Tag Archives: #moon

Dated One of the Oldest Craters on the Moon (Planetary Science)

A new analysis of a sample of lunar rock collected by astronauts on the Apollo 17 mission reveals that the Serenity basin is even older than previously thought. The formation of this large crater, estimated thanks to new dating techniques and numerical simulations, dates back to 4.2 billion years ago, even before the intense late bombardment that produced many of the impact craters on the Moon.

Even with the naked eye, the Moon shows more or less dark areas which, when observed in more detail, tell the billions of years of history of our natural satellite. While on Earth the meteorological phenomena, water and tectonic activity tend to erase the signs of the celestial bodies that have affected it during its long history, the absence of these elements on the Moon forever preserves the memory of each impact on its surface. Now, by studying a sample of the lunar soil brought back to Earth in 1972 by astronauts from the Apollo 17 mission , the latest in the historic NASA series, an international team of researchers has refined the estimate of the age of the crater known as the Serenitatis basin , or basin. of Serenity, created by an impact 4.2 billion years ago .

Since the first observations, the Serenity basin – which includes the most famous sea ​​of ​​Serenity , the landing site not only of Apollo 17 but also of the Soviet robotic mission Luna 21 in 1973 – has been considered one of the oldest of the great craters on the face of the Moon turning towards our planet. Estimating its age through the analysis of the rocks collected by astronauts was one of the scientific objectives of the Apollo 17 mission – the one that, among the six landed on the lunar surface, brought back most of the samples, over one hundred kilos. In the past, analysis of the samples from this mission had associated most of them with a more recent impact, linked to the formation of the nearby Imbrium basin, whose material would have been thrown over great distances, covering much of the ‘near face’ of the Moon. This mixing complicates the determination of the actual age of the Serenity basin, initially indicating a value of approximately 3.8–3.9 billion years.

The new study, based in particular on a rock collected by astronauts at Station 8 on the route of their second extravehicular activity, now pushes this estimate back by 300 million years . The results of the research, led by the Open University (UK) and with the participation of researchers from the University of Portsmouth (UK), the Royal Ontario Museum, the University of Toronto and the Université de Sherbrooke (Canada), Swedish Museum of Natural History (Sweden) and Curtin University (Australia), have been published in Nature Communications Earth and Environment .

“We have long observed this fascinating specimen and tried to unravel its complex radiogenic ages,” says lead author Ana Černok of the Open University, Royal Ontario Museum and the University of Toronto. “It has been difficult to establish the exact link of the samples with the Serenitatis basin since the Apollo 17 collection was reported, because it was not easy to distinguish between the samples formed by the Imbrium event and those formed by Serenitatis.”

The Geoscience Atom Probe Facility at Curtin University, used in this study. Credits: Curtin University

To obtain accurate dating of the sample, the team used an innovative technique from materials science, atomic probe tomography , along with numerical simulations of the impacts. The combination of these methods made it possible to link the microscopic-scale study of a small sample of the moon to the moment when, billions of years ago, a celestial body hit the surface of the Moon. «The dating techniques (uranium-lead geochronology) have suggested that this sample of the Serenitatis basin on the Moon is very old, about 4.2 billion years, that is, only about 350 million years younger than the entire Solar System, making it a precious sample for knowing the primordial evolution of the Moon and the origin of our planet “, explains the co-authorKatarina Miljkovic , associate professor at Curtin University.

In the history of the Earth-Moon system, this result indicates that the crater may even precede the beginning of the ‘ late heavy bombardment – in English late heavy bombardment (LHB), or the time during which the planets of the inner solar system were subjected to numerous impacts from asteroids and comets, which is between 4.1 and 3.8 billion years ago. Alternatively, the new measure could call into question the very duration of the Lhb, in support of a more prolonged period whose very early stages could coincide with the formation of the Serenitatis basin.

The new-technique analysis of a long-studied lunar sample also offers a new key to studying the atomic-scale processes occurring in minerals hit by extreme astronomical impacts. The distribution of the atoms in the analyzed sample, Miljkovic points out, shows that it “underwent not one, but two impact events. The second impact transported the sample close to its resting place where it was collected by the astronauts ».

Featured image: The Serenity basin, one of the oldest craters on the near side of the Moon, landing site for the Apollo 17 mission. Credits: Wikipedia

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Queqiao: The Bridge Between Earth and the Far Side of the Moon (Astronomy)

Researchers explain the design of the relay communication satellite that enabled us to peek at the hidden face of the moon

Because of a phenomenon called gravitational locking, the Moon always faces the Earth from the same side. This proved useful in the early lunar landing missions in the 20th century, as there was always a direct line of sight for uninterrupted radiocommunications between Earth ground stations and equipment on the Moon. However, gravitational locking makes exploring the hidden face of the moon–the far side–much more challenging, because signals cannot be sent directly across the Moon towards Earth.

Still, in January 2019, China’s lunar probe Chang’e-4 marked the first time a spacecraft landed on the far side of the Moon. Both the lander and the lunar rover it carried have been gathering and sending back images and data from previously unexplored areas. But how does Chang’e-4 probe communicate with the Earth? The answer is Queqiao, a relay communications satellite, explains Dr. Lihua Zhang from DFH Satellite Co., Ltd., China.

As explained by Dr. Zhang in a review paper recently published in Space: Science & Technology, Queqiao is an unprecedented satellite designed specifically for one purpose: to act as a bridge between Chang’e-4 probe and the Earth. Queqiao was launched in 2018 and put into orbit around a point ‘behind’ the Moon. This point is known as the Earth-Moon Libration point 2, where a special case of gravitational balance allows Queqiao to maintain an orbit such that it has almost constant direct line of sight with both the far side of the Moon and the Earth. Getting the satellite into this peculiar orbit required careful planning and maintenance management, and the success of this operation set a precedent for future attempts at putting satellites in orbit around other Earth-Moon libration points.

From its stable place in space, Queqiao helped guide the soft-landing and surface operations of Chang’e-4 probe and has been our intermediary with it ever since. The satellite is equipped with two different kinds of antennas: a parabolic antenna and several spiral antennas. The former, which has a large diameter of 4.2 m, was designed to send and receive signals on the X band (7-8GHz) to and from the rover and lander on the surface of the Moon. Its large size is related the expected noise levels and the low intensity of the transmissions that are sent by surface equipment.

On the other hand, the spiral antennas operate on the S band (2-4 GHz) and communicate with Earth ground stations, forwarding commands to the lunar surface equipment and exchanging telemetry and tracking data. Most notably, all these different links can transmit and receive simultaneously, making Queqiao highly versatile. The review paper addresses other important design considerations for Queqiao and future relay satellites, such as the use of regenerative forwarding, the various link data rates involved, and data storage systems for when no Earth ground station is accessible.

Over two years of exploration, a great amount of data has been received from the rover and lander through Queqiao. “Scientists in both China and other countries have conducted analysis and research based on the retrieved data, and they have produced valuable scientific results. The longer the operational life of Queqiao, the more scientific outcomes will be achieved,” remarks Dr. Zhang. Based on current predictions, Queqiao should be operable on mission orbit for at least five years.

Dr. Zhang also addressed the prospects for future lunar missions and how relay communication systems should evolve to support them. Many unexplored areas on the Moon, such as the largest crater at the South Pole, call for multiple relay satellites to maintain constant communication links, which poses an expensive and time-consuming challenge. But what if relay satellites were suitable for more than a single mission? “A sustainable communication and navigation infrastructure should be established to benefit all lunar missions rather than dealing with each mission independently,” comments Dr. Zhang, “This infrastructure should adopt an open and extensible architecture and provide flexible, interoperable, cross-supportable, and compatible communications services, which are critical to the success of future lunar explorations.” It’s likely that future endeavors on the far side of the Moon will be a test on how well we can cooperate to unveil the secrets of our natural satellite.

Featured image: The far side of the Moon always faces away from the Earth, making communications from lunar equipment there much more challenging. Fortunately, relay communication satellites can act as a bridge or stepping stone between transmission from the far side towards Earth ground stations. © Space: Science & Technology


Provided by Cactus Communications

Researchers Prepare To Send Fungi For A Ride Around the Moon (Astronomy / Biology)

Microbiologists at the U.S. Naval Research Laboratory are preparing experimental samples of fungi to send for a ride around the moon tentatively scheduled for later in 2021 or early 2022.

The experiment aims to provide insight into fungi’s natural defenses against radiation, a phenomenon that could prove useful for future space exploration and sustained life in space.

“During this past year, we successfully completed the Scientific Verification Test to ensure the experiment is working in our lab, which is the first step of this project,” said Zheng Wang, NRL microbiologist and the principal investigator on this project. “Additionally, since October 2020 we have accomplished Experimental Verification Test at Kennedy Space Center, which mimics the flight environment for about two months.”

Fungi have natural mechanisms to protect from and repair DNA damage caused by radiation. Those mechanisms enable the fungi to withstand several hundred times more radiation than humans. This experiment will study the melanin in fungi (which may assist in protecting them from damage), as well as DNA repair pathways (which repair damage once it occurs). The fungus used for this experiment will be Aspergillus niger, a black mold commonly used in laboratories and industry and also one of the predominant fungi detected on the International Space Station (ISS). 

“We are looking at fungi that are extremely resistant to radiation and trying to figure out why,” said Jillian Romsdahl, a microbiologist and NRC postdoctoral fellow on the project. “But we are also looking at a bigger question of how biological systems adapt to deep space, which has implications for people trying to travel to Mars or further.”

The researchers are preparing four different samples of Aspergillus niger — one wild type strain and three mutated strains that were genetically engineered in the laboratory. One mutated strain is defective in making melanin, so it can be compared to the wild type strain that does produce melanin. 

The other two mutated strains will be deficient in DNA repair pathways. Wang’s group wants to know how important those DNA pathways are in protecting the fungal cells against damage caused by radiation. They also want to know if the radiation stimulates new DNA pathways not yet discovered.

During the actual experiment, the fungal samples will be stored in NASA’s Orion capsule and launched into space, where it will travel around the moon for three weeks. Once complete, NASA will return the specimens to NRL for analysis.

Researchers plan to compare the samples to look for changes to the DNA and other biomolecules. The fungal cells will undergo a thorough analysis of morphological, physiological, and chemical changes.

Long-term, researchers hope to use the knowledge gained to investigate new ways to prevent radiation damage to humans and equipment in space. 

The NRL team is investigating these research questions from other angles as well. Wang’s research group was recently selected by NASA to study how melanized fungal cells adapt to Mars-like conditions using NASA’s Antarctic balloon platform. The team is also collaborating with DoD’s Space Testing Program and ISS National Laboratory to send fungal samples to the International Space Station to study how microgravity and radiation alter production of beneficial biomaterials and biomolecules. 

“Fungi are great at adapting”, Wang said. If we can harness their natural defense mechanisms, we could leverage biological systems to develop protective mechanisms for equipment or astronauts. As a DoD lab, NRL is in a great position for this. We have the facilities and the capabilities.”

Zachary Schultzhaus, a former Jerome and Isabella Karle Distinguished Scholar Fellow and another researcher on the project, said he believes it is also feasible to grow fungus in space to produce different molecules for therapeutic applications, like medicine or vitamins. Instead of carrying all of the food and medicine needed for a mission, astronauts could produce it on demand. He hopes to delve deeper into the idea once this current research project concludes. 

NRL’s work on investigating the roles of melanin and DNA repair on adaptation and survivability of fungi in deep space is funded by NASA, and is scheduled to continue through 2022. 

Featured image: Drs. Zachary Schultzhaus (left), Zheng Wang (center), and Jillian Romsdahl (right) from the U.S. Naval Research Laboratory’s fungal biology research team observe a fungal agar plate in Washington, D.C., Nov. 13, 2019. The fungus Aspergillus niger, along with its three mutant strains, are slated to rotate the moon on NASA’s Orion Space Capsule in 2021 so researchers can improve their understanding of the fungi’s natural and adapted defenses against radiation. (U.S. Navy photo by Sarah Peterson)

Provided by US Naval Research Laboratory

Moon Mission Delays Could Increase Risks From Solar Storms (Astronomy)

Planned missions to return humans to the Moon need to hurry up to avoid hitting one of the busiest periods for extreme space weather, according to scientists conducting the most in-depth ever look at solar storm timing.

Scientists at the University of Reading studied 150 years of space weather data to investigate patterns in the timing of the most extreme events, which can be extremely dangerous to astronauts and satellites, and even disrupt power grids if they arrive at Earth.

The researchers found for the first time that extreme space weather events are more likely to occur early in even-numbered solar cycles, and late in odd-numbered cycles – such as the one just starting. They are also more likely during busy periods of solar activity and in bigger cycles, mirroring the pattern for moderate space weather.

The findings, published in the journal Solar Physics, could have implications for the NASA-led Artemis mission, which plans to return humans to the moon in 2024, but which could be delayed to the late 2020s.

Professor Mathew Owens, a space physicist at the University of Reading, said: “Until now, the most extreme space-weather events were thought to be random in their timing and thus little could be done to plan around them.

“However, this research suggests they are more predictable, generally following the same ‘seasons’ of activity as smaller space-weather events. But they also show some important differences during the most active season, which could help us avoid damaging space-weather effects.  

“These new findings should allow us to make better space weather forecasts for the solar cycle that is just beginning and will run for the decade or so. It suggests any significant space missions in the years ahead – including returning astronauts to the Moon and later, onto Mars – will be less likely to encounter extreme space-weather events over the first half of the solar cycle than the second.”

Extreme space weather is driven by huge eruptions of plasma from the Sun, called coronal mass ejections, arriving at Earth, causing a global geomagnetic disturbance.

Previous research has generally focused on how big extreme space weather events can be, based on observations of previous events. Predicting their timing is far more difficult because extreme events are rare, so there is relatively little historic data in which to identify patterns.

In the new study, the scientists used a new method applying statistical modelling to storm timing for the first time. They looked at data from the past 150 years – the longest period of data available for this type of research – recorded by ground-based instruments that measure magnetic fields in the Earth’s atmosphere, located in the UK and Australia.

The Sun goes through regular 11-year cycles of its magnetic field, which is seen in the number of sunspots on its surface. During this cycle the Sun’s magnetic north and south poles switch places. Each cycle includes a solar maximum period, where solar activity is at its greatest, and a quiet solar minimum phase.

Previous research has shown moderate space weather is more likely during the solar maximum than the period around the solar minimum, and more likely during cycles with a larger peak sunspot number. However, this is the first study that shows the same pattern is also true of extreme events.

The major finding, though, was that extreme space weather events are more likely to occur early in even-numbered solar cycles, and late in odd-numbered cycles, such as cycle 25, which began in December 2019.

The scientists believe this could be because of the orientation of the Sun’s large-scale magnetic field, which flips at solar maximum so it is pointing opposite to Earth’s magnetic field early in even cycles and late in odd cycles. This theory will need more investigation.

This new research on space weather timing allows predictions to be made for extreme space weather during solar cycle 25. It could therefore be used to plan the timing of activities that could be affected by extreme space weather, such as power grid maintenance on Earth, satellite operations, or major space missions.

The findings suggest that any major operations planned beyond the next five years will have to make allowances for the higher likelihood of severe space weather late in the current solar cycle between 2026 and 2030.

major solar eruption in August 1972, between NASA’s Apollo 16 and 17 missions, was strong enough that it could have caused major technical or health problems to astronauts had it occurred while they were en route or around the Moon.

Provided by University of Reading

Measuring the Moon’s Nano Dust is No Small Matter (Planetary Science)

Like a chameleon of the night sky, the Moon often changes its appearance. It might look larger, brighter or redder, for example, due to its phases, its position in the solar system or smoke in Earth’s atmosphere. (It is not made of green cheese, however.)

Another factor in its appearance is the size and shape of moon dust particles, the small rock grains that cover the moon’s surface. Researchers at the National Institute of Standards and Technology (NIST) are now measuring tinier moon dust particles than ever before, a step toward more precisely explaining the Moon’s apparent color and brightness. This in turn might help improve tracking of weather patterns and other phenomena by satellite cameras that use the Moon as a calibration source.

NIST researchers and collaborators have developed a complex method of measuring the exact three-dimensional shape of 25 particles of moon dust collected during the Apollo 11 mission in 1969. The team includes researchers from the Air Force Research Laboratory, the Space Science Institute and the University of Missouri-Kansas City.

These researchers have been studying moon dust for several years. But as described in a new journal paper, they now have X-ray nano computed tomography (XCT), which allowed them to examine the shape of particles as small as 400 nanometers (billionths of a meter) in length.

The research team developed a method for both measuring and computationally analyzing how the dust particle shapes scatter light. Follow-up studies will include many more particles, and more clearly link their shape to light scattering. Researchers are especially interested in a feature called “albedo,” moonspeak for how much light or radiation it reflects.

The recipe for measuring the Moon’s nano dust is complicated. First you need to mix it with something, as if making an omelet, and then turn it on a stick for hours like a rotisserie chicken. Straws and dressmakers’ pins are involved too.

“The procedure is elaborate because it is hard to get a small particle by itself, but one needs to measure many particles for good statistics, since they are randomly distributed in size and shape,” NIST Fellow Ed Garboczi said.

“Since they are so tiny and because they only come in powders, a single particle needs to be separated from all the others,” Garboczi continued. “They are too small to do that by hand, at least not in any quantity, so they must be carefully dispersed in a medium. The medium must also freeze their mechanical motion, in order to be able to get good XCT images. If there is any movement of the particles during the several hours of the XCT scan, then the images will be badly blurred and generally not usable. The final form of the sample must also be compatible with getting the X-ray source and camera close to the sample while it rotates, so a narrow, straight cylinder is best.”

The procedure involved stirring the Apollo 11 material into epoxy, which was then dripped over the outside of a tiny straw to get a thin layer. Small pieces of this layer were then removed from the straw and mounted on dressmakers’ pins, which were inserted into the XCT instrument.

The XCT machine generated X-ray images of the samples that were reconstructed by software into slices. NIST software stacked the slices into a 3D image and then converted it into a format that classified units of volume, or voxels, as either inside or outside the particles. The 3D particle shapes were identified computationally from these segmented images. The voxels making up each particle were saved in separate files that were forwarded to software for solving electromagnetic scattering problems in the visible to the infrared frequency range.

The results indicated that the color of light absorbed by a moon dust particle is highly sensitive to its shape and can be significantly different from that of spherical or ellipsoidal particles of the same size. That doesn’t mean too much to the researchers — yet.

“This is our first look at the influence of actual shapes of lunar particles on light scattering and focuses on some fundamental particle properties,” co-author Jay Goguen of the Space Science Institute said. “The models developed here form the basis of future calculations that could model observations of the spectrum, brightness and polarization of the moon’s surface and how those observed quantities change during the moon’s phases.”

The authors are now studying a wider range of moon dust shapes and sizes, including particles collected during the Apollo 14 mission in 1971. The moon dust samples were loaned to NIST by NASA’s Curation and Analysis Planning Team for Extraterrestrial Materials program.

Featured image: Colorized screenshots of the exact shapes of moon dust collected during the Apollo 11 mission. NIST researchers and collaborators developed a method of measuring these nanoscale particles as a prelude to studying their light-scattering properties. © Credit: E. Garboczi/NIST and A. Sharits/AFRL

Paper: S. Baidya, M. Melius, A.M. Hassan, A. Sharits, A.N. Chiaramonti, T. Lafarge, J.D. Goguen and E.J. Garboczi. Optical Scattering Characteristics of 3D Lunar Regolith Particles Measured using X-Ray Nano Computed Tomography. IEEE Geoscience and Remote Sensing Letters. Published online April 27, 2021. DOI: 10.1109/LGRS.2021.3073344

Provided by NIST

Galileo Will Help Lunar Pathfinder Navigate Around Moon (Astronomy)

ESA’s Lunar Pathfinder mission to the Moon will carry an advanced satellite navigation receiver, in order to perform the first ever satnav positioning fix in lunar orbit. This experimental payload marks a preliminary step in an ambitious ESA plan to expand reliable satnav coverage – as well as communication links – to explorers around and ultimately on the Moon during this decade.

Due for launch by the end of 2023 into lunar orbit, the public-private Lunar Pathfinder comsat will offer commercial data relay services to lunar missions – while also stretching the operational limits of satnav signals.

Galileo constellation © ESA

Navigation satellites like Europe’s Galileo constellation are intended to deliver positioning, navigation and timing services to our planet, so most of the energy of their navigation antennas radiates directly towards the Earth disc, blocking its use for users further away in space. 

“But this is not the whole story,” explains Javier Ventura-Traveset, leading ESA’s Galileo Navigation Science Office and coordinating ESA lunar navigation activities. “Navigation signal patterns also radiate sideways, like light from a flashlight, and past testing shows these antenna ‘side lobes’ can be employed for positioning, provided adequate receivers are implemented.”

Galileo ‘side lobe’ signals © ESA

Just like people or cars on the ground, satellites in low-Earth orbit rely heavily on satnav signals to determine their orbital position, and since ESA proved higher-orbit positioning was possible, a growing number of satellites in geostationary orbit today employ satnav receivers.

But geostationary orbit is 35 786 km up, while the Moon is more than ten times further away, at an average distance of 384 000 km. In 2019 however, NASA’s Magnetospheric Multiscale Mission acquired GPS signals to perform a fix and determine its orbit from 187 166 km away, close to halfway the Earth-Moon distance.

Lunar Pathfinder will relay signals from other Moon missions © ESA

Javier adds: “This successful experimental evidence provides us high confidence since the receiver we will embark on Lunar Pathfinder will have a significantly improved sensitivity, employ both Galileo and GPS signals and will also feature a high-gain satnav antenna.”

This high sensitivity receiver’s main antenna was developed through ESA’s General Support Technology Programme, with the receiver’s main unit developed through ESA’s Navigation Innovation and Support Programme, NAVISP.

The receiver project is led by ESA navigation engineer Pietro Giordano: “The high sensitivity receiver will be able to detect very faint signals, millions of times weaker than the ones received on Earth. The use of advanced on-board orbital filters will allow to achieve unprecedented orbit determination accuracy on an autonomous basis.”

Lunar Pathfinder’s receiver is projected to achieve positioning accuracy of around 100 m – more accurate than traditional ground tracking.

The availability of satnav will allow the performance of ‘Precise Orbit Determination’ for lunar satellites, notes Werner Enderle, Head of ESA’s Navigation Support Office: “Traditional orbit determination for lunar orbiting satellites is performed by radio ranging, using deep space ground stations. This Lunar Pathfinder demonstration will be a major milestone in lunar navigation, changing the entire approach. It will not only increase spacecraft autonomy and sharpen the accuracy of results, it will also help to reduce operational costs.”  

While lunar orbits are often unstable, with low-orbiting satellites drawn off course by the lumpy mass concentrations or ‘mascons’ making up the Moon , Lunar Pathfinder is planned to adopt a highly-stable ‘frozen’ elliptical orbit, focused on the lunar south pole – a leading target for future expeditions.

Lunar Pathfinder will focus coverage on the Moon’s south pole © ESA

Earth – and its satnav constellations – should remain in view of Lunar Pathfinder for the majority of testing. The main challlenge will be overcoming the limited geometry of satnav signals all coming from the same part of the sky, along with the low signal power.

Lunar Pathfinder’s demonstration that terrestrial satnav signals can be employed to navigate in lunar orbits will be an important early step in ESA’s Moonlight initiative. Supported through three ESA Directorates, Moonlight will go on to establish a Lunar Communication and Navigation Service.

 “Over this coming decade, ESA aims to contribute to building up a common communications and navigation infrastructure for all lunar missions based on dedicated lunar satellites,” explains Bernhard Hufenbach, managing commercialisation and innovation initiatives for space exploration at ESA.

“Moonlight will allow to support missions that cannot use Earth satnav signals, such as landers on the far side and is planning to cover the current gap towards the needs expressed by the Global Exploration community, targeting positioning accuracy below 50 metres.”

Extending satnav to the Moon © ESA

As well as facilitating lunar exploration, these satnav signals might one day become a tool for science in their own right, used, for example, to perform reflectometry across the lunar surface; sounding the scant dusty ‘exosphere’ that surrounds the Moon or by providing a common time reference signal across the Moon, to be used for fundamental physics or astronomy experiments.

So as well as marking a first in the history of satellite navigation, Javier notes that Lunar Pathfinder’s satnav experiment will have larger consequences: “This will become the first ever demonstration of GPS and Galileo reception in lunar orbit, opening the door to a complete way to navigate spacecraft in deep space, enabling human exploration of the Moon.”

Featured image: Lunar Ride and phone home service

Provided by ESA

PSI’s Bill Hartmann Asks: Do Rings Around Lunar Impact Basins Need to be Perfect Circles & is That Important? (Planetary Science)

These two images are from the paper “Effects of early intense bombardment on megaregolith evolution and on lunar (and planetary) surface samples” in Meteoritics and Planetary Science (November 2020) by PSI senior scientist emeritus, Bill Hartmann, and Alessandro Morbidelli, a well-known French/Italian dynamicist at the Observatoire de la Cote d’Azur, in Nice, France. The images show the best-preserved impact basin, “Orientale,” (discovered on the east “edge” of the moon by Hartmann and Kuiper in 1962). Morbidelli and co-workers in 2018 produced a new computer model of lunar cratering history, showing intense bombardment in the first few hundred million years after lunar formation about 4.5 million years ago, with declining impact rates since then (contrary to the now discarded “late heavy bombardment” theory that proposed negligible cratering in the first 500 million years after lunar formation). Hartmann and Morbidelli conclude that many giant impact basins, like Orientale, formed in the first few hundred million years, many of which have been since obliterated by later cratering.

On this radar-based topographic map of the lunar impact basin Orientale, blue and purple show the lower elevations and red shows the highest elevation. Credit: NASA

In past years, some lunar scientists proposed that the largest visible impact scar on the Moon may be the region known as ‘Oceanus Procellarum,’ a depressed, lava-covered region visible to the naked eye. It is partly obliterated by the more recent “Imbrium Impact Basin,” dated by many Apollo mission rock samples at age 3.9 billion years. However, the gravity-mapping team using the “GRAIL” orbiting instrument in 2011-12 argued against Procellarum being impact-related, because they found linear, not circular, structures surrounding Oceanus Procellarum below the Moon’s surface. These they interpreted “as part of the lunar magma plumbing system – the conduits that fed lava to the surface during ancient volcanic eruptions.” The Hartmann and Morbidelli illustration shows, however, that linear elements alone do not disprove an impact origin. The “rings” around Orientale and other basins contain linear elements, marked in white lines in the color image below. The illustration also shows that giant impacts created parts of the “lunar plumbing system.” The innermost white line (east side) can be seen in the black and white photo to have lava extrusions all along its base. In other words, as has been known for several decades, the linear segments in the “rings” of impact basins did “feed lava to the surface.”

Hartmann and Morbidelli agree that while Oceanus Procellarum is not yet proven to be an impact scar impacts of that size would deform the spherical shape of the moon, and the physical mechanics of the readjustment of the moon to spherical shape are not well understood.

Featured image: This photo of the lunar impact basin Orientale was taken by a lunar Orbiter. © NASA

Provided by PSI

Apollo Rock Samples Capture Key Moments in the Moon’s Early History, Study Finds (Planetary Science)

A new analysis of samples brought back from the Moon to helps clear up questions about the isotopic composition of Moon’s interior.

Volcanic rock samples collected during NASA’s Apollo missions bear the isotopic signature of key events in the early evolution of the Moon, a new analysis found. Those events include the formation of the Moon’s iron core, as well as the crystallization of the lunar magma ocean — the sea of molten rock thought to have covered the Moon for around 100 million years after the it formed. 

The analysis, published in the journal Science Advances, used a technique called secondary ion mass spectrometry (SIMS) to study volcanic glasses returned from the Apollo 15 and 17 missions, which are thought to represent some of the most primitive volcanic material on the Moon. The study looked specifically at sulfur isotope composition, which can reveal details about the chemical evolution of lavas from generation, transport and eruption. 

“For many years it appeared as though the lunar basaltic rock samples analyzed had a very limited variation in sulfur isotope ratios,” said Alberto Saal, a geology professor at Brown University and study co-author. “That would suggest that the interior of the Moon has a basically homogeneous sulfur isotopic composition. But using modern in situ analytical techniques, we show that the isotope ratios of the volcanic glasses actually have a fairly wide range, and those variations can be explained by events early in lunar history.”

The sulfur signature of interest is the ratio of the “heavy” sulfur-34 isotope to the lighter sulfur-32. Initial studies of lunar volcanic samples found that they uniformly leaned toward the heavier sulfur-34. The nearly homogeneous sulfur isotope ratio was in contrast with large variations in other elements and isotopes detected in the lunar samples.  

This new study looked at 67 individual volcanic glass samples and their melt inclusions — tiny blobs of molten lava trapped within crystals inside the glass. Melt inclusions capture the lava before sulfur and other volatile elements are released as gas during eruption — a process called degassing. As such, they offer a pristine picture of what the original source lava was like.  Using the SIMS at the Carnegie Institution for Science, Saal with his colleague, the late Carnegie scientist Eric Hauri, were able to measure the sulfur isotopes in these pristine melt inclusions and glasses, and use those results to calibrate a model of the degassing process for all the samples.

“Once we know the degassing, then we can estimate back the original sulfur isotope composition of the sources that produced these lavas,” Saal said. 

Those calculations revealed that the lavas had been derived from different reservoirs within the interior of the Moon with a wide range of sulfur isotope ratios. The researchers then showed that the range of values detected in the samples could be explained by events in the Moon’s early history. 

The lighter isotope ratio in some of the volcanic glasses, for example, is consistent with the segregation of the iron core from the early molten Moon. When an iron core separates from other material in a planetary body, it takes a bit of sulfur with it. The sulfur that’s taken tends to be the heavier sulfur-34 isotope, leaving the remaining magma enriched in the lighter sulfur-32.

“The values we see in some of the volcanic glasses are fully consistent with models of the core segregation process,” Saal said. 

The heavier isotope values can be explained by the further cooling and crystallization of the early molten Moon. The crystallization process removes sulfur from the magma pool, producing solid reservoirs with heavier sulfur-34. That process is the likely source of the heavier isotope values found in some of the volcanic glasses and basaltic rocks returned from the Moon.

“Our results suggest that these samples record these critical events in lunar history,” Saal said. “As we keep looking at these samples with newer and better techniques, we keep learning new things.” 

More work needs to be done — and more samples need to be analyzed — to fully understand the sulfur isotopic composition of the Moon, Saal says. But these new results help to clarify long-standing questions about the composition of the Moon’s interior, and they bring scientists one step closer to understanding the formation and early history of the Moon.

The research was funded by NASA’s Solar System Workings program (80NSSC20K0461).

Reference: Alberto E. Saal and Erik H. Hauri, “Large sulfur isotope fractionation in lunar volcanic glasses reveals the magmatic differentiation and degassing of the Moon”, Science Advances  24 Feb 2021: Vol. 7, no. 9, eabe4641 DOI: 10.1126/sciadv.abe4641

Provided by Brown University

Students In Scientific Writing Course Review ‘Lava Worlds’ in Academic Publication (Earth Science)

In the early solar system, rocky planets, such as Earth, Mercury, Venus and Mars, and the Moon may have been ‘lava worlds,’ with oceans of magma blanketing the surface, according to planetary scientists. Similar magma-covered planets may orbit close to other stars and can be studied directly . Five earth sciences graduate students in the University of Hawai‘i at Mānoa’s School of Ocean and Earth Science and Technology (SOEST), along with their professor, published a scientific review of this stage in planetary evolution that may determine the later atmospheric composition and potential habitability of planets like Earth.

A critical skill for success in graduate studies and a career in the sciences is clear and concise writing. Courses in scientific writing such as those taught by Earth sciences professor Eric Gaidos are an opportunity for SOEST graduate students to develop their skills and get experience with publication.

This is the fourth time students in Gaidos’s writing class have successfully published their work in an academic journal.

“The introduction to scientific writing was invaluable and something that I was looking for,” said Kelly Truax, co-author and SOEST graduate student. “My first career was a mix of the arts and education which is a vastly different writing style. It became easier after working on this paper to understand the differences in tonality and structure. The project also offered a unique opportunity to write about subject matter outside of my research and receive feedback from all parties involved.”

This topic is particularly timely for the scientific community because NASA’s Transiting Exoplanet Survey Satellite is surveying the entire sky searching for close-in planets around bright stars—including “lava worlds” and the James Webb Space Telescope, scheduled to launch later this year will usher in a new era of precise measurements of those objects.

“I was interested in writing this paper on lava worlds because planetary volcanology has always been fascinating to me,” said Rebecca deGraffenried, co-author and SOEST graduate student.“It’s always fun to consider a process on Earth, and think about how that process would change under the range of conditions present on exoplanets. Particularly since I started studying Kīlauea, I’ve been interested in lava lakes. So this paper afforded the opportunity to both learn more about lava lakes in general and lava lakes on other worlds.”

Participating in a guided collaboration within the cohort is a significant feature of this approach to the course.

“Balancing the work with classes and research gave me confidence that I could balance everything,” said Truax. “Ultimately, the camaraderie around the work and the experiences along the way were invaluable and allowed for the rare chance to write predominantly with my peers versus those later into their careers.”

Said Gaidos, “This course was an opportunity for the students not only to pursue their individual scientific interests and improve their writing skills, but also to learn to work as a team toward a common goal, and then see a tangible result from their collective effort.”

The authors on the publication in the journal Geochemistry are Keng-Hsien Chao, Rebecca deGraffenried, Mackenzie Lach, William Nelson, Kelly Truax and Eric Gaidos.

Featured image: Halemaumau lava lake in Kilauea, taken in November 2013. Credit: Tom Shea.

Reference: Keng-Hsien Chao, Rebecca deGraffenried, Mackenzie Lach, William Nelson, Kelly Truax, Eric Gaidos, “Lava Worlds: From Early Earth to Exoplanets”, Geochemistry, 2021, 125735, ISSN 0009-2819,

Provided by SOEST