Svalbard lost “Record-breaking” ice in 2024

 In 2024, Svalbard lost “Record-breaking” ice, more than any year on record

Glaciers in Arctic Svalbard experienced unprecedented melting during summer 2024, contributing to global sea-level rise. New research shows the summer of 2024 was a “record-breaking” melt season in Svalbard, raising concerns about the scale of future glacial ice melts under climate change. Svalbard, an Arctic archipelago which is technically a part of Norway, lies about halfway between the northernmost part of Norway and the North Pole. Currently, about 60% of Svalbard's surface is covered in glaciers, but these glaciers are melting rapidly. During the summer of 2024, Svalbard experienced a record-breaking heat wave which melted more of its glaciers than ever before.

The team was made up of a collaboration of scientists including researchers from the University of Oslo and the Norwegian Meteorological Institute. The loss of glacial ice in the Norwegian archipelago is predicted to have significant impacts on the local and global environment possibly leading to rising sea levels and impacting the ocean currents. Svalbard experienced extraordinarily high temperatures last summer. The researchers found that the sea surface temperatures of the surrounding areas in the Barents and Norwegian Seas were 3.5 to 5°C above the 1991–2020 baseline. The impact of these kinds of events is not limited to the local region, but has far-reaching consequences and can act as a harbinger of things to come. Massive glacier melts contribute to global sea-level rise and impact ocean circulation, marine ecosystems and local communities. Determining glacial mass loss and placing it in a historical and future climate context is essential for understanding these impacts.

“Combining in situ observations, remote sensing, and modelling, we quantify the mass loss of all glaciers on Svalbard during the record-warm summer of 2024, that by far exceeds previous levels,” write the researchers. “The summer of 2024 on Svalbard thus provided a window into Arctic glacier meltdown in a warmer future.” The analysis shows that the summer glacial melt in Svalbard in 2024 resulted in around 61.7 gigatons of ice melting. This is 1% of Svalbard total ice mass. This loss contributed to approximately 0.16mm of water to global sea level rise although, when considering the melting of nearby areas too, this figure jumps to 0.27mm. Thomas Vikhamar Schuler, a researcher from the University of Oslo in Norway, and his team set out to quantify the impact of the six-week heat wave of the summer of 2024. To do this, they utilized in situ glacier measurements from aluminium poles fixed in the ice as reference markers to record changes in the glacier's surface, remote sensing data from satellites and climate modelling using the CryoGrid model. They determined mass loss through both surface melt and ice calving, when chunks of ice break off glaciers and fall into the ocean, at marine glacier fronts.

“Affecting global sea-level rise, mass loss from Arctic glaciers has implications far beyond their geographical location,” write the authors. “By injecting buoyant freshwater, meltwater runoff from land to the ocean has far-reaching implications for ocean circulation near shore and in fjords and fuels a variety of ecological communities across a wide range of the food chain.” Svalbard is home to 6% of the world’s glacier area outside of Greenland and Antarctica. If the all the glaciers on Svalbard were to melt, scientists predict this would account for a 1.7cm sea level rise. Despite being 50 times smaller than Greenland, the amount of ice lost in Svalbard is on par with Greenland's ice loss of 55 ± 35 gigatons. Most of this melting occurred during a six-week period. Even past models did not predict this magnitude of ice loss until much later. The region of circum-Barents, which includes Svalbard, Franz Josef Land and Novaya Zemlya, lost a total of 102.1 ± 22.9 gigatons of ice in 2024. This amounts to a contribution of 0.27 ± 0.06 mm to global sea-level rise. That may not sound like much, but the study authors explain that this contribution corresponds to half of the sea-level contribution of all Arctic glaciers estimated for 2006–2015, placing the circum-Barents region among the strongest contributors to the global sea-level rise in 2024.

The research team found much of the melting occurred within a 6-week period. Across this time, the atmospheric conditions were warmer than usual, and the area was experiencing a marine heat wave. Under current climate conditions, these temperatures are extremely rare however, some climate models suggest that these levels may become more common by the end of the 21st century. “We find that temperature levels as in 2024 represent a rare situation for contemporary climate conditions but will be frequently reached in a few decades,” write the authors. The team also conducted climate modelling based on their findings, which predicted that these kinds of extreme summers will become common by 2100, even under optimistic emission scenarios. "Our study shows that 2024 summer temperatures will be frequently reached in just a few decades and exceeded toward the end of the 21st century. The summer of 2024 on Svalbard thus provided a window into Arctic glacier meltdown in a warmer future, highlighting the severe mass loss of glaciers and its repercussions in other regions of the Arctic beyond Svalbard," the study authors write. “This suggests further that the summer of 2024 may represent the normal situation in 2100, and the observed mass loss of glaciers in 2024 indeed provides a view into future glacier meltdown in Svalbard and probably other parts of the Arctic.” Just last year, a NASA study found that the Greenland Ice sheet lost more ice than previously estimated with 179 of the 207 glaciers in focus having retreated significantly since 1985. According to the World Meteorological Organisation, 5 of the past 6 years have seen the most glacier retreat in human record, with 2022–2024 claiming the largest 3-year loss of glacier mass in recent history. 

Largest Gold Reserve in space

 NASA scientists discover the largest gold reserve in the universe and planning how to reach it

What if we told you that we could all be billionaires because there is gold in space? Well, get ready, because NASA has identified an asteroid called Psyche which might contain the largest reserve of precious metals in the universe, including gold, iron, and nickel. NASA’s identification of the asteroid Psyche, potentially the largest reserve of precious metals in the universe, has sparked massive speculation about future space mining possibilities, as the asteroid holds an estimated value of 700 trillion euros. This massive figure has sparked a wave of speculation about the economic possibilities of space mining, fuelling the dream that “we could all be millionaires,” but even though the discovery is impressive, we shouldn’t get ahead of ourselves, because there’s still a long way to go.

NASA’s recent findings regarding the asteroid Psyche have captivated global attention, as the celestial body situated in the asteroid belt between Mars and Jupiter is believed to contain abundant reserves of precious metals such as gold, iron, and nickel. This revelation has led to heated discussions about the economic possibilities of space mining. Despite the tantalizing possibilities, experts urge caution in anticipating rapid transformations in wealth distribution. Discovered in 1852 by the Italian astronomer Annibale de Gasparis, the Psyche asteroid has gone from being just another asteroid to one of the most exciting prospects for science. What was once just another rock in space is now a mine more valuable than the entire economy of Earth. Can you imagine getting access to one of these rocks? Look, anything which comes from space already costs a fortune (haven’t you seen that they auction off a piece of Mars for $4 million?).

The Psyche asteroid has evolved from an ordinary space rock to a focal point of scientific interest and economic speculation. Psyche’s estimated surface area exceeds 165,000 square km's, and its metal-rich composition includes iron, nickel and gold, which is believed to account for 30% to 60% of its total volume. All of this is mixed with silicates. Just to give you an idea, its value far exceeds the combined GDP of all the countries in the world. For whatever reason, it’s in our interest to intercept it, right? NASA’s heightened interest in Psyche culminated in the launch of the Psyche mission. This mission aims to reach the asteroid by 2029 employing solar-electric propulsion, with plans for an extensive study using advanced instruments such as spectrometers, magnetometers and multispectral cameras. While there is curiosity surrounding potential economic gains from Psyche, the mission’s primary objective is to glean insights into the formation of rocky planets and evaluate whether Psyche represents one of the original building blocks of our solar system. Psyche is located between Mars and Jupiter, in the asteroid belt, and it is believed to be the exposed core of an ancient forming planet. It was first discovered in the 19th century by Annibale de Gasparis, but it wasn’t until 2023 that NASA started paying more attention. Maybe because its estimated value reaches 700 trillion dollars.

The lofty dream of harvesting the asteroid’s resources, however, remains beyond our reach at the moment. The reality of space mining is fraught with technological, financial and regulatory challenges which must be addressed before any such ventures can materialize. The notion of retrieving substantial amounts of gold, for example, while tantalizing, is not factored into current plans, despite private companies and space agencies already exploring the feasibility of extra-terrestrial mining. As we said, it was in 2023 when NASA began to take a much greater interest in this piece of rock, thus promoting the Psyche mission, which will use solar-electric propulsion to reach the asteroid after a flyby of Mars. The spacecraft is expected to arrive at its destination in 2029 and, once there, will begin a detailed study. But wait a second. The mission isn’t meant to make us billionaires (after all, that money would go to the usual people) but rather to understand how rocky planets formed. Could Psyche be one of the original building blocks of our solar system? That’s what they want to find out!

The notion of a new ‘gold rush’ in space raises questions about the potential societal implications. Should a mission successfully transport more gold to Earth than the planet’s existing annual production, the ripple effects could drastically alter economic conditions and heighten debates over regulatory frameworks. Issues of legal ownership, ethical usage and environmental impact remain unresolved, prompting the need for comprehensive discussions on the management of space-derived resources. Sure, the idea of bringing gold from space sounds tempting and gets us excited, but space mining is still in its early stages. It requires a lot of technology and an incredible investment, so for now, exploiting galactic resources is not the plan, even if it sounds very, very attractive. Of course, there are already people eyeing the idea. Private companies and space agencies are already developing technologies to make it possible. Some experts believe that in the coming decades we’ll see the first mining operations off the planet, but from our point of view, there is still a lot to regulate before that happens.

Psyche’s allure remains tantalizing, but the road to capitalizing on its full potential is marked by obstacles that include not only technological advancements but also the establishment of cooperative international frameworks to manage access and distribution effectively. The discovery of Psyche has generated excitement, but also controversy. What would happen if a single mission brought more gold to Earth than the planet’s entire annual production? How would access to those resources be regulated? What countries or companies would have control? Space mining raises legal, ethical and environmental challenges which still don’t have an answer. But one thing is certain: the gold in space is already firing up the collective imagination. As discussions around Space Psyche advance, the global community must brace for the profound shifts which could accompany an era of space mining, acknowledging both its potential benefits and far-reaching ramifications around the world.

World’s rarest mineral

 Story of the world’s rarest mineral, It was found only once

In the world of minerals, rarity often lies in the hands of humankind, crafted through ingenious processes and human ingenuity. However, there exists an exceptional exception to this rule, where nature itself has crafted a unique masterpiece. Among the Earth’s 6,000 identified minerals, only one is known from just a single sample, kyawthuite. A single gemstone from Myanmar holds the title of Earth's rarest mineral. Deep in the Myanmar Mogok region, a tiny reddish-orange crystal sat unnoticed. To the untrained eye, it seemed like many other stones, polished by water, overlooked by miners seeking sapphires. But this unassuming gem, later named kyawthuite, is unlike anything else on Earth; or at least, anything else that we know of. It is the rarest mineral known to science, with only a single specimen ever discovered.

kyawthuite, a mineral so rare that it exists in just one known specimen, a stunning gemstone unearthed near Mogok, Myanmar. In 2015, the International Mineralogical Association (IMA) officially recognized this mineral, marking its place in geological history. Kyawthuite, with its mesmerizing transparent reddish-orange hue, captivates the eyes and the imagination. The single specimen, a mere 1.61 carats in weight (approximately 0.3 grams), possesses an intriguing chemical composition: Bi3+Sb5+O4, with trace amounts of tantalum. What sets kyawthuite apart is not the scarcity of its constituent elements, bismuth and antimony, but the extraordinary circumstances of its formation. The only sample found thus far has sparked immense intrigue among scientists and collectors alike. The kyawthuite crystal was discovered in 2010 by sapphire hunters in the Chaung Gyi Valley, near Mogok, Myanmar. Initially mistaken for an ordinary gem, it was later identified as unique by Dr. Kyaw Thu, a prominent mineralogist. After extensive analysis, the International Mineralogical Association (IMA) officially recognized kyawthuite as a new mineral in 2015. Today, the sole specimen resides in the Natural History Museum of Los Angeles County, where it is safeguarded as a geological treasure.

Bismuth and antimony, both rare metals, hold intriguing positions in the Earth's crust. While bismuth outstrips gold in terms of abundance, antimony surpasses silver. The Earth's crust is awash with oxygen, the most abundant element of all. In the quest to understand kyawthuite's scarcity, scientists point to the unique conditions under which it was birthed, rather than any inherent shortage of its elemental ingredients. The density of kyawthuite is a staggering eight times that of water, making the gemstone appear even smaller than its weight suggests. Caltech's mineral database describes its crystalline structure as consisting of checkerboard sheets of octahedra Sb5+O6, running parallel to Bi3+ atoms. Kyawthuite is a bismuth-antimony oxide, with the chemical formula Bi₃⁺Sb₅⁺O₄, with traces of tantalum. These elements, though not exceedingly rare individually, formed under unique conditions which scientists are only beginning to understand. Natural History Museum of Los Angeles County, displaying the only known piece of kyawthuite (the smallest of the set), as well as various other gemstones. Kyawthuite is thought to have originated in pegmatite, an igneous rock formed during the late stages of magma crystallization. Myanmar’s geology, shaped by the collision of the Indian and Asian tectonic plates, provided the intense heat and pressure needed for such rare minerals to form. This cataclysmic event during the Paleocene-Eocene epoch not only created kyawthuite but also endowed the region with a wealth of gemstones, including the deep-red crystals of painite, the world’s second-rarest mineral; a borate mineral containing the rare pairing of zirconium and boron. Myanmar’s rich mineral deposits come with a sobering backdrop. Decades of political instability, military control and human rights abuses cast a shadow over its gemstone trade. 

Remarkably, kyawthuite stands alone as the sole recognized bismuth-antimony oxide mineral and is named in honour of Dr. Kyaw Thu, a former geologist at Yangon University. The tale of kyawthuite's discovery is equally captivating. This unique mineral was stumbled upon by sapphire hunters in the bed of a stream. Its significance did not go unnoticed, and the IMA formally acknowledged kyawthuite as a distinctive mineral. Its scientific description was subsequently published in 2017, cementing its status as a geological marvel. The Mogok region of Upper Myanmar has been known for centuries as the “Valley of Rubies” due to the high-quality rubies which are mined there. The area is also known for producing other precious gemstones like spinel, sapphire, chrysolite or peridot, tourmaline and even rare gemstones. Despite all gemstone mining being officially illegal in Myanmar following the expiration of the last mining license in 2020, gemstone mining has boomed since the 2021 coup. Tens of thousands of informal miners have filled the void left by the end of official mining, and are being exploited by the military as well as non-state armed groups. These ethical concerns have prompted some to boycott materials sourced from Myanmar, limiting the study and commercialization of its rare minerals.

Perhaps other specimens of kyawthuite are lurking somewhere in Myanmar. But political challenges and the sheer odds of repeating such a geological fluke make another discovery unlikely. For now, the tiny orange gem in Los Angeles may be the first and last of its kind. According to Caltech Professor George Rossman, the geological abundance of such gemstones in Myanmar is a consequence of the intense pressure and heat generated during the collision of India with Asia, a cataclysmic event which forged these unique geological treasures. However, despite Myanmar's potential as a hotspot for rare minerals, decades of conflict and international sanctions have hindered the discovery and dissemination of these precious specimens to the scientific community. Many remain hidden from the world's gaze, awaiting their moment to reveal the secrets of our planet's geological history. In a world where human innovation often defines rarity, kyawthuite stands as a testament to the Earth's ability to craft its own masterpieces. This single gemstone, with its captivating beauty and unique composition, invites us to ponder the mysteries of our planet's geological past. As scientists continue to explore the hidden corners of the Earth, who knows what other extraordinary treasures they may unearth, waiting to captivate our imaginations and deepen our understanding of the natural world around us.

Global Rare Earth Elements Transformation

 Global Rare Earth Elements and their Importance  

As global tensions rise, so does the competition for access to these minerals. Recent headlines show the stakes: China has halted rare earth exports to the US, and a deal was just signed to secure US access to Ukraine’s mineral resources. A rare earth metals report by none other than a state-backed research institute is not only likely to unsettle the Chinese authorities, it has also come as a bolt out of the blue for the rest of the world. A report by the Chinese Academy of Sciences released a few days ago said China’s dominance in the rare earths sector could be nearing the end. Rare earth elements are everywhere, in your smartphone screen, in the MRI machine at the hospital, in the battery of an electric vehicle and even in oil and gas refining. They are a key ingredient of modern life. Following are the some of the important points:-

 US is actively seeking alternatives to China's rare earth supply, including exploring domestic deposits and building alliances with other refining networks.

 A Chinese research institute predicts China's share of rare earth materials could significantly decrease by 2035 due to new mines and emerging sources globally.

New discoveries in Africa, Brazil and US, along with challenges to China's dominance, are reshaping the rare earth ecosystem and potentially redistributing market power. 

But the disclosure does not stop there. It also outlines how the opening of new mines in Australia, South Africa and other countries, as well as Greenland’s Kvanefjeld project, may reshape the rare earths ecosystem in the coming years. This also serves to underline why the US is so keen on Greenland. Some experts believe that the changing scenario might favour the US. Despite their name, rare earth elements aren’t actually scarce; what’s rare is finding them in high enough concentrations to mine economically. These deposits are scattered unevenly across the globe and often buried deep underground, shaping who controls their production and the global supply chain. Scientists at Tufts University are trying to better understand how and why rare earth minerals ended up where they did. Their research reveals how the movement of continents over billions of years helped form these valuable deposits. To explain how this mineral drama began, we need to go back in time. Way back. Earth’s surface is always on the move. Over millions of years, massive landmasses shift, collide and break apart, reshaping the planet in the process.

The latest study is a rare admission of a forthcoming fundamental shift. The CAS team used advanced “agent-based” modelling to simulate demand and mining prospects globally between 2025 and 2040. Though this accurately simulated about 1,000 global deposits and over 140 viable mines, it did not factor in political influences. Based on the results, the research team concluded that China’s roughly 62% share of raw material could drop to about 28% as early as 2035. The primary reasoning is the new emerging sources of rare earth metals. Incidentally, the research team is from the CAS Ganjiang Innovation Academy in Ganzhou in eastern China, one of the world’s largest critical metal production centres. “Most of us are familiar with Pangea, the supercontinent that formed about 300 million years ago and that the current seven continents broke off from to form their present-day arrangement,” said Jill VanTongeren, professor and chair of the Department of Earth and Climate Sciences. “But Pangea is only the most recent supercontinent. Throughout Earth history, there have been at least five major supercontinent cycles, periods when continents all come together and then spread back out again into different pieces. We think this process happens roughly every 500 million years.”

China’s dominance of the supply chain for rare earths and other critical metals is near-total. The country sits on about 60% of global reserves and processes about 90% of all rare earth metals. Because of this, Beijing enjoys a near-monopoly in the supply of rare earth materials, which are essential for electric vehicles, electronics and even military equipment. As continents drifted apart, they created rifts, places where the Earth’s tectonic plates pulled away from each other. These rifting zones became birthplaces for rare earth element-rich magmas. “As the rocks are pushed apart, they decompress, causing melting. It’s kind of like taking the lid off a soda bottle, and the bubbles rise to the surface,” said VanTongeren. “Those early magmas contain the highest abundance of rare earth and other incompatible elements that then enter the crust, either erupting in volcanic centres or solidifying at depth.” Some of these mineral-rich magmas cooled and stayed near the surface. Others got dragged back down into the mantle or remain buried too deep to mine with today’s technology.

Today, the number of economically viable rare earth deposits is limited. China dominates the market, with nearly 70% of global production coming from its Bayan Obo mine. The US has a smaller operation at Mountain Pass in California, and a few other countries have scattered deposits. Since China produces about 2/3rd of the world’s total rare earth metals supply, the US has been on the lookout for alternatives. A 2024 report by the US Geological Survey said there were about 110 MT of deposits spread around the world. Of this, about 44 MT are in China, another 22 MT are in Brazil, followed by 21 MT in Vietnam, and 10 MT in Russia. In the late 1990s and early 2000s, China flooded the market with rare earth minerals, driving down prices and shutting down other global producers. That move reshaped global dependence. In response, the US took steps to re-establish a domestic supply. Recent investments from the 2021 Infrastructure and Jobs Act and the Department of Defence aim to restart full operations at the Mountain Pass mine, though it could take up to a decade. There’s also hope that Ukraine’s mineral deposits could help diversify supply. But for now, their potential remains unclear.

Now, it seems that Africa may also become a big player in the rare earth supply chain. Led by South Africa’s Steenkampskraal mine and other projects in Tanzania, experts predict Africa’s share may go up to from about 1% to 7% by 2040. But there is a red flag to consider, as Chinese investments fund many of the African projects, something the US looks at with consternation. “Political boundaries and the desire to obtain access to mineral resources have been the source of economic and military conflicts throughout human history,” said VanTongeren. “This is likely to continue as the world shifts toward green energy and a greater dependence on rare earth elements in the future.” VanTongeren’s work tracks these mineral stories from source to surface. Her fieldwork has taken her from a ship near Antarctica to platinum mines in South Africa, Morocco’s mountains, and even a lithium discovery in Maine. “It’s a fascinating area of study partly because it lies at the intersection of science, economics and politics,” she said. Back on the Tufts campus, this intersection takes a more visual form.

Brazil’s Serra Verde and other projects related to heavy rare earths like dysprosium could meet about 13% of the global supply by 2040. However, there are caveats, such as environmental regulations. The neodymium-rich Mount Weld mine in Australia and the Olympic Dam mines, which produce copper and uranium as by-products, are building US-allied refining networks to bypass China. Tucked into the basement of Lane Hall, the P.T. Barnum Mineral Collection offers a glimpse into the Earth’s treasures. It includes thousands of mineral specimens, some collected by Barnum himself. He was an early supporter of Tufts and a major collector of natural history in the 1800s. “In the late 1800s, it was considered fashionable for many prominent individuals to accumulate their own natural history collections,” noted VanTongeren. “P.T. Barnum was one of the biggest collectors of the time. His collection of animals, plants and minerals was among the first gifts to Tufts University and part of an endowment to establish Tufts as one of the major natural history museums in the country.” After a fire destroyed the Barnum Museum in 1975, the mineral collection moved to Lane Hall. Now, it’s about to move again, this time to Bacon Hall, the new home for the Department of Earth and Climate Sciences. VanTongeren hopes this new home will be more than just a storage site. She wants it to become a space that encourages curiosity and exploration, not just for scientists, but for everyone.

Beijing disclosed earlier that it had found a huge rare earth deposit in the south western province of Yunnan. According to reports quoting China’s Geological Survey, the 1.5 million ton deposit contains medium and heavy rare earths, including over 470,000 tons of elements like praseodymium and neodymium. At the time of the announcement, experts said that the discovery would only further consolidate China’s prominence as the global rare earth leader. But US researchers announced in late 2024 that they had identified a domestic treasure trove of critical minerals in the country’s coal ash deposits. The report also claimed that coal ash, a by-product from burning coal for energy typically written off as industrial waste, could hold about 11 MT of rare earth elements, or about eight times more than known domestic rare earth reserves. This discovery, made by a team from The University of Texas at Austin, reveals a whopping US $8.4 billion worth of rare earths. The report led some experts to opine that harnessing these reserves could dramatically alter the supply chain dynamics for rare earth metals and reduce US dependence on others.

Zealandia : Earth’s Hidden Continent

  Scientists discovered Earth’s missing and hidden 8th continent  

Earth’s surface is divided into two types of crust, continental and oceanic, and into 14 major tectonic plates. In combination, these divisions provide a powerful descriptive framework in which to understand and investigate Earth’s history and processes. In the past 50 years there has been great emphasis and progress in measuring and modelling aspects of plate tectonics at various scales. Simultaneously, there have been advances in our understanding of continental rifting, continent-ocean boundaries (COBs), and the discovery of a number of micro­-continental fragments which were stranded in the ocean basins during supercontinent breakups. But what about the major continents? Continents are Earth’s largest surficial solid objects, and it seems unlikely that a new one could ever be proposed. The Glossary of Geology defines a continent as “one of the Earth’s major land masses, including both dry land and continental shelves. It is generally agreed that continents have all the following attributes: (1) high elevation relative to regions floored by oceanic crust; 

(2) a broad range of siliceous igneous, metamorphic, and sedimentary rocks; 

(3) thicker crust and lower seismic velocity structure than oceanic crustal regions; 

(4) well-defined limits around a large enough area to be considered a continent rather than a microcontinent or continental fragment. 

The first three points are defining elements of continental crust and are explained in many geoscience textbooks and reviews. The last point, how “major” a piece of continental crust has to be to be called a continent, is almost never discussed. The progressive accumulation of bathymetric, geological and geophysical data since the nineteenth century has led many authors to apply the adjective continental to New Zealand and some of its nearby submarine plateaus and rises. “New Zealand” was listed as a continent by Cogley (1984), but he noted that its continental limits were very sparsely mapped. The name Zealandia was first proposed by Luyendyk (1995) as a collective name for New Zealand, the Chatham Rise, Campbell Plateau, and Lord Howe Rise. “By dating these rocks and studying the magnetic anomalies they presented,” the researchers said, “we were able to map the major geological units across North Zealandia.” Beneath the turquoise waters of the South Pacific hides a massive secret, Zealandia, a sunken landmass stretching nearly two million square miles. Though mostly underwater, this geological giant has sparked debate as a possible eighth continent. Just 5% of its surface peeks above sea level, making it one of Earth’s most elusive landforms.

Here we reassess a variety of geoscience data sets and show that a substantial part of the southwest Pacific Ocean consists of a continuous expanse of continental crust. Further­more, the 4.9 Mkm2 area of continental crust is large and separate enough to be considered not just as a continental fragment or a microcontinent, but as an actual continent, Zealandia. This is not a sudden discovery but a gradual realization; as recently as 10 years ago we would not have had the accumulated data or confidence in interpretation to this stage. Since it was first proposed by Luyendyk (1995), the use of the name Zealandia for a southwest Pacific continent has had moderate uptake. However, it is still not well known to the broad international science community. A correct accounting of Earth’s continents is important for multiple fields of natural science; the purpose is to formally put forth the scientific case for the continent of Zealandia and explain why its identification is important. New Zealand and New Caledonia are large, isolated islands in the southwest Pacific Ocean. They have never been regarded as part of the Australian continent, although the geographic term Australasia often is used for the collective land and islands of the southwest Pacific region. 

Zealandia wasn’t always underwater. Its story begins over 100 million years ago when it was part of the vast southern supercontinent, Gondwana. The ancient land once held what would become Africa, South America, Antarctica, Australia and the Indian subcontinent. As Gondwana slowly broke apart, Zealandia’s own journey began. Roughly 85 million years ago, the southern section split from what is now West Antarctica. About 25 million years later, the northern section detached from Australia. These shifts pushed Zealandia away from its neighbors, setting the stage for its quiet descent beneath the ocean’s surface. Unlike nearby continents, Zealandia didn’t stay afloat. During the Paleogene period, its crust thinned and cooled. This shift triggered its gradual sinking. Today, only New Zealand and New Caledonia remain above water, offering hints of the massive landmass which lies beneath. A tectonic boundary now divides Zealandia into northern and southern sections, tracing along the Pacific and Australian plates. Continents and their continental shelves vary in height but are always elevated relative to oceanic crust. The elevation is a function of many features, fundamentally lithosphere density and thickness, as well as plate tectonics. The accuracy and precision of seafloor mapping have improved greatly over the past decades and a deliberately chosen colour ramp on a satellite gravity-derived bathymetry map provides an excellent visualization of the extent of continental crust. The approximate edge of Zealandia can be placed where the oceanic abyssal plains meet the base of the continental slope, at water depths between 2500 and 4000 m below sea level. The precise position of the foot of the continental slope around Zealandia was established during numerous surveys in support of New Zealand’s Law of the Sea submission. Zealandia is everywhere substantially elevated above the surrounding oceanic crust. The main difference with other continents is that it has much wider and deeper continental shelves than is usually the case. Zealandia has a modal elevation of ~−1100 m and is ~94% submerged below current sea level. The highest point of Zealandia is Aoraki–Mount Cook at 3724 m.

Although the idea of an underwater continent first surfaced decades ago, it struggled to gain wide scientific support. But recent findings have changed that. With new data and sharper tools, researchers are reevaluating Zealandia’s geological identity, and taking it seriously. One breakthrough came from a study led by geologist Nick Mortimer and a team from GNS Science. Their work offers strong evidence for Zealandia’s continental status, pushing this sunken world into the scientific spotlight. The team conducted geological surveys across the northern stretches of Zealandia, employing advanced dredging techniques. They collected a range of rock samples from the Fairway Ridge to the Coral Sea, including sandstone, mudstone, limestone and basaltic lava. These samples provided crucial insights into Zealandia's geological timeline. “By dating these rocks and analysing their magnetic anomalies, we mapped the major geological units of North Zealandia,” the team explained. This marked the completion of the first comprehensive offshore geological mapping of the Zealandia continent.

By itself, relatively high elevation is not enough to establish that a piece of crust is continental. Essential geological ground truth for Zealandia is provided by the many island outcrop, drill core, xenolith and seabed dredge samples of Paleozoic and Mesozoic greywacke, schist, granite and other siliceous continental rocks which have been found within its limits. Many of these have been obtained from expeditions in the past 20 years. Orogenic belts, of which the Median Batholith and Haast Schist are parts, can be tracked through onland New Zealand and across Zealandia. Thus, there is a predictable regional coherency and continuity to the offshore basement geology. Traditionally, continents have been subdivided into cratons, platforms, Phanerozoic orogenic belts, narrow rifts and broad extensional provinces. Eurasia, Africa, North America, South America, Antarctica, and Australia all contain Precambrian cratons. Precambrian cratonic rocks have not yet been discovered within Zealandia, but their existence has been postulated on the basis of Rodinian to Gondwanan age detrital zircon ratios. Geologically, Zealandia comprises multiple Phanerozoic orogenic belts on which a broad extensional province and several narrow rift zones have been superimposed. 

Atop its geological basement rocks, Zealandia has a drape of at least two dozen spatially separate Late Cretaceous to Holocene sedimentary basins. These typically contain 2–10-km-thick sequences of terrigenous and calcareous strata and include a widespread continental breakup. The Zealandia Megasequence provides a Zealandia-wide stratigraphic record of continental rifting, and marine transgression events, similar to that seen in formerly conjugate east Australian basins. The retrieved rocks tell a captivating story. Some sandstone samples date back approximately 95 million years to the Late Cretaceous period. Granite and volcanic pebbles from as far as 130 million years ago reveal Zealandia's Early Cretaceous past. Basalt samples, meanwhile, represent more recent history, originating from the Eocene epoch around 40 million years ago. These findings challenge previous assumptions about Zealandia’s formation. Conventional theories suggested a strike-slip breakup, where tectonic plates slide past each other horizontally. However, Mortimer’s team proposed a different scenario. They believe plate stretching created subduction-like fractures, leading to the formation of the Tasman Sea. Subsequent tectonic activity further thinned Zealandia’s crust, relegating it to an underwater existence.

Continental crust varies considerably in thickness and physical properties. Most of Zealandia’s crust is thinner than the 30–46 km which is typical of most continents, studies show that it is everywhere thicker than the ~7-km-thick crust of the ocean basins. Collectively, the crustal structure results show that the rock samples are not from separate continental fragments or blocks now separated by oceanic crust, but are from a single continental mass. The thinnest crust within Zealandia is in the 2200-km-long and 200–300-km-wide New Caledonia Trough, where the water depth varies from 1500 to 3500 m. This raises the question as to whether the trough is floored by oceanic crust or is a failed continental rift. Two wide-angle seismic profiles across the trough near New Caledonia both show ~2–5 km of sedimentary cover over 8.5 km of crustal basement which has a velocity of ~7 km−1 throughout much of its thickness. These profiles as atypical of normal oceanic crust. The implications of Zealandia’s geological evolution extend beyond academic interest. Understanding its unique features, such as crustal thinning up to 65%, sheds light on broader tectonic processes. These insights also highlight Zealandia’s role in shaping the Pacific region's dynamic geology.  According to Science researcher, “Zealandia’s underwater status in no way diminishes its geological significance.” Its vast expanse and diverse rock formations make it a valuable natural laboratory for studying Earth's tectonic history.

Where oceanic crust abuts continental crust, various kinds of continent-ocean boundaries (COBs) define natural edges to continents. Tectonic plate boundaries, with or without intervening oceanic crust, provide the basis for continent-continent boundaries between Africa and Eurasia, and North and South America. The six commonly recognized geological continents (Africa, Eurasia, North America, South America, Antarctica, and Australia) are thus not only large but they are also spatially isolated by geologic and/or bathymetric features. The edges of Australia and Zealandia continental crust approach to within 25 km across the Cato Trough. The Cato Trough is 3600 m deep and floored by oceanic crust. The Australian and Zealandian COBs here coincide with, and have been created by, the Cato Fracture Zone along which there has been ~150 km of dextral strike slip movement, linking Paleogene spreading centres in the Tasman and Coral seas. This spatial and tectonic separation, along with intervening oceanic crust, means that the Zealandia continental crust is physically separate from that of Australia. If the Cato Trough did not exist, and the Australian continent was 4.9 Mkm2 larger than previously thought. Being >1 Mkm2 in area, and bounded by well-defined geologic and geographic limits, Zealandia is, by our definition, large enough to be termed a continent. At 4.9 Mkm2, Zealandia is substantially bigger than any features termed microcontinents and continental fragments, ~12× the area of Mauritia and ~6× the area of Madagascar. It is also substantially larger than the area of the largest intraoceanic large igneous province, the Ontong Java Plateau (1.9 Mkm2). Zealandia is about the same area as greater India.

Zealandia remains an active area of research. Its submerged status poses challenges, but advances in technology, such as deep-sea dredging and seismic imaging, continue to unlock its secrets. Ongoing studies aim to refine our understanding of this hidden continent, offering a more comprehensive picture of Earth's geological past. As scientists continue to explore Zealandia, they not only reveal the continent's mysteries but also enhance our understanding of the planet’s ever-evolving story. The importance of Zealandia is not so much that there is now a case for a formerly little-known continent, but that, by virtue of its being thinned and submerged, but not shredded into microcontinents, it is a new and useful continental end member. Zealandia started to separate from Gondwana in the Late Cretaceous as an ~4000-km-long ribbon continent but has since undergone substantial intra­continental deformation, to end up in its present shape and position. To date, Zealandia is little-mentioned and/or entirely overlooked in comparative studies of continental rifting and of COBs. By including Zealandia in investigations, we can discover more about the rheology, cohesion and extensional deformation of continental crust and lithosphere.

Zealandia illustrates that the large and the obvious in natural science can be overlooked. Based on various lines of geological and geophysical evidence, particularly those accumulated in the last two decades, we argue that Zealandia is not a collection of partly submerged continental fragments but is a coherent 4.9 Mkm2 continent. Currently used conventions and definitions of continental crust, continents, and microcontinents require no modification to accommodate Zealandia. The scientific value of classifying Zealandia as a continent is much more than just an extra name on a list. That a continent can be so submerged yet unfragmented makes it a useful and thought-provoking geodynamic end member in exploring the cohesion and breakup of continental crust.

'Supergiant' Gold reserves discovered

  China hits jackpot with discovery of  'Supergiant' Gold Deposit in Hunan  

The US$80 billion hoard is the latest fruit of China’s drive to find new domestic precious minerals reserves. China has discovered a “massive” new goldfield containing reserves worth tens of billions of dollars in the central province of Hunan, as it steps up efforts to boost domestic reserves of strategic minerals. A "supergiant" deposit of high-quality gold ore containing an estimated 1,000 metric tons (1,100 US tons) of the precious metal was discovered in central China. Geologists identified more than 40 new gold veins located less than 2,000 metres (6,560 feet) underground at the Wangu gold mine in Pingjiang county, bringing the total gold resources in the mine’s core area to 300.2 tonnes, the Hunan Provincial Geological Institute said. Valued at up to approximately 600 billion yuan or US$83 billion, the discovery could be one of the largest and most lucrative reservoirs of gold ever uncovered, surpassing the 900 metric tons estimated to lie within the mother of all gold reserves, South Deep mine in South Africa.

The new find is classified as a “massive” reserve, with its more than 1,000 tonnes of gold deposits estimated to be worth about 600 billion yuan (US$82.8 billion) based on current market prices. Liu Yongjun, the institute’s vice-president, said the discovery was a major achievement for China’s mineral exploration strategy. The statement also claimed that the find was “significant in helping safeguard the country’s resource security”. Some commentators are not yet convinced of the deposit's scale and feasibility, but if the discovery becomes verified, it will represent a major find for China. The Geological Bureau of Hunan Province announced the detection of 40 gold veins within a depth of 2 km's (1.2 miles) in the northeast Hunan county of Pingjiang. The Wangu goldfield is one of China’s most important gold-mining hubs. Since 2020, provincial authorities have invested more than 100 million yuan on mineral exploration in the area. These alone were thought to contain 300 metric tons of gold, with 3D modeling suggesting additional reserves may be found to a depth of 3 km's.

"Many drilled rock cores showed visible gold," said bureau prospector Chen Rulin at the time of the discovery. Core samples suggest every metric ton of ore could contain as much as 138 grams (nearly 5 ounces) of gold, an extraordinary level of quality considering ore excavated from underground mines is considered high grade if it contains more than 8 grams. Demand for gold in China has surged over the past couple of years, as consumers and retail investors boosted their gold holdings in reaction to domestic and global economic uncertainty. However, the rush to buy up gold has recently started to wane, after China’s central bank suspended its gold purchases in May and the dollar strengthened against the yuan. China already dominates the world's gold market with reserves considered to be in excess of 2,000 tons earlier, its mining industry contributing around 10 % of the global output. The price of gold has fallen to a near-two-month low, and retail gold jewellery prices have also declined. Gold jewellery from popular Chinese chains such as Chow Tai Fook and Chow Sang Sang were selling for about 720 yuan (US$99) per gram, down from 820 yuan.

Announcements of the findings initially contributed to a further increase in the already skyrocketing gold price, with demands for the resource generally rising strongly in time of global economic uncertainty. China has stepped up investment in mineral resources exploration in recent years, with a 2021-25 development plan calling for greater efforts to bolster domestic mineral reserves and production. Just how many bonanzas of the valuable ore remain yet to be discovered around the world is unclear, with experts divided on whether we've reached peak gold. Forged in the furnaces of embracing stars long before Earth was formed, our planet's glittering veins are a finite resource that take eons to precipitate into an easily mineable form.

Core samples taken around the periphery of the Hunan site hint that the deposit may extend even further than initial predictions, making the reservoir beneath its soil a true dragon's haul. The discovery in 2024 capped off what was a notable year for gold discoveries. The new discovery is estimated to contain around 1,000 metric tons of gold. Based on these findings, we might be far from exhausting economically viable reserves. In March 2024, a treasure hunter in England found what was estimated to perhaps be the biggest gold nugget ever found in the country. The large gold nugget, nicknamed "Hiro's Nugget," weighing 64.8 grams. And just months later, research by scientists in Australia discovered a new mechanism which may lead to the formation of gold, suggesting the seismic activity of earthquakes actually plays a role in the creation of large nuggets. Last year, the china’s exploration investment rose 8 %, year on year, reaching 110.5 billion yuan, which helped boost reserves of strategic resources including oil, natural gas, rare earths and gold.

In September, 4.96 million tonnes of rare earths were discovered in the Liangshan Yi autonomous prefecture, a remote part of the southwestern province of Sichuan. But that's not all. In addition to learning more about how gold naturally forms, scientists are also investigating new things that can be done to manipulate the precious resource. A study published earlier reported the creation of a new kind of two-dimensional gold called 'goldene', measuring only a single layer of atoms in height, which has some interesting properties not seen in the three-dimensional form of gold. While gold is an ancient metal that has been prized all throughout human history, there's clearly a lot we're still finding out about it. A few months earlier, 43.2 tonnes of gold reserves were found in the northwestern province of Qinghai. And in May 2023, the Xiling gold mine in the eastern province of Shandong confirmed it had identified an additional 200 tonnes of gold reserves, raising its total reserves to 580 tonnes.

Mars' climate

 Mars' atmosphere : 

The weather on Mars

A new study by researchers including those at the University of Tokyo revealed that atmospheric gravity waves play a crucial role in driving latitudinal air currents on Mars, particularly at high altitudes. The findings, based on long-term atmospheric data, offer a fresh perspective on the behaviours of Mars’  middle atmosphere, highlighting fundamental differences from Earth’s. The study applied methods developed to explore Earth’s atmosphere to quantitatively estimate the influence of gravity waves on Mars’ planetary circulation. According to ESA, Mars' atmosphere is composed of 95.32% carbon dioxide, 2.7% nitrogen, 1.6% argon and 0.13% oxygen. The atmospheric pressure at the surface is 6.35 mbar which is over 100 times less than Earth's. Humans therefore cannot breathe Martian air. The thermal impact of dust storms on Mars is significant, and is thought to play a similar role to that of water vapour in Earth’s atmosphere. For crewed Mars exploration efforts, we need to find a way to generate oxygen from the thin, carbon dioxide atmosphere and an experiment carried out on NASA's Perseverance rover has demonstrated it is possible. The rover used its MOXIE (short for "Mars Oxygen In-Situ Resource Utilization Experiment") to successfully convert carbon dioxide to oxygen on Mars. "MOXIE has more work to do, but the results from this technology demonstration are full of promise as we move toward our goal of one day seeing humans on Mars." Jim Reuter, associate administrator of NASA's Space Technology Mission Directorate, said. 

Despite it being a very cold planet, Mars is quite a hot topic these days. With human visitation seemingly on the horizon, it will pay to know more about the conditions there so all involved can plan and prepare accordingly. Something that has become possible to explore in detail in recent years is a range of Martian atmospheric phenomena. Naturally, a lot of the methods used for this originate from the study of our own atmosphere, and thanks to this, we can see how things on Mars differ greatly and what the implications of this might be. Mars' atmosphere is over 100 times thinner than Earth's and is primarily composed of carbon dioxide, nitrogen and argon gases. Oxidized dust particles kicked up from the Martian surface fill the atmosphere turning Mars' skies a rusty tan colour, according to NASA. Water exists on Mars but the atmosphere is too thin for it to last long on the surface in a liquid state. Instead, water on Mars is found below the surface of the polar regions as water-ice and also as seasonal briny water flows down hillsides and crater walls. Despite Mars' thin atmosphere, the Red Planet still exhibits a dynamic climate and extreme weather events including impressive dust storms and even snow! But Mars hasn't always been this way. NASA's MAVEN mission scientists reported that Mars once had a thick atmosphere that could have supported surface liquid water on the surface for extended periods of time.  

“On Earth, large-scale atmospheric waves caused by the planet’s rotation, known as Rossby waves, are the primary influence on the way air circulates in the stratosphere, or the lower part of the middle atmosphere. But study shows that on Mars, gravity waves (GWs) have a dominant effect at the mid and high latitudes of the middle atmosphere,” said Professor Kaoru Sato from the Department of Earth and Planetary Science. “Rossby waves are large-scale atmospheric waves, or resolved waves, whereas GWs are unresolved waves, meaning they are too fine to be directly measured or modelled and must be estimated by more indirect means.” Close up image of the surface of Mars shows white specks of salt deposits and numerous craters. Image from NASA's Mars Reconnaissance Orbiter shows the Bosporos Planum plain on the Red Planet. The white specks are salt deposits found within a dry channel, a clue to its watery past. Early in its history Mars had a thick enough atmosphere for water to run on its surface. According to NASA, some surface features suggest that Mars experienced huge floods about 3.5 billion years ago. Orbital pictures show vast river plains and possible ocean boundaries, while several Mars rovers have found evidence of water-soaked rocks on the surface (such as hematite or clay). However, for reasons that are still poorly understood, the Martian atmosphere thinned. Mars is much colder than Earth due to the thin atmosphere and the fact it is farther from the sun. The average temperature on Mars is about minus 80 degrees Fahrenheit (minus 60 degrees Celsius), although it can vary from minus 195 F (minus 125 C) near the poles during the winter to as much as a comfortable 70 F (20 C) at midday near the equator. Like Earth, Mars has four seasons but due to the Red Planet's eccentric orbit, the length of each season varies more than on Earth. A Year on Mars is almost twice as long as one on Earth. Following is the length of seasons on Mars and Earth according to NASA Science:-

Season (Northern Hemisphere) Length of Martian season (sols) Length of Earth season                                                                                                                                   (days)

Spring                                                                 194                                              93

Summer                                                                 178                                               93

Autumn                                                                 142                                              90

Winter                                                                 154                                              89

Not to be confused with gravitational waves from massive stellar bodies, GWs are an atmospheric phenomenon when a packet of air rises and falls due to variations in buoyancy. This oscillating motion is what gives rise to GWs. Due to the small-scale nature of them and the limitations of observational data, researchers have previously found it challenging to quantify their significance in the Martian atmosphere. So research team turned to the Ensemble Mars Atmosphere Reanalysis System (EMARS) dataset, produced by a range of space-based observations over many years, to analyse seasonal variations up there. “We found something interesting, that GWs facilitate the rapid vertical transfer of angular momentum, significantly influencing the meridional, or north-south, in the middle atmosphere circulations on Mars,” said graduate student Anzu Asumi. “It’s interesting because it more closely resembles the behaviour seen in Earth’s mesosphere rather than in our stratosphere. This suggests existing Martian atmospheric circulation models may need to be refined to better incorporate these wave effects, potentially improving future climate and weather simulations.”

Mars' ice caps, made of water ice and carbon dioxide, shrink and grow in response to the seasons. These seasonal changes to the ice caps affect Mars' atmosphere, which responds as one large interconnected system, according to ESA. "The lower and middle levels of Mars' atmosphere appear to be coupled to the upper levels: there's a clear link between them throughout the martian year," says Beatriz Sánchez-Cano, a planetary scientist at the University of Leicester, UK. "Each winter, up to a third of the mass in Mars' atmosphere condenses to form an icy layer at each of the planet's poles. Every spring, some of the mass within these caps sublimates to re-join the atmosphere, and the caps visibly shrink as a result," ESA stated. Giant dust devils routinely kick up the oxidized iron dust that covers Mars' surface. Dust is also a permanent part of the atmosphere, with higher amounts of it in the northern fall and winter, and lower amounts in the northern spring and summer. The dust storms of Mars are the largest in the solar system, capable of blanketing the entire planet and lasting for months. These usually take place in the spring or summer. The research also underscores the importance of planetary comparisons in atmospheric science. Mars’ similarity to Earth in terms of rotational speed and axial tilt makes it an ideal test case for studying planetary weather systems. At the same time, its distinct characteristics, such as a thin carbon dioxide-rich atmosphere and pronounced seasonal variations, offer insights into alien atmospheres. By analysing these differences, researchers can improve their understanding of fundamental atmospheric dynamics, which may ultimately contribute to better climate models for Earth too.

These dust storms can play havoc with Mars exploration missions and can even ground flights (yes Earth isn't the only planet where flights can be delayed due to poor weather!). NASA's Ingenuity Mars helicopter was due to make its 19th flight on the Red Planet on 5 Jan, 2022, when a dust storm near Jazero Crater had other plans. "Most notable was a sharp drop in air density, about a 7% deviation below what was observed pre-dust storm," Jonathan Bapst and Michael Mischna, of Ingenuity's weather/environment team, said. "This observed decrease would have put density below the lower threshold of safe flight and would have imparted undue risk to the spacecraft. We also observed the effect of dust in the amount of sunlight absorbed by Ingenuity's solar array, which fell well below normal 'clear sky' levels, a drop of about 18%." Over a month passed until Ingenuity was clear to fly again, finally acing its 19th flight on 8 Feb, 2022. “Looking ahead, we plan to investigate the impact of Martian dust storms on atmospheric circulation. So far, our analysis has focused on years without major dust storms,” said Sato. “However, these storms dramatically alter atmospheric conditions, and we suspect they may intensify the role of GWs in circulation. Our research lays the groundwork for forecasting Martian weather, which will be essential for ensuring the success of future Mars missions.”

One theory as to why dust storms can grow so big on Mars starts with airborne dust particles absorbing sunlight, warming the Martian atmosphere in their vicinity. Warm pockets of air flow toward colder regions, generating winds. Strong winds lift more dust off the ground, which in turn heats the atmosphere, raising more wind and kicking up more dust. An earlier study further suggested that the momentum of Mars, which is affected by other planets, generates planet-circling dust storms when that momentum is at its greatest during the early part of the dust storm season. At times, it even snows on Mars. The Martian snowflakes, made of carbon dioxide rather than water, are thought to be very small particles that create a fog effect rather than appearing as falling snow. The north and south polar regions of Mars are capped by ice, much of it made from carbon dioxide, not water. Mars' early atmosphere was very different from the one we see today. Future studies will examine how these storms lead to significant shifts in global atmospheric patterns. With these advancements, the prospect of accurately predicting atmospheric conditions on Mars moves one step closer to reality. At some point in Mars' history, the Red Planet lost much of its atmosphere, transforming it from a warm wet world to the cold arid plains we see today, said ESA.

The atmosphere of Mars changes over the course of a day because the ground gets extremely cold at night on Mars, down to around minus 160°C. At such cold temperatures, both major and minor constituents of the atmosphere might either condense (snow, frost) or just stick to the soil grains a lot more than they do at warmer temperatures. Because of differing condensation temperatures and "stickiness", the composition can change significantly with the temperature. During the day, the gases are released from the soil at varying rates as the ground warms, until the next night. It stands to reason that similar processes happen seasonally, as the water (H2O) and carbon dioxide (CO2) condense as frost and snow at the winter pole in large quantities while sublimating (evaporating directly from solid to gas) at the summer pole. It gets complicated because it can take quite a while for gas released at one pole to reach the other. Many species may be more sticky to soil grains than to ice of the same material, so for those chemicals, the diurnal change could be more significant than the seasonal change. The leading theory is that Mars' light gravity, coupled with its lack of global magnetic field, left the atmosphere vulnerable to pressure from the solar wind, the constant stream of particles coming from the sun. Over millions of years, the sun's pressure stripped the lighter molecules from the atmosphere, thinning it out. This process is being investigated by NASA's MAVEN (Mars Atmosphere and Volatile Evolution) mission. Other researchers hypothesize that perhaps a giant impact by a small body would have stripped the atmosphere away. The seasonal variation changes the global air pressure on Mars and changes which gases are in the air. On Mars, the air pressure can change globally by ±8%, depending on the season. The result is that there's no specific place, time of day, or season that fully represents THE composition of Mars' atmosphere. Finally, sunlight drives atmospheric chemistry by way of solar ultraviolet light breaking down CO2 and H2O molecules which are then free to react in new ways. As a result, the changing pressure and abundance of H2O and CO2 changes the abundance of carbon monoxide (CO), oxygen (O2), ozone (O3) and other trace species.

Mars once was a more Earth-like planet, but it was the ancient Earth that it resembled, a planet with a CO2-rich atmosphere and no free oxygen, with extensive oceans that may have been frozen-over much of the time. We don't know for certain what chemicals were in the atmosphere of Earth besides CO2, N2 and H2O prior to the rise of widespread oxygen-producing photosynthesis which radically altered Earth's atmosphere. There could have been gases like methane (CH4) and ammonia (NH3), sulphur-bearing gases, and other gases which are not common today. We don't see those gases in Mars' atmosphere today, either, but possibly they were there in the past. The Sun has also been slowly increasing in luminosity, so that Mars and Earth of a few billion years ago had less sunlight to warm them, but more CO2 in the atmosphere to hold in the heat. Mars of a few billion years ago probably had exposed lakes and oceans, and probably had rain. Given how much uncertainty there is about how Earth's atmosphere may have been different when it was a younger and "less Earth-like" planet, it is awfully hard to make an educated guess as to what Mars' ancient atmosphere may have been like. Earth is particularly challenging because there has been constant chemistry and weathering as well as plate tectonics remaking the planet's surface over billions of years, minerals reacting with the atmosphere and sinking to the bottom of the oceans, then buried by tectonics. As we continue to gather new information about Mars, it may end up being our best guide to what Earth once was like, because the water chemistry on Mars, and plate tectonics, turned off a long time ago, leaving the rocks of that time intact for us to examine.

The most obvious reason to think that Mars once had a much more dense atmosphere is that there are clear signs all over Mars of erosion by water in processes that occur on Earth but could not occur on Mars as it is today. There are river channels, eroded valleys, rocks worn into round river cobbles and dumped at the end of valleys, consistent with the way that rivers deposit rocks. More has changed than just the amount of water. Under current conditions, a puddle of liquid water at the surface would quickly evaporate, or freeze and then sublimate, because of the extremely low air pressure. For water to have once persisted long enough to flow in large quantities and to pool, the air pressure had to be much greater. From the surface, rovers have detected salt minerals layered in patterns that are consistent with the way that salty water forms lakes on Earth which evaporate over long periods of time in places like the Great Salt Lake or the Dead Sea, and in fully dried lakes such as salt flats in the American West, in Africa and numerous other places. From orbit, we have observed "bathtub rings" in large depressions in the surface and detected minerals which can only form when materials dissolve in water and have time to react with each other and accumulate in large quantities. What we lack is a good estimate of how much more dense the atmosphere once was. An important clue is in the isotopes of atmospheric gas atoms. Atoms in gases exist in different versions, called isotopes, that each have the same number of protons and electrons, but different numbers of neutrons in the nucleus. There are two stable versions of carbon, and three stable versions of oxygen. 

The ratio that we measure now between the abundance of stable isotopes depends on the original ratio when the planet formed, and then how it changed over time as heavy or light isotopes (more or fewer neutrons) were removed from the atmosphere by chemistry to form solids, or escaped to space. Hydrogen, nitrogen, and argon atoms are all enriched in heavy isotopes, consistent with losing a lot of gas to space, which removes the light isotopes faster than the heavy ones. Carbon and oxygen, which make the main atmospheric gas, carbon dioxide (CO2), are much more confusing. We need an estimate of what the isotope ratios actually are today, what they once were in the deep past, and how quickly each kind of isotope is lost from the atmosphere. With those things, we can estimate how much atmosphere has been lost and thus estimate how much atmosphere Mars once had. It will be a slow and messy process of gradually improving measurements, vigorous disagreements, improving understanding and comparing results from entirely different methods to hone in on the truth.

The telescopic measurements need to be tested with other measurements, from Earth and at the surface of Mars, to determine whether it is a real process, whether it is routine, or whether the interpretation is a misunderstanding of the data. A powerful argument against my interpretation is that laboratory measurements do not yet show any process that could be effective enough to make this happen to the extent that the measurements appear to show. Also, we don't have the data (yet) to show whether there is a significant seasonal effect in atmospheric isotope ratios on Mars. There probably is not, because lab measurements show that freezing pure ices of CO2 does not result in significantly changing isotope ratios in the remaining gas. But that could be incorrect in the complex environment of a planet's surface. Many types of rock can only form at the surface, where water dissolves both the minerals and the atmosphere so that they can react with each other to form new compounds that can condense to form new minerals. Examples on Earth include limestones (carbonate minerals) and many iron-bearing minerals. The goal of the Perseverance rover mission on Mars now is to obtain samples of surface rocks in the mouth of an ancient river by drilling into the interior of rocks in the streambed to extract pencils of material. The exterior of these rocks has been weathered by the modern Mars environment, but the interior represents the chemical conditions under which the rock formed. This includes the relative rate at which different chemical reactions happened (a thermometer), what was dissolved in the water (including the atmosphere), and what isotope ratios were present for different elements. It is a tremendously ambitious and complex undertaking, involving many first-time events. Much of what we need to investigate to understand ancient Mars is far beyond the capability of instruments that can be made small, light and efficient enough to fit onto a spacecraft. We need these samples from Mars to be returned to Earth where we can use the great variety of instruments we have here to study them completely.