SPACE
The rotation of a nearby star stuns astronomers
image:
A nearby star V889 Herculis rotates the fastest at a latitude of about 40 degrees.
view moreCredit: Jani Närhi, University of Helsinki
Astronomers from the University of Helsinki have found that the rotational profile of a nearby star, V889 Herculis, differs considerably from that of the Sun. The observation provides insights into the fundamental stellar strophysics and helps understanding the activity of the Sun, its spot structures and eruptions.
The Sun rotates the fastest at the equator, whereas the rotation rate slows down at higher latitudes and is the slowest as the polar regions. But a nearby Sun-like star V889 Herculis, some 115 light years away in the constellation of Hercules, rotates the fastest at a latitude of about 40 degrees, while both the equator and polar regions rotate more slowly.
Similar rotational profile has not been observed for any other star. The result is stunning because stellar rotation has been considered a well-understood fundamental physical parameter but such a rotational profile has not been predicted even in computer simulations.
– We applied a newly developed statistical technique to the data of a familiar star that has been studied in the University of Helsinki for years. We did not expect to see such anomalies in stellar rotation. The anomalies in the rotational profile of V889 Herculis indicate that our understanding of stellar dynamics and magnetic dynamos are insufficient, explains researcher Mikko Tuomi who coordinated the research
Dynamics of a ball of plasma
The target star V889 Herculis is much like a young Sun, telling a story about the history and evolution of the Sun. Tuomi emphasises that it is crucial to understand stellar astrophysics in order to, for instance, predict activity-induced phenomena on the Solar surface, such as spots and eruptions.
Stars are spherical structures where matter is in the state of plasma, consisting of charged particles. They are dynamical objects that hang in a balance between the pressure generated in nuclear reactions in their cores and their own gravity. They have no solid surfaces unlike many planets.
The stellar rotation is not constant for all latitudes – an effect known as differential rotation. It is caused by the fact that hot plasma rises to the star's surface via a phenomenon called convection, which in turn has an effect on the local rotation rate. This is because angular momentum must be conserved and the convection occurs perpendicular to the rotational axis near equator whereas it is parallel to the axis near the poles.
However, many factors such as stellar mass, age, chemical composition, rotation period, and magnetic field have effects on the rotation and give rise to variations in the differential rotation profiles.
A statistical method for determining rotational profile
Thomas Hackman, docent of astronomy, who participated in the research, explains that the Sun has been the only star for which studying the rotational profile has been possible.
– Stellar differential rotation is a very crucial factor that has an effect on the magnetic activity of stars. The method we have developed opens a new window into the inner workings of other stars.
The astronomers at the Department of Particle Physics and Astrophysics of the Helsinki University have determined the rotational profile of two nearby young stars by applying a new statistical modelling to long-baseline brightness observations. They modelled the periodic variations in the observations by accounting for the differences in the apparent spot movement at different latitudes. The spot movement then enabled estimating the rotational profile of the stars.
The second one of the targets stars, LQ Hydrae in the constellation of Hydra, was found to be rotating much like a rigid body -- the rotation appeared unchanged from the equator to the poles, which indicates that the differences are very small.
Observations from the Fairborne Observatory
The researchers base their results on the observations of the target stars from the Fairborn observatory. The brightnesses of the stars have been monitored with robotic telescopes for around 30 years, which provides insights into the behaviour of the stars over a long period of time.
Tuomi appreciates the work of senior astronomer Gregory Henry, of Tennessee University, United States, who leads the Fairborne observational campaign.
– For many years, Greg's project has been extremely valuable in understanding the behaviour of nearby stars. Whether the motivation is to study the rotation and properties of young, active stars or to understand the nature of stars with planets, the observations from Fairborn Observatory have been absolutely crucial. It is amazing that even in the era of great space-based observatories we can obtain fundamental information on the stellar astrophysics with small 40cm ground-based telescopes.
The target stars V889 Herculis and LQ Hydrae are both roughly 50 million yeara old stars that in many respects resemble the young Sun. They both rotate very rapidly, with rotation periods of only about one and half days. For this reason, the long-baseline brightness observations contain many rotational cycles. The stars were selected as targets because they have been observed for decades and because they have both been studied actively at the University of Helsinki.
Original article: Mikko Tuomi, J. Jyri Lehtinen, W. Gregory Henry, Thomas Hackman. Characterising the stellar differential rotation based on largest-spot statistics from ground-based photometry. A&A, 2024. DOI: https://doi.org/10.1051/0004-6361/202449861
Further information
Researcher Mikko Tuomi, University of Helsinki, tel +358 40 500 7454, mikko.tuomi@helsinki.fi
University Researcher Thomas Hackman, University of Helsinki, thomas.hackman@helsinki.fi
Postdoctoral Researcher Jyri Lehtinen, University of Turku (FINCA) and University of Helsinki, jyri.j.lehtinen@helsinki.fi
Journal
Astronomy and Astrophysics
Method of Research
Data/statistical analysis
Subject of Research
Not applicable
Article Title
Characterising the stellar differential rotation based on largest-spot statistics from ground-based photometry
What no one has seen before – simulation of gravitational waves from failing warp drive
University of Potsdam
Warp drives are staples of science fiction, and in principle could propel spaceships faster than the speed of light. Unfortunately, there are many problems with constructing them in practice, such as the requirement for an exotic type of matter with negative energy. Other issues with the warp drive metric include the difficulties for those in the ship in actually controlling and deactivating the bubble.
This new research is the result of a collaboration between specialists in gravitational physics at Queen Mary University of London, the University of Potsdam, the Max Planck Institute (MPI) for Gravitational Physics in Potsdam and Cardiff University. Whilst it doesn't claim to have cracked the warp drive code, it explores the theoretical consequences of a warp drive “containment failure” using numerical simulations. Dr Katy Clough of Queen Mary University of London, the first author of the study explains: “Even though warp drives are purely theoretical, they have a well-defined description in Einstein’s theory of General Relativity, and so numerical simulations allow us to explore the impact they might have on spacetime in the form of gravitational waves.”
The results are fascinating. The collapsing warp drive generates a distinct burst of gravitational waves, a ripple in spacetime that could be detectable by gravitational wave detectors that normally target black hole and neutron star mergers. Unlike the chirps from merging astrophysical objects, this signal would be a short, high-frequency burst, and so current detectors wouldn't pick it up. However, future higher-frequency instruments might, and although no such instruments have yet been funded, the technology to build them exists. This raises the possibility of using these signals to search for evidence of warp drive technology, even if we can't build one ourselves.
Prof Tim Dietrich from the University of Potsdam comments: “For me, the most important aspect of the study is the novelty of accurately modelling the dynamics of negative energy spacetimes, and the possibility of extending the techniques to physical situations that can help us better understand the evolution and origin of our universe, or the processes at the centre of black holes.”
Warp speed may be a long way off, but this research already pushes the boundaries of our understanding of exotic spacetimes and gravitational waves. The researchers plan to investigate how the signal changes with different warp drive models.
Link to Publication: Clough, Katy, Tim Dietrich, and Sebastian Khan. 2024. What No One Has Seen before: Gravitational Waveforms from Warp Drive Collapse. The Open Journal of Astrophysics 7 (July). https://doi.org/10.33232/001c.121868
Link to Press Release of Queen Mary University of London: https://www.qmul.ac.uk/media/news/2024/se/new-study-simulates-gravitational-waves-from-failing-warp-drive.html
Link to AEI Research Highlight: https://www.aei.mpg.de/1171367/what-no-one-has-seen-before-new-study-simulates-gravitational-waves-from-failing-warp-drive
Contact:
Prof. Dr. Tim Dietrich, Institute of Physics and Astronomy and Max Planck Institute for Gravitational Physics (Albert Einstein Institute) Potsdam
Tel.: +49 331 977-230160
E-Mail: tim.dietrich@uni-potsdam.de
Journal
The Open Journal of Astrophysics
Researchers discover graphene flakes in lunar soil sample
image:
(a) Laser scanning confocal microscopy image and height distribution. (b) Backscattered electron SEM image and (c) Raman spectra corresponding to different areas. (d) TEM image, Cs-corrected HAADF-STEM image, and the corresponding EELS Fe L-edge spectra for different areas. (e) Cs-corrected HRTEM images. (f) HAADF-STEM image. (g) EDS elemental maps showing spatial distributions of the elements. (h) HRTEM images of the corresponding regions marked in (f).
view moreCredit: ©Science China Press
A recent study, published in National Science Review, revealed the existence of naturally formed few-layer graphene, a substance consisting of carbon atoms in a special, thin-layered structure.
The team, led by professors Meng Zou, Wei Zhang and senior engineer Xiujuan Li from Jilin University and Wencai Ren from the Chinese Academy of Sciences’ Institute of Metal Research, analyzed an olive-shaped sample of lunar soil, about 2.9 millimeters by 1.6 mm, retrieved from the Chang’e 5 mission in 2020.
According to the team, scientists generally believe that some 1.9 percent of interstellar carbon exists in the form of graphene, with its shape and structure determined by the process of its formation.
Using a special spectrometer, researchers found an iron compound that is closely related to the formation of graphene in a carbon-rich section of the sample. They then used advanced microscopic and mapping technologies to confirm that the carbon content in the sample comprised “flakes” that have two to seven layers of graphene.
The team proposed that the few-layer graphene may have formed in volcanic activity in the early stages of the moon’s existence, and been catalyzed by solar winds that can stir up lunar soil and iron-containing minerals that helped transform the carbon atoms’ structure. They added that impact processes from meteorites, which create high-temperature and high-pressure environments, may also have led to the formation of graphene.
On Earth, graphene is becoming a star in materials sciences due to its special features in optics, electrics and mechanics. The team believes their study could help develop ways to produce the material inexpensively and expand its use.
“The mineral-catalyzed formation of natural graphene sheds light on the development of low-cost scalable synthesis techniques of high-quality graphene,” the paper said. “Therefore, a new lunar exploration program may be promoted, and some forthcoming breakthroughs can be expected.”
###
See the article:
Discovery of natural few-layer graphene on the Moon
https://doi.org/10.1093/nsr/nwae211
Journal
National Science Review
First full 2-D spectral image of aurora borealis from a hyperspectral camera
Acquisition of aurora spectral images succeeded
image:
Images of observing color differences in the aurora borealis using the advanced equipment. High energy electrons make the aurora glow at lower altitudes, producing a purple light.
view moreCredit: National Institute for Fusion Science
Auroras are natural luminous phenomena caused by the interaction of electrons falling from the sky and the upper atmosphere. Most of the observed light consists of emission lines of neutral or ionized nitrogen and oxygen atoms and molecular emission bands, and the color is determined by the transition energy levels, molecular vibrations and rotations. There is a variety of characteristic colors of auroras, such as green and red, but there are multiple theories about the emission process by which they appear in different types of auroras, and to understand the colors of auroras, the light must be broken down. Comprehensive (temporal and spatial) spectral observations are needed to study auroral emission processes and colors in detail.
Complementarily, the National Institute for Fusion Science (NIFS) has been observing the emission of light from plasma in a magnetic field in the Large Helical Device (LHD). Various systems have been developed to measure the spectrum of light emitted from the plasma, and the processes of energy transport and atomic and molecular emission have been studied. By applying this technology and knowledge to auroral observations, we can contribute to the understanding of auroral luminescence and the study of the energy production process of electrons that gives rise to auroral luminescence.
Aurora observation uses optical filters to obtain images of specific colors, which has the disadvantage of a limited acquisition wavelength with low resolution. On the other hand, a hyperspectral camera has the advantage of obtaining a spatial distribution of the spectrum with high wavelength resolution. We started a plan to develop a high-sensitivity hyperspectral camera in 2018 by combining a lens spectrometer with an EMCCD camera, which had been used in the LHD, with an image-sweep optical system using galvanometer mirrors.
It took five years from the planning stage to develop a highly sensitive system capable of measuring auroras at 1kR (1 kilo-Rayleigh). In May 2023, this system was installed at KEOPS at the Swedish Space Corporation's Esrange Space Center in Kiruna, Sweden, which is located just below the auroral belt and can observe auroras with high frequency. The system succeeded in acquiring hyperspectral images of the auroras, that is, two-dimensional images of them broken down by wavelength. Observations began in September 2023, and the data has been acquired remotely in Japan.
Auroral emission intensities and the observation positions were calibrated, based on the positions of stars obtained after installation, and the data will be made publicly available and ready to use. Using the observation data from an aurora break-up that occurred on October 20, 2023, we clarified what kind of data could be viewed using this system. In the process, we estimated the energy of electrons from the intensity ratio of light at different wavelengths, which led to the publication of this paper.
Figure 1 shows the difference in the color of the aurora when electrons arrive at low energies and speeds and when they arrive at high energies and speeds. When the electrons are slow, they emit strong red light at high altitudes. On the other hand, when the electrons are fast, they penetrate to lower altitudes and emit a strong green or purple light. Figure 2 is a two-dimensional image of auroras resolved into each color (wavelength) observed with the state-of-the-art hyperspectral camera. The different distribution by color was observed because the elements that produce the light differ according to the height at which the light is generated. Thus, we have succeeded in developing a device that can obtain two-dimensional images of the various colors produced by the aurora borealis.
From the ratio of the intensity of the red light (630nm) to the purple light (427.8nm), we can determine the energy of the incoming electrons that caused the aurora. Using the hyperspectral camera (HySCAI), which is capable of fine spectroscopy of light, the energy of the incoming electrons during the auroral explosion observed at this time was estimated to be 1600 electron volts (an energy equivalent to the voltage of about 1000 dry-cell batteries). There were no major discrepancies with previously known values, indicating that the observations were valid. The Hyperspectral Camera (HySCAI) is expected to contribute to solving important auroral issues such as the distribution of precipitating electrons, their relationship to auroral color, and the mechanism of auroral emission.
For the first time, a detailed spatial distribution of color (a two-dimensional image), a hyperspectral image of the aurora borealis, has been obtained. Many previous auroral studies have used a system in which light is selected by a filter that passes only certain wavelengths. This system compensates for the disadvantage of observing only a limited number of wavelengths. By observing detailed changes in the spectrum, it will contribute to the advancement of auroral research. On the other hand, the system will also provide insight into energy transport due to the interaction between charged particles and waves in a magnetic field, which is also attracting attention in fusion plasmas. It is expected that this interdisciplinary study will be advanced in cooperation with universities and research institutes in Japan and abroad, and will contribute to the development of worldwide aurora research.
Images of auroras resolved into each color (wavelength) observed with the state-of-the-art hyperspectral camera (HySCAI).
Credit
This work is adapted from "https://doi.org/10.57451/s40623-024-02039-y" by Springer Nature.Journal
Earth Planets and Space
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Development of Hyperspectral Camera for Auroral Imaging
Article Publication Date
2-Aug-2024
COSPAR 2024: Embracing team spirit in space research
The Committee on Space Research (COSPAR) has successfully concluded its 45th COSPAR Scientific Assembly in Busan, Korea, held from 13 to 21 July. This prestigious event brought together more than 3,000 experts and leaders from 55 countries in all major fields of space science, under the theme “Team Spirit in Space Research”. This biennial event, actively supported by major space organizations, is a benchmark for fostering dialogue and collaboration within the global space science community.
Bringing space leaders together
Of particular note this time was the showcasing of the newly-formed Korea Aerospace Administration (KASA), with the participation of Youngbin Yoon, Administrator of KASA, in the Opening Ceremony Roundtable. For the first time ever, COSPAR brought together space leaders from KASA, NASA, China National Space Administration, Agenzia Spaziale Italiana (ASI), the Indian Space Research Organisation (ISRO), the Institute of Space and Astronautical Science/Japan Aerospace Exploration Agency (ISAS/JAXA), and the UAE Space Agency. Youngbin Yoon shared his vision of the future of space activity in Korea, and the discussions on the next decade of space science programs from each agency was a highlight of the Assembly. John Lee, Deputy Administrator of Mission Directorate, KASA, also delivered an interdisciplinary lecture introducing the new Korea Aerospace Administration later in the week.
Space-Weather Roadmap presented
Another significant highlight of this Assembly was the introduction of COSPAR’s new community-driven Space-Weather Roadmap. Presented by a consortium of hundreds of scientists led by COSPAR’s Panel on Space Weather, this roadmap provides key recommendations for the global space weather community.
Space sustainability gained traction as a major recurring theme, underscoring our collective responsibility to ensure the long-term viability of space activities. The COSPAR Panel on Planetary Protection, a reference in upholding the 1967 Outer Space Treaty and providing accepted guidelines on planetary protection, presented the recently updated Planetary Protection Policy during COSPAR 2024.
To respond to the dynamic changes in the space sector, COSPAR’s Committee on Industry Relations (CIR) enables global space companies to engage with COSPAR’s scientific community. CIR organized several events during the Assembly. The panel discussion “Space 2050 – Our Future Shaped by Today’s Space Technology Advances” was particularly important by bringing experts from industry to stimulate the conversation about the challenges of space ventures in the next decades, involving all stakeholders in the space ecosystem.
COSPAR 2024: a platform for dialogue
The key strength of COSPAR 2024 is providing this platform for dialogue across nations, disciplines and sectors, enabling the formation of new international partnerships. During the Assembly, multiple interagency and B2B side meetings took place, formally and informally.
COSPAR President, Professor Pascale Ehrenfreund says: “The South Korean hospitality has been exceptional, making everyone feel welcome and valued. I want to extend my deepest gratitude to the Local Organizing Committee under the leadership of Dr James Park, and the Scientific Program Committee led by Dr Dong-Hun Lee. The selection of Busan as the host city for COSPAR 2024 underscores COSPAR’s commitment to international regional diversity and our dedication to shaping the future of the global space eco-system.”
COSPAR 2028 to be hosted in Dubai
COSPAR 2024 concluded with the news of the successful bid by the Mohamed Bin Rashid Space Research Center (MBRSC) to host the 47th COSPAR Scientific Assembly (COSPAR 2028). COSPAR is therefore proud to announce that COSPAR 2028 will be held in Dubai, United Arab Emirates, at the Dubai International Convention and Exhibition Centre, from 8 to 16 July 2028. The global space science community looks forward to building on the momentum generated in Busan. The event has set a precedent for future assemblies, demonstrating the power of international cooperation in shaping the trajectory of space science.
The 46th COSPAR Scientific Assembly (COSPAR 2026) is scheduled to be held in Florence, Italy, 1-9 August 2026, where the community will once again gather, this time in the city of the Renaissance, to share knowledge, celebrate achievements, and forge new paths in the exploration of space.
Issued by COSPAR Communications, Ms Leigh FERGUS
leigh.fergus@cosparhq.cnes.fr https://cosparhq.cnes.fr/
Key Statistics about COSPAR 2024:
Total number of participants: 3,070 from 55 countries
Total number of Quarter Days of presentations: 614
Total number of Oral Presentations: 2,475
Total number of Posters: 280
Total number of Exhibitors: 43
Total number of Sponsors: 61
Note to Editors
COSPAR, the largest international scientific society dedicated to promoting global cooperation in space research, was established in 1958. It serves as a neutral platform for scientific dialogue among scientists from around the world. Today, COSPAR comprises 46 national scientific institutions and 13 international scientific unions, with 13,000 space scientists actively participating in its activities, including attending assemblies, contributing to panels and roadmaps, and publishing in its journals. COSPAR’s core mission is to facilitate dialogue and encourage international collaboration among space stakeholders across the globe. It operates through scientific commissions, panels and task groups that encompass all disciplines of space science, from Earth and atmospheric sciences to planetary science, astrophysics, solar and space plasma physics, and life and microgravity sciences.
COSPAR Social Media
Scientists pin down the origins of the moon’s tenuous atmosphere
The barely-there lunar atmosphere is likely the product of meteorite impacts over billions of years, a new study finds.
Massachusetts Institute of Technology
While the moon lacks any breathable air, it does host a barely-there atmosphere. Since the 1980s, astronomers have observed a very thin layer of atoms bouncing over the moon’s surface. This delicate atmosphere — technically known as an “exosphere” — is likely a product of some kind of space weathering. But exactly what those processes might be has been difficult to pin down with any certainty.
Now, scientists at MIT and the University of Chicago say they have identified the main process that formed the moon’s atmosphere and continues to sustain it today. In a study appearing in Science Advances, the team reports that the lunar atmosphere is primarily a product of “impact vaporization.”
In their study, the researchers analyzed samples of lunar soil collected by astronauts during NASA’s Apollo missions. Their analysis suggests that over the moon’s 4.5-billion-year history its surface has been continuously bombarded, first by massive meteorites, then more recently, by smaller, dust-sized “micrometeoroids.” These constant impacts have kicked up the lunar soil, vaporizing certain atoms on contact and lofting the particles into the air. Some atoms are ejected into space, while others remain suspended over the moon, forming a tenuous atmosphere that is constantly replenished as meteorites continue to pelt the surface.
The researchers found that impact vaporization is the main process by which the moon has generated and sustained its extremely thin atmosphere over billions of years.
“We give a definitive answer that meteorite impact vaporization is the dominant process that creates the lunar atmosphere,” says the study’s lead author, Nicole Nie, an assistant professor in MIT’s Department of Earth, Atmospheric, and Planetary Sciences. “The moon is close to 4.5 billion years old, and through that time the surface has been continuously bombarded by meteorites. We show that eventually, a thin atmosphere reaches a steady state because it’s being continuously replenished by small impacts all over the moon.”
Nie’s co-authors are Nicolas Dauphas, Zhe Zhang, and Timo Hopp at the University of Chicago, and Menelaos Sarantos at NASA Goddard Space Flight Center.
Weathering’s roles
In 2013, NASA sent an orbiter around the moon to do some detailed atmospheric reconnaissance. The Lunar Atmosphere and Dust Environment Explorer (LADEE, pronounced "laddie") was tasked with remotely gathering information about the moon’s thin atmosphere, surface conditions, and any environmental influences on the lunar dust.
LADEE’s mission was designed to determine the origins of the moon’s atmosphere. Scientists hoped that the probe’s remote measurements of soil and atmospheric composition might correlate with certain space weathering processes that could then explain how the moon’s atmosphere came to be.
Researchers suspect that two space weathering processes play a role in shaping the lunar atmosphere: impact vaporization and “ion sputtering” — a phenomenon involving solar wind, which carries energetic charged particles from the sun through space. When these particles hit the moon’s surface, they can transfer their energy to the atoms in the soil and send those atoms sputtering and flying into the air.
“Based on LADEE’s data, it seemed both processes are playing a role,” Nie says. “For instance, it showed that during meteorite showers, you see more atoms in the atmosphere, meaning impacts have an effect. But it also showed that when the moon is shielded from the sun, such as during an eclipse, there are also changes in the atmosphere’s atoms, meaning the sun also has an impact. So, the results were not clear or quantitative.”
Answers in the soil
To more precisely pin down the lunar atmosphere’s origins, Nie looked to samples of lunar soil collected by astronauts throughout NASA’s Apollo missions. She and her colleagues at the University of Chicago acquired 10 samples of lunar soil, each measuring about 100 milligrams — a tiny amount that she estimates would fit into a single raindrop.
Nie sought to first isolate two elements from each sample: potassium and rubidium. Both elements are “volatile,” meaning that they are easily vaporized by impacts and ion sputtering. Each element exists in the form of several isotopes. An isotope is a variation of the same element, that consists of the same number of protons but a slightly different number of neutrons. For instance, potassium can exist as one of three isotopes, each one having one more neutron, and there being slightly heavier than the last. Similarly, there are two isotopes of rubidium.
The team reasoned that if the moon’s atmosphere consists of atoms that have been vaporized and suspended in the air, lighter isotopes of those atoms should be more easily lofted, while heavier isotopes would be more likely to settle back in the soil. Furthermore, scientists predict that impact vaporization, and ion sputtering, should result in very different isotopic proportions in the soil. The specific ratio of light to heavy isotopes that remain in the soil, for both potassium and rubidium, should then reveal the main process contributing to the lunar atmosphere’s origins.
With all that in mind, Nie analyzed the Apollo samples by first crushing the soils into a fine powder, then dissolving the powders in acids to purify and isolate solutions containing potassium and rubidium. She then passed these solutions through a mass spectrometer to measure the various isotopes of both potassium and rubidium in each sample.
In the end, the team found that the soils contained mostly heavy isotopes of both potassium and rubidium. The researchers were able to quantify the ratio of heavy to light isotopes of both potassium and rubidium, and by comparing both elements, they found that impact vaporization was most likely the dominant process by which atoms are vaporized and lofted to form the moon’s atmosphere.
“With impact vaporization, most of the atoms would stay in the lunar atmosphere, whereas with ion sputtering, a lot of atoms would be ejected into space,” Nie says. “From our study, we now can quantify the role of both processes, to say that the relative contribution of impact vaporization versus ion sputtering is about 70:30 or larger.” In other words, 70 percent or more of the moon’s atmosphere is a product of meteorite impacts, whereas the remaining 30 percent is a consequence of the solar wind.
“The discovery of such a subtle effect is remarkable, thanks to the innovative idea of combining potassium and rubidium isotope measurements along with careful, quantitative modeling,” says Justin Hu, a postdoc who studies lunar soils at Cambridge University, who was not involved in the study. “This discovery goes beyond understanding the moon’s history, as such processes could occur and might be more significant on other moons and asteroids, which are the focus of many planned return missions.”
“Without these Apollo samples, we would not be able to get precise data and measure quantitatively to understand things in more detail,” Nie says. “It’s important for us to bring samples back from the moon and other planetary bodies, so we can draw clearer pictures of the solar system’s formation and evolution.”
This work was supported, in part, by NASA and the National Science Foundation.
###
Written by Jennifer Chu, MIT News
Journal
Science Advances
Article Title
Lunar Soil Record of Atmosphere Loss over Eons
Article Publication Date
2-Aug-2024
DART forward: Five papers shed new light on asteroids from world’s first planetary defense test
image:
The various geological features observed on Didymos helped researchers tell the story of Didymos’ origins. The asteroid’s triangular ridge (first panel from left), and the so-called smooth region and its likely older, rougher “highland” region (second panel from left) can be explained through a combination of slope processes controlled by elevation (third panel from left). The fourth panel shows the effects of spin-up disruption that Didymos likely underwent to form Dimorphos.
view moreCredit: Credit: Johns Hopkins APL/Olivier Barnouin
In the months that followed NASA’s Double Asteroid Redirection Test (DART) mission, which sent a spacecraft to intentionally collide with an asteroid moonlet, the science team verified that kinetic impact was a viable deflection technique, proving one effective method of preventing future asteroid strikes on Earth.
Since then, researchers have continued studying data collected from the successful experiment, focusing specifically on surface features of the binary asteroid system, composed of moonlet Dimorphos and parent asteroid Didymos.
In recently published papers in Nature Communications, the team explored the geology of the asteroid system encountered in 2022 to characterize its origin and evolution, and constrain its physical characteristics. Researchers from the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, with team members from several international partner institutions led five papers that provided a detailed overview and interpretation of the geological findings.
APL scientists Olivier Barnouin and Ronald-Louis Ballouz led a paper that analyzed the geology of both asteroids and drew conclusions about their surface materials and interior properties. From images captured by DART and its accompanying LICIACube CubeSat contributed by the Italian Space Agency (ASI), the team observed the smaller asteroid Dimorphos’ topography, which featured boulders of varying sizes. In comparison, the larger asteroid Didymos was smoother at lower elevations, although rocky at higher elevations, with more craters than Dimorphos. The authors inferred that Dimorphos likely spun off from Didymos in a “large mass shedding event.” There are natural processes that can accelerate the spins of small asteroids, and there is growing evidence that these processes may be responsible for reshaping these bodies or even forcing material to be spun off their surfaces.
Analysis suggested that both Didymos and Dimorphos have weak surface characteristics, which led the team to posit that Didymos has a surface age 40-130 times older than Dimorphos, with the former estimated to be 12.5 million years old and the latter less than 300,000 years old. The low surface strength of Dimorphos likely contributed to DART’s significant impact on its orbit.
“The images and data that DART collected at the Didymos system provided a unique opportunity for a close-up geological look at a near-Earth asteroid binary system,” said Barnouin. “From these images alone, we were able to infer a great deal of information on geophysical properties of both Didymos and Dimorphos, and expand our understanding of the formation of these two asteroids. We also better understand why DART was so effective in moving Dimorphos.”
Maurizio Pajola, of the National Institute for Astrophysics (INAF), and co-authors led a paper comparing the shapes and sizes of the various boulders and their distribution patterns on the two asteroids’ surfaces. They determined that the physical characteristics of Dimorphos indicate it formed in stages, likely of material inherited from its parent asteroid Didymos. That conclusion reinforces the prevailing theory that some binary asteroid systems arise from shed remnants of a larger primary asteroid accumulating into a new asteroid moonlet.
Alice Lucchetti, also of INAF, and colleagues found that thermal fatigue — the gradual weakening and cracking of a material caused by heat — could rapidly break up boulders on the surface of Dimorphos, generating surface lines and altering the physical characteristics of this type of asteroid more quickly than previously thought. The DART mission was likely the first observation of such a phenomenon on this type of asteroid.
Supervised by ISAE-SUPAERO researcher Naomi Murdoch and colleagues, students Jeanne Bigot and Pauline Lombardo led a paper that determined Didymos’ bearing capacity — the surface’s ability to support applied loads — to be at least 1,000 times lower than that of dry sand on Earth or lunar soil. This is considered an important parameter for understanding and predicting the response of a surface, including for the purposes of displacing an asteroid.
Colas Robin, also of ISAE-SUPAERO, and co-authors analyzed the surface boulders on Dimorphos, comparing them with those on other rubble pile asteroids, including Itokawa, Ryugu and Bennu. The researchers found the boulders shared similar characteristics, suggesting all these types of asteroids formed and evolved in a similar fashion. The team also noted that “the elongated nature of the boulders around the DART impact site implies that they were likely formed through impact processing.”
These latest findings form a more robust overview of the origins of the Didymos system and add to the understanding of how such planetary bodies were formed. They also provide new insights into why DART was so effective in shifting Dimorphos’ orbit. As the European Space Agency’s (ESA) Hera mission prepares to revisit DART’s collision site in 2026 to further analyze the aftermath of the first-ever planetary defense test, this research provides a series of tests for what Hera will find, and contributes to current and future exploration missions while bolstering planetary defense capabilities.
APL managed the DART mission for NASA’s Planetary Defense Coordination Office as a project of the agency’s Planetary Missions Program Office. NASA provided support for the mission from several centers, including the Jet Propulsion Laboratory in Southern California; Goddard Space Flight Center in Greenbelt, Maryland; Johnson Space Center in Houston; Glenn Research Center in Cleveland; and Langley Research Center in Hampton, Virginia.
Dydymos Ridge Formation [VIDEO] |
Based on the internal and surface properties described in Barnouin et al. (2024), this video demonstrates how the spin-up of asteroid Didymos could have led to the growth of its equatorial ridge and the formation of the smaller asteroid Dimorphos, seen orbiting the former near the end of the clip. Particles are colored according to their speeds, with the scale shown at the top, along with the continually changing spin period of Didymos.
Credit
Credit: University of Michigan/Yun Zhang and Johns Hopkins APL/Olivier Barnouin
Journal
Nature Communications
Method of Research
Systematic review
Subject of Research
Not applicable
Article Title
The Geology and Evolution of the Near-Earth Binary Asteroid System (65803) Didymos
Key to rapid planet formation
Ludwig-Maximilians-Universität München
A team of LMU researchers has developed a new model to explain the formation of giant planets such as Jupiter, which furnishes deeper insights into the processes of planet formation and could expand our understanding of planetary systems.
Our solar system is our immediate cosmic neighborhood. We know it well: the Sun at the center; then the rocky planets Mercury, Venus, Earth, and Mars; and then the asteroid belt; followed by the gas giants Jupiter and Saturn; then the ice giants Uranus and Neptune; and finally the Kuiper belt with its comets. But how well do we really know our home? Previous theories have assumed that giant planets are formed by collisions and accumulations of asteroid-like celestial bodies, so-called planetesimals, and the subsequent accretion of gas over the course of millions of years. However, these models explain neither the existence of gas giants located far from their stars nor the formation of Uranus and Neptune.
From grain of dust to giant planet
Astrophysicists from LMU, the ORIGINS cluster, and MPS have developed the first ever model to incorporate all the necessary physical processes that play a role in planet formation. Using this model, they have shown that annular perturbations in protoplanetary disks, so-called substructures, can trigger the rapid formation of multiple gas giants. The results of the study match the latest observations and indicate that the formation of giant planets could happen more efficiently and quickly than previously thought.
With their model, the researchers demonstrate how millimeter-sized dust particles accumulate aerodynamically in the turbulent gas disk, and how this initial perturbation in the disk traps dust and prevents it from disappearing off in the direction of the star. This accumulation makes the growth of planets very efficient, as suddenly a lot of “building material” is available within a compact area and the right conditions for planet formation are present.
“When a planet gets large enough to influence the gas disk, this leads to renewed dust enrichment farther out in the disk,” explains Til Birnstiel, Professor of Theoretical Astrophysics at LMU and member of the ORIGINS Cluster of Excellence. “In the process, the planet drives the dust – like a sheepdog chasing its herd – into the area outside its own orbit.” The process begins anew, from inside to outside, and another giant planet can form. “This is the first time a simulation has traced the process whereby fine dust grows into giant planets,” observes Tommy Chi Ho Lau, lead author of the study and doctoral candidate at LMU.
Variety of gas giants in our and other solar systems
In our solar system, the gas giants are situated at a distance of around 5 astronomical units (au) (Jupiter) to 30 au (Neptune) from the Sun. For comparison, the Earth is some 150 million kilometers from the Sun, which is equivalent to 1 au.
The study shows that in other planetary systems, a perturbation could set the process in motion at much larger distances and still happen very rapidly. Such systems have been observed frequently in recent years by the ALMA radio observatory, which has found gas giants in young disks at a distance beyond 200 au. However, the model also explains why our solar system apparently stopped forming additional planets after Neptune: the building material was simply used up.
The results of the study match current observations of young planetary systems that have pronounced substructures in their disks. These substructures play a decisive role in planet formation. The study indicates that the formation of giant planets and gas giants proceeds with greater efficiency and speed than previously assumed. These new insights could refine our understanding of the origin and development of the giant planets in our solar system and explain the diversity of observed planetary systems.
Journal
Astronomy and Astrophysics
Article Title
Sequential giant planet formation initiated by disc substructure
Article Publication Date
1-Aug-2024
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