author of the research.
“Our study is the first to look at such a large sample size and examine the entire epigenome, so it’s not just looking at the stress control genes as in previous studies, it’s looking at all the epigenomic sites available right now that you can study,” she says.
The research examines five separate categories of stress that expectant moms face during pregnancy. They are financial stress, conflict with a partner, conflict with a family member or friend, abuse (including physical, emotional and mental) and death of a friend or relative, plus a cumulative score that combines all the categories.
“We found that when mom experienced a cumulative amount of stress during pregnancy, there was, in fact, an association with DNA methylation in umbilical cord blood, which is a kind of epigenetic modification in the baby that’s developing in the womb,” Ruehlmann says. “An epigenetic modification is something that doesn’t change the sequence of the DNA, however the DNA is modified which is something that’s dynamic and can change in response to environmental exposures. Therefore, it’s something that can be turned on or off later in the child’s life or something that can maybe not do anything, it’s still unknown. It’s thought to be a mechanism of gene expression control.”
Ruehlmann says another unknown is how this process impacts children once they are born.
“We found five specific locations of DNA methylation with three different maternal stressors during pregnancy,” she says. “One was cumulative stress and the stressor specific domains of conflict with family/friends, abuse (physical, sexual and emotional) and death of a close friend/relative that were associated with DNA methylation in the developing fetus. These were occurring in genes that have shown to be involved in neurodevelopment. The next steps are to do some functional analyses to see how these genes really work and how the DNA methylation affects their expression.”
Ruehlmann describes the process as being a huge puzzle.
“Epigenetic modifications are a very dynamic process, there are a lot of changes that can happen in response to environmental factors,” she says. “What you’re seeing biologically at the beginning of fetal development you might not see the outcome of until later on during a child’s development. It’s fascinating as a biologist to begin to uncover some of the biological clues to how neurodevelopment is affected during fetal development. There are a lot of pieces to the puzzle that have yet to be connected. It’s very exciting.”
The study’s corresponding author is Kelly Brunst from the UC Department of Environmental and Public Health Sciences. The work in this study was supported by grants T32ES010957 (Ruehlmann) and R00ES024116 and P30ES006096 (Brunst).
IMAGE: DIAGRAM OF THE THREE BROAD STRATEGIES FOR CONSTRUCTING EFFICIENT INTERFACIAL SOLAR EVAPORATION SYSTEMS TO RELIEVE WORLDWIDE FRESHWATER SHORTAGES.view more
CREDIT: NANO RESEARCH ENERGY, TSINGHUA UNIVERSITY PRESS
Freshwater is essential for human life and the scarcity of freshwater is a critical issue in parts of the world today. In recent years, scientists have put great efforts into developing desalination technologies so that clean water can be produced from seawater. Interfacial solar evaporation (ISE) is a technology that holds promise for helping to relieve worldwide freshwater shortages. A team of researchers has undertaken a review study of the strategies available for constructing efficient ISE systems.
The team’s paper examines the energy nexus in two-dimensional and three-dimensional solar evaporators and reviews the strategies for design and fabrication of highly efficient ISE systems. Their summarized work offers perspectives for guiding the future design of ISE systems toward practical applications.
ISE is a desalination technology that produces freshwater through a process that is both environmentally friendly and sustainable. With this technology, solar energy is harnessed to evaporate and purify water. The technology uses photothermal evaporators to convert heat from sunlight to be localized at the evaporation surface for efficient vapor generation instead of dissipation into the bulk water and environment.
Traditional desalination technologies such as membrane filtration and thermal distillation consume large amounts of electricity derived from fossil fuels, so they are not considered to be environmentally friendly. Scientists continue to search for new desalination technologies that use green and sustainable energy sources. Recent work in ISE technologies has been focused primarily on optimizing energy management. Researchers have improved photothermal material and evaporator design with a goal of attaining more efficient energy use. This is achieved through three pathways: minimizing the energy loss from evaporation system to the environment, extending the energy input from the environment to enhance the evaporation process, and reducing evaporation enthalpy so the vaporization process is more efficient.
The team’s review systematically summarizes these pathways for enhancing practical solar evaporation performance. “We clearly demonstrate that the evaporation rate can be significantly enhanced by either applying materials with highly efficient light-to-heat conversion or structure design of state-of-art evaporators with smart energy management strategies,” said Li Yu, a professor at the Shenzhen Technology University.
“The main principles for achieving highly efficient solar evaporation include avoiding energy loss from the evaporation systems to the environment, expanding energy input from the surrounding air and bulk water, making full use of the existing energy already in the evaporation systems, and lowering the evaporation enthalpy,” said Haolan Xu, a professor at the University of South Australia.
The team offers five recommendations to be considered in moving next-generation ISE systems toward practical applications:
The first recommendation is to introduce new energy sources for ISE. Because solar light intensity significantly varies, it is important to explore new energy sources for all-day, all-weather, and all-season ISE systems.
The second recommendation is to continuously explore novel photothermal materials. The team suggests that the next-stage development of photothermal materials needs to focus on maximizing the use of thermal energy in both macroscale and micro-nanoscale.
The third recommendation is to explore innovative designs for photothermal evaporators. These next-generation evaporators should maximize energy harvest and water evaporation, while improving the water flow to ensure balanced water supply and evaporation.
The fourth recommendation is to improve water production in a limited space. In an ISE system, water evaporation and collection are two main parts. Although researchers have achieved very high solar evaporation rates, highly efficient water collection is rarely reported. Next-generation ISE systems need to have an excellent water evaporation module and an efficient vapor condensing module that fits in a compact space.
The team’s fifth recommendation focuses on the importance of developing large-scale ISE systems for practical applications, such as seawater desalination and wastewater treatment. They suggest that small evaporators be produced as units and assembled to form a larger interconnected system.
Looking ahead the team sees the potential for ISE technologies providing practical applications for meeting the freshwater scarcity problem. “In the current context of worldwide clean water shortages and advocacy for low carbon emission technologies, ISE is now accepted as one of the most promising technologies to solve the global clean water scarcity issues. However, there is still a long way to go to push forward the real-world applications of ISE technology,” said Yingying Zhang, a professor at Tsinghua University.
The research team includes Yida Wang from Tsinghua University and the University of South Australia; Junqing Hu and Li Yu from Shenzhen Technology University; Xuan Wu and Haolan Xu from the University of South Australia; and Yingying Zhang from Tsinghua University.
The research is funded by the National Natural Science Foundation of China, the National Key Basic Research and Development Program, Shenzhen Science and Technology Research Project, and Australian Research Council.
Nano Research Energy is launched by Tsinghua University Press, aiming at being an international, open-access and interdisciplinary journal. We will publish research on cutting-edge advanced nanomaterials and nanotechnology for energy. It is dedicated to exploring various aspects of energy-related research that utilizes nanomaterials and nanotechnology, including but not limited to energy generation, conversion, storage, conservation, clean energy, etc. Nano Research Energy will publish four types of manuscripts, that is, Communications, Research Articles, Reviews, and Perspectives in an open-access form.
SciOpen is a professional open access resource for discovery of scientific and technical content published by the Tsinghua University Press and its publishing partners, providing the scholarly publishing community with innovative technology and market-leading capabilities. SciOpen provides end-to-end services across manuscript submission, peer review, content hosting, analytics, and identity management and expert advice to ensure each journal’s development by offering a range of options across all functions as Journal Layout, Production Services, Editorial Services, Marketing and Promotions, Online Functionality, etc. By digitalizing the publishing process, SciOpen widens the reach, deepens the impact, and accelerates the exchange of ideas.
Recent Progress of Photodetector based on Carbon Nanotube Film and Application in Optoelectronic Integration.
Defying gravity
UNIVERSITY OF WARSAW, FACULTY OF PHYSICS
IMAGE: IN A BAG OF MIXED NUTS, AFTER SHAKING, SMALLER NUTS FILL IN THE GAPS CREATED AT THE BOTTOM, PUSHING THE LARGER BRAZIL NUTS TO THE TOP.view more
CREDIT: USER:MELCHOIR, CC BY-SA 3.0 <HTTP://CREATIVECOMMONS.ORG/LICENSES/BY-SA/3.0/>, VIA WIKIMEDIA COMMONS
Physicists from the University of Utrecht and the Faculty of Physics at the University of Warsaw have observed - for the first time experimentally - the Brazil nut effect in a mixture of charged colloidal particles. Until now, it was thought that an influx of external energy was required to create this effect - but the researchers were able to confirm that the process can occur spontaneously. The findings, published in The Proceedings of the National Academy of Sciences (PNAS), could find applications in a wide range of fields, from geology to soft matter physics.
Surely it has ever happened to you to shake an open bag of mixed nuts. Have you noticed that after such a procedure, the largest nuts in the mixture - Brazil nuts - float to the top? The phenomenon of large objects rising to the surface of a mixture of small objects, bearing the professional name of granular convection, is popularly referred to “the Brazil nut effect" and occurs commonly in nature. It can also be observed by shaking, for example, a bucket of sand and pebbles.
This unusual effect contradicts the intuition that heavier objects should sink to the bottom due to gravity and inertia force. This is the case with the phenomenon of sedimentation, common in nature, a process involving the sinking of solid particles dispersed in a liquid, under the influence of gravity or inertia forces. Sedimentation plays a role in processes such as the formation of sedimentary rocks, and is also used to purify water and wastewater or isolate cells from blood.
Brazil nut effect in charged colloids
Until now, it was thought that an influx of external energy, such as shaking the bag, was necessary to create the Brazil nut effect. However, theoretical models being developed suggested that the phenomenon could occur spontaneously, without the supply of external energy. The theoretical calculations were confirmed experimentally for the first time by a group of experimental and theoretical physicists from the University of Utrecht and the Faculty of Physics at the University of Warsaw. The results of the study appeared in a paper published in the journal The Proceedings of the National Academy of Sciences of the United States of America (PNAS). - We have shown that the Brazil nut effect can take place in a mixture of charged colloidal particles driven solely by Brownian motions and repulsion of electric charges, emphasizes Jeffrey Everts from the Faculty of Physics at the University of Warsaw, who, under the direction of René van Roij of the Institute for Theoretical Physics of the Utrecht University, carried out the theoretical calculations for the experiment. Marjolein van der Linden, working under the direction of Alfons van Blaaderen of the Debye Institute for Nanomaterials Science of the Utrecht University, was responsible for the experimental part of the study.
Colloidal mixture
The researchers used charged polymethylmethacrylate particles with different diameters (large and small) to carry out the experiment. A low-polar solvent, cyclohexyl bromide, was used as a dispersing agent.
As the researchers point out, although in both granular (e.g., nut) and colloidal mixtures the "Brazil nut effect" occurs, the mechanisms for its formation are completely different. In the case of a nut mixture, as a result of shaking, smaller nuts fill in the gaps created at the bottom, pushing the larger nuts to the top. Meanwhile, the charged particles in the colloid make Brownian motion as a result of collisions with the surrounding solvent molecules. – Each particle is positively charged. Heavier but larger particles have a greater charge, so they repel each other more strongly, making them move upward more easily than smaller but lighter particles, Jeffrey Everts explains.
The discovery of the “Brazil nut effect” in mixtures of colloidal particles can be used in many fields from geology to soft matter physics. It can also find application in industry such as in the stability of paint and ink.
Physics and astronomy at the University of Warsaw appeared in 1816 as part of the then Faculty of Philosophy. In 1825, the Astronomical Observatory was established. Currently, the Faculty of Physics at the University of Warsaw consists of the following institutes: Experimental Physics, Theoretical Physics, Geophysics, the Department of Mathematical Methods in Physics and the Astronomical Observatory. The research covers almost all areas of modern physics, on scales from quantum to cosmological. The Faculty's research and teaching staff consists of over 250 academic teachers. About 1100 students and over 170 doctoral students study at the Faculty of Physics at the University of Warsaw. The University of Warsaw ranks in Shanghai Global Ranking of Academic Subjects among the world's top 75 units educating in physics.
SCIENTIFIC PUBLICATION:
M. N. van der Linden, J. C. Everts, R. van Roij, A. van Blaaderen Realization of the Brazil-nut effect in charged colloids without external driving. https://www.pnas.org/doi/10.1073/pnas.2213044120
CONTACT:
Dr. Jeffrey Everts Faculty of Physics University of Warsaw email: jeffrey.everts@fuw.edu.pl Phone: +48 22 55 32 974
IMAGE: A FALSE-COLOUR IMAGE TAKEN BY THE SUPERBIT TELESCOPE SOON AFTER LAUNCH IN VISIBLE AND ULTRA-VIOLET LIGHT OF THE "TARANTULA NEBULA” - A NEIGHBOURHOOD OF THE LARGE MAGELLANIC CLOUD WHERE NEW STARS ARE BEING BORN.view more
CREDIT: SUPERBIT
Astronomers have successfully launched a balloon-borne telescope which has begun capturing images of the Universe on its first research flight.
SuperBIT is a collaboration between Durham University, UK, the University of Toronto, Canada, Princeton University, USA, and NASA.
It launched from Wānaka, New Zealand (Aotearoa) earlier this week, following a two-year delay due to the Covid pandemic.
Carried by seasonally stable winds for about three months, it will circumnavigate the southern hemisphere several times - imaging the sky all night, then using solar panels to recharge its batteries during the day.
SuperBIT flies at 33.5km altitude, above 99.5 per cent of the Earth’s atmosphere. It takes high-resolution images like those of the Hubble Space Telescope, but with a wider field of view.
The science goal for this first flight is to measure the properties of dark matter, a heavy but invisible type of material. Dark matter is all around us but poorly understood.
SuperBIT will test whether dark matter particles can bounce off each other, by mapping the dark matter around clusters of galaxies that are colliding with neighbouring galaxy clusters.
Various theories about dark matter suggest that, during a collision, some dark matter might either slow down, spread out, or get chipped off.
The researchers say that if they can map dark matter leaving the collision, they could finally start to learn what it is made of.
Professor Richard Massey, of Durham University’s Department of Physics, said: “It takes the gravity from an entire galaxy to move dark matter and SuperBIT will look at clusters of galaxies that happen to be colliding with each other.
“Essentially, we’re using the largest particle accelerators in the Universe, to smash lumps of dark matter and see where the bits fly.
“If dark matter goes ‘crunch’, or if bits are chipped off, we could finally start to learn what it’s made of.”
Although dark matter is invisible, SuperBIT will map where it is by the way it bends passing rays of light, a technique known as gravitational lensing.
While telescopes on the ground have to squint through the Earth’s atmosphere – meaning their view can become blurred - space-based telescopes get a clear view of the light that has travelled billions of years from the distant universe.
A false-colour image taken by the SuperBIT telescope soon after launch in visible and ultra-violet light of a pair of galaxies smashing into each other. As they collide, the “Antennae galaxies” NGC 4038 and NGC 4039 are ripping strips off each other and opening themselves for inspection.
CREDIT
SuperBIT
SuperBIT is the first ever balloon-borne telescope capable of taking wide-field images with resolution limited only by the laws of optics.
During its final test flight in 2019, SuperBIT demonstrated extraordinary pointing stability, with variation of less than one thirty-six thousandth of a degree for more than an hour.
SuperBIT cost about $5million/£4.1million, almost 1,000 times less than an equivalent satellite. Not only is helium cheaper than rocket fuel, but the ability of SuperBIT to return to Earth via parachute meant the team could tweak its design over several test flights.
Reusable spacecraft can also be reconfigured and upgraded. For example, the development team buy a new camera shortly before each launch, because modern detectors are improving so rapidly. Using cutting-edge technology has kept SuperBIT young.
The team already has funding to upgrade SuperBIT’s 0.5 metre aperture telescope to 1.6 metres, which would boost light gathering power tenfold, with a wider-angle lens and more megapixels. The relatively cheap cost may even make it possible for a fleet of space telescopes to offer time to astronomers around the world.
The public can follow SuperBIT’s flight status on NASA’s website here.
Funding for the SuperBIT mission has been provided by NASA, the Canadian Space Agency, and the Royal Society.
ENDS
The SuperBIT telescope nestled among its solar panels and communications antennae. Picked up at dawn, ready to be carried to the launch pad beside the runway at Wānaka airport.
CREDIT
Richard Massey.
CAPTION
The international SuperBIT science team will return to their homes after launch. Members from Canada, USA, UK and Australia will monitor the telescope from different time zones for the next 100 days.
CREDIT
SuperBIT science team
Asteroid’s comet-like tail Is not made of dust, solar observatories reveal
Scientists thought asteroid Phaethon, which is the source of the Geminid meteor shower, was shedding dust to form a comet-like tail, but NASA solar observatories show the tail isn't dusty.
IMAGE: THIS ILLUSTRATION DEPICTS ASTEROID PHAETHON BEING HEATED BY THE SUN. THE ASTEROID’S SURFACE GETS SO HOT THAT SODIUM INSIDE PHAETHON’S ROCK LIKELY VAPORIZES AND VENTS INTO SPACE, CAUSING IT TO BRIGHTEN LIKE A COMET AND FORM A TAIL.view more
CREDIT: NASA/JPL-CALTECH/IPAC
A weird asteroid has just gotten a little weirder.
We have known for a while that asteroid 3200 Phaethon acts like a comet. It brightens and forms a tail when it’s near the Sun, and it is the source of the annual Geminid meteor shower, even though comets are responsible for most meteor showers. Scientists had blamed Phaethon’s comet-like behavior on dust escaping from the asteroid as it’s scorched by the Sun. However, a new study using two NASA solar observatories reveals that Phaethon’s tail is not dusty at all but is actually made of sodium gas.
“Our analysis shows that Phaethon’s comet-like activity cannot be explained by any kind of dust,” said California Institute of Technology PhD student Qicheng Zhang, who is the lead author of a paper published in the Planetary Science Journal reporting the results.
Asteroids, which are mostly rocky, do not usually form tails when they approach the Sun. Comets, however, are a mix of ice and rock, and typically do form tails as the Sun vaporizes their ice, blasting material off their surfaces and leaving a trail along their orbits. When Earth passes through a debris trail, those cometary bits burn up in our atmosphere and produce a swarm of shooting stars – a meteor shower.
After astronomers discovered Phaethon in 1983, they realized that the asteroid’s orbit matched that of the Geminid meteors. This pointed to Phaethon as the source of the annual meteor shower, even though Phaethon was an asteroid and not a comet.
In 2009, NASA’s Solar Terrestrial Relations Observatory (STEREO) spotted a short tail extending from Phaethon as the asteroid reached its closest point to the Sun (or “perihelion”) along its 524-day orbit. Regular telescopes hadn’t seen the tail before because it only forms when Phaethon is too close to the Sun to observe, except with solar observatories. STEREO also saw Phaethon’s tail develop on later solar approaches in 2012 and 2016. The tail’s appearance supported the idea that dust was escaping the asteroid’s surface when heated by the Sun.
However, in 2018, another solar mission imaged part of the Geminid debris trail and found a surprise. Observations from NASA’s Parker Solar Probe showed that the trail contained far more material than Phaethon could possibly shed during its close approaches to the Sun.
Zhang’s team wondered whether something else, other than dust, was behind Phaethon’s comet-like behavior. “Comets often glow brilliantly by sodium emission when very near the Sun, so we suspected sodium could likewise serve a key role in Phaethon’s brightening,” Zhang said.
An earlier study, based on models and lab tests, suggested that the Sun’s intense heat during Phaethon’s close solar approaches could indeed vaporize sodium within the asteroid and drive comet-like activity.
Hoping to find out what the tail is really made of, Zhang looked for it again during Phaethon’s latest perihelion in 2022. He used the Solar and Heliospheric Observatory (SOHO) spacecraft — a joint mission between NASA and the European Space Agency (ESA) – which has color filters that can detect sodium and dust. Zhang’s team also searched archival images from STEREO and SOHO, finding the tail during 18 of Phaethon’s close solar approaches between 1997 and 2022.
In SOHO’s observations, the asteroid’s tail appeared bright in the filter that detects sodium, but it did not appear in the filter that detects dust. In addition, the shape of the tail and the way it brightened as Phaethon passed the Sun matched exactly what scientists would expect if it were made of sodium, but not if it were made of dust.
This evidence indicates that Phaethon’s tail is made of sodium, not dust.
“Not only do we have a really cool result that kind of upends 14 years of thinking about a well-scrutinized object,” said team member Karl Battams of the Naval Research Laboratory, “but we also did this using data from two heliophysics spacecraft – SOHO and STEREO – that were not at all intended to study phenomena like this.”
Zhang and his colleagues now wonder whether some comets discovered by SOHO – and by citizen scientists studying SOHO images as part of the Sungrazer Project – are not comets at all.
“A lot of those other sunskirting ‘comets’ may also not be ‘comets’ in the usual, icy body sense, but may instead be rocky asteroids like Phaethon heated up by the Sun,” Zhang explained.
Still, one important question remains: If Phaethon doesn’t shed much dust, how does the asteroid supply the material for the Geminid meteor shower we see each December?
Zhang’s team suspects that some sort of disruptive event a few thousand years ago – perhaps a piece of the asteroid breaking apart under the stresses of Phaethon’s rotation – caused Phaethon to eject the billion tons of material estimated to make up the Geminid debris stream. But what that event was remains a mystery.
More answers may come from an upcoming Japan Aerospace Exploration Agency (JAXA) mission called DESTINY+ (short for Demonstration and Experiment of Space Technology for Interplanetary voyage Phaethon fLyby and dUst Science). Later this decade, the DESTINY+ spacecraft is expected to fly past Phaethon, imaging its rocky surface and studying any dust that might exist around this enigmatic asteroid.
