ST/ The Moon is 40 million years older than previously thought

November 9th 2023

Space biweekly vol.87, 24th October — 9th November

TL;DR

By analyzing tiny lunar crystals gathered by Apollo 17 astronauts in 1972, researchers recalculated the age of the Earth’s Moon. Although previous assessments estimated the Moon as 4.425 billion years old, the new study discovered it is actually 4.46 billion years old — 40 million years older than previously thought.
An international team has spotted a remote blast of cosmic radio waves lasting less than a millisecond. This ‘fast radio burst’ (FRB) is the most distant ever detected. Its source was pinned down by the European Southern Observatory’s (ESO) Very Large Telescope (VLT) in a galaxy so far away that its light took eight billion years to reach us. The FRB is also one of the most energetic ever observed; in a tiny fraction of a second it released the equivalent of our Sun’s total emission over 30 years.
Two years after the striking discovery that a near-Earth asteroid could be a chunk of the moon, another UArizona research group has found that a rare pathway could have enabled this to happen.
NASA’s JWST has discovered a new, never-before-seen feature in Jupiter’s atmosphere. The high-speed jet stream, which spans more than 3,000 miles wide, sits over Jupiter’s equator above the main cloud decks. The discovery of this jet is giving insights into how the layers of Jupiter’s famously turbulent atmosphere interact with each other, and how Webb is uniquely capable of tracking those features.
Researchers have shown it’s theoretically possible for black holes to exist in perfectly balanced pairs — held in equilibrium by a cosmological force — mimicking a single black hole.
Scientists have announced the results of an unprecedented collaboration to search for the source of the largest-ever seismic event recorded on Mars. The study rules out a meteorite impact, suggesting instead that the quake was the result of enormous tectonic forces within Mars’ crust.
Using tools hitched to the nose cone of their research planes and sampling more than 11 miles above the planet’s surface, researchers have discovered significant amounts of metals in aerosols in the atmosphere, likely from increasingly frequent launches and returns of spacecraft and satellites. That mass of metal is changing atmospheric chemistry in ways that may impact Earth’s atmosphere and the ozone layer.
An unexpectedly high number of young stars has been identified in the direct vicinity of a supermassive black hole and water ice has been detected at the center of our galaxy.
The ability to have access to the Internet or use a mobile phone anywhere in the world is taken more and more for granted, but the brightness of the Internet and telecommunications satellites that enable global communications networks could pose problems for ground-based astronomy. Scientists confirm that recently deployed satellites are as bright as stars seen by the unaided eye.
Before human research is conducted during commercial spaceflights, it should be ‘ethically cleared to launch,’ according to a global team of scientists, health policy experts and commercial spaceflight professionals.
And more!

Space industry in numbers

The global smart space market size is projected to grow from USD 9.4 billion in 2020 to USD 15.3 billion by 2025, at a Compound Annual Growth Rate (CAGR) of 10.2% during the forecast period. The increasing venture capital funding and growing investments in smart space technology to drive market growth.

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

Space industry news

Latest research

4.46 Ga zircons anchor chronology of lunar magma ocean

by J Greer, B Zhang, D Isheim, D.N. Seidman, A. Bouvier, P.R. Heck in Geochemical Perspectives Letters

Led by researchers at the Field Museum and the University of Glasgow, the study was made possible by Northwestern University’s atom-probe tomography facility, which “nailed down” the age of the oldest crystal in the sample. By revealing the age of these telltale zircon crystals — found hidden within dust collected from the Moon — researchers were able to piece together the timeline of the Moon’s formation.

“This study is a testament to immense technological progress we have made since 1972 when the last manned Moon mission returned to Earth,” said Northwestern’s Dieter Isheim, who co-authored the study. “These samples were brought to Earth half-a-century ago, but only today do we have the necessary tools to perform microanalysis at the requisite level, including atom-probe tomography.”

The atom-by-atom analysis enabled researchers to count how many atoms in the zircon crystals have undergone radioactive decay. When an atom undergoes decay, it sheds protons and neutrons to transform into different elements. Uranium, for example, decays into lead. Because scientists have established how long it takes for this process to unfold, they can assess the age of a sample by looking at the proportion of uranium and lead atoms.

Secondary electron images of zircon Z14. a) Top-down image showing SIMS pits, b) image tilted at 55°, showing zircon with Pt deposit to be lifted out. The approximate positions of the sampling locations (A to D shown in red) for the successful APT runs are labelled. Scale bars shown.

“Radiometric dating works a little bit like an hourglass,” said the Field Museum’s Philipp Heck, the study’s senior author. “In an hourglass, sand flows from one glass bulb to another, with the passage of time indicated by the accumulation of sand in the lower bulb. Radiometric dating works similarly by counting the number of parent atoms and the number of daughter atoms they have transformed to. The passage of time can then be calculated because the transformation rate is known.”

Isheim is a research associate professor of materials science and engineering at Northwestern’s McCormick School of Engineering and manager of Northwestern’s Center for Atom-Probe Tomography (NUCAPT). David Seidman, the Walter P. Murphy Professor Emeritus of Materials Science and Engineering at McCormick and founding director of NUCAPT, also co-authored the study. Heck is the Field Museum’s Robert A. Pritzker Curator for Meteorites and Polar Studies, senior director of the Negaunee Interactive Research Center and professor at the University of Chicago. Jennika Greer, a research associate professor at the University of Glasgow, is the study’s lead author. When the research began, she was a Ph.D. candidate in Heck’s laboratory.

More than 4 billion years ago, when the solar system was still young and the Earth was still growing, a giant Mars-sized object crashed into the Earth. A colossal hunk broke off Earth to form the Moon, and the energy of the impact melted the rock that eventually became the Moon’s surface.

“When the surface was molten like that, zircon crystals couldn’t form and survive,” Heck said. “So, any crystals on the Moon’s surface must have formed after this lunar magma ocean cooled. Otherwise, they would have been melted and their chemical signatures would be erased.”

Nearest neighbour distribution of Pb for all analysed tomographic datasets. To the left are the distributions of Pb atoms (shown as distance between pairs; D-pair) in the sample (red) and randomised distributions (black). On the right are plots of mass spectra of each of the 5 datasets for the mass-to-charge-state ratio (MtCSR) range around Pb. The red dashed lines define the range of the Pb peak that was included in the nearest neighbour calculation.

Because the crystals must have formed after the magma ocean cooled, determining the age of the zircon crystals would reveal the minimum possible age of the Moon. But, to pinpoint the maximum possible age of the Moon, researchers turned to Northwestern’s atom-probe tomography instruments.

“In atom-probe tomography, we start by sharpening a piece of the lunar sample into a very sharp tip, using a focused ion beam microscope, almost like a very fancy pencil sharpener,” Greer said. “Then, we use UV lasers to evaporate atoms from the surface of that tip. The atoms travel through a mass spectrometer, and how fast they move tells us how heavy they are, which in turn tells us what they’re made of.”

After determining the materials in the sample and performing radiometric dating, the researchers concluded that the oldest crystals are about 4.46 billion years old. That means the Moon must be at least that old.

It’s important to know when the Moon formed, Heck said, because “the Moon is an important partner in our planetary system. It stabilizes the Earth’s rotational axis. It’s the reason there are 24 hours in a day. It’s the reason we have tides. Without the Moon, life on Earth would look different. It’s a part of our natural system that we want to better understand, and our study provides a tiny puzzle piece in that whole picture.”

Researchers have recorded images of a solar eclipse with the ‘ring of fire’ effect in radio waves.

A luminous fast radio burst that probes the Universe at redshift 1

by S. D. Ryder, K. W. Bannister, S. Bhandari, A. T. Deller, R. D. Ekers, M. Glowacki, A. C. Gordon, K. Gourdji, C. W. James, C. D. Kilpatrick, W. Lu, L. Marnoch, V. A. Moss, J. X. Prochaska, H. Qiu, E. M. Sadler, S. Simha, M. W. Sammons, D. R. Scott, N. Tejos, R. M. Shannon in Science

An international team has spotted a remote blast of cosmic radio waves lasting less than a millisecond. This ‘fast radio burst’ (FRB) is the most distant ever detected. Its source was pinned down by the European Southern Observatory’s (ESO) Very Large Telescope (VLT) in a galaxy so far away that its light took eight billion years to reach us. The FRB is also one of the most energetic ever observed; in a tiny fraction of a second it released the equivalent of our Sun’s total emission over 30 years.

The discovery of the burst, named FRB 20220610A, was made in June last year by the ASKAP radio telescope in Australia and it smashed the team’s previous distance record by 50 percent.

“Using ASKAP’s array of dishes, we were able to determine precisely where the burst came from,” says Stuart Ryder, an astronomer from Macquarie University in Australia and the co-lead author of the study. “Then we used [ESO’s VLT] in Chile to search for the source galaxy, finding it to be older and further away than any other FRB source found to date and likely within a small group of merging galaxies.”

The discovery confirms that FRBs can be used to measure the ‘missing’ matter between galaxies, providing a new way to ‘weigh’ the Universe. Current methods of estimating the mass of the Universe are giving conflicting answers and challenging the standard model of cosmology.

“If we count up the amount of normal matter in the Universe — the atoms that we are all made of — we find that more than half of what should be there today is missing,” says Ryan Shannon, a professor at the Swinburne University of Technology in Australia, who also co-led the study. “We think that the missing matter is hiding in the space between galaxies, but it may just be so hot and diffuse that it’s impossible to see using normal techniques.”

Artist’s impression of a record-breaking fast radio burst.

“Fast radio bursts sense this ionised material. Even in space that is nearly perfectly empty they can ‘see’ all the electrons, and that allows us to measure how much stuff is between the galaxies,” Shannon says.

Finding distant FRBs is key to accurately measuring the Universe’s missing matter, as shown by the late Australian astronomer Jean-Pierre (‘J-P’) Macquart in 2020. “J-P showed that the further away a fast radio burst is, the more diffuse gas it reveals between the galaxies. This is now known as the Macquart relation. Some recent fast radio bursts appeared to break this relationship. Our measurements confirm the Macquart relation holds out to beyond half the known Universe,” says Ryder.

“While we still don’t know what causes these massive bursts of energy, the paper confirms that fast radio bursts are common events in the cosmos and that we will be able to use them to detect matter between galaxies, and better understand the structure of the Universe,” says Shannon.

Lunar ejecta origin of near-Earth asteroid Kamo’oalewa is compatible with rare orbital pathways

by Jose Daniel Castro-Cisneros, Renu Malhotra, Aaron J. Rosengren in Communications Earth & Environment

In 2021, a team of University of Arizona astronomers suggested that a recently discovered near-Earth asteroid, Kamo`oalewa, could be a chunk of the moon. Two years after the striking discovery, another UArizona research group has found that a rare pathway could have enabled this to happen.

So far, only distant asteroids from beyond the orbit of Mars have been considered a source of near-Earth asteroids, said Renu Malhotra, Regents Professor of Planetary Sciences and a senior author on the paper.

“We are now establishing that the moon is a more likely source of Kamo`oalewa,” Malhotra said.

The implication is that many more lunar fragments remain to be discovered among the near-Earth asteroid population. UArizona researchers decided to study Kamo`oalewa for two reasons. Kamo`oalewa is uncommon in that it is Earth’s quasi-satellite, a term used for asteroids whose orbits are so Earth-like that they appear to orbit Earth even though they actually orbit the sun.

The other peculiar aspect of Kamo`oalewa is its longevity, said Jose Daniel Castro-Cisneros, the study’s lead author and a graduate student in the Department of Physics. Kamo`oalewa is expected to remain as a companion of the Earth for millions of years, which is its remarkable feature, Castro-Cisneros said, unlike other known objects that stay in these very Earth-like orbits only for a few decades. Aaron Rosengren, a former assistant professor in the Department of Aerospace and Mechanical Engineering, in the College of Engineering, was part of the study. Rosengren is now at the University of California, San Diego.

The 2021 study found that Kamo`oalewa’s spectrum was unlike that of other near-Earth asteroids but matched most closely that of the moon. Based on this, the team hypothesized that the asteroid could have been ejected from the lunar surface as a result of a meteoroidal impact.

Summary of orbital outcomes of lunar ejecta particles in orbital parameter space.

In the new study, Malhotra and her team wanted to determine the feasibility for a knocked-off piece of the moon to get into this quasi-satellite orbit — a phenomenon that is quite unlikely, Malhotra said. Moon fragments that have enough kinetic energy to escape the Earth-moon system also have too much energy to land in the Earth-like orbits of quasi-satellites, she said. With numerical simulations that accurately account for the gravitational forces of all the solar system’s planets, Malhotra’s group found that some lucky lunar fragments could actually find their way to such orbits. Kamo`oalewa could be one of those fragments created during an impact on the moon in the past few million years, according to the study.

Throughout its history, the moon has been bombarded by asteroids, which is evident in the numerous impact craters preserved on its surface, explained Malhotra. Impact craters are created when asteroids or meteorites crash into the surface of a planet or the moon. Impacts cause lunar material to be ejected from the moon’s surface, but most of that material usually falls back on the moon, she said.

Some of the ejected materials fall on Earth, and that’s how we get meteorites from the moon, Malhotra said. But a small fraction could escape the gravity of both the moon and the Earth and end up orbiting around the sun like other near-Earth asteroids. Numerical simulation suggests that Kamo`oalewa could be one of even tinier fractions that gained entry into the hard-to-reach Earth’s co-orbital space.

The study’s findings could help understand more about near-Earth asteroids, which are considered a hazard to Earth, Malhotra said. More detailed studies of Kamo`oalewa and determining this asteroid’s origin in a specific impact crater on the moon will provide useful insights on impact mechanics, she said.

In the future, Castro-Cisneros said the team is planning to identify the specific conditions that allowed the orbital pathway of Kamo`oalewa. The group is also aiming to work on determining Kamo`oalewa’s exact age, he said.

“We looked at Kamo`oalewa’s spectrum only because it was in an unusual orbit,” Malhotra said. “If it had been a typical near-Earth asteroid, no one would have thought to find its spectrum and we wouldn’t have known Kamo`oalewa could be a lunar fragment.”

An intense narrow equatorial jet in Jupiter’s lower stratosphere observed by JWST

by Ricardo Hueso, Agustín Sánchez-Lavega, et al in Nature Astronomy

NASA’s James Webb Space Telescope has discovered a new, never-before-seen feature in Jupiter’s atmosphere. The high-speed jet stream, which spans more than 3,000 miles (4,800 kilometers) wide, sits over Jupiter’s equator above the main cloud decks. The discovery of this jet is giving insights into how the layers of Jupiter’s famously turbulent atmosphere interact with each other, and how Webb is uniquely capable of tracking those features.

“This is something that totally surprised us,” said Ricardo Hueso of the University of the Basque Country in Bilbao, Spain, lead author on the paper describing the findings. “What we have always seen as blurred hazes in Jupiter’s atmosphere now appear as crisp features that we can track along with the planet’s fast rotation.”

The research team analyzed data from Webb’s NIRCam (Near-Infrared Camera) captured in July 2022. The Early Release Science program — jointly led by Imke de Pater from the University of California, Berkeley and Thierry Fouchet from the Observatory of Paris — was designed to take images of Jupiter 10 hours apart, or one Jupiter day, in four different filters, each uniquely able to detect changes in small features at different altitudes of Jupiter’s atmosphere.

“Even though various ground-based telescopes, spacecraft like NASA’s Juno and Cassini, and NASA’s Hubble Space Telescope have observed the Jovian system’s changing weather patterns, Webb has already provided new findings on Jupiter’s rings, satellites, and its atmosphere,” de Pater noted.

NIRCam images of Jupiter.

While Jupiter is different from Earth in many ways — Jupiter is a gas giant, Earth is a rocky, temperate world — both planets have layered atmospheres. Infrared, visible, radio, and ultraviolet light wavelengths observed by these other missions detect the lower, deeper layers of the planet’s atmosphere — where gigantic storms and ammonia ice clouds reside.

On the other hand, Webb’s look farther into the near-infrared than before is sensitive to the higher-altitude layers of the atmosphere, around 15–30 miles (25–50 kilometers) above Jupiter’s cloud tops. In near-infrared imaging, high-altitude hazes typically appear blurry, with enhanced brightness over the equatorial region. With Webb, finer details are resolved within the bright hazy band.

The newly discovered jet stream travels at about 320 miles per hour (515 kilometers per hour), twice the sustained winds of a Category 5 hurricane here on Earth. It is located around 25 miles (40 kilometers) above the clouds, in Jupiter’s lower stratosphere.

By comparing the winds observed by Webb at high altitudes, to the winds observed at deeper layers from Hubble, the team could measure how fast the winds change with altitude and generate wind shears.

While Webb’s exquisite resolution and wavelength coverage allowed for the detection of small cloud features used to track the jet, the complementary observations from Hubble taken one day after the Webb observations were also crucial to determine the base state of Jupiter’s equatorial atmosphere and observe the development of convective storms in Jupiter’s equator not connected to the jet.

“We knew the different wavelengths of Webb and Hubble would reveal the three-dimensional structure of storm clouds, but we were also able to use the timing of the data to see how rapidly storms develop,” added team member Michael Wong of the University of California, Berkeley, who led the associated Hubble observations.

The researchers are looking forward to additional observations of Jupiter with Webb to determine if the jet’s speed and altitude change over time.

“Jupiter has a complicated but repeatable pattern of winds and temperatures in its equatorial stratosphere, high above the winds in the clouds and hazes measured at these wavelengths,” explained team member Leigh Fletcher of the University of Leicester in the United Kingdom. “If the strength of this new jet is connected to this oscillating stratospheric pattern, we might expect the jet to vary considerably over the next 2 to 4 years — it’ll be really exciting to test this theory in the years to come.”
“It’s amazing to me that, after years of tracking Jupiter’s clouds and winds from numerous observatories, we still have more to learn about Jupiter, and features like this jet can remain hidden from view until these new NIRCam images were taken in 2022,” continued Fletcher.

Static Black Binaries in de Sitter Space

by Óscar J. C. Dias, Gary W. Gibbons, Jorge E. Santos, Benson Way in Physical Review Letters

Researchers from the University of Southampton, together with colleagues from the universities of Cambridge and Barcelona, have shown it’s theoretically possible for black holes to exist in perfectly balanced pairs — held in equilibrium by a cosmological force — mimicking a single black hole.

Black holes are massive astronomical objects that have such a strong gravitational pull that nothing, not even light, can escape. They are incredibly dense. A black hole could pack the mass of the Earth into a space the size of a pea.

Conventional theories about black holes, based on Einstein’s theory of General Relativity, typically explain how static or spinning black holes can exist on their own, isolated in space. Black holes in pairs would eventually be thwarted by gravity attracting and colliding them together. However, this is true if one assumes the Universe is standing still. But what about one which is constantly moving? Could pairs of black holes exist in harmony in an ever expanding Universe, perhaps masquerading as one?

“The standard model of cosmology assumes that the Big Bang brought the Universe into existence and that, approximately 9.8 billion years ago, it became dominated by a mysterious force, coined ‘dark energy’, which accelerates the Universe at a constant rate,” says Professor Oscar Dias of the University of Southampton.

Two black holes at fixed distance. Credit: APS/Alan Stonebraker.

Scientists refer to this mysterious force as a ‘cosmological constant’. In a Universe explained by Einstein’s theory with a cosmological constant, black holes are immersed in a cosmological accelerated background. This moves the theoretical goal posts over how black holes can interact and exist together.

Through complex numerical methods, the team behind this latest study show that two static (non-spinning) black holes can exist in equilibrium — their gravitational attraction offset by the expansion associated with a cosmological constant. Even in the acceleration of an ever expanding Universe, the black holes remain locked at a fixed distance from one another. As hard as expansion may try to pull them apart, the gravitational attraction compensates.

“Viewed from a distance, a pair of black holes whose attraction is offset by cosmic expansion would look like a single black hole. It might be hard to detect whether it is a single black hole or a pair of them,” comments Professor Dias.
Professor Jorge Santos of the University of Cambridge adds: “Our theory is proven for a pair of static black holes, but we believe it could be applied to spinning ones too. Also, it seems plausible that our solution could hold true for three or even four black holes, opening up a whole range of possibilities.”

A Tectonic Origin for the Largest Marsquake Observed by InSight

by Benjamin Fernando, Ingrid J. Daubar, et al in Geophysical Research Letters

A global team of scientists have announced the results of an unprecedented collaboration to search for the source of the largest ever seismic event recorded on Mars. The study, led by the University of Oxford, rules out a meteorite impact, suggesting instead that the quake was the result of enormous tectonic forces within Mars’ crust.

The quake, which had a magnitude of 4.7 and caused vibrations to reverberate through the planet for at least six hours, was recorded by NASA’s InSight lander on May 4 2022. Because its seismic signal was similar to previous quakes known to be caused by meteoroid impacts, the team believed that this event (dubbed ‘S1222a’) might have been caused by an impact as well, and launched an international search for a fresh crater.

Although Mars is smaller than Earth, it has a similar land surface area because it has no oceans. In order to survey this huge amount of ground — 144 million km2 — study lead Dr Benjamin Fernando of the University of Oxford sought contributions from the European Space Agency, the Chinese National Space Agency, the Indian Space Research Organisation, and the United Arab Emirates Space Agency. This is thought to be the first time that all missions in orbit around Mars have collaborated on a single project. Each group examined data from their satellites orbiting Mars to look for a new crater, or any other tell-tale signature of an impact (e.g. a dust cloud appearing in the hours after the quake).

After several months of searching, the team announced today that no fresh crater was found. They conclude that the event was instead caused by the release of enormous tectonic forces within Mars’ interior. The results indicate that the planet is much more seismically active than previously thought.

Seismograms from the S1222a event and the two confirmed impact-generated events, S1000a and S1094b.

Dr Fernando said: ‘We still think that Mars doesn’t have any active plate tectonics today, so this event was likely caused by the release of stress within Mars’ crust. These stresses are the result of billions of years of evolution; including the cooling and shrinking of different parts of the planet at different rates. We still do not fully understand why some parts of the planet seem to have higher stresses than others, but results like these help us to investigate further. One day, this information may help us to understand where it would be safe for humans to live on Mars and where you might want to avoid!’
He added: ‘This project represents a huge international effort to help solve the mystery of S1222a, and I am incredibly grateful to all the missions who contributed. I hope this project serves as a template for productive international collaborations in deep space.’

Dr Daniela Tirsch, Science Coordinator for the High Resolution Stereo Camera on board the European Space Agency’s Mars Express Spacecraft said: ‘This experiment shows how important it is to maintain a diverse set of instruments at Mars, and we are very glad to have played our part in completing the multi-instrumental and international approach of this study.’

From China, Dr Jianjun Liu (National Astronomical Observatories, Chinese Academy of Sciences) added: ‘We are willing to collaborate with scientists around the world to share and apply this scientific data to get more knowledge about Mars, and are proud to have provided data from the colour imagers on Tianwen-1 to contribute to this effort.’

Dr Dimitra Atri, Group Leader for Mars at New York University Abu Dhabi and contributor of data from the UAE’s Hope Spacecraft, said: ‘This has been a great opportunity for me to collaborate with the InSight team, as well as with individuals from other major missions dedicated to the study of Mars. This really is the golden age of Mars exploration!’

Dr Constantinos Charalambous of Imperial College London, a co-author on the study, said: ‘The absence of a crater in our image search for S1222a marks a significant milestone in interpreting seismic signals on Mars, crucial for distinguishing impact events from tectonic forces on the Red Planet.’

S1222a was one of the last events recorded by InSight before its end of mission was declared in December 2022. The team are now moving forward by applying knowledge from this study to future work, including upcoming missions to the Moon and Saturn’s moon Titan.

Metals from spacecraft reentry in stratospheric aerosol particles

by Daniel M. Murphy, Maya Abou-Ghanem, Daniel J. Cziczo, Karl D. Froyd, Justin Jacquot, Michael J. Lawler, Christopher Maloney, John M. C. Plane, Martin N. Ross, Gregory P. Schill, Xiaoli Shen in Proceedings of the National Academy of Sciences

The Space Age is leaving fingerprints on one of the most remote parts of the planet — the stratosphere — which has potential implications for climate, the ozone layer and the continued habitability of Earth.

Using tools hitched to the nose cone of their research planes and sampling more than 11 miles above the planet’s surface, researchers have discovered significant amounts of metals in aerosols in the atmosphere, likely from increasingly frequent launches and returns of spacecraft and satellites. That mass of metal is changing atmospheric chemistry in ways that may impact Earth’s atmosphere and ozone layer.

“We are finding this human-made material in what we consider a pristine area of the atmosphere,” said Dan Cziczo, one of a team of scientists who published a study. “And if something is changing in the stratosphere — this stable region of the atmosphere — that deserves a closer look.” Cziczo, professor and head of the Department of Earth, Atmospheric, and Planetary Sciences in Purdue’s College of Science, is an expert in atmospheric science who has spent decades studying this rarefied region.

Led by Dan Murphy, an adjunct professor in the Department of Earth, Atmospheric, and Planetary Sciences and a researcher at the National Oceanic and Atmospheric Administration, the team detected more than 20 elements in ratios that mirror those used in spacecraft alloys. They found that the mass of lithium, aluminum, copper and lead from spacecraft reentry far exceeded those metals found in natural cosmic dust. Nearly 10% of large sulfuric acid particles — the particles that help protect and buffer the ozone layer — contained aluminum and other spacecraft metals.

Scientists estimate that as many as 50,000 more satellites may reach orbit by 2030. The team calculates that means that, in the next few decades, up to half of stratospheric sulfuric acid particles would contain metals from reentry. What effect that could have on the atmosphere, the ozone layer and life on Earth is yet to be understood.

Scientists have long suspected that spacecraft and satellites were changing the upper atmosphere, but studying the stratosphere, where we don’t live and even the highest flights enter only briefly, is challenging.

As part of NASA’s Airborne Science Program, Murphy and his group fly a WB-57 airplane to sample the atmosphere 11.8 miles (19 km) above the ground in Alaska, where circumpolar clouds tend to form. Similar measurements were made by Cziczo and his group from an ER-2 aircraft over the continental United States. Both groups use instruments hitched to the nose cone to ensure that only the freshest, most undisturbed air is sampled.

Like the view of the unruffled surface of the ocean, the stratosphere appears untroubled — at least to human eyes. Life and civilization take place mostly on the planet’s surface and in the troposphere, the atmosphere’s very lowest layer. The stratosphere is a surprisingly stable and seemingly serene layer of the atmosphere.

The stratosphere is also the realm of the ozone layer: that gaseous marvel that acts as a global tent to shield the planet and all life on it from the searing, scorching rays of ultraviolet radiation. Without the ozone layer, life would likely never have arisen on Earth. And without it, life is unlikely to be able to continue.

The last decades have been eventful for the stratosphere. The ozone layer came under threat from chlorofluorocarbons in the 1980s, and only coordinated, sustained global efforts of governments and corporations have begun to bear fruit in repairing and replenishing it.

“Shooting stars streak through the atmosphere,” Cziczo said. “Often, the meteor burns up in the atmosphere and doesn’t even become a meteorite and reach the planet. So the material it was made from stays in the atmosphere in the form of ions. They form very hot gas, which starts to cool and condense as molecules and fall into the stratosphere. The molecules find each other and knit together and form what we call meteorite smoke. Scientists recently started noticing that the chemical fingerprint of these meteoritic particles was starting to change, which made us ask, ‘Well, what changed?’ because meteorite composition hasn’t changed. But the number of spacecraft has.”

Examples of mass spectra of single particles in the stratosphere.

Spacecraft launches, and returns, were once international events. The launches of Sputnik and the Mercury missions were front-page news. Now, a quickening tide of innovation and loosening regulation means that dozens of countries and corporations are able to launch satellites and spacecraft into orbit. All those satellites have to be sent up on rockets — and most of that material, eventually, comes back down.

Like the wakes of great ships trolling through the ocean, rockets leave behind them a trail of metals that may change the atmosphere in ways scientists don’t yet understand.

“Just to get things into orbit, you need all this fuel and a huge body to support the payload,” Cziczo said. “There are so many rockets going up and coming back and so many satellites falling back through the atmosphere that it’s starting to show up in the stratosphere as these aerosol particles.”

Of course, shooting stars were the first space-delivery system. Meteorites fall through the atmosphere every day. The heat and friction of the atmosphere peel material off them, just as they do off human-made artifacts. However, while hundreds of meteors enter the Earth’s atmosphere every day, they are increasingly being rivaled by the mass of metals that comprise the tons of Falcon, Ariane and Soyuz rockets that boost spacecraft into space and return again to Earth’s surface.

“Changes to the atmosphere can be difficult to study and complex to understand,” Cziczo said. “But what this research shows us is that the impact of human occupation and human spaceflight on the planet may be significant — perhaps more significant than we have yet imagined. Understanding our planet is one of the most urgent research priorities there is.”

**The Evaporating Massive Embedded Stellar Cluster IRS 13 Close to Sgr A*. I. Detection of a Rich Population of Dusty Objects in the IRS 13 Cluster**

by Florian Peißker, Michal Zajaček, Lauritz Thomkins, Andreas Eckart, Lucas Labadie, Vladimír Karas, Nadeen B. Sabha, Lukas Steiniger, Maria Melamed in The Astrophysical Journal

An unexpectedly high number of young stars has been identified in the direct vicinity of a supermassive black hole and water ice has been detected at the center of our galaxy.

An international team led by Dr Florian Peißker at the University of Cologne’s Institute of Astrophysics has analysed in detail a young star cluster in the immediate vicinity of the super massive black hole Sagittarius A* (Sgr A*) in the centre of our galaxy and showed that it is significantly younger than expected. This cluster, known as IRS13, was discovered more than twenty years ago, but only now has it been possible to determine the cluster members in detail by combining a wide variety of data — taken with various telescopes over a period of several decades. The stars are a few 100,000 years old and therefore extraordinarily young for stellar conditions. By comparison, our sun is about 5 billion years old. Due to the high-energy radiation as well as the tidal forces of the galaxy, it should in fact not be possible for such a large number of young stars to be in the direct vicinity of the super massive black hole.

Sketch of a class I YSO.

In connection with the current study, a further outstanding result has also been published. For the first time, the James Webb Space Telescope (JWST) was used to record a spectrum free of atmospheric interference from the Galactic Center. A prism on board the telescope was developed at the Institute of Astrophysics in the working group led by Professor Dr Andreas Eckart, a co-author of the publication. The present spectrum shows that there is water ice in the Galactic Center. This water ice, which is often found in the dusty discs around very young stellar objects, is another independent indicator of the young age of some stars near the black hole.

In addition to the unexpected detection of young stars and water ice by the JWST, the researchers led by Dr Peißker have also found that IRS13 has a turbulent history of formation behind it. The study results suggest that IRS13 migrated toward the super massive black hole through friction with the interstellar medium, collisions with other star clusters, or internal processes. From a certain distance, the cluster was then ‘captured’ by the gravitation of the black hole. In this process, a bow shock may have formed at the top of the cluster from the dust surrounding the cluster, similar to the tip of a ship in the water. The associated increase in dust density then stimulated further star formation. This is an explanation why these young stars are above all in the top or front of the cluster.

“The analysis of IRS13 and the accompanying interpretation of the cluster is the first attempt to unravel a decade-old mystery about the unexpectedly young stars in the Galactic Center,” according to Dr Peißker. “In addition to IRS13, there is a star cluster, the so-called S-cluster, which is even closer to the black hole and also consists of young stars. They are also significantly younger than would be possible according to accepted theories.” The findings on IRS13 provide the opportunity in further research to establish a connection between the direct vicinity of the black hole and regions several light years away.

Dr Michal Zajaček, second author of the study and scientist at Masaryk University in Brno (Czech Republic), added: “The star cluster IRS13 seems to be the key to unravelling the origin of the dense star population at the centre of our galaxy. We have gathered extensive evidence that very young stars within the range of the super massive black hole may have formed in star clusters such as IRS13. This is also the first time we have been able to identify star populations of different ages — hot main sequence stars and young emerging stars — in the cluster so close to the centre of the Milky Way.”

The high optical brightness of the BlueWalker 3 satellite

by Sangeetha Nandakumar, Siegfried Eggl, et al in Nature

The ability to have access to the Internet or use a mobile phone anywhere in the world is taken more and more for granted, but the brightness of Internet and telecommunications satellites that enable global communications networks could pose problems for ground-based astronomy. University of Illinois Urbana-Champaign aerospace engineer Siegfried Eggl coordinated an international study confirming recently deployed satellites are as bright as stars seen by the unaided eye.

“From our observations, we learned that AST Space Mobile’s BlueWalker 3 — a constellation prototype satellite featuring a roughly 700 square-foot phased-array antenna — reached a peak brightness of magnitude 0.4, making it one of the brightest objects in the night sky,” Eggl said. “Although this is record breaking, the satellite itself is not our only concern. The untracked Launch Vehicle Adapter had an apparent visual magnitude of 5.5, which is also brighter than the International Astronomical Union recommendation of magnitude 7.”

For comparison, the brightness of the stars we can see with an unaided eye is between minus 1 and 6 magnitude, minus 1 being the brightest. Sirius, the brightest star, is minus 1. Planets like Venus can sometimes be a bit brighter — closer to minus 4, but the faintest stars we can see are roughly magnitude 6.

“One might think if there are bright stars, a few more bright satellites won’t make a difference. But several companies plan to launch constellations,” Eggl said. “For example, Starlink already has permission to launch thousands of satellites, but they’ll probably get their full request of tens of thousands granted eventually.

Measured brightness from nine passes of BlueWalker 3 as observed from Steward Observatory. The colored dots correspond to measurements of the optical brightness of the BlueWalker 3 satellite. At its peak BlueWalker 3 reached 0.4 magnitudes, which made it one of the brightest objects in the night sky.

“And that’s just one constellation of satellites. Europe and China want their own constellations and so does Russia. Just those in the United States being negotiated with the FCC amount to 400,000 satellites being launched in the near future. There are only 1,000 stars you can see with the unaided eye. Adding 400,000 bright satellites that move could completely change the night sky.”

Eggl is a member of the International Astronomical Union Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference, IAU.

“BlueWalker 3 is so bright that most of the big telescopes such as the Rubin Observatory believe it could obliterate large parts of exposures,” Eggl said. “They already have to avoid observing Mars and Venus for the same reason, but we know where the planets are so we can dodge them. We cannot accurately predict where all the satellites will be years in advance. Just accepting recurring data loss in multi-billion-dollar observatories is not an option either.”

He said although satellites won’t necessarily damage the telescope’s CCDs, or charge-coupled devices, they will still cause data loss from the streaks. Extremely bright satellites could ruin the entire field of view, like trying to stargaze when someone periodically shines a flashlight into your eyes.

Eggl said several solutions to the problem are being explored in collaboration with the Laboratory for Advanced Space Systems at Illinois and satellite operators such as SpaceX.

“Starlink is looking at making their satellites’ surfaces darker, which absorbs more and reflects less visible sunlight. But the absorption generates heat. The satellites then have to emit infrared light which means observations in optical wavelengths don’t have as large of a problem, but infrared observations might. And heat is one of the biggest engineering problems that we have in space. So, painting everything black comes with repercussions,” he said.

Another idea from SpaceX is to make satellites’ solar panels more reflective with dielectric mirrors. The mirrors allow the satellites to change the direction of the reflection so that it’s not pointing directly at the Earth.

“If SpaceX can make the solar panels point in a different direction to avoid glints, or use these mirror tricks, they might solve a lot of the problems we have with the optical flaring of Starlink satellites,” Eggl said. “With other providers, it’s not quite as easy. AST has gigantic satellites, with hundreds of square feet of electronic phased arrays, that they need to communicate with cell phones on the ground. If they made satellites smaller more of their radio signals would leak out through so-called ‘side lobes’ potentially affecting radio astronomy sites.

Eggl said AST also prefers to keep the satellite pointed toward the surface of the Earth to achieve maximum efficiency. Starlink solutions may not easily translate to AST satellites and new mitigation strategies are needed.

“We are trying to work with the space industry, where possible,” he said. “We want to solve this together so it’s a collaborative effort that everybody can sign onto because that’s the fastest route to get things done.”

Ethically cleared to launch?

by Vasiliki Rahimzadeh, Jennifer Fogarty, et al in Science

A global, multidisciplinary team of bioethicists, health policy experts, commercial spaceflight professionals and space health researchers, including Rachael Seidler from the University of Florida, has developed guiding principles and best practices to help ensure human research conducted in space is safe and inclusive.

The proposed ethical guidelines were released Friday in a policy paper published in Science and are the result of a workshop held at the Banbury Center of Cold Spring Harbor Laboratory funded by the Translational Research Institute for Space Health, or TRISH, at Baylor College of Medicine.

“With commercial companies taking more people each year to space, opportunities for human space travel are rapidly expanding,” said Seidler, a professor of applied physiology and kinesiology at UF, “and it’s important that experiments taking place in space are as safe and productive as possible.”

About 30 individuals participated in the workshop, most of whom were health policy experts, scientists with expertise in bioethics, government regulators, and representatives from private spaceflight companies, Seidler said.

“We outlined potential ethical concerns facing the future of commercial space research and established guidelines for those who are traveling to space on their own dime,” she said. “We made our recommendations, and hopefully that will kickstart conversations.”

While there are many government-sponsored research missions in space that operate under clear ethical guidelines, few guidelines and best practices exist for conducting responsible research in the commercial sector, said Dr. Vasiliki Rahimzadeh, first author of the paper and assistant professor at the Center for Medical Ethics and Health Policy at Baylor.

“Now is the time to develop that ethical framework, and it must be a multidisciplinary effort across the private and public sector,” she said.

In the paper, the team proposes ethical guidelines for commercial space research based on four principles: social responsibility of research participants, scientific excellence in gathering research data, proportionality in balancing risks of spaceflight, and global stewardship in diverse participation. The authors also outline the need for adapting existing research practices and policies to commercial space flight, including informed consent, data protection, and steps to minimize health risks to participants.

The paper’s authors point out that what is learned through space health research is valuable not only for future spaceflight but also for informing health issues on Earth.

“That’s why it was important to have had the private space companies at the table helping establish best practices,” Seidler said. “They are participating in something that is paving the way for everyone and can benefit all mankind.”