Science

The remarkable aurora in early May this year demonstrated the power that solar storms can emit as radiation, but occasionally the sun does something far more destructive. Known as “solar particle events,” these blasts of protons directly from the surface of the sun can shoot out like a searchlight into space.

Records show that around every thousand years Earth gets hit by an extreme solar particle event, which could cause severe damage to the ozone layer and increase levels of ultraviolet (UV) radiation at the surface.

We analyzed what happens during such an extreme event in a paper published July 1 in the Proceedings of the National Academy of Sciences. We also show that at times when Earth’s magnetic field is weak, these events could have a dramatic effect on life across the planet.

Earth’s critical magnetic shield

Earth’s magnetic field provides a crucial protective cocoon for life, deflecting electrically charged radiation from the sun. In the normal state, it functions like a gigantic bar magnet with field lines rising from one pole, looping around, and plunging back down at the other pole, in a pattern sometimes described as an “inverted grapefruit.” The vertical orientation at the poles allows some ionizing cosmic radiation to penetrate down as far as the upper atmosphere, where it interacts with gas molecules to create the glow we know as the aurora.

However, the field changes a great deal over time. In the past century, the north magnetic pole has wandered across northern Canada at a speed of around 40 kilometers per year, and the field has weakened by more than 6%. Geological records show there have been periods of centuries or millennia when the geomagnetic field has been very weak or even entirely absent.

We can see what would happen without Earth’s magnetic field by looking at Mars, which lost its global magnetic field in the ancient past, and most of its atmosphere as a result. In May, not long after the aurora, a strong solar particle event hit Mars. It disrupted the operation of the Mars Odyssey spacecraft, and caused radiation levels at the surface of Mars about 30 times higher than what you would receive during a chest X-ray.

The power of protons

The sun’s outer atmosphere emits a constant fluctuating stream of electrons and protons known as the “solar wind.” However, the sun’s surface also sporadically emits bursts of energy, mostly protons, in solar particle events—which are often associated with solar flares.

Protons are much heavier than electrons and carry more energy so they reach lower altitudes in Earth’s atmosphere, exciting gas molecules in the air. However, these excited molecules emit only X-rays, which are invisible to the naked eye.

Hundreds of weak solar particle events occur every solar cycle (roughly 11 years) but scientists have found traces of much stronger events throughout Earth’s history. Some of the most extreme were thousands of times stronger than anything recorded with modern instruments.

Extreme solar particle events

These extreme solar particle events occur roughly every few millennia. The most recent one happened around 993 AD, and was used to show that Viking buildings in Canada used timber cut in 1021 AD.

Less ozone, more radiation

Beyond their immediate effect, solar particle events can also kickstart a chain of chemical reactions in the upper atmosphere that can deplete ozone. Ozone absorbs harmful solar UV radiation, which can damage eyesight and also DNA (increasing the risk of skin cancer), as well as impacting the climate.

In our new study, we used large computer models of global atmospheric chemistry to examine the impacts of an extreme solar particle event.

We found such an event could deplete ozone levels for a year or so, raising UV levels at the surface and increasing DNA damage. But if a solar proton event arrived during a period when Earth’s magnetic field was very weak then ozone damage would last six years, increasing UV levels by 25% and boosting the rate of solar-induced DNA damage by up to 50%.

Particle blasts from the past

How likely is this deadly combination of weak magnetic field and extreme solar proton events? Given how often each of them occurs, it appears likely they happen together relatively often.

In fact, this combination of events may explain several mysterious occurrences in Earth’s past.

The most recent period of weak magnetic field—including a temporary switch in north and south poles—began 42,000 years ago and lasted about 1,000 years. Several major evolutionary events occurred around this time, such as the disappearance of the last Neanderthals in Europe and the extinctions of marsupial megafauna including giant wombats and kangaroos in Australia.

An even bigger evolutionary event has also been linked to Earth’s geomagnetic field. The origin of multicellular animals at the end of the Ediacaran period (from 565 million years ago), recorded in fossils in South Australia’s Flinders Ranges, occurred after a 26-million-year period of weak or absent magnetic field.

Similarly, the rapid evolution of diverse groups of animals in the Cambrian Explosion (around 539 million years ago) has also been related to geomagnetism and high UV levels. The simultaneous evolution of eyes and hard body shells in multiple unrelated groups has been described as the best means to both detect and avoid the harmful incoming UV rays, in a “flight from light.”

We are still only starting to explore the role of solar activity and Earth’s magnetic field in the history of life.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Recently, a team of researchers from Pohang University of Science and Technology (POSTECH), the Korea Research Institute of Chemical Technology, and Chonnam National University has developed a technique to separate well-mixed mixtures.

The research team led by Professor Jee-hoon Han from the Department of Chemical Engineering at POSTECH created a technology for the efficient synthesis and purification of ionic liquids. Their research was recently featured as the cover paper in the online edition of Industrial & Engineering Chemistry Research.

Professor Jee-hoon Han collaborated on the research with Director Ji Hoon Park, Principal Researcher Soo Min Kim, and Researcher Myungho Choi from CO₂ & Energy Research Center at the Korea Research Institute of Chemical Technology, and Chonnam National University Professor Jaewon Byun.

Ionic liquids are salts that remain in a liquid state at room temperature or even at relatively low temperatures due to strong electrical interactions between their ions. Unlike common salts, they possess unique properties such as nonflammability, low volatility, and thermal and chemical stability, making them valuable for various industrial applications including catalysts and electrolytes.

One of the most studied ionic liquids is [bmim][BF₄], known for its high stability and low toxicity. However, the complex and expensive process of removing impurities such as lithium chloride (LiCl) during synthesis has been a significant barrier to the technology’s commercialization.

In this study, the researchers employed halocarbon refrigerants—specifically, chlorodifluoromethane (Rf-22)—to synthesize the ionic liquid [bmim][BF₄] more economically and efficiently than traditional methods.

By using Rf-22 as a phase separation mediator, they were able to induce a mixture containing methylimidazole to separate into two distinct layers, similar to the separation of oil and water.

The team observed phase separation by varying the ratios of [bmim][BF₄], water, and halocarbon mixtures. They then applied the collected data to a ternary phase diagram model. This model visually represents the composition and phases of a mixture containing three different components and is used to predict the phase formed based on the proportions of each ingredient.

Using the ternary phase diagram modeling, the researchers successfully produced high-purity [bmim][BF₄] with a purity exceeding 99%. Additionally, they were able to effectively recover and recycle the layer containing methylimidazole which did not participate in the synthesis reaction.

The team then conducted process simulations to evaluate the economic feasibility of the purification technology developed in this study. Based on a cost analysis for producing 1 ton of [bmim][BF₄] per day, they determined that the minimum selling price would be about $12,000 per ton. This is more competitive than existing process technologies, demonstrating the potential for commercializing the technology.

Professor Jee-hoon Han of POSTECH stated, “We hope this research will advance the commercialization of ionic liquids and provide practical industrial solutions based on our understanding of these substances.”

Principal Researcher Soo Min Kim from the Korea Research Institute of Chemical Technology said, “This technique can also be applied to other solvents, enabling the synthesis of a wide range of high-purity ionic liquids.”

Using the repurposed equipment, a team including Imperial College London researchers have measured parts of the Martian atmosphere that were previously impossible to probe. This includes areas that can block radio signals if not properly accounted for—crucial for future Mars habitation missions.

The results of the first 83 measurements, analyzed by Imperial researchers and European Space Agency (ESA) colleagues across Europe, are published today in the journal Radio Science.

To achieve this, ExoMars’ Trace Gas Orbiter (TGO) teamed up with another ESA spacecraft orbiting the red planet: Mars Express (MEX). The two craft maintain a radio link, so that as one passes behind the planet, radio waves cut through the deeper layers of the Martian atmosphere.

Changes in the atmosphere’s refractivity—how it bends the radio waves—cause tiny but detectable shifts in the radio frequencies received by the spacecraft. By analyzing this shift, scientists can determine the density of the lower atmosphere and the electron density in the ionosphere—a charged upper layer of the atmosphere. The technique is called mutual radio occultation.

Lead author of the study Jacob Parrott, a Ph.D. student from the Department of Physics at Imperial, said, “The systems on MEX and TGO were not initially designed to do this—the radio antennas we used were made for communication between orbiters and rovers on the planet’s surface. We had to reprogram them while inflight to carry out this new science.

“This innovative technique is likely to be a game-changer for future missions, proving that mutual radio occultation between two orbiting spacecraft is an economical way to extract more scientific value from existing equipment.”

Dream teamwork

Previously, radio occultation was conducted using the radio link from a Mars orbiter to large ground stations on Earth. The radio signal from the orbiter would be monitored as the spacecraft “set” (was occulted) behind Mars, meaning the signal passed through the layers of the planet’s atmosphere.

Using two orbiting craft to take this measurement is already a common way to investigate the Earth’s atmosphere: thousands of such measurements occur between global navigation satellites, where the data they provide are used for atmospheric monitoring and weather prediction.

However, this method had only been used on Mars three times before; by NASA in 2007 as a hardware demonstration. The new use by the two ESA spacecraft marks the first time this technique has been routinely applied to another planet.

Now its viability has been proven, the scientists and engineers behind the work are looking into how to expand the use of this technique in future Mars missions.

Study co-author Dr. Colin Wilson, Project Scientist for the ExoMars Trace Gas Orbiter and Mars Express at ESA, said, “ESA has now demonstrated the viability of this technique, which could be transformational for Mars science in the future.

“There are currently seven spacecraft orbiting Mars; as the number of spacecraft increases, as it will in coming decades, the number of radio occultation opportunities increases rapidly. Therefore, this technique will be an increasingly important tool for studying Mars.”

More measurements, more insights

Spacecraft-to-spacecraft occultation allows more measurements to be taken and allows new regions of the atmosphere to be probed.

Because conventional radio occultation measurements on Mars involve a radio link to a ground station on Earth, the measurement location is fixed relative to Earth’s slow movement. This makes it hard to capture global changes on Mars, as researchers are often looking at the same spots.

Additionally, this method can only sample near sunset and sunrise because of Earth’s proximity to the sun, limiting our view of Mars’ atmosphere.

Moreover, traditional radio occultation suffers from “occultation seasons,” where measurements are only possible for a few months each year due to the spacecraft’s orbit. For example, Mars Express could only perform radio occultation for two months in 2022.

Mutual radio occultation overcomes these problems, allowing researchers for the first time to explore the entire depth of Mars’ ionosphere around noon and midnight.

To date, little has been known about people living in north-western Saudi Arabia during the Neolithic—the period traditionally defined by the shift to humans controlling food production and settling into communities with agriculture and domesticated animals.

The piecemeal evidence available hinted traditional ideas—of small struggling groups constantly on the move across the barren lands—needed to be revisited.

Now, an Australian-led team has released new research in the journal Levant on monumental buildings we call “standing stone circles.” The findings are helping to rewrite what we know about the people who lived on this land between 6,500 and 8,000 years ago.

Our evidence reveals what they ate, what tools they used and even the jewelry they wore. It leads us to think these people weren’t struggling so much after all, but rather had found complex and strategic ways to thrive on the land for millennia.

The project

Over the past five years, our team of researchers has studied 431 standing stone circles in the AlUla and Khaybar regions of north-west Saudi Arabia, as part of an ongoing project sponsored by the Royal Commission for AlUla. Of the 431 structures, 52 have been surveyed in detail and 11 excavated.

Our latest findings come from a selection of buildings found on the Harrat ‘Uwayrid—a volcanic plateau formed over millennia. The dense clusters of standing stone circles on the harrat show us how complex these mobile pastoralist communities actually were. We also recovered remnants left behind by the people who lived in these buildings for more than 1,000 years.

We used a range of modern and traditional techniques to tackle the practical limitations of working in such a remote and rugged landscape. Aerial survey by helicopter helped us identify examples of the dwellings across 40,000 square kilometers of basalt and sandy desert. Drones were also used to make plans of the sites, some almost three hectares in size.

More than just a house

Ours is the first published evidence for domestic architecture from this period. These buildings are substantial, between 4 and 8 meters wide. They are formed by two concentric rows of large stones placed end-to-end in a circle.

We theorize the space created between the two rows of stone acted as a foundation for timber posts wedged between the rows to support the dwelling’s roof. Another slab in the center supported a central timber post lashed to it.

Based on the tools and animal remains we’ve found, we think the occupants probably threw animal skins across the top of the structure to enclose it, forming a roof of sorts.

These structures—which we think of more as shelters than “houses”—were used for any and all activities. Inside, we found evidence of stone tool-making, cooking and eating, as well as lost and broken tools used for processing animal hides.

A diverse palate

Our analysis of the animal bones found inside the structures shows these people mostly ate domesticated species, such as goats, sheep and a smaller number of cattle. They supplemented this with wild species such as gazelles and birds.

This means they could respond to changes in their environment with flexibility—giving them resilience at a time when climate change would have been affecting the availability of water and vegetation.

This adaptability also extended to their use of plants. They left behind many grindstones—slabs of basalt worn flat by the grinding of wild grasses and local plants.

Nomadic or mobile?

We assume these people didn’t stay in one place, since they lived in buildings that could be partially dismantled and moved. Goats and sheep also need fresh pastures and water to survive.

That said, these people spent enough time at each site to justify the time and effort required to source and manipulate basalt blocks weighing up to 1 ton each. This suggests they returned to these locations time and again for hundreds of years, if not more than 1,200 years.

They left behind materials collected from near and far. While the local basalt was sufficient for everyday tools, the best materials made from chert (a tough sedimentary rock) were brought up to the Harrat Uwayrid to make fine arrowheads, drills and scrapers.

They also collected red stone to be crushed into pigment. It may have been used for rock art, or perhaps for painting bodies and hides.

Small shells were brought from the Red Sea (some 120 kilometers away) to make beads. Other objects we found included bracelets and pendants carved and polished from exotic stone.

Trading in the Levant

It seems likely these people formed a culturally distinct group who interacted with their neighbors in the Levant to the north, a region which includes modern-day Jordan, Palestine and Syria, among others.

Our findings suggest they imported their animals and stone tool technologies. Some of the tools resemble those found at earlier sites across Jordan, which suggests they either traded or learned how to make them from further north.

Domesticated goats and sheep would have also been sourced from further afield, as there were no wild versions of these animals in the area. Everything they brought was incorporated usefully into their way of life, to suit the lands they already knew so well.

Our work is just beginning to fill in the gaps of what life was like in north-western Arabia, helping reintroduce it—and its people—into the picture of the wider region.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Researchers at The University of Western Australia’s ARC Industrial Transformation Research Hub for Transforming Energy Infrastructure through Digital Engineering (TIDE) have made a significant mathematical breakthrough that could help transform ocean research and technology.

Research Fellow Dr. Lachlan Astfalck, from UWA’s School of Physics, Mathematics and Computing, and his team developed a new method for spectral density estimation, addressing long-standing biases and paving the way for more accurate oceanographic studies.

The study was published in the journal Biometrika, known for its emphasis on original methodological and theoretical contributions of direct or potential value in applications.

“Understanding the ocean is crucial for numerous fields, including offshore engineering, climate assessment and modeling, renewable technologies, defense and transport,” Dr. Astfalck said.

“Our new method allows researchers and industry professionals to advance ocean technologies with greater confidence and accuracy.”

Spectral density estimation is a mathematical technique used to measure the energy contribution of oscillatory signals, such as waves and currents, by identifying which frequencies carry the most energy.

“Traditionally, Welch’s estimator has been the go-to method for this analysis due to its ease of use and widespread citation, however this method has an inherent risk of bias, which can distort the expected estimates based on the model’s assumption, a problem often overlooked,” Dr. Astfalck said.

The TIDE team developed the debiased Welch estimator, which uses non-parametric statistical learning to remove these biases.

“Our method improves the accuracy and reliability of spectral calculations without requiring specific assumptions about the data’s shape or distribution, which is particularly useful when dealing with complex data that doesn’t follow known analytical patterns, such as internal tides in oceanic shelf regions,” Dr. Astfalck said.

The new method was recently applied in a TIDE research project by Senior Lecturer at UWA’s Oceans Graduate School and TIDE collaborator, Dr. Matt Rayson, to look at complex non-linear ocean processes.

“The ocean is difficult to measure and understand and the work we are doing is all about uncovering some of those mysteries,” Dr. Rayson said.

“The new method means we can better understand ocean processes, climate models, ocean currents and sediment transport, bringing us closer to developing the next generation of numerical ocean models.”