Hidden magmatism discovered at the Chang'e-6 lunar landing site

Lunar igneous activities including intrusive and extrusive magmatism, and their products contain significant information about the lunar interior and its thermal state. Their distribution is asymmetrical on the nearside and farside, reflecting the global lunar dichotomy. In addition to previously returned lunar samples all from nearside (Apollo, Luna, and Chang'e-5), samples from the South Pole-Aitken (SPA) basin on the farside have long been thought to hold the key to rebalancing the asymmetrical understandings of the Moon and disclosing the lunar dichotomy conundrum.

Earlier this year, the Chang'e-6 mission of the Chinese Lunar Exploration Program, successfully launched on May 3, landed on the lunar surface on June 2, and returned to the Earth on June 25 carrying a total of 1935.3g of lunar soils. It is the world's first lunar farside sample-return mission, which landed in the south of the Apollo basin within the SPA basin on the farside. These precious samples would open a window to solve the long-standing question of lunar dichotomy, even reshape human's knowledge of our closest neighbour. However, compared with the well-known mare volcanism surrounding the Chang'e-6 landing site, the intrusive magmatic activities have a much more obscure presence and origin, impeding future sample analyses when they are available for application.

In a recent research paper published in The Astrophysical Journal Letters, Dr Yuqi QIAN, Professor Joseph MICHALSKI and Professor Guochun ZHAO from the Department of Earth Sciences at The University of Hong Kong (HKU) and their domestic and international collaborators have comprehensively studied the intrusive magmatism of the Chang'e-6 landing site and its surroundings based on remote sensing data. The study revealed their extensive distributions and obscure nature with significant implications for the petrogenesis of lunar plutonic rocks and the Chang'e-6 mission, which will facilitate scientists' further study of lunar farside.

The study has found that intrusive magmatism is widespread in the SPA basin. They occur in various forms including sills beneath floor-modified craters, linear and ring dikes shown by gravity data, and Mg-suite intrusions with characteristic spectral absorptions. These observations agree with the intermediate-thick crust of SPA where intrusion is favored. Landing in the SPA basin, Chang'e-6 likely collected plutonic rocks, excavated and transported by adjacent impact craters to the sampling site, that could be examined by the ongoing sample studies. They have discovered two heavily degraded floor-fractured craters, inspiring to identify more similar features on the Moon. All indicate that intrusive magmatism is abundant in the Chang'e-6 sampling region.

This study has traced potential plutonic materials in the Chang'e-6 samples and found that Mg-suite materials highly likely exist, primarily from the western peak ring of the Apollo basin delivered by Chaffee S crater. These Mg-rich materials contain crucial information on the origin of mysterious KREEP-poor Mg-suite rocks. Samples from both the intrusive and extrusive magmatism from the never sampled farside, especially the mysterious Mg-suite, will shed further light on solving the lunar dichotomy conundrum and a series of fundamental scientific questions relating to secondary crust building and early evolution of the Moon.

Professor Xianhua LI, an academician of the Chinese Academy of Science (CAS), and a leader of China's lunar sample studies from the Institute of Geology and Geophysics (CAS), said: 'The results of this research set a significant geological framework to study plutonic rocks in the Chang'e-6 samples, especially Mg-suite rocks.' Professor Li emphasised: 'Their petrogenesis and timing are unclear, and this research would dramatically help to understand their origin mechanism.'

'This research is an excellent example of HKU's deep involvement in the China's Lunar Exploration Program,' said Professor Guochun ZHAO, an academician of the Chinese Academy of Science and Chair Professor of Earth Sciences (HKU). 'Lunar and space exploration programs are an important component of China's goal to become a scientific and technological power, and HKU's proactive involvement in these programs will bring additional resources for Hong Kong to become an international centre for science and innovation,' he continued.

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Scientists devise method to secure Earth's biodiversity on the moon

New research led by scientists at the Smithsonian proposes a plan to safeguard Earth's imperiled biodiversity by cryogenically preserving biological material on the moon. The moon's permanently shadowed craters are cold enough for cryogenic preservation without the need for electricity or liquid nitrogen, according to the researchers.

The paper, published today in BioScience and written in collaboration with researchers from the Smithsonian's National Zoo and Conservation Biology Institute (NZCBI), Smithsonian's National Museum of Natural History, Smithsonian's National Air and Space Museum and others, outlines a roadmap to create a lunar biorepository, including ideas for governance, the types of biological material to be stored and a plan for experiments to understand and address challenges such as radiation and microgravity. The study also demonstrates the successful cryopreservation of skin samples from a fish, which are now stored at the National Museum of Natural History.

"Initially, a lunar biorepository would target the most at-risk species on Earth today, but our ultimate goal would be to cryopreserve most species on Earth," said Mary Hagedorn, a research cryobiologist at NZCBI and lead author of the paper. "We hope that by sharing our vision, our group can find additional partners to expand the conversation, discuss threats and opportunities and conduct the necessary research and testing to make this biorepository a reality."

The proposal takes inspiration from the Global Seed Vault in Svalbard, Norway, which contains more than 1 million frozen seed varieties and functions as a backup for the world's crop biodiversity in case of global disaster. By virtue of its location in the Arctic nearly 400 feet underground, the vault was intended to be capable of keeping its seed collection frozen without electricity. However, in 2017, thawing permafrost threatened the collection with a flood of meltwater. The seed vault has since been waterproofed, but the incident showed that even an Arctic, subterranean bunker could be vulnerable to climate change.

Unlike seeds, animal cells require much lower storage temperatures for preservation (-320 degrees Fahrenheit or -196 degrees Celsius). On Earth, cryopreservation of animal cells requires a supply of liquid nitrogen, electricity and human staff. Each of these three elements are potentially vulnerable to disruptions that could destroy an entire collection, Hagedorn said.

To reduce these vulnerabilities, scientists needed a way to passively maintain cryopreservation storage temperatures. Since such cold temperatures do not naturally exist on Earth, Hagedorn and her co-authors looked to the moon.

The moon's polar regions feature numerous craters that never receive sunlight due to their orientation and depth. These so-called permanently shadowed regions can be −410 degrees Fahrenheit (−246 degrees Celsius) -- more than cold enough for passive cryopreservation storage. To block out the DNA-damaging radiation present in space, samples could be stored underground or inside a structure with thick walls made of moon rocks.

At the Hawai?i Institute of Marine Biology, the research team cryopreserved skin samples from a reef fish called the starry goby. The fins contain a type of skin cell called fibroblasts, the primary material to be stored in the National Museum of Natural History's biorepository. When it comes to cryopreservation, fibroblasts have several advantages over other types of commonly cryopreserved cells such as sperm, eggs and embryos. Science cannot yet reliably preserve the sperm, eggs and embryos of most wildlife species. However, for many species, fibroblasts can be cryopreserved easily. In addition, fibroblasts can be collected from an animal's skin, which is simpler than harvesting eggs or sperm. For species that do not have skin per se, such as invertebrates, Hagedorn said the team may use a diversity of types of samples depending on the species, including larvae and other reproductive materials.

The next steps are to begin a series of radiation exposure tests for the cryopreserved fibroblasts on Earth to help design packaging that could safely deliver samples to the moon. The team is actively seeking partners and support to conduct additional experiments on Earth and aboard the International Space Station. Such experiments would provide robust testing for the prototype packaging's ability to withstand the radiation and microgravity associated with space travel and storage on the moon.

If their idea becomes a reality, the researchers envision the lunar biorepository as a public entity to include public and private funders, scientific partners, countries and public representatives with mechanisms for cooperative governance akin to the Svalbard Global Seed Bank.

"We aren't saying what if the Earth fails -- if the Earth is biologically destroyed this biorepository won't matter," Hagedorn said. "This is meant to help offset natural disasters and, potentially, to augment space travel. Life is precious and, as far as we know, rare in the universe. This biorepository provides another, parallel approach to conserving Earth's precious biodiversity."

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Scientists pin down the origins of the moon's tenuous atmosphere

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."

Read more at Science Daily

The hidden role of the Milky Way in ancient Egyptian mythology

Ancient Egyptians were known for their religious beliefs and astronomical knowledge of the Sun, Moon, and planets, but up until now it has been unclear what role the Milky Way played in Egyptian religion and culture.

A new study by a University of Portsmouth astrophysicist sheds light on the relationship between the Milky Way and the Egyptian sky-goddess Nut.

Nut is goddess of the sky, who is often depicted as a star-studded woman arched over her brother, the earth god Geb.

She protects the earth from being flooded by the encroaching waters of the void, and plays a key role in the solar cycle, swallowing the Sun as it sets at dusk and giving birth to it once more as it rises at dawn.

The paper draws on ancient Egyptian texts and simulations to argue that the Milky Way might have shone a spotlight, as it were, on Nut's role as the sky.

It proposes that in winter, the Milky Way highlighted Nut's outstretched arms, while in summer, it traced her backbone across the heavens.

Associate Professor in Astrophysics, Dr Or Graur, said: "I chanced upon the sky-goddess Nut when I was writing a book on galaxies and looking into the mythology of the Milky Way. I took my daughters to a museum and they were enchanted by this image of an arched woman and kept asking to hear stories about her.

"This sparked my interest and I decided to combine both astronomy and Egyptology to do a double analysis -- astronomical and cross-cultural -- of the sky-goddess Nut, and whether she really could be linked to the Milky Way."

Dr Graur drew from a rich collection of ancient sources including the Pyramid Texts, Coffin Texts, and the Book of Nut and compared them alongside sophisticated simulations of the Egyptian night sky.

He found compelling evidence that the Milky Way highlighted Nut's divine presence.

Furthermore, Dr Graur connected Egyptian beliefs with those of other cultures, showing similarities in how different societies interpret the Milky Way.

He said: "My study also shows that Nut's role in the transition of the deceased to the afterlife and her connection to the annual bird migration are consistent with how other cultures understand the Milky Way. For example, as a spirits' road among different peoples in North and Central America or as the Birds' Path in Finland and the Baltics.

Read more at Science Daily

The metalens meets the stars

Metalenses have been used to image microscopic features of tissue and resolve details smaller than a wavelength of light. Now they are going bigger.

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a 10-centimeter-diameter glass metalens that can image the sun, the moon and distant nebulae with high resolution.

It is the first all-glass, large-scale metalens in the visible wavelength that can be mass produced using conventional CMOS fabrication technology.

The research is published in ACS Nano.

"The ability to accurately control the size of tens of billions of nanopillars over an unprecedentedly large flat lens using state-of-the-art semiconductor foundry processes is a nanofabrication feat that opens exciting new opportunities for space science and technology," said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS and senior author of the paper.

Most flat metalenses, which use millions of pillar-like nanostructures to focus light, are about the size of a piece of glitter.

In 2019, Capasso and his team developed a centimeter-scale metalens using a technique called deep-ultraviolet (DUV) projection lithography,which projects and forms a nanostructure pattern that can be directly etched into the glass wafer, eliminating the time-consuming writing and deposition processes that were required for previous metalenses.

DUV projection lithography is commonly used to pattern fine lines and shapes in silicon chips for smartphones and computers.

Joon-Suh Park, a former graduate student at SEAS and current postdoctoral fellow in Capasso's team, demonstrated that the technique could not only be used to mass produce metalenses but also increase their size for applications in virtual and augmented reality.

But making the metalens even larger for applications in astronomy and free-space optical communications posed an engineering problem.

"There is a major limitation with the lithography tool because these tools are used to make computer chips, so chip size is restricted to no more than 20 to 30 millimeters," said Park, co-first author of the paper.

"In order to make a 100-millimeter diameter lens, we needed to find a way around this limitation."

Park and the team developed a technique to stitch together several patterns of nanopillars using the DUV projection lithography tool.

By dividing the lens into 25 sections but using only the 7 sections of a quadrant considering the rotational symmetry, the researchers showed that DUV projection lithography could pattern 18.7 billion designed nanostructures onto a 10-centimeter circular area in a matter of minutes.

The team also developed a vertical glass etching technique that allows the creation of high-aspect ratio, smooth-sidewall nanopillars etched into glass.

"Using the same DUV projection lithography, one could produce large-diameter, aberration-correcting meta-optics or even larger lenses on larger glass diameter wafers as the corresponding CMOS foundry tools become increasingly available in the industry," said Soon Wei Daniel Lim, a postdoctoral fellow at SEAS and co-first author of the paper.

Lim played a lead role in the full simulation and characterization of all the possible fabrication errors that could arise during mass-manufacturing processes and how they could impact the optical performance of metalenses.

After addressing possible manufacturing challenges, the researchers demonstrated the power of the metalens in imaging celestial objects.

Mounting the metalens on a tripod with a color filter and camera sensor, Park and the team took to the roof of Harvard's Science Center.

There, they imaged the Sun, the moon and the North America nebula, a dim nebula in the constellation Cygnus about 2,590 light years away.

"We were able to get very detailed images of the Sun, the moon and the nebula that are comparable to images taken by conventional lenses" said Arman Amirzhan, a graduate student in the Capasso Lab and co-author of the paper.

Using only the metalens, the researchers were able to image the same cluster of sunspots as a NASA image taken that same day.

The team also demonstrated that the lens could survive exposure to extreme heat, extreme cold and the intense vibrations that would occur during a space launch without any damage or loss in optical performance.

Because of its size and monolithic glass composition, the lens could also be used for long-range telecommunications and directed energy transport applications.

Read more at Science Daily

Exploding stars

When massive stars or other stellar objects explode in the Earth's cosmic neighborhood, ejected debris can also reach our solar system. Traces of such events are found on Earth or the Moon and can be detected using accelerator mass spectrometry, or AMS for short. An overview of this exciting research is provided in the scientific journal Annual Review of Nuclear and Particle Science (DOI: 10.1146/annurev-nucl-011823-045541) by Prof. Anton Wallner of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), who soon plans to decisively advance this promising branch of research with the new, ultrasensitive AMS facility "HAMSTER."

In their paper, HZDR physicist Anton Wallner and colleague Prof. Brian D. Fields from the University of Illinois in Urbana, USA, provide an overview of near-Earth cosmic explosions with a particular focus on events that occurred three and, respectively, seven million years ago.

"Fortunately, these events were still far enough away, so they probably did not significantly impact the Earth's climate or have major effects on the biosphere. However, things get really uncomfortable when cosmic explosions occur at a distance of 30 light-years or less," Wallner explains. Converted into the astrophysical unit parsec, this corresponds to less than eight to ten parsecs.

Once massive stars have burned up all their fuel, their cores collapse into an ultra-dense neutron star or a black hole, while at the same time, hot gas is ejected outward at a high velocity. A large part of the gas and dust finely dispersed between the stars is carried away by an expanding shock wave. Like a giant balloon with bumps and dents, this envelope also sweeps up any material already present in space. After many thousands of years, the remnants of a supernova have expanded to a diameter of several 10 parsecs, spreading out ever more slowly until the motion finally ceases.

A nearby explosion has the potential to severely disrupt the Earth's biosphere and cause a mass extinction similar to the asteroid impact 66 million years ago. The dinosaurs and many other animal species fell victim to that event. "If we consider the time period since the solar system's formation, which spans billions of years, very close cosmic explosions cannot be ruled out," Wallner emphasizes.

Nevertheless, supernovae only occur in very heavy stars with more than eight to ten times the mass of our sun. Such stars are rare. One of the closest candidates of this size is the red supergiant Betelgeuse in the constellation of Orion, located at a safe distance of about 150 parsecs from our solar system.

Production of interstellar isotopes

Many new atoms are generated during cosmic explosions or shortly before and during the supernova -- among them also a number of radioactive atoms. Wallner is particularly interested in the radioactive iron isotope with the atomic mass of 60. About half of these isotopes, called iron-60 for short, have turned into a stable nickel isotope after 2.6 million years. Therefore, all iron-60 that was present at the Earth's formation some 4,500 million years ago has long since disappeared.

"Iron-60 is extremely rare on Earth because, by natural means, it is not produced in any significant amount. However, it is produced in large quantities just before a supernova takes place. If this isotope now turns up in sediments from the ocean floor or in material from the surface of the moon, it probably came from a supernova or another similar process in space that has taken place near Earth only a few million years ago," Wallner summarizes.

The same applies to the plutonium isotope with the atomic mass of 244. However, this plutonium-244 is more likely generated by the collision of neutron stars than by supernovae. Thus, it is an indicator of the nucleosynthesis of heavy elements. After a period of 80 million years, about half of the plutonium-244 isotope has turned into other elements. Therefore, the slowly decaying plutonium-244 is, in addition to iron-60, another indicator of galactic events and the production of new elements in the last millions of years.

"Exactly how often, where, and under what conditions these heavy elements are produced is currently the subject of intense scientific debate. Plutonium-244 also requires explosive events and, according to theory, is produced similarly to the elements gold or platinum, which have always occurred naturally on Earth but consist of stable atoms today," Wallner explains.

Dust particles as cosmic cargo vessels

But how do these isotopes get to Earth in the first place? The iron-60 atoms ejected by the supernova like to congregate in dust particles. So do the plutonium-244 isotopes, which were possibly created in other events and swept up by the supernova's expanding envelope. After cosmic explosions at a distance of more than ten but less than 150 parsecs, according to theory, the solar wind and the magnetic field of the heliosphere prevent individual atoms from reaching the Earth. However, the iron-60 and plutonium-244 atoms trapped in dust particles continue to fly toward the Earth and the Moon, where they can eventually trickle down to the surface.

Even with a supernova occurring within the so-called "kill radius" of less than ten parsecs, not even a microgram of matter from the envelope will land on each square centimeter. In fact, only very few iron-60 atoms per square centimeter reach the Earth each year. This poses an enormous challenge to "investigators" like physicist Anton Wallner: Within a one-gram sediment sample, perhaps a few thousand iron-60 atoms are distributed like needles in a haystack among billions times billions of the ubiquitous and stable iron atoms with the atomic mass of 56. On top of that, even the most sensitive measurement method may only detect every five thousandth particle, i.e., a maximum of only a few iron-60 atoms in a typical measurement sample.

Such extremely low concentrations can only be determined with Accelerator Mass Spectrometry, short AMS. One of these facilities, the Dresden AMS (DREAMS), is located at the HZDR, soon to be joined by the Helmholtz Accelerator Mass Spectrometer Tracing Environmental Radionuclides (HAMSTER). Since AMS facilities around the globe are designed differently, the various facilities can complement each other in the search for rare isotopes from supernova explosions.

20 years for just one thousand iron-60 atoms

Isotopes of the same element but with a different mass, like the naturally occurring iron-56, are removed with mass filters. Atoms of other elements with the same mass as the target object iron-60, for example, the naturally occurring nickel-60, also interfere. Even after very complex chemical preparation of the samples, they are still billions of times more abundant than iron-60 and must be separated in a special accelerator facility using nuclear physics methods.

In the end, perhaps five individual iron-60 atoms are identified in a measuring process that lasts several hours. Pioneering work on iron-60 detection was conducted at TU Munich. Presently, however, Canberra at the Australian National University is the only existing facility worldwide that is sensitive enough to perform such measurements.

In total, only about one thousand iron-60 atoms have been measured in the past 20 years. For the interstellar plutonium-244, which occurs in concentrations more than 10,000 times lower, only data for individual atoms were available for a long time. Only recently has it been possible to determine about a hundred plutonium-244 atoms at a specialized infrastructure in Sydney -- similar to the HAMSTER facility currently under development at the HZDR.

However, only certain samples are suitable for investigation, which act as archives to preserve these atoms coming from space for millions of years. Samples from the Earth's surface, for example, are rapidly "diluted" by geological processes. Sediments and crusts from the deep sea, which slowly form undisturbed on the ocean floor, are ideal. Alternatively, samples from the lunar surface are suitable because disruptive processes are hardly a problem.

On a research trip until the beginning of November 2023, Wallner and his colleagues will hunt for further cosmic isotopes at particularly suitable AMS facilities in the Australian cities of Canberra (iron-60) and Sydney (plutonium-244). For this purpose, he has received a number of lunar samples from the U.S. space agency NASA.

Read more at Science Daily

The remains of an ancient planet lie deep within Earth

In the 1980s, geophysicists made a startling discovery: two continent-sized blobs of unusual material were found deep near the center of the Earth, one beneath the African continent and one beneath the Pacific Ocean. Each blob is twice the size of the Moon and likely composed of different proportions of elements than the mantle surrounding it.

Where did these strange blobs -- formally known as large low-velocity provinces (LLVPs) -- come from? A new study led by Caltech researchers suggests that they are remnants of an ancient planet that violently collided with Earth billions of years ago in the same giant impact that created our Moon.

The study, published in the journal Nature on November 1, also proposes an answer to another planetary science mystery. Researchers have long hypothesized that the Moon was created in the aftermath of a giant impact between Earth and a smaller planet dubbed Theia, but no trace of Theia has ever been found in the asteroid belt or in meteorites. This new study suggests that most of Theia was absorbed into the young Earth, forming the LLVPs, while residual debris from the impact coalesced into the Moon.

The research was led by Qian Yuan, O.K. Earl Postdoctoral Scholar Research Associate in the laboratories of both Paul Asimow (MS '93, PhD '97), the Eleanor and John R. McMillan Professor of Geology and Geochemistry; and Michael Gurnis, the John E. And Hazel S. Smits Professor of Geophysics and Clarence R. Allen Leadership Chair, director of Caltech's Seismological Laboratory, and director of the Schmidt Academy for Software Engineering at Caltech.

Scientists first discovered the LLVPs by measuring seismic waves traveling through the earth. Seismic waves travel at different speeds through different materials, and in the 1980s, the first hints emerged of large-scale three-dimensional variations deep within the structure of Earth. In the deepest mantle, the seismic wave pattern is dominated by the signatures of two large structures near the Earth's core that researchers believe possess an unusually high level of iron. This high iron content means the regions are denser than their surroundings, causing seismic waves passing through them to slow down and leading to the name "large low velocity provinces."

Yuan, a geophysicist by training, was attending a seminar about planet formation given by Mikhail Zolotov, a professor at Arizona State University, in 2019. Zolotov presented the giant-impact hypothesis, while Qian noted that the Moon is relatively rich in iron. Zolotov added that no trace had been found of the impactor that must have collided with the Earth.

"Right after Mikhail had said that no one knows where the impactor is now, I had a 'eureka moment' and realized that the iron-rich impactor could have transformed into mantle blobs," says Yuan.

Yuan worked with multidisciplinary collaborators to model different scenarios for Theia's chemical composition and its impact with Earth. The simulations confirmed that the physics of the collision could have led to the formation of both the LLVPs and the Moon. Some of Theia's mantle could have become incorporated into the Earth's own, where it ultimately clumped and crystallized together to form the two distinct blobs detectable today at Earth's core-mantle boundary today; other debris from the collision mixed together to form the Moon.

Given such a violent impact, why did Theia's material clump into the two distinct blobs instead of mixing together with the rest of the forming planet? The researchers' simulations showed that much of the energy delivered by Theia's impact remained in the upper half of the mantle, leaving Earth's lower mantle cooler than estimated by earlier, lower-resolution impact models. Because the lower mantle was not totally melted by the impact, the blobs of iron-rich material from Theia stayed largely intact as they sifted down to the base of the mantle, like the colored masses of paraffin wax in a turned-off lava lamp. Had the lower mantle been hotter (that is, if it had received more energy from the impact), it would have mixed more thoroughly with the iron-rich material, like the colors in a stirred pot of paints.

The next steps are to examine how the early presence of Theia's heterogeneous material deep within the earth might have influenced our planet's interior processes, such as plate tectonics.

Read more at Science Daily

The Moon is 40 million years older than previously thought

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.

The study was published today (Oct. 23) in the journal Geochemical Perspectives Letters.

"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.

"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."

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."

Read more at Science Daily

New findings suggest Moon may have less water than previously thought

A team including Southwest Research Institute's Dr. Raluca Rufu recently calculated that most of the Moon's permanently shadowed regions (PSRs) are at most around 3.4 billion years old and can contain relatively young deposits of water ice. Water resources are considered key for sustainable exploration of the Moon and beyond, but these findings suggest that current estimates for cold-trapped ices are too high.

The current tilt of the Moon's spin axis combined with its orbital inclination -- the angle to Earth's orbital plane -- and the Sun's low angle creates permanent shadows at its poles. PSRs are some of the coldest spots in the solar system, allowing them to trap volatile chemicals, including water ice, that would immediately transform directly from a solid to a gas in the harsh, airless sunshine that falls in most other places on the Moon.

"We think the Earth-Moon system formed following a giant impact between early Earth and another protoplanet," said Rufu, a Sagan Fellow who is the second author of a Science Advances paper. "The Moon formed from the impact-generated debris disk, migrating away from Earth over time. Around 4.1 billion years ago the Moon experienced a major spin axis reorientation when its tilt reached high angles before it damped down to the configuration we see today. As the axial tilt decreased, PSRs appeared at the poles and grew over time."

The team used AstroGeo22, a new Earth-Moon evolution simulation tool, to calculate the Moon's axial tilt over time. Together with surface height measurements from the Lunar Orbital Altimeter Laser data (LOLA), the team estimated the evolution of the shadowed areas over time.

"The time evolution of the Moon-Earth distance remained an unsolved problem for half a century," Rufu said. "However, these new geological proxies for the history of the Earth-Moon system allow us to calculate the Moon's axial tilt and the extent of PSRs over time."

In 2009, NASA crashed the two-ton Atlas Centaur rocket body, part of the Lunar Crater Observation and Sensing Satellite (LCROSS), near the south pole of the Moon. It struck the floor of Cabeus crater, creating a plume of debris examined for the presence of water and other chemicals in the lunar regolith. A shepherding satellite travelling four minutes behind the Centaur and several Earth-orbiting satellites, including the Hubble Space Telescope, monitored the impact.

"Our work suggests that Cabeus crater became a PSR less than a billion years ago. The various volatiles detected in the plume created by LCROSS indicate that ice-trapping continued into relatively recent times," said Norbert Schörghofer, the lead author of this paper from the Planetary Science Institute. "Impacts and outgassing are potential sources of water but peaked early in lunar history, when the present-day PSRs did not yet exist. The age of PSRs largely determines the amount of water ice that could be trapped in the lunar polar regions. Information about the abundance of water ice in PSRs is particularly important in planning for upcoming crewed and uncrewed missions to the Moon searching for water."

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Electrons from Earth may be forming water on the Moon

A team of researchers, led by a University of Hawai'i (UH) at Manoa planetary scientist, discovered that high energy electrons in Earth's plasma sheet are contributing to weathering processes on the Moon's surface and, importantly, the electrons may have aided the formation of water on the lunar surface. The study was published today in Nature Astronomy.

Understanding the concentrations and distributions of water on the Moon is critical to understanding its formation and evolution, and to providing water resources for future human exploration. The new discovery may also help explain the origin of the water ice previously discovered in the lunar permanently shaded regions.

Due to Earth's magnetism, there is a force field surrounding the planet, referred to as the magnetosphere, that protects Earth from space weathering and damaging radiation from the Sun. Solar wind pushes the magnetosphere and reshapes it, making a long tail on the night side. The plasma sheet within this magnetotail is a region consisting of high energy electrons and ions that may be sourced from Earth and the solar wind.

Previously, scientists mostly focused on the role of high energy ions on the space weathering of the Moon and other airless bodies. Solar wind, which is composed of high energy particles such as protons, bombards the lunar surface and is thought to be one of the primary ways in which water has been formed on the Moon.

Building on his previous work that showed oxygen in Earth's magnetotail is rusting iron in the Moon's polar regions, Shuai Li, assistant researcher in the UH Manoa School of Ocean and Earth Science and Technology (SOEST), was interested in investigating the changes in surface weathering as the Moon passes through Earth's magnetotail, an area that almost completely shields the Moon from solar wind but not the Sun's light photons.

"This provides a natural laboratory for studying the formation processes of lunar surface water," said Li. "When the Moon is outside of the magnetotail, the lunar surface is bombarded with solar wind. Inside the magnetotail, there are almost no solar wind protons and water formation was expected to drop to nearly zero."

Li and co-authors analyzed the remote sensing data that were collected by the Moon Mineralogy Mapper instrument onboard India's Chandrayaan 1 mission between 2008 and 2009. Specifically they assessed the changes in water formation as the Moon traversed through Earth's magnetotail, which includes the plasma sheet.

"To my surprise, the remote sensing observations showed that the water formation in Earth's magnetotail is almost identical to the time when the Moon was outside of the Earth's magnetotail," said Li. "This indicates that, in the magnetotail, there may be additional formation processes or new sources of water not directly associated with the implantation of solar wind protons. In particular, radiation by high energy electrons exhibits similar effects as the solar wind protons."

"Altogether, this finding and my previous findings of rusty lunar poles indicate that the mother Earth is strongly tied with its Moon in many unrecognized aspects," said Li.

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Why the day is 24 hours long: Astrophysicists reveal why Earth's day was a constant 19.5 hours for over a billion years

A team of astrophysicists at the University of Toronto (U of T) has revealed how the slow and steady lengthening of Earth's day caused by the tidal pull of the moon was halted for over a billion years.

They show that from approximately two billion years ago until 600 million years ago, an atmospheric tide driven by the sun countered the effect of the moon, keeping Earth's rotational rate steady and the length of day at a constant 19.5 hours.

Without this billion-year pause in the slowing of our planet's rotation, our current 24-hour day would stretch to over 60 hours.

The study describing the result, 'Why the day is 24 hours long; the history of Earth's atmospheric thermal tide, composition, and mean temperature,' was published today in the journal Science Advances. Drawing on geological evidence and using atmospheric research tools, the scientists show that the tidal stalemate between the sun and moon resulted from the incidental but enormously consequential link between the atmosphere's temperature and Earth's rotational rate.

The paper's authors include Norman Murray, a theoretical astrophysicist with U of T's Canadian Institute for Theoretical Astrophysics (CITA); graduate student Hanbo Wu, CITA and Department of Physics, U of T; Kristen Menou, David A. Dunlap Department of Astronomy & Astrophysics and Department of Physical & Environmental Sciences, University of Toronto Scarborough; Jeremy Laconte, Laboratoire d'astrophysique de Bordeaux and and a former CITA postdoctoral fellow; and Christopher Lee, Department of Physics, U of T.

When the moon first formed some 4.5 billion years ago, the day was less than 10 hours long. But since then, the moon's gravitational pull on the Earth has been slowing our planet's rotation, resulting in an increasingly longer day. Today, it continues to lengthen at a rate of some 1.7 milliseconds every century.

The moon slows the planet's rotation by pulling on Earth's oceans, creating tidal bulges on opposite sides of the planet that we experience as high and low tides. The gravitational pull of the moon on those bulges, plus the friction between the tides and the ocean floor, acts like a brake on our spinning planet.

"Sunlight also produces an atmospheric tide with the same type of bulges," says Murray. "The sun's gravity pulls on these atmospheric bulges, producing a torque on the Earth. But instead of slowing down Earth's rotation like the moon, it speeds it up."

For most of Earth's geological history, the lunar tides have overpowered the solar tides by about a factor of ten; hence, the Earth's slowing rotational speed and lengthening days.

But some two billion years ago, the atmospheric bulges were larger because the atmosphere was warmer and because its natural resonance -- the frequency at which waves move through it -- matched the length of day.

The atmosphere, like a bell, resonates at a frequency determined by various factors, including temperature. In other words, waves -- like those generated by the enormous eruption of the volcano Krakatoa in Indonesia in 1883 -- travel through it at a velocity determined by its temperature. The same principle explains why a bell always produces the same note if its temperature is constant.

Throughout most of Earth's history that atmospheric resonance has been out of sync with the planet's rotational rate. Today, each of the two atmospheric "high tides" take 22.8 hours to travel around the world; because that resonance and Earth's 24-hour rotational period are out of sync, the atmospheric tide is relatively small.

But during the billion-year period under study, the atmosphere was warmer and resonated with a period of about 10 hours. Also, at the advent of that epoch, Earth's rotation, slowed by the moon, reached 20 hours.

When the atmospheric resonance and length of day became even factors -- ten and 20 -- the atmospheric tide was reinforced, the bulges became larger and the sun's tidal pull became strong enough to counter the lunar tide.

"It's like pushing a child on a swing," says Murray. "If your push and the period of the swing are out of sync, it's not going to go very high. But, if they're in sync and you're pushing just as the swing stops at one end of its travel, the push will add to the momentum of the swing and it will go further and higher. That's what happened with the atmospheric resonance and tide."

Along with geological evidence, Murray and his colleagues achieved their result using global atmospheric circulation models (GCMs) to predict the atmosphere's temperature during this period. The GCMs are the same models used by climatologists to study global warming. According to Murray, the fact they worked so well in the team's research is a timely lesson.

"I've talked to people who are climate change skeptics who don't believe in the global circulation models that are telling us we're in a climate crisis," says Murray. "And I tell them: We used these global circulation models in our research, and they got it right. They work."

Despite its remoteness in geological history, the result adds additional perspective to the climate crisis. Because the atmospheric resonance changes with temperature, Murray points out that our current warming atmosphere could have consequences in this tidal imbalance.

Read more at Science Daily

Large sub-surface granite formation signals ancient volcanic activity on Moon's dark side

A large formation of granite discovered below the lunar surface likely was formed from the cooling of molten lava that fed a volcano or volcanoes that erupted early in the Moon's history -- as long as 3.5 billion years ago.

A team of scientists led by Matthew Siegler, an SMU research professor and research scientist with the Planetary Science Institute, has published a study in Nature that used microwave frequency data to measure heat below the surface of a suspected volcanic feature on the Moon known as Compton-Belkovich. The team used the data to determine that the heat being generated below the surface is coming from a concentration of radioactive elements that can only exist on the Moon as granite.

Granites are the igneous rock remnants of the plumbing systems below extinct volcanos. The granite formation left when lava cools without erupting is known as a batholith.

"Any big body of granite that we find on Earth used to feed a big bunch of volcanoes, much like a large system is feeding the Cascade volcanoes in the Pacific Northwest today," Siegler said. "Batholiths are much bigger than the volcanoes they feed on the surface. For example, the Sierra Nevada mountains are a batholith, left from a volcanic chain in the western United States that existed long ago."

The lunar batholith is located in a region of the Moon previously identified as a volcanic complex, but researchers are surprised at its size, with an estimated diameter of 50 kilometers.

Granite is somewhat common on Earth, and its formation is generally driven by water and plate tectonics, which aid in creating large melt bodies below the Earth's surface. However, granites are extremely rare on the Moon, which lacks these processes.

Finding this granite body helps explain how the early lunar crust formed.

"If you don't have water it takes extreme situations to make granite," Siegler said. "So, here's this system with no water, and no plate tectonics -- but you have granite.

Was there water on the moon -- at least in this one spot? Or was it just especially hot?"

Read more at Science Daily

Mix-and-match kit could enable astronauts to build a menagerie of lunar exploration bots

When astronauts begin to build a permanent base on the moon, as NASA plans to do in the coming years, they'll need help. Robots could potentially do the heavy lifting by laying cables, deploying solar panels, erecting communications towers, and building habitats. But if each robot is designed for a specific action or task, a moon base could become overrun by a zoo of machines, each with its own unique parts and protocols.

To avoid a bottleneck of bots, a team of MIT engineers is designing a kit of universal robotic parts that an astronaut could easily mix and match to rapidly configure different robot "species" to fit various missions on the moon. Once a mission is completed, a robot can be disassembled and its parts used to configure a new robot to meet a different task.

The team calls the system WORMS, for the Walking Oligomeric Robotic Mobility System. The system's parts include worm-inspired robotic limbs that an astronaut can easily snap onto a base, and that work together as a walking robot. Depending on the mission, parts can be configured to build, for instance, large "pack" bots capable of carrying heavy solar panels up a hill. The same parts could be reconfigured into six-legged spider bots that can be lowered into a lava tube to drill for frozen water.

"You could imagine a shed on the moon with shelves of worms," says team leader George Lordos, a PhD candidate and graduate instructor in MIT's Department of Aeronautics and Astronautics (AeroAstro), in reference to the independent, articulated robots that carry their own motors, sensors, computer, and battery. "Astronauts could go into the shed, pick the worms they need, along with the right shoes, body, sensors and tools, and they could snap everything together, then disassemble it to make a new one. The design is flexible, sustainable, and cost-effective."

Lordos' team has built and demonstrated a six-legged WORMS robot. Last week, they presented their results at IEEE's Aerospace Conference, where they also received the conference's Best Paper Award.

MIT team members include Michael J. Brown, Kir Latyshev, Aileen Liao, Sharmi Shah, Cesar Meza, Brooke Bensche, Cynthia Cao, Yang Chen, Alex S. Miller, Aditya Mehrotra, Jacob Rodriguez, Anna Mokkapati, Tomas Cantu, Katherina Sapozhnikov, Jessica Rutledge, David Trumper, Sangbae Kim, Olivier de Weck, Jeffrey Hoffman, along with Aleks Siemenn, Cormac O'Neill, Diego Rivero, Fiona Lin, Hanfei Cui, Isabella Golemme, John Zhang, Jolie Bercow, Prajwal Mahesh, Stephanie Howe, and Zeyad Al Awwad, as well as Chiara Rissola of Carnegie Mellon University and Wendell Chun of the University of Denver.

Animal instincts

WORMS was conceived in 2022 as an answer to NASA's Breakthrough, Innovative and Game-changing (BIG) Idea Challenge -- an annual competition for university students to design, develop, and demonstrate a game-changing idea. In 2022, NASA challenged students to develop robotic systems that can move across extreme terrain, without the use of wheels.

A team from MIT's Space Resources Workshop took up the challenge, aiming specifically for a lunar robot design that could navigate the extreme terrain of the moon's South Pole -- a landscape that is marked by thick, fluffy dust; steep, rocky slopes; and deep lava tubes. The environment also hosts "permanently shadowed" regions that could contain frozen water, which, if accessible, would be essential for sustaining astronauts.

As they mulled over ways to navigate the moon's polar terrain, the students took inspiration from animals. In their initial brainstorming, they noted certain animals could conceptually be suited to certain missions: A spider could drop down and explore a lava tube, a line of elephants could carry heavy equipment while supporting each other down a steep slope, and a goat, tethered to an ox, could help lead the larger animal up the side of a hill as it transports an array of solar panels.

"As we were thinking of these animal inspirations, we realized that one of the simplest animals, the worm, makes similar movements as an arm, or a leg, or a backbone, or a tail," says deputy team leader and AeroAstro graduate student Michael Brown. "And then the lightbulb went off: We could build all these animal-inspired robots using worm-like appendages.'"

Snap on, snap off

Lordos, who is of Greek descent, helped coin WORMS, and chose the letter "O" to stand for "oligomeric," which in Greek signifies "a few parts."

"Our idea was that, with just a few parts, combined in different ways, you could mix and match and get all these different robots," says AeroAstro undergraduate Brooke Bensche.

The system's main parts include the appendage, or worm, which can be attached to a body, or chassis, via a "universal interface block" that snaps the two parts together through a twist-and-lock mechanism. The parts can be disconnected with a small tool that releases the block's spring-loaded pins.

Appendages and bodies can also snap into accessories such as a "shoe," which the team engineered in the shape of a wok, and a LiDAR system that can map the surroundings to help a robot navigate.

"In future iterations we hope to add more snap-on sensors and tools, such as winches, balance sensors, and drills," says AeroAstro undergraduate Jacob Rodriguez.

The team developed software that can be tailored to coordinate multiple appendages. As a proof of concept, the team built a six-legged robot about the size of a go-cart. In the lab, they showed that once assembled, the robot's independent limbs worked to walk over level ground. The team also showed that they could quickly assemble and disassemble the robot in the field, on a desert site in California.

In its first generation, each WORMS appendage measures about 1 meter long and weighs about 20 pounds. In the moon's gravity, which is about one-sixth that of Earth's, each limb would weigh about 3 pounds, which an astronaut could easily handle to build or disassemble a robot in the field. The team has planned out the specs for a larger generation with longer and slightly heavier appendages. These bigger parts could be snapped together to build "pack" bots, capable of transporting heavy payloads.

"There are many buzz words that are used to describe effective systems for future space exploration: modular, reconfigurable, adaptable, flexible, cross-cutting, et cetera," says Kevin Kempton, an engineer at NASA's Langley Research Center, who served as a judge for the 2022 BIG Idea Challenge. "The MIT WORMS concept incorporates all these qualities and more."

Read more at Science Daily

Flat, pancake-sized metalens images lunar surface in an engineering first

Astronomers and amateurs alike know the bigger the telescope, the more powerful the imaging capability. To keep the power but streamline one of the bulkier components, a Penn State-led research team created the first ultrathin, compact metalens telescope capable of imaging far-away objects, including the moon.

Metalenses comprise tiny, antenna-like surface patterns that can focus light to magnify distant objects in the same way as traditional curved glass lenses, but they have the advantage of being flat. Though small, millimeters-wide metalenses have been developed in the past, the researchers scaled the size of the lens to eight centimeters in diameter, or about four inches wide, making it possible to use in large optical systems, such as telescopes. They published their approach in Nano Letters.

"Traditional camera or telescope lenses have a curved surface of varying thickness, where you have a bump in the middle and thinner edges, which causes the lens to be bulky and heavy," said corresponding author Xingjie Ni, associate professor of electrical engineering and computer science at Penn State. "Metalenses use nano-structures on the lens instead of curvature to contour light, which allows them to lay flat."

That is one of the reasons, Ni said, modern cellphone camera lenses protrude from the body of the phone: the thickness of the lenses take up space, though they appear flat since they are hidden behind a glass window.

Metalenses are typically made using electron beam lithography, which involves scanning a focused beam of electrons onto a piece of glass, or other transparent substrate, to create antenna-like patterns point by point. However, the scanning process of the electron beam limits the size of the lens that can be created, as scanning each point is time-consuming and has low throughput.

To create a bigger lens, the researchers adapted a fabrication method known as deep ultraviolet (DUV) photolithography, which is commonly used to produce computer chips.

"DUV photolithography is a high-throughput and high-yield process that can produce many computer chips within seconds," Ni said. "We found this to be a good fabrication method for metalenses because it allows for much larger pattern sizes while still maintaining small details, which allows the lens to work effectively."

The researchers modified the method with their own novel procedure, called rotating wafer and stitching. Researchers divided the wafer, on which the metalens was fabricated, into four quadrants, which were further divided into 22 by 22 millimeter regions -- smaller than a standard postage stamp. Using a DUV lithography machine at Cornell University, they projected a pattern onto one quadrant through projection lenses, which they then rotated by 90 degrees and projected again. They repeated the rotation until all four quadrants were patterned.

"The process is cost-effective because the masks containing the pattern data for each quadrant can be reused due to the rotation symmetry of the metalens," Ni said. "This reduces the manufacturing and environmental costs of the method."

As the size of the metalens increased, the digital files required to process the patterns became significantly larger, which would take a long time for the DUV lithography machine to process. To overcome this issue, the researchers compressed the files using data approximations and by referencing non-unique data.

"We utilized every possible method to reduce the file size," Ni said. "We identified identical data points and referenced existing ones, gradually reducing the data until we had a usable file to send to the machine for creating the metalens."

Using the new fabrication method, the researchers developed a single-lens telescope and captured clear images of the lunar surface -- achieving greater resolution of objects and much farther imaging distance than previous metalenses. Before the technology can be applied to modern cameras, however, researchers must address the issue of chromatic aberration, which causes image distortion and blurriness when different colors of light, which bend in different directions, enter a lens.

"We are exploring smaller and more sophisticated designs in the visible range, and will compensate for various optical aberrations, including chromatic aberration," Ni said.

Read more at Science Daily

Collision may have formed the Moon in mere hours, simulations reveal

Billions of years ago, a version of our Earth that looks very different than the one we live on today was hit by an object about the size of Mars, called Theia -- and out of that collision the Moon was formed. How exactly that formation occurred is a scientific puzzle researchers have studied for decades, without a conclusive answer.

Most theories claim the Moon formed out of the debris of this collision, coalescing in orbit over months or years. A new simulation puts forth a different theory -- the Moon may have formed immediately, in a matter of hours, when material from the Earth and Theia was launched directly into orbit after the impact.

"This opens up a whole new range of possible starting places for the Moon's evolution," said Jacob Kegerreis, a postdoctoral researcher at NASA's Ames Research Center in California's Silicon Valley, and lead author of the paper on these results published in The Astrophysical Journal Letters. "We went into this project not knowing exactly what the outcomes of these high-resolution simulations would be. So, on top of the big eye-opener that standard resolutions can give you misleading answers, it was extra exciting that the new results could include a tantalisingly Moon-like satellite in orbit."

The simulations used in this research are some of the most detailed of their kind, operating at the highest resolution of any simulation run to study the Moon's origins or other giant impacts. This extra computational power showed that lower-resolution simulations can miss out on important aspects of these kinds of collisions, allowing researchers to see new behaviors emerge in a way previous studies just couldn't see.

A Puzzle of Planetary History

Understanding the Moon's origins requires using what we know about the Moon -- our knowledge of its mass, orbit, and the precise analysis of lunar rock samples -- and coming up with scenarios that could lead to what we see today.

Previously prevailing theories could explain some aspects of the Moon's properties quite well, such as its mass and orbit, but with some major caveats. One outstanding mystery has been why the composition of the Moon is so similar to Earth's. Scientists can study the composition of a material based on its isotopic signature, a chemical clue to how and where an object was created. The lunar samples scientists have been able to study in labs show very similar isotopic signatures to rocks from Earth, unlike rocks from Mars or elsewhere in the solar system. This makes it likely that much of the material that makes up the Moon originally came from Earth.

In previous scenarios where Theia sprayed out into orbit and mixed with only a little material from Earth, it's less likely we'd see such strong similarities -- unless Theia was also isotopically similar to Earth, an unlikely coincidence. In this theory, more Earth material is used to create the Moon, particularly its outer layers, which could help to explain this similarity in composition.

There have been other theories proposed to explain these similarities in composition, such as the synestia model -- where the Moon is formed inside a swirl of vaporized rock from the collision -- but these arguably struggle to explain the Moon's current orbit.

This faster, single-stage formation theory offers a cleaner and more elegant explanation for both these outstanding issues. It could also give new ways to find answers for other unsolved mysteries. This scenario can put the Moon into a wide orbit with an interior that isn't fully molten, potentially explaining properties like the Moon's tilted orbit and thin crust -- making it one of the most enticing explanations for the Moon's origins yet.

Getting closer to confirming which of these theories is correct will require analysis of future lunar samples brought back to Earth for study from NASA's future Artemis missions. As scientists gain access to samples from other parts of the Moon and from deeper beneath the Moon's surface, they will be able to compare how real-world data matches up to these simulated scenarios, and what they indicate about how the Moon has evolved over its billions of years of history.

A Shared Origin

Beyond simply learning more about the Moon, these studies can bring us closer to understanding how our own Earth became the life-harboring world it is today.

"The more we learn about how the Moon came to be, the more we discover about the evolution of our own Earth," said Vincent Eke, a researcher at Durham University and a co-author on the paper. "Their histories are intertwined -- and could be echoed in the stories of other planets changed by similar or very different collisions."

The cosmos is filled with collisions -- impacts are an essential part of how planetary bodies form and evolve. On Earth, we know that the impact with Theia and other changes throughout its history are part of how it was able to gather the materials necessary for life. The better scientists can simulate and analyze what's at play in these collisions, the more prepared we are to understand how a planet could evolve to be habitable like our own Earth.

Read more at Science Daily

Saturn V was loud but didn't melt concrete

The Saturn V carried man to the moon and remains the most powerful rocket to successfully launch to orbit. It captures the imagination -- but sometimes, it might capture a bit too much imagination. Abundant internet claims about the acoustic power of the rocket suggest that it melted concrete and lit grass on fire over a mile away.

Such ideas are undeniably false. In The Journal of the Acoustical Society of America, published on behalf of the Acoustical Society of America by AIP Publishing, researchers from Brigham Young University used a physics-based model to estimate the acoustic levels of the Saturn V. They obtained a value of 203 decibels, which matched the very limited data from the 1960s.

To put that number into perspective, commercial jet engines range from around 120 to 160 decibels.

"Decibels are logarithmic, so every 10 decibels is an order of magnitude increase," said author Kent L. Gee, of BYU. "One hundred and seventy decibels would be equivalent to 10 aircraft engines. Two hundred would be 10,000 engines!"

While the Saturn V was extremely loud, that kind of power is nowhere near enough to melt concrete or start grass fires. If reports about these phenomena are true, they likely stem from radiative heating via the plume or debris.

Some of the misunderstanding comes from confusing sound power with sound pressure. The former is like the wattage from a light bulb. The latter is like the brightness from the same bulb: It depends on how far away you're standing. Mistakes in calculations, changes to the decibel reference system, and the propagation of misinformation have also led to compounding errors.

"The Saturn V has taken on this sort of legendary, apocryphal status," said Gee. "We felt that, as part of the JASA special issue on Education in Acoustics, it was an opportunity to correct misinformation about this vehicle."

NASA's Space Launch System (SLS) Artemis 1 launch is scheduled for the fall of this year, when it will send humans back to the moon and surpass the Saturn V in terms of power and noise. The researchers have used their framework to predict SLS's sound levels, and they plan to make acoustical measurements at its launch to help to further refine predictions.

Read more at Science Daily

One more clue to the Moon's origin

Humankind has maintained an enduring fascination with the Moon. It was not until Galileo's time, however, that scientists really began study it. Over the course of nearly five centuries, researchers put forward numerous, much debated theories as to how the Moon was formed. Now, geochemists, cosmochemists, and petrologists at ETH Zurich shed new light on the Moon's origin story. In a study just published in the journal, Science Advances, the research team reports findings that show that the Moon inherited the indigenous noble gases of helium and neon from Earth's mantle. The discovery adds to the already strong constraints on the currently favoured "Giant Impact" theory that hypothesizes the Moon was formed by a massive collision between Earth and another celestial body.

Meteorites from the Moon to Antarctica

During her doctoral research at ETH Zurich, Patrizia Will analysed six samples of lunar meteorites from an Antarctic collection, obtained from NASA. The meteorites consist of basalt rock that formed when magma welled up from the interior of the Moon and cooled quickly. They remained covered by additional basalt layers after their formation, which protected the rock from cosmic rays and, particularly, the solar wind. The cooling process resulted in the formation of lunar glass particles amongst the other minerals found in magma. Will and the team discovered that the glass particles retain the chemical fingerprints (isotopic signatures) of the solar gases: helium and neon from the Moon's interior. Their findings strongly support that the Moon inherited noble gases indigenous to the Earth. "Finding solar gases, for the first time, in basaltic materials from the Moon that are unrelated to any exposure on the lunar surface was such an exciting result," says Will.

Without the protection of an atmosphere, asteroids continually pelt the Moon's surface. It likely took a high-energy impact to eject the meteorites from the middle layers of the lava flow similar to the vast plains known as the Lunar Mare. Eventually the rock fragments made their way to Earth in the form of meteorites. Many of these meteorite samples are picked up in the deserts of North Africa or in, in this case, the "cold desert" of Antarctica where they are easier to spot in the landscape.

Grateful Dead lyrics inspire lab instrument

In the Noble Gas Laboratory at ETH Zurich resides a state-of-the-art noble gas mass spectrometer named, "Tom Dooley" -- sung about in the Grateful Dead tune by the same name. The instrument got its name, when earlier researchers, at one point, suspended the highly sensitive equipment from the ceiling of the lab to avoid interference from the vibrations of everyday life. Using the Tom Dooley instrument, the research team was able to measure sub-millimetre glass particles from the meteorites and rule out solar wind as the source of the detected gases. The helium and neon that they detected were in a much higher abundance than expected.

The Tom Dooley is so sensitive that it is, in fact, the only instrument in the world capable of detecting such minimal concentrations of helium and neon. It was used to detect these noble gases in the 7 billion years old grains in the Murchison meteorite -- the oldest known solid matter to-date.

Searching for the origins of life

Knowing where to look inside NASA's vast collection of some 70,000 approved meteorites represents a major step forward. "I am strongly convinced that there will be a race to study heavy noble gases and isotopes in meteoritic materials," says ETH Zurich Professor Henner Busemann, one of the world's leading scientists in the field of extra-terrestrial noble gas geochemistry. He anticipates that soon researchers will be looking for noble gases such as xenon and krypton which are more challenging to identify. They will also be searching for other volatile elements such as hydrogen or halogens in the lunar meteorites.

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Scientists discover places on the moon where it's always 'sweater weather'

Future human explorers on the moon might have 99 problems but staying warm or cool won't be one. A team led by planetary scientists at UCLA has discovered shady locations within pits on the moon that always hover around a comfortable 63 degrees Fahrenheit.

The pits, and caves to which they may lead, would make safer, more thermally stable base camps for lunar exploration and long-term habitation than the rest of the moon's surface, which heats up to 260 degrees during the day and drops to 280 degrees below zero at night.

Pits were first discovered on the moon in 2009, and since then, scientists have wondered if they led to caves that could be explored or used as shelters. About 16 of the more than 200 pits are probably collapsed lava tubes, said Tyler Horvath, a UCLA doctoral student in planetary science, who led the new research. Two of the most prominent pits have visible overhangs that clearly lead to some sort of cave or void, and there is strong evidence that another's overhang may also lead to a large cave.

Lava tubes, also found on Earth, form when molten lava flows beneath a field of cooled lava or a crust forms over a river of lava, leaving a long, hollow tunnel. If the ceiling of a solidified lava tube collapses, it opens a pit that can lead into the rest of the cavelike tube.

Horvath processed images from the Diviner Lunar Radiometer Experiment -- a thermal camera and one of six instruments on NASA's robotic Lunar Reconnaissance Orbiter -- to find out if the temperature within the pits diverged from those on the surface.

Focusing on a roughly cylindrical 100-meter-deep depression about the length and width of a football field in an area of the moon known as the Mare Tranquillitatis, Horvath and his colleagues used computer modeling to analyze the thermal properties of the rock and lunar dust and to chart the pit's temperatures over a period of time.

The results, recently published in the journal Geophysical Research Letters, revealed that temperatures within the permanently shadowed reaches of the pit fluctuate only slightly throughout the lunar day, remaining at around 63 degrees. If a cave extends from the bottom of the pit, as images taken by the Lunar Reconnaissance Orbiter Camera suggest, it too would have this relatively comfortable temperature.

The research team, which also included UCLA professor of planetary science David Paige and Paul Hayne of the University of Colorado Boulder, believes the shadowing overhang is responsible for the steady temperature, limiting how hot things get during the day and preventing heat from radiating away at night. Meanwhile, the sunbaked part of the pit floor hits daytime temperatures close to 300 degrees, some 40 degrees hotter than the moon's surface.

"Because the Tranquillitatis pit is the closest to the lunar equator, the illuminated floor at noon is probably the hottest place on the entire moon," said Horvath.

A day on the moon lasts nearly 15 Earth days, during which the surface is constantly bombarded by sunlight and is frequently hot enough to boil water. Unimaginably cold nights also last about 15 Earth days. Inventing heating and cooling equipment that can operate under these conditions and producing enough energy to power it nonstop could prove an insurmountable barrier to lunar exploration or habitation. Solar power -- NASA's most common form of power generation -- doesn't work at night, after all. (NASA currently has no plans to establish an exploration base camp or habitations on the moon.)

Building bases in the shadowed parts of these pits allows scientists to focus on other challenges, like growing food, providing oxygen for astronauts, gathering resources for experiments and expanding the base. The pits or caves would also offer some protection from cosmic rays, solar radiation and micrometeorites.

"Humans evolved living in caves, and to caves we might return when we live on the moon," said Paige, who leads the Diviner Lunar Radiometer Experiment.

Diviner has been mapping the moon continuously since 2009, producing NASA's second largest planetary dataset and providing the most detailed and comprehensive thermal measurements of any object in our solar system, including Earth. The team's current work on lunar pits has improved data from the Diviner experiment.

"Because nobody else had looked at things this small with Diviner, we found that it had a bit of double vision, causing all of our maps to a be a bit blurry," said Horvath. The team worked to align the many images taken by the instrument until they could achieve an accurate thermal reading down to the level of single pixel. This process yielded much higher resolution maps of the moon's surface.

Data from the early stages of this lunar pit thermal modeling project were used to help develop the thermal management system of the rover for NASA's proposed Moon Diver mission. Horvath and Hayne were part of the science team for this mission, which aims to have the rover rappel into the Tranquillitatis pit to research the layers of lava flows seen in its walls and to explore any existing cave.

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New method to map the surface of the moon increases accuracy to unprecedented levels

Topography: The surface of the moon and rocky planets, Mars in particular, are of huge interest to anyone trying to explore our solar system. The surface must be known in as much detail as possible, for missions to land safely, or for any robotic vessel to drive across the surface. But until now, the methods to analyze images from e.g. orbiting spacecraft have entailed a huge work load and immense computer power -- with limited results. A project from now former PHD student at the Niels Bohr Institute, University of Copenhagen, Iris Fernandes, has changed that. Studying the limestone formation Stevns Klint in Denmark, she developed a method to interpret shadows in images, so the exact topography can be extracted.The method is even much quicker and less work-intensive. The result is now published Planetary and Space Science 218.

Human space exploration entails high levels of safety -- so precise images of the terrain are adamant

The topography of any surface will create shades, when the sunlight hits it. We can clearly see the shades in the pictures of e.g. the Moon, but we don't know the elevation of the terrain. So we can see the topography changes, but not how much! It is necessary to be able to see even very small features to ensure safe landing or movement of e.g. a rover. Not to mention the safety of astronauts.

If a rover can't see details, it could get stuck in sand surfaces or hit rocks -- and being able to see interesting geological formations to find rich geological environments for research purposes is also of great importance.

Former limitations in topography assessment have now been largely eradicated

When satellites orbit a planet, they can take pictures in reasonable quality of the surface. But in order to establish an interpretation of the exact topography, good enough for landing the hugely expensive equipment or perhaps even astronauts, a lot of ad hoc information still needs to be processed.

The method of using the shades existed before, but it was computationally inefficient, and still had to rely on assumptions. The new method uses a much more direct and precise calculation, it doesn't rely on a whole set of parameters to be fed into the computer, and it can even calculate the uncertainties and the accuracy.

"This method is fast, it is precise and it doesn't have to rely on any assumptions. Previously," Iris Fernandes says, "if you posed the question: How precise is the assessment of the topography -- there really wasn't a satisfactory answer.

Now the precise topography is revealed, and we can even quantify the uncertainties."

Scientific curiosity can lead you to surprising places

"I was involved in a project where we wanted to use pictures from Stevns Klint to model patterns in the surface. I even presented this method in a conference in L.A. But the shades presented a challenge, because the algorithm "saw" the shades as geological features.

It created a bias in the model. We needed to find ways to remove the shades, in order to remove the bias.

I was always interested in planets, and I knew the surface of the moon was being studied. There aren't many disturbing features on the Moon, so it was ideal for removing the bias.

When we filtered away the shades, we could see what they were "hiding," so to speak -- the surface shapes," Iris Fernandes explains.

Resolution of existing images presented a new problem -- and a new approach

When work on the Moon started, the discrepancy of the different resolutions in images and the topography data turned out to be tremendous. A new problem appeared, in other words. "How could we combine different sources of data in different resolutions?

It presented a huge mathematical problem -- and this is really what the study is about.

This is where former research had come to a stop. What we did differently than former attempts to solve this, was that we focused on the mathematics and narrowed it down to a challenging mathematical equation. Basically, to see if this equation could solve the problem.

And it did," Iris Fernandes smiles. "You could say that we, my supervisor, Professor Klaus Mosegaard and I, found the mathematical key to a door that had remained closed for many years."

The way forward

The focus now is improving the method even more. Wherever there are data available on rock-formation in the solar system, like the Moon, Mars, asteroids or the like, the method can be applied to extract precise topographic details.

The images used for this task, can be images from satellites or even the rovers themselves, presently on the ground on Mars -- or any mobile robot in the future.

The purposes for achieving correct topographic analysis can be different, it could be the safety of the equipment or astronauts or finding geologically interesting sites.

There is a wide array of possible applications, in other words. "It is a sort of computer vision thing," Iris Fernandes says: "When, for instance, a robot has some form of machinery to interact with the environment, the method can help in navigation or the "eye-hand coordination," because it is less computational "heavy" and thus faster.

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Porosity of the moon's crust reveals bombardment history

Around 4.4 billion years ago, the early solar system resembled a game of space rock dodgeball, as massive asteroids and comets, and, later, smaller rocks and galactic debris pummeled the moon and other infant terrestrial bodies. This period ended around 3.8 billion years ago. On the moon, this tumultuous time left behind a heavily cratered face, and a cracked and porous crust.

Now MIT scientists have found that the porosity of the moon's crust, reaching well beneath the surface, can reveal a great deal about the moon's history of bombardment.

In a study appearing in Nature Geoscience, the team has shown through simulations that, early on in the bombardment period, the moon was highly porous -- almost one-third as porous as pumice. This high porosity was likely a result of early, massive impacts that shattered much of the crust.

Scientists have assumed that a continuous onslaught of impacts would slowly build up porosity. But surprisingly, the team found that nearly all the moon's porosity formed rapidly with these massive imapcts, and that the continued onslaught by smaller impactors actually compacted its surface. These later, smaller impacts acted instead to squeeze and compact some of the moon's existing cracks and faults.

From their simulations, the researchers also estimated that the moon experienced double the number of impacts as can be seen on the surface. This estimate is lower than what others have assumed.

"Previous estimates put that number much higher, as many as 10 times the impacts as we see on the surface, and we're predicting there were fewer impacts," says study co-author Jason Soderblom, a research scientist in MIT's Department of Earth, Atmospheric and Planetary Sciences (EAPS). "That matters because that limits the total material that impactors like asteroids and comets brought to the moon and terrestrial bodies, and gives constraints on the formation and evolution of planets throughout the solar system."

The study's lead author is EAPS postdoc Ya Huei Huang, along with collaborators at Purdue University and Auburn University.

A porous record

In the team's new study, the researchers looked to trace the moon's changing porosity and use those changes below the surface to estimate the number of impacts that occurred on its surface.

"We know the moon was so bombarded that what we see on the surface is no longer a record of every impact the moon has ever had, because at some point, impacts were erasing previous impacts," Soderblom says. "What we're finding is that the way impacts created porosity in the crust is not destroyed, and that can give us a better constraint on the total number of impacts that the moon was subject to."

To trace the evolution of the moon's porosity, the team looked to measurements taken by NASA's Gravity Recovery and Interior Laboratory, or GRAIL, an MIT-designed mission that launched twin spacecraft around the moon to precisely map the surface gravity.

Researchers have converted the mission's gravity maps into detailed maps of the density of the moon's underlying crust. From these density maps, scientists have also been able to map the current-day porosity throughout the lunar crust. These maps show that regions surrounding the youngest craters are highly porous, while less porous regions surround older craters.

Crater chronology

In their new study, Huang, Soderblom and their colleagues looked to simulate how the moon's porosity changed as it was bombarded with first large and then smaller impacts. They included in their simulation the age, size, and location of the 77 largest craters on the moon's surface, along with GRAIL-derived estimates of each crater's current-day porosity. The simulation includes all known basins, from the oldest to the youngest impact basins on the moon, and span ages between 4.3 billion and 3.8 billion years old.

For their simulations, the team used the youngest craters with the highest current-day porosity as a starting point to represent the moon's initial porosity in the early stages of the lunar heavy bombardment. They reasoned that older craters that formed in the early stages would have started out highly porous but would have been exposed to further impacts over time that compacted and reduced their initial porosity. In contrast, younger craters, though they formed later on, would have experienced fewer if any subsequent impacts. Their underlying porosity would then be more representative of the moon's initial conditions.

"We use the youngest basin that we have on the moon, that hasn't been subject to too many impacts, and use that as a way to start as initial conditions," Huang explains. "We then use an equation to tune the number of impacts needed to get from that initial porosity to the more compacted, present-day porosity of the oldest basins."

The team studied the 77 craters in chronological order, based on their previously determined ages. For each crater, the team modeled the amount by which the underlying porosity changed compared to the initial porosity represented by the youngest crater. They assumed a bigger change in porosity was associated with a larger number of impacts, and used this correlation to estimate the number of impacts that would have generated each crater's current-day porosity.

These simulations showed a clear trend: At the start of the lunar heavy bombardment, 4.3 billion years ago, the crust was highly porous -- about 20 percent (by comparison, the porosity of pumice is about 60 to 80 percent). Closer to 3.8 billion years ago, the crust became less porous, and remains at its current-day porosity of about 10 percent.

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