Tag Archives: atmosphere

Snowfall in the Alps is full of plastics particles

New research from the Swiss Federal Laboratories For Materials Science And Technology (EMPA), Utrecht University, and the Austrian Central Institute for Meteorology and Geophysics showcase the scale and huge range of pollution carried through the atmosphere.

The research site at Sonnblick. Image credits ZAMG / Christian Schober via Flickr.

The findings suggest that around 3,000 tons of nanoplastic particles are deposited in Switzerland every year, including the most remote Alpine regions. Most are produced in cities around the country, but others are particles from the ocean that get introduced into the atmosphere by waves. Some of these travel as far as 2000 kilometers through the air before settling, the team explains, originating from the Atlantic.

Such results build on a previous body of research showing that plastic pollution has become ubiquitous on Earth, with nano- and microplastics, in particular, being pervasive on the planet.

Plastic snow

Although we’re confident that the Earth has a plastic problem, judging by the overall data we have so far, the details of how nanoplastics travel through the air are still poorly understood. The current study gives us the most accurate record of plastic pollution in the air to date, according to the authors.

For the study, the researchers developed a novel chemical method that uses a mass spectrometer to measure the plastic contamination levels of different samples. These samples were obtained from a small area on the Hoher Sonnenblick mountain in the Hohe Tauern National Park, Austria, at an altitude of around 3100 meters from sea level. This area was selected as an observatory of the Central Institute for Meteorology and Geodynamics and has been in operation here since 1886.

The samples were collected on a daily basis, in all types of weather, at 8 AM. They consisted of samples of the top layer of snow, which were harvested and processed taking extreme care not to contaminate them with nanoplastics from the air or the researchers’ clothes. According to their measurements, about 43 trillion miniature plastic particles land in Switzerland every year — equivalent to around 3,000 tons.

In the lab, the team measured nanoplastic content in each sample and then analyzed these particles to try and determine their origin. Wind and weather data from all over Europe were also used in order to help determine the particles’ origins. Most of the particles were likely produced and released into the atmosphere in dense urban areas. Roughly one-third of the particles found in the samples came from within 200 kilometers. However, around 10% of the total (judging from their level of degradation and other characteristics) were blown to the mountain from over 2000 kilometers away, from the Atlantic; these particles were likely formed in the ocean from larger debris and introduced into the atmosphere by the spray of waves.

Plastic nanoparticles are produced by weathering and mechanical abrasion from larger pieces of plastic. These are light enough to be comparable to a gas in behavior. Their effect on human health is not yet known, but we do know that they end up deep into our lungs, where they could enter our bloodstream. What they do there, however, is still a mystery.

The current study doesn’t help us understand their effects any better, but it does put the scale of nanoplastic pollution into perspective. These estimates are very high compared to other studies, and more research is needed to verify them — but for now, they paint a very concerning picture.

The paper “Nanoplastics transport to the remote, high-altitude Alps” has been published in the journal Environmental Pollution.

The lowest level of the atmosphere is expanding because of global warming

Credit: Flickr, J-No.

The copious amounts of greenhouse gases that human activity has released into the atmosphere have predictably warmed the troposphere, the first 18-20 km layer of the atmosphere where all living things can be found. The troposphere is now a full one degree Celsius hotter, on average, than it used to be during the Industrial Revolution in the 19th century. But the troposphere is not only getting hotter, it’s growing thicker too.

Climate scientists led by Jane Liu from the University of Toronto analyzed a trove of atmospheric data pertaining to things such as pressure, temperature, and humidity collected by weather balloons and GPS satellites between 1980 and 2020. They used these measurements to build a model of how the troposphere’s dimensions have changed across the decades, specifically in the northern hemisphere where the troposphere height is believed to be more influenced by greenhouse gases than in the southern hemisphere.

The analysis showed that the tropopause — the boundary layer between the troposphere and the stratosphere — has increased in altitude at a rate of about 53.3 meters per decade between 2001 and 2020. This rate is slightly higher than the one experienced between 1980 and 2000, a period when there were considerably fewer carbon emissions than seen today.

The rate of increase in the altitude of the troposphere excluded natural variations such as El Niño or volcanic eruptions, the authors reported in the journal Science Advances.

According to the researchers, tropopause altitude is a proxy for anthropogenic climate change. The tropopause is now found higher than it used to be just a decade ago because it has been pushed by the expansion of the troposphere, which in turn was driven by an increase in the concentration of CO2, methane, and other greenhouse gases.

“Our work tells us human-activity-induced climate change can make a difference to many aspects of our daily lives,” Liu told New Scientist. “Now we see it… in changes to our tropopause height.”

Meanwhile, as the troposphere is getting thicker, the stratosphere is thinning. In the stratosphere, greenhouse gases have the opposite effect, cooling it with increased concentration. In the past three decades, temperatures in the stratosphere have dropped by between 5 and 10 degrees Celsius.

In a 2021 study published in the journal Environmental Research Letters, an international team of researchers from the Czech Republic, Austria, Germany, and the USA, found that the stratosphere, the second layer of the atmosphere, is 400 meters thinner than it was in the 1980s.

Why do stars twinkle, or do they twinkle at all? For astronomers, this is important

When we look at the sky, we see different types of objects. Some are man-made (like the International Space Station), some are from our solar system (like Venus or Saturn), but many are twinkling, shiny objects — of course, stars from outside our solar system.

Stars have fascinated humans since time immemorial, especially because sometimes, they seem to twinkle. Stars don’t actually twinkle per se — the twinkling we observe here has more to do with the atmosphere on Earth rather than the stars themselves. There are three main factors that influence how stars “twinkle”, and to truly understand them, we need to take a short dive into some atmospheric physics.

A view of the stars photographed at Klein Flintbek. Behind the tree with the red lights is the Kiel telecommunications tower. The light pollution (Kiel) is also easy to see. Credits: Fabian Horst.


The first physical phenomenon that makes stars appear to twinkle is turbulence.

We observe stars that are far away because the light that they emit reaches our eyes (or telescopes). But in order to do that, it must first pass through the atmosphere. That means that light is indirectly subjected to phenomena that affect the Earth’s atmosphere.

Turbulence is a phenomenon that often happens on smaller scales. In the atmosphere, we have large-scale phenomena like cold fronts or hurricanes happening every day, but inside these events, turbulence is significant on a small scale. So cold fronts bring large thunderstorms, the clouds within the front can make the sky turbulent, and that’s when the airplane pilot tells you “Ladies and gentlemen, we’re experiencing some turbulence.”

Image credits: AEES.gov.

There are several types of turbulence, including one called thermal turbulence — which happens when there is a mix between hotter and colder air. This could happen whether the sky is cloudy or not. When a mass of air in the atmosphere is hotter than its surroundings, it starts to rise, creating convective currents. Basically, you end up with moving columns or pockets of heated air that arise from warmer surfaces of the earth.

These moving pockets of air can create turbulence, and in the process, they also distort light that passes through them.

When it comes to stars, twinkling is caused by the passing of light through different layers of the turbulent atmosphere. This is more pronounced near the horizon than directly overhead since light rays near the horizon pass through denser layers of the atmosphere, but twinkling (technically called scintillation) can be observed on all parts of the sky.

But there’s more to this story.


Schematic diagram illustrating how optical wavefronts from a distant star may be perturbed by a layer of turbulent mixing in the atmosphere. The vertical scale of the wavefronts plotted is highly exaggerated.

When light passes through any medium (including the Earth’s atmosphere), some of it is reflected back, while some passes through the atmosphere, but at a different angle — something called refraction. When the atmosphere is turbulent in a region, the refraction angle is not constant, so light can change path quickly. 

Altering the refractive index changes the apparent position of objects, just like the straw in a glass of water experiment, it looks bent. So the turbulent sky, constantly changing the refractive index makes stars appear to be moving, so they twinkle, or scintillate

The different refraction index in water (versus air) makes objects appear bent. If this is happening quickly and in multiple places, it can make objects appear twinkling.

Due to scale differences, if an astronomical object is large enough compared to the turbulence, it won’t affect the way we see it. But the light of a smaller object (or one that’s farther away) will be affected as it crosses the turbulent air. That’s the reason why planets twinkle less (or almost don’t twinkle at all) — they are closer and it makes them ‘bigger’ compared to the turbulence.

Fortunately, atmospheric scientists developed a way to monitor changes in the refractive index of the atmosphere due to turbulence. They use instruments to measure the turbulence and use it to try to estimate a future outcome.

Different skies

For astronomers, twinkling can be quite problematic. So they look for the “best sky” to avoid the phenomenon. Usually, this means an environment whose climate is very dry. When that’s not possible, they try to find the dryness by placing the instruments at a high altitude. Whenever is possible to combine altitude and mostly dry weather, they have a good spot for a telescope.

In the images above we see the difference very clearly: both skies were clear when the images were taken, but one (on the left) was less turbulent than the other (on the right). On the left, we see a video of a star recorded on Mount Fuji in Japan — the star appears to be bouncing chaotically due to a turbulent sky. On the right, we see a recording of the same star taken on the Andes Mountains in Chile, a very dry, high-altitude area; the star bounces, but much less than in the Japanese images.

A map of all ground-based telescopes that the MST have procured to observe during K2C9. Credits: 10.1088/1538-3873/128/970/124401

So stars don’t exactly twinkle, but they do appear to twinkle from here on Earth. For astronomers, though, making sure they eliminate the “twinkling” is important.

Of course, if you set your telescopes in space, you don’t have these problems because your observation point is above the atmosphere. But even here on Earth, astronomers are careful to pick the best locations for placing large optical telescopes. They typically look for the driest areas, at the highest altitude possible, without any light pollution. There’s another consideration: because the air is usually flowing from west to east because of Earth’s rotation, a way to avoid pollution is placing telescopes on west coasts or in ilands in the middle of the ocean. This rules out the vast majority of places on Earth, which is why astronomers are so particular about where they place their telescopes.

Airborne microplastics have a growing influence on the climate, but we need more data

Airborne microplastic particles could start having a significant effect on the world’s climate in the future, a new paper reports.

An airborne microplastic sampling station at Kaitorete Spit in Canterbury, New Zealand. Image credits Alex Aves.

New research at the University of Canterbury, New Zealand, found that airborne microplastics reflect part of the sunlight incoming to the Earth’s surface, thus cooling down the climate. For now, this effect is extremely slight. However, as the quantity of microplastics in the air is bound to increase in the coming decades, this effect will grow in magnitude.


“Yes, we focussed on airborne microplastics,” Dr. Laura Revell, Senior Lecturer of Environmental Physics at the University of Canterbury and the paper’s corresponding author told ZME Science in an email. “These were first reported in Paris in 2015 and have since been reported in a range of urban and remote regions.”

“However, we believe that microplastics may be co-emitted from the ocean with sea spray, leading to the concept of the ‘plastic cycle’ i.e., microplastics might be carried with the winds over some distance, be deposited to land, get washed into a river, be transported into the ocean, and then re-enter the atmosphere.”

Microplastics are a growing environmental concern. They’re already present in soils, water, air, and their levels are steadily increasing. Some microplastics are produced directly, for items such as cosmetics, while others are the result of plastic items breaking down in landfills.

Due to their small size and weight, such particles can easily be picked up by winds and carried over immense distances. Large cities such as London or Beijing show huge concentrations of such particles, likely due to how much plastic is used within their boundaries.

That being said, we’re just beginning to understand their full impact as airborne contaminants. The present study helps further our understanding in this regard, by uncovering the interaction between these particles and the planet’s climate. According to the authors, this is the first time the direct effects of airborne microplastics on climate has been calculated.

Other airborne solutions (‘aerosols’) are known to have an effect on the Earth’s climate either by scattering or reflecting incoming sunlight back into space, cooling everything down, or by absorbing radiation on certain frequencies, which warms the planet up.

Against that backdrop, the authors set out to determine what effect airborne microplastics have in this regard. They used climate modeling software to determine the radiative effect (i.e., reflective of absorbing) of common airborne microplastic particles. They focused primarily on the lower layers of the atmosphere, where much of the microplastic contamination is located. Overall, they report, these particles scatter solar radiation, which amounts to them having a minor cooling effect on the climate at surface level.

Exactly how much cooling they produce, however, the team can’t say for sure. We simply don’t have enough measurements of the quantity and distribution of microplastics in the atmosphere, nor do we have solid data on their chemical composition and physical properties.

Further muddying the issue is that microplastic particles can also have a warming effect, which may partially or completely counteract the cooling they cause through the scattering of light.

“After we calculated the optical properties of microplastics to understand how they absorb and scatter light, we realised that we would see them absorbing infrared radiation and contributing to the greenhouse effect. That moment was a surprise, as up until then we had been thinking about microplastics as efficient scatterers of solar radiation,” Dr. Revell adds for ZME Science.

This absorption takes place on a frequency interval of infrared light where greenhouse gasses such as CO2 don’t really capture much energy. In other words, these microplastics tap into energy that’s not readily captured by the current drivers of climate warming.

“Microplastics may therefore contribute to greenhouse warming, although in a very small way (since they have such a small abundance in the atmosphere at present),” Dr. Revell adds. “The dominant effect we see in our calculations with respect to interaction with light, [however] is that microplastics scatter solar radiation (leading to a minor cooling influence).”

In closing, she told me that more recent studies on the topic of airborne microplastics are reporting “quite high” concentrations of these particles in certain areas of the world, such as Beijing. Dr. Revell explains that this is likely due to improvements in technology allowing researchers to pick up on particles of much smaller diameters than before — which passed by undetected before. All of this uncertainty in the data obviously does not bode well for our conclusions.

“Our initial estimates of the climate effects of airborne microplastics are just that — estimates — and will no doubt be revised in future as new studies are performed and gaps in our knowledge are filled,” Dr. Revell concluded for ZME Science.

However, one thing we do know for sure is that with plastic pollution on the rise, the effects of microplastics on the climate are only going to become worse. It’s very likely that it already shapes atmospheric heating or cooling on the local level, the authors explain. If steps are not taken to limit the mismanagement of plastic waste, this effect will grow in magnitude and keep influencing the climate for a long period in the future.

The paper “Direct radiative effects of airborne microplastics” has been published in the journal Nature.

Lightning discharges help clean the air of some greenhouse gases

Lightning could have an important ecological function, a duo of new paper reports. According to the findings, such discharges play an important role in clearing gases like methane from the atmosphere.

Image credits Abel Escobar.

As we all know, thunderbolt and lightning, very, very frightening. However, they also seem to be quite fresh. The immense heat and energy released by lightning bolts break apart nitrogen and oxygen molecules in the air, which mix into hydroxyl radicals and hydroperoxyl radical — OH and HO2, respectively. In turn, these highly reactive chemical compounds go on to alter the atmosphere’s chemistry, in particular jump-starting the processes that degrade greenhouse gas compounds such as methane.

Bolt Cleaning

“Through history, people were only interested in lightning bolts because of what they could do on the ground,” says William H. Brune, distinguished professor of meteorology at Penn State and co-author on both of the new papers. “Now there is increasing interest in the weaker electrical discharges in thunderstorms that lead to lightning bolts.”

Data for this research was collected by an instrument plane flown above Colorado and Oklahoma in 2012. The plane followed thunderstorms and lightning discharges in order to understand their effect on the atmosphere.

Initially, the team assumed that the spikes in OH and HO2 signals (atmospheric levels) their devices were picking up must be errors, so they removed them from the dataset to study at a later time. The issue was that the instrument recorded high levels of hydroxyl and hydroperoxyl in stretches of the cloud where there was no visible lightning. A few years ago, Brune actually took the time to analyze it.

Working with a graduate student and research associate, he showed that the spikes could be produced both by sparks and “subvisible discharges” in the lab. After this, they performed a fresh analysis of the thunderstorm and lightning data from 2012.

“With the help of a great undergraduate intern,” said Brune, “we were able to link the huge signals seen by our instrument flying through the thunderstorm clouds to the lightning measurements made from the ground.”

Planes avoid flying through the center of thunderstorms because it’s simply dangerous for them, Brune explains, but they can be used to sample the top portion of the clouds which spread in the direction of the wind — this area of a storm is known as ‘the anvil’. Visible lightning is formed in the part of the anvil near the thunderstorm core.

Most bolts never strike the ground, he adds. This lightning is particularly important for affecting ozone and some greenhouse gas in the upper atmosphere. While we did know that lightning can split water to form hydroxyl and hydroperoxyl, this is the first time it has actually been observed in a live thunderstorm.

The researchers found hydroxyl and hydroperoxyl in areas with subvisible lightning, but very little evidence of ozone and no signs of nitric oxide (which requires visible lightning to form) in these areas. If this type of lightning occurs routinely, its outputs of hydroxyl and hydroperoxyl should be included in atmospheric models (they are not, currently).

Both of these compounds interact with some gases like methane, breaking them down through chemical reactions, and preventing them from realizing their full greenhouse potential.

“Lightning-generated OH (hydroxyl) in all storms happening globally can be responsible for a highly uncertain but substantial 2% to 16% of global atmospheric OH oxidation,” the team explains.

“These results are highly uncertain, partly because we do not know how these measurements apply to the rest of the globe,” said Brune. “We only flew over Colorado and Oklahoma. Most thunderstorms are in the tropics. The whole structure of high plains storms is different than those in the tropics. Clearly, we need more aircraft measurements to reduce this uncertainty.”

The first paper “Extreme oxidant amounts produced by lightning in storm clouds” has been published in the journal Science.

The second paper, “Electrical Discharges Produce Prodigious Amounts of Hydroxyl and Hydroperoxyl Radicals” has been published in the Journal of Geophysical Research: Atmospheres.

Australia’s wildfires created a ‘record-breaking’ smoke plume in the upper atmosphere

Australia’s bushfires set a record for the largest smoke cloud generated by a wildfire, a new paper reports. The plume was at least three times larger than any previously recorded one.

Image credits Terri Sharp.

Researchers at the University of Saskatchewan’s (USask) Institute of Space and Atmospheric Studies say that last winter’s Australian wildfires created a smoke cloud that pushed all the way to the stratosphere, some 35 kilometers above the surface, and reached incredible sizes. At its largest, it measured 1,000 kilometers across. The cloud remained intact for three months and traveled over 66,000 kilometers.

King smoke

“When I saw the satellite measurement of the smoke plume at 35 kilometres, it was jaw dropping. I never would have expected that,” said Adam Bourassa, professor of physics and engineering physics, who led the USask group which played a key role in analyzing NASA satellite data.

The fires seen in Australia this year were so devastating that the summer of 2020 has been nicknamed the “Black Summer“. It’s an apt name — the blazes claimed over 5.8 million hectares of forest in the continent’s southeast and bellowed massive amounts of smoke.

An international research team led by Sergey Khaykin from Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS) in France. The findings, they hope, will help us better understand how wildfires interact with and affect our planet’s atmosphere.

“We’re seeing records broken in terms of the impact on the atmosphere from these fires,” said Bourassa. “Knowing that they’re likely to strike more frequently and with more intensity due to climate change, we could end up with a pretty dramatically changed atmosphere.”

Bourassa’s team has experience in a specific type of satellite measurement that can pick up on smoke in the upper layers of the atmosphere. He explains that wildfires such as those in Australia and Western Canada (in 2017, the world’s second-largest to date) got so big that they generated their own clouds, Pyrocumulonimbus, and their own thunderstorms.

These thunderstorms create powerful updrafts that propel smoke and air all the way to the stratosphere, which is higher than the altitudes that commercial jets typically fly at.

The team used a satellite-mounted device called a spectrometer to analyze the plumes. In essence, they measured how much sunlight was scattered (reflected) from the atmosphere back to the satellite, which gave them a detailed layer-by-layer look at the atmosphere.

One finding, that Bourassa calls “amazing” is that this smoke starts absorbing sunlight and heating up. When it gets hot enough, it starts “to rise in a swirling vortex ‘bubble’, and it just rose and rose higher and higher through the atmosphere.”

Another finding was that the smoke from Australia’s wildfires blocked sunlight from reaching the surface to an extent never seen before. The issue was compounded by the fact that the stratosphere is typically quite stable, meaning aerosol particles such as those in smoke can remain in suspension here for months on end, having a disproportionately-high effect on climate.

The paper “The 2019/20 Australian wildfires generated a persistent smoke-charged vortex rising up to 35 km altitude” has been published in the journal Communications Earth & Environment.

Pluto’s beating icy heart makes and breaks atmospheric winds

Not that long ago, all we knew about Pluto was a few colored pixels — it was the best our satellites could do. We would be easily forgiven for thinking that Pluto was a frozen, barren, and… well, boring world. But while Pluto is frozen and almost certainly barren, it’s anything but boring.

The New Horizons missions showed us Pluto as we’ve never seen or dreamed before. Far from a quiet marble at the periphery of our solar system, Pluto has an active geology which, in many regards, is surprisingly similar to that of Earth.

Pluto’s famous heart feature might be more important than we thought. Can we call it a planet now? Image credits: NASA.

It was in July 2015 that the New Horizons spacecraft allowed us to see Pluto as never before. More than 98 percent of Pluto’s surface consists of solid nitrogen, with traces of methane and carbon monoxide. This frozen nitrogen forms glaciers and plains, and is affected by geological faults and fissures — just like on Mars and Earth. In fact, Pluto’s geology is every bit as complex and exciting as Mars’, the New Horizons team announced.

Now, as data continues to be analyzed, we’re learning even more about Pluto. In a new study, researchers describe how Pluto’s “icy heart” controls the planetoid’s atmospheric processes.

The Tombaugh Regio formation is the largest bright surface feature on Pluto. From afar, it looks like an oversized cartoon heart. But upon closer inspection, the feature is nothing short of amazing.

Although they might look similar, the two lobes of the feature are geologically distinct. The western lobe, Sputnik Planitia, is smoother than the eastern, and probably has a different geological origin. It is this lobe, Sputnik Planitia, that the new study focused on.

Sputnik Planitia, in detail — note the differences between the left and right ‘heart’ lobes. Image credits: NASA.

The feature is believed to have originated as an impact basin that subsequently collected volatile ices. The basin’s composition is dominated by nitrogen, which also comprises most of Pluto’s thin atmosphere. During the day, when Pluto is exposed to the sun, a layer of this nitrogen melts and turns into vapor which flows into the atmosphere. At night, when it gets cold, the vapor condenses and once again, forms ice.

This cycle, researchers found, pushes Pluto’s atmosphere to circulate in the opposite direction of its spin — a unique phenomenon. The way the process works, heating during the day and cooling during the night, is akin to a heartbeat coming from Pluto’s heart-like feature.

“This highlights the fact that Pluto’s atmosphere and winds—even if the density of the atmosphere is very low—can impact the surface,” said Tanguy Bertrand, an astrophysicist and planetary scientist at NASA’s Ames Research Center in California and the study’s lead author.

Much like Pluto’s geology, its atmosphere is also very active. Just to get it out of the way — it’s 100,000 times thinner than that of Earth’s and incapable of supporting life as we know it; nevertheless, it features active processes and might even shape features on the surface.

“Before New Horizons, everyone thought Pluto was going to be a netball—completely flat, almost no diversity,” Bertrand said. “But it’s completely different. It has a lot of different landscapes and we are trying to understand what’s going on there.”

The airflow caused by the Sputnik Planitia basin is like wind patterns on Earth, bearing a striking similarity to the Kuroshio current on the west side of the North Pacific Ocean. Just like Kuroshio, Sputnik Planitia’s high cliffs trap cold air inside the basin, where it circulates and becomes stronger. The basin is an important driver and regulator of atmospheric processes. It’s the beating heart behind Pluto’s atmospheric bloodlines.

“Sputnik Planitia may be as important for Pluto’s climate as the ocean is for Earth’s climate,” Bertrand said. “If you remove Sputnik Planitia—if you remove the heart of Pluto—you won’t have the same circulation,” he added.

Pluto is a remarkable place, researchers conclude, and it’s amazing that we can understand it in such detail.

“It’s very much the kind of thing that’s due to the topography or specifics of the setting,” Bertrand happily concludes. “I’m impressed that Pluto’s models have advanced to the point that you can talk about regional weather.”

The study has been published in the Journal of Geophysical Research: Planets.

A new study says oxygen buildup on Earth was “inevitable,” and maybe on other planets, too

While the history of oxygen on Earth is believed to have started with microorganisms or plate tectonics, a new paper reports that this may not be the case.

Image via Pixabay.

The study suggests that the distinct oxygenation events that shaped the Earth’s atmosphere into what it is today may have happened spontaneously, rather than through particularities of our planet (such as biological and tectonic activity). The findings give new insight into the possible history of our planet and offer renewed hope of finding oxygen on alien worlds.


“Based on this work, it seems that oxygenated planets may be much more common than previously thought, because they do not require multiple — and very unlikely — biological advances, or chance happenings of tectonics,” says study lead author Lewis Alcott, a postgraduate researcher in the School of Earth and Environment at Leeds.

“This research really tests our understanding of how the Earth became oxygen rich, and thus able to support intelligent life.”

Until roughly 2.4 billion years ago, Earth’s atmosphere held no meaningful levels of oxygen. This is due to the gas’s high chemical reactivity — it will bind with almost everything, scrubbing it out of the air. However, that’s when the first of three oxygenation events in our planet’s history occurred.

The first is known as the “Great Oxidation Event”. Subsequent oxygenation events occurred around 800 million years ago and 450 million years ago, leading to the concentrations of atmospheric oxygen of today.

In order to understand how it came to be, the team modified a well-established model of Earth’s marine biogeochemistry to make it run during the entire history of the planet. This model, they report, also produced three different oxygenation events all by itself. This, the team explains, strongly suggests that that beyond early photosynthetic microbes and the initiation of plate tectonics — both of which were established by around three billion years ago — it was simply a matter of time before oxygen would reach the necessary level to support complex life.

While previous research into the appearance of oxygen in Earth’s atmosphere focused on biological revolutions (where life such as algae essentially ‘bioengineers‘ oxygen-rich atmospheres) and tectonic revolutions (the generation of oxygen through volcanic processes), this study highlighted a series of feedback between the global phosphorus, carbon and oxygen cycles. These three together are capable of rapidly shifting ocean and atmospheric oxygen levels without any input from life or tectonics, the team explains. The transitions are driven by the way the marine phosphorus cycle responds to changing oxygen levels, and how this impacts photosynthesis, which requires phosphorus.

The results should bolster our hopes of finding alien planets with oxygen gas present in their atmosphere. While this isn’t a prerequisite for life, it is, to the best of our understanding, essential for the evolution of large, complex organisms — which require a lot of energy.

“Our model suggests that oxygenation of the Earth to a level that can sustain complex life was inevitable, once the microbes that produce oxygen had evolved,” explains study co-author Professor Simon Poulton, also from the School of Earth and Environment at Leeds.

“Our work shows that the relationship between the global phosphorus, carbon and oxygen cycles is fundamental to understanding the oxygenation history of the Earth. This could help us to better understand how a planet other than our own may become habitable,” adds Dr Benjamin Mills, senior author of the study.

The paper “Stepwise Earth oxygenation is an inherent property of global biogeochemical cycling” has been published in the journal Science.

Curiosity rover stumbles upon mystery of oxygen on Mars

NASA scientists have noticed baffling seasonal changes in oxygen on Mars. The concentration of the gas, which many creatures on Earth require in order to breathe, rises and falls with the seasons in a way that scientists cannot yet explain, pointing towards mysterious chemical sources.

A self-portrait taken by NASA’s Curiosity rover taken on Sol 2082 (June 15, 2018). A Martian dust storm has reduced sunlight and visibility at the rover’s location in Gale Crater. Image Credit: NASA/JPL-Caltech/MSSS.

For the past six years that it has been on Mars, the Sample Analysis at Mars (SAM) mobile chemistry lab inside the Curiosity rover, has been sniffing the air above Gale Crater. The analysis confirmed the readings made by other science experiments since the 1970s, finding that the Martian atmosphere is made of 95% CO2, 2.6% nitrogen, 1.9% argon, 0.16% molecular oxygen (O2), and 0.06% carbon monoxide.

These molecules mix together and circulate around the planet due to changes in air pressure throughout the year. According to NASA, these seasonal changes are due to the freezing of CO2 over the poles during winter, which lowers the air pressure across the planet, and the evaporation of CO2 during spring and summer, which raises air pressure as the gas mixes across the Martian atmosphere.

The waxing and waning of CO2 concentrations at Gale Crater are followed by similar changes in nitrogen and argon — so, naturally, scientists thought that oxygen would follow the same curve. For some reason, though, this isn’t happening. Instead, the amount of oxygen in the air rises throughout spring and summer by as much as 30% and then drops back to predictable levels in fall. This pattern repeated each spring, however, the amount of oxygen added to the atmosphere varied — in other words, something must be producing it and something must be removing it.

“The first time we saw that, it was just mind-boggling,” said Sushil Atreya, professor of climate and space sciences at the University of Michigan in Ann Arbor.

What could explain this peculiar pattern? What could be adding oxygen to the atmosphere and what could be subtracting it?

Credit: Melissa Trainer/Dan Gallagher/NASA Goddard.

The SAM instrument itself is well calibrated and the readings are fine, NASA says. Perhaps, CO2 or water might have released the oxygen when the molecules were broken apart in the atmosphere. Later, solar radiation might break the molecular oxygen, leaving two single oxygen atoms free to escape into space. However, this explanation doesn’t stand because there would have to be five times more water than you can find on Mars to produce the extra oxygen and CO2 doesn’t break apart that fast. Moreover, it would take at least a decade for oxygen to break apart and disappear due to solar radiation.

There’s something out there that might explain this, but the truth is that, for now at least, scientists are left in the dark.

“We’re struggling to explain this,” said Melissa Trainer, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland who led this research. “The fact that the oxygen behavior isn’t perfectly repeatable every season makes us think that it’s not an issue that has to do with atmospheric dynamics. It has to be some chemical source and sink that we can’t yet account for.”

The explanation might be tied to another mysterious gas on Mars: methane. Since Curiosity arrived on Mars, the rover’s chemical sensors were able to detect methane, albeit in extremely minute quantities of 0.00000004% on average. The methane concentration also rises and falls seasonally, increasing by about 60% during the summer months. What’s more, the methane concentration in the atmosphere also spikes randomly and significantly at times. Again, scientists do not know why this is happening. But, what may be causing the spikes of methane could also be responsible for the skewed oxygen patterns. Sometimes, the two gases appear to fluctuate in tandem, for instance.

“We’re beginning to see this tantalizing correlation between methane and oxygen for a good part of the Mars year,” Atreya said. “I think there’s something to it. I just don’t have the answers yet. Nobody does.”

On Earth, oxygen and methane can both be produced by organisms but NASA says that on Mars their source isn’t likely to be biological. Instead, the gases are likely produced by chemical processes related to water and rock. One possible source for the extra springtime oxygen is the Martian soil, which contains hydrogen peroxide and perchlorates. Heat and humidity might release oxygen from the soil.

“We have not been able to come up with one process yet that produces the amount of oxygen we need, but we think it has to be something in the surface soil that changes seasonally because there aren’t enough available oxygen atoms in the atmosphere to create the behavior we see,” said Timothy McConnochie, assistant research scientist at the University of Maryland in College Park and another co-author of the paper.

The findings appeared in the Journal of Geophysical Research: Planets.

New capture technology scrubs atmospheric CO2 on the cheap

A novel carbon capture technique can scrub the gas out from the air even at relatively low concentrations, such as the roughly 400 parts per million (ppm) currently found in the atmosphere.

We have a climate problem: namely, we’re making the planet hotter and hotter. This change is caused by a build-up of greenhouse gases released by our various activities, and carbon dioxide (CO2) is the single most important such gas. Tackling climate heating hinges on our ability to reduce emissions or to find ways of scrubbing them from the air. Since the former would involve at least some economic contraction, neither industry nor politicians are very keen on it. So there’s quite a lot of interest in developing the latter approach.

Most of the methods available today need high concentrations of CO2 (such as the smoke emitted by fossil fuel-based power plants) to function. The methods that can work with low concentrations, on the other hand, are energy-intensive and expensive, so there’s little economic incentive for their use. However, new research from MIT plans to change this state of affairs.

Convenient cleaning

“The greatest advantage of this technology over most other carbon capture or carbon absorbing technologies is the binary nature of the adsorbent’s affinity to carbon dioxide,” explains MIT postdoc Sahag Voskian, who developed the work during his PhD.

“This binary affinity allows capture of carbon dioxide from any concentration, including 400 parts per million, and allows its release into any carrier stream, including 100 percent CO2.”

The technique relies on passing air through a stack of electrochemical plates. The process Voskian describes is that the electrical charge state of the material — charged or uncharged — causes it to either have no affinity to CO2 whatsoever or a very high affinity for the compound. To capture CO2, all you need to do is hook the material up to a charged battery or another power source; to pump it out, you cut the power.

The team says this comes in stark contrast to carbon-capture technologies today, which rely on intermediate steps involving large energy expenditures (usually in the form of heat) or pressure differences.

Essentially, the system functions the same way a battery would, absorbing CO2 around its electrodes as it charges up, and releasing it as it discharges. The team envisions successive charge-discharge cycles as the device is in operation, with fresh air or feed gas being blown through the system during the charging cycle, and then pure, concentrated carbon dioxide being blown out during the discharge phase.

The electrochemical plates are coated with a polyanthraquinone and carbon nanotubes composite. This gives the plates a natural affinity for carbon dioxide and helps speed up the reaction even at low concentrations. During the discharge phase, these reactions take place in reverse, generating part of the power needed for the whole system during this time. The whole system operates at room temperature and normal air pressure, the team explains.

The authors hope the new approach can help reduce CO2 production and increase capture efforts. Some bottling plants burn fossil fuels to generate CO2 for fizzy drinks, and some farmers also burn fuels to generate CO2 for greenhouses. The team says the new device can help them get the carbon they need from thin air, while also cleaning the atmosphere. Alternatively, the pure carbon dioxide stream could be compressed and injected underground for long-term disposal, or even made into fuel through a series of chemical and electrochemical processes.

“All of this is at ambient conditions — there’s no need for thermal, pressure, or chemical input,” says Voskian. “It’s just these very thin sheets, with both surfaces active, that can be stacked in a box and connected to a source of electricity.”

Compared to other existing carbon capture technologies, this system is quite energy efficient, using about one gigajoule of energy per ton of carbon dioxide captured. Other existing methods use up to 10 gigajoules per ton, depending on the inlet carbon dioxide concentration, Voskian says.

The paper “Faradaic electro-swing reactive adsorption for CO2 capture” has been published in the journal Energy & Environmental Science.

Antarctic ozone hole at its smallest recorded size ever

The ozone hole over the Antarctic registered its smallest annual peak on record (tracking began in 1982) according to an announcement by the National Oceanic and Atmospheric Administration (NOAA) and NASA on Monday.

Image credits NASA Ozone Watch.

Each year, an ozone hole forms during the Southern Hemisphere’s late winter as the solar rays power chemical reactions between the ozone molecules and man-made compounds of chlorine and bromine. Governments around the world are working together to cut down on the ozone-depleting chemicals that created this hole, and it definitely helps.

However, the two agencies warn that we’re still far from solving the problem for good. The small peak in the ozone hole’s surface likely comes from unusually mild temperatures in that layer of the atmosphere seen during this year, they add.

Good but not done

NASA and NOAA explain that the ozone hole consists of an area of heavily-depleted ozone in the upper reaches of the stratosphere. This hole is centered on Antarctica, between 7 and 25 miles (11 and 40 kilometers) above the surface. At its largest recorded size in 2019, the hole extended for 6.3 million square miles (September 8) and then shrank to less than 3.9 million square miles (during the rest of September and October). While that definitely sounds like and is a lot of surface, it’s better than it used to be.

“During years with normal weather conditions, the ozone hole typically grows to a maximum of about 8 million square miles,” the agencies said in a news release.

It’s the third time we’ve seen a similar phenomenon — weather systems slowing down stratospheric ozone loss — take place over in the last 40 years. Below-average spikes in the size of the ozone hole were also recorded in 1988 and 2002.

The stratosphere’s ozone layer helps deflect ultraviolet (UV) radiation incoming from the sun. That’s very good news if you like being alive as UV rays are highly energetic and will cause harm to the DNA of living organisms. UV exposure can lead to skin cancer or cataracts for animals and damages plantlife.

A host of chemicals that used to be employed for refrigeration, including chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs), break down ozone molecules in the stratosphere — which exposes the surface to greater quantities of UV. These compounds can last for several decades in the atmosphere and are extremely damaging to ozone during that time, breaking it down in huge quantities.

Humanity bunched together to control the production and release of such chemicals under the Montreal Protocol of 1988, which has drastically reduced CFC emissions worldwide. The ozone layer has been steadily recovering since then, but there’s still a long way to go.

“It’s a rare event that we’re still trying to understand,” Susan Strahan, an atmospheric scientist at the NASA’s Goddard Space Flight Center in Maryland, said in a news release. “If the warming hadn’t happened, we’d likely be looking at a much more typical ozone hole.”

The reactions that break down ozone take place most effectively on the surface of high-flying clouds, but milder-than-average temperatures above Antarctica this year inhibited cloud formation and made them dissipate faster, NASA explains. Since there were fewer clouds to sustain these reactions, a considerable amount of ozone made it unscathed. In a divergence from the norm, NOAA reports that there were no areas above the frozen continent this year that completely lacked ozone.

Warming in the shape of “sudden stratospheric warming” events, were unusually strong this year, NOAA adds. Temperatures in September were 29˚F (16˚C) warmer than usual (at 12 mi/19 km altitude) on average, “which was the warmest in the 40-year historical record for September by a wide margin” according to NASA.

Warmer air weakened the Antarctic polar vortex, a current of high-speed air circling the South Pole that typically keeps the coldest air near or over the pole itself, which slowed significantly (from an average wind speed of 161 mph / 260 kmph to 67 mph / 107 kmph). The slowed-down vortex allowed air to sink lower in the stratosphere, where it warmed and inhibited cloud formation. It’s also likely that it allowed for ozone-rich air from other parts of the Southern Hemisphere to move in.

Key variable used to study Mars’ ancient atmosphere varies during the day

New research is helping to improve our understanding of how Mars lost its atmosphere — and how much of it the planet lost.

Image via Wikimedia.

A new study led by NASA shows that a key tracer used to estimate how much atmosphere the planet lost changes with the temperature and time of day on Mars. The work should help make sense of previous measurements of the tracer, which have found wildly conflicting results. Having an accurate measurement of this tracer — a particular isotope of the oxygen atom — will enable us to estimate whether Mars has ever been habitable and what it was like on its surface.

The air that was

“We know Mars had more atmosphere. We know it had flowing water. We do not have a good estimate for the conditions apart from that — how Earthlike was the Mars environment? For how long?” said Timothy Livengood of the University of Maryland, College Park and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who led the study.

Even today, Mars has features such as dry riverbeds and mineral compounds that form in liquid water which point to much milder days in its past. One element that’s critical for such a past is a thick atmosphere that could retain enough heat for water to stay liquid on the surface.

However, Mars has lost all that atmosphere today, which transformed its climate from one that could (potentially) nurture life to the dry and freezing environment found by NASA missions such as MAVEN, Curiosity, and the Viking missions of 1976.

Naturally, researchers have a lot of questions regarding the Red Planet’s ancient atmosphere. One way to estimate its nature and properties is to look at oxygen isotopes — lighter isotopes escape into space faster than light ones, so the remaining atmosphere gets enriched in heavier ones.

In Mars’ case, the lighter (and more common) isotope of oxygen is 16O, while the heavier one is 18O. By analyzing the relative amount of each of these isotopes, researchers can get a good idea of how thick the atmosphere was on early Mars.

The glaring flaw in this approach is that the 18O/16O ratio has been measured several times, producing various readings. The new paper provides a way to resolve this discrepancy by showing that the ratio can change during the Martian day.

“Previous measurements on Mars or from Earth have obtained a variety of different values for the isotope ratio,” said Livengood. “Ours are the first measurements to use a single method in a way that shows the ratio actually varying within a single day, rather than comparisons between independent devices.”

“In our measurements, the isotope ratio varies from being about 9% depleted in heavy isotopes at noon on Mars to being about 8% enriched in heavy isotopes by about 1:30pm compared to the isotope ratios that are normal for Earth oxygen.”

This range of ratios, they explain, is consistent with previously reported measurements. This suggests that those measurements were corrent, but disagreed because the dynamics of the Martian atmosphere are more complex than we assumed.

These ratio changes throughout the day are likely a routine occurrence caused by changes in ground temperature, the team explains. Molecules with heavier isotopes likely stick to cold surface grains at night more than the lighter isotopes which are freed (thermally desorbed) as the surface warms up during the day.

As Mars’ atmosphere is mostly made up of carbon dioxide (CO2), the team studied oxygen isotopes bound up in CO2 molecules. For the observations, they used the Heterodyne Instrument for Planetary Winds and Composition developed at NASA Goddard, currently installed at the NASA Infrared Telescope Facility on Mauna Kea, Hawaii.

“While trying to understand the broad spread in estimated isotope ratios that we retrieved from the observations, we noticed that they were correlated with the surface temperature that we also obtained,” said Livengood. “That was the insight that set us on this path.”

The paper “Evidence for diurnally varying enrichment of heavy oxygen in Mars atmosphere” has been published in the journal Icarus.

Exoplanet concept.

Spitzer confirms: no atmosphere on nearby exoplanet

New Spitzer telescope observations reveal that a nearby rocky exoplanet doesn’t have an atmosphere.

Exoplanet concept.

Artist’s concept of HD 219134b, the nearest confirmed rocky exoplanet found to date outside our solar system.
Image credits NASA / JPL-Caltech.

Christened LHS 3844b, the exoplanet is 1.3 times larger than our planet, orbits its star in 11 hours, and — as confirmed by this study — is also telluric (rocky) in make-up. However, don’t start packing just yet: LHS 3844b seems to be very hot and lacking in atmosphere — literally and figuratively.

No (air) pressure

A new study reports that exoplanets like LHS 3844b — hot, rocky planets orbiting small stars — do not retain substantial atmospheres, or any atmosphere at all.

Most known rocky exoplanets orbit around stars that have 60% or less of the diameter of the Sun (i.e. dwarf stars). Past research has predicted that such planets don’t retain an atmosphere, however, this has yet to be proven or disproven. Researchers are especially interested in finding rocky exoplanets with atmospheres as they are prime candidates for both extraterrestrial life and potential future homes in space.

LHS 3844b does not appear to have an atmosphere, according to observations reported in Nature this week. LHS 3844 b is an extrasolar planet (exoplanet) located 48 light years away from Earth in the constellation Indus. It orbits a red dwarf star named LHS 3844, and was one of the first exoplanets discovered by the Transiting Exoplanet Survey Satellite (TESS).  

It goes about its merry way just 0.06839 AU (1 AU, or ‘astronomical unit’ is roughly equal to the distance between the Earth and Sun) away from the star, which is extremely close.

The team, led by Laura Kreidberg from the Harvard & Smithsonian Center for Astrophysics in Cambridge, Massachusetts, analyzed 100 hours’ worth of observations by the Spitzer telescope in search of an atmosphere and other defining features on LHS 3844b.

Their efforts revealed that LHS 3844b is a hot, rocky planet (confirming a previous hypothesis), with a surface similar to that of Mercury. Heat-distribution and chemical-composition modelling suggest that it doesn’t have a thick atmosphere, which was likely stripped away by radiation from its host dwarf star. The team says its likely that LHS 3844b completely lacks any atmospheric cover at all, as it’s doubtful even a thin atmosphere could persist under the expected conditions on the planet.

In other words, LHS 3844b is probably a bare chunk of rock.

However, all of you hoping to find our home away from home, fret not. We’ve found a lot of other exoplanets so far, all of which NASA conveniently put together in this map. Some of them are bound to have atmospheres and conditions that would support life as we know it. And, perhaps even more excitingly, some of them might harbor their own takes on life. 

Until we find a way to get there, telescope observations are our best way to sieve those few special ones from the lot.

The paper “Absence of a thick atmosphere on the terrestrial exoplanet LHS 3844b” has been published in the journal Nature.

Rusted metal.

Iron-breathing bacteria might have delayed Earth’s oxygenation for almost one billion years

New research shows that early life on Earth relied on a completely different type of photosynthesis — and that delayed the formation of the atmosphere as we breathe it today.

Rusted metal.

Image via Pixabay.

It’s no understatement to say that life today is wholly dependent on photosynthesis. Not only does it power plants (which directly or indirectly feed everybody else), but it also provides the oxygen we breathe. At least as far as the oxygen-producing photosynthesis of today is concerned. This reaction is what led to the appearance of free oxygen in Earth’s atmosphere, something which was unheard of 2.3 billion years ago (as oxygen is very reactive).

However, we have evidence that oxygen-releasing photosynthesis evolved much earlier in our planet’s history, even as early as 3 billion years ago. New research looking into why Earth’s atmosphere took so long to oxygenate suggests that it may simply have been a case of good ol’ fashioned competition at play.


“The striking lag has remained an enduring puzzle in the fields of Earth history and planetary science,” says Christopher Reinhard, an assistant professor in the School of Earth and Atmospheric Sciences (EAS) and the paper’s corresponding author.

Reinhard and his colleagues, led by EAS postdoctoral researcher Kazumi Ozaki, suggest that an older form of photosynthesis may have delayed the oxygenation of Earth’s atmosphere. Chemical conditions in Earth’s early oceans helped prop-up this competitor, against which oxygen-releasing photosynthesizers could not compete effectively at the time.

Modern photosynthesizers break apart water and release oxygen gas. Primitive ones, the team explains, substitute iron ions for water — and release rust instead of oxygen gas. Through a combination of experimental microbiology, genomics, and large-scale biogeochemical modeling, the team found that these primitive photosynthesizers are “fierce competitors for light and nutrients,” Ozaki explains.

“We propose that their ability to outcompete oxygen-producing photosynthesizers is an important component of Earth’s global oxygen cycle,” Ozaki, now an assistant professor in the Department of Environmental Science at Toho University, in Japan, adds.

The findings help us better understand how geology and the biosphere worked to change the Earth’s atmosphere into what we have today. It also helps us better understand the path life took on our planet; as much as oxygenation was a boon to animals like us, it was an environmental catastrophe for organisms at the time. The findings could also help us refine our search for Earth-like planets, or planets harboring alien life, as they give us a better understanding of how life itself can change a planet — and to what extent.

“Our results contribute to a deeper knowledge of the biological factors controlling the long-term evolution of Earth’s atmosphere,” Ozaki says. “They offer a better mechanistic understanding of the factors that promote oxygenation of the atmospheres of Earth-like planets beyond our solar system.”

The results “yield an entirely new vantage from which to build theoretical models of Earth’s biogeochemical oxygen cycle,” Reinhard adds.

The paper “Anoxygenic photosynthesis and the delayed oxygenation of Earth’s atmosphere” has been published in the journal Nature.


The Earth’s atmosphere extends twice as far as the Moon, technically

The Earth’s atmosphere actually reaches to the Moon — and then some!


The Earth and its hydrogen envelope, or geocorona, as seen from the Moon. This ultraviolet picture was taken in 1972 with a camera operated by Apollo 16 astronauts on the Moon.
Image credits NASA via ESA.

New research says that Earth’s gaseous cover reaches up to 630,000 kilometers away, over 50 times the diameter of the planet. The findings were drawn from observations by the ESA/NASA Solar and Heliospheric Observatory, SOHO.

More is actually more

“The moon flies through Earth’s atmosphere,” says Igor Baliukin of Russia’s Space Research Institute, lead author of the paper presenting the results. “We were not aware of it until we dusted off observations made over two decades ago by the SOHO spacecraft.”

The interface between Earth’s atmosphere and outer space, the place where the two kind-of mix together, is called the geocorona. Starting from data recorded by the SWAN instrument on the SOHO, the team calculated precisely how far away the outskirts of the geocorona are. It’s twice as far as the Moon, they report.


Illustration of the geocorona (not to scale).
Image credits SOHO / ESA.

Apollo 16 astronauts — some of the last people to ever land on the moon — took a telescope up to our planet’s natural satellite which they used to capture an image of Earth’s geocorona, glowing brightly in ultraviolet light. This UV light was produced by the interaction between sunlight and hydrogen atoms. The atoms emit (but also absorb) a very particular wavelength of UV light known as Lyman-alpha when interacting with sunlight. We can’t really see it down here, as Lyman-alpha light is quickly absorbed and dissipated in the atmosphere — but you can see it from outer space.

“At that time, the astronauts on the lunar surface did not know that they were actually embedded in the outskirts of the geocorona,” says Jean-Loup.

SOHO currently orbits much further away from Earth than those astronauts were located — some 1.5 million kilometers away from our planet, towards the sun. This distance offered a good vantage point to observe the geocorona. Furthermore, the SWAN instrument aboard SOHO comes equipped with a hydrogen absorption cell, which the team used to selectively measure Lyman-alpha light from the geocorona and filter out that of hydrogen atoms further away in interplanetary space.

They report that Earth’s geocorona gets smooshed down on its dayside (the one facing the sun), which in turn produces an area of higher hydrogen density on its night side. “Dense” here is a relative term — this isn’t the atmosphere we known and love down at the surface level. Hydrogen densities peak at about 70 atoms per cubic centimeters at roughly 60,000 kilometers above the surface, and dip as low as 0.2 atoms per cubic centimeters around the moon.

“On Earth we would call it vacuum, so this extra source of hydrogen is not significant enough to facilitate space exploration,” says Igor.

“There is also ultraviolet radiation associated to the geocorona, as the hydrogen atoms scatter sunlight in all directions, but the impact on astronauts in lunar orbit would be negligible compared to the main source of radiation – the sun,” says Jean-Loup Bertaux.

SOHO’s SWAN instrument imaged Earth and its extended atmosphere on three occasions between 1996 and 1998. The team decided to retrieve this data from the archives for further analysis — and that’s how this discovery was born.

“Data archived many years ago can often be exploited for new science,” says Bernhard Fleck, ESA SOHO project scientist. “This discovery highlights the value of data collected over 20 years ago and the exceptional performance of SOHO.”

The paper “SWAN/SOHO Lyman‐α mapping: the Hydrogen Geocorona Extends Well Beyond The Moon” has been published in the Journal of Geophysical Research: Space Physics.


Bombs dropped during the Second World War were felt to the edge of space

The Second World War brought unprecedented destruction upon the face of the Earth — one that reached up to the edge of space, new research reveals.


Image via Pixabay.

Allied bombing raids during the Second World War caused shockwaves so strong that they weakened the ionosphere, the electrified layer of the atmosphere that reaches up to 1000 km (621 mi) above ground, reports a new paper from the University of Reading.

High-altitude bombing

“The images of neighbourhoods across Europe reduced to rubble due to wartime air raids are a lasting reminder of the destruction that can be caused by man-made explosions,” says Chris Scott, Professor of Space and Atmospheric Physics at Reading and one of the paper’s coauthors. “But the impact of these bombs way up in the Earth’s atmosphere has never been realised until now.”

“It is astonishing to see how the ripples caused by man-made explosions can affect the edge of space. Each raid released the energy of at least 300 lightning strikes. The sheer power involved has allowed us to quantify how events on the Earth’s surface can also affect the ionosphere.”

World War Two was perhaps the single most calamitous war humanity has ever embarked upon. Fueled by an already-ripened Industrial Revolution and incredible technological leaps, belligerent countries unleashed unprecedented destruction upon their foes’ troops and homelands.

So awesome was their fury that not even the ionosphere escaped unscathed. The team drew on daily records collected by the Radio Research Center in Sough, UK, between 1943-45, a period that saw rapid development of radio and radio-based technology (such as radar). Among other research topics, scientists at the center shot sequences of shortwave radio pulses at heights between 100 and 300 km (62 to 186 mi) above the Earth’s surface in order to better understand the height and ionization levels of layers within the upper atmosphere.

Their work helped reveal the existence of the ionosphere — and now, it’s helping researchers understand how natural forces from below, like lightning, volcanic eruptions, or earthquakes, affect this layer of our atmosphere.

The ionosphere underpins several technologies such as radio communications, GPS systems, radio telescopes, and some variations of radar, as it helps bounce radio signals back down towards the surface (instead of letting them escape to outer space). So it’s not hard to see why we want to have as comprehensive an understanding of it as possible. Being a highly-charged layer, the ionosphere is strongly influenced by solar activity.

However, scientific modeling has revealed that our star alone cannot account for all the waxing and waning we see in this layer. Ground-level activity has to account for the rest.

Higher-altitude effects

To help us understand how ground-level events influence this layer, the team studied the ionosphere’s response around the time of 152 large Allied air raids in Europe.

The team focused on Allied bombing runs over continental Europe rather than attacks more close to the center — such as the infamous London ‘Blitz’ — due to their more sporadic nature. The Blitz was a monumental and sustained bombing effort, but its continuous nature (and the fact that relatively little information is available to accurately time and locate individual runs) made it much more difficult for the team to tease out its effects from natural, seasonal variations in the ionosphere. In other words, Nazi Germany dropped so many bombs on Britain and for so long, that it ruined the data sample.

Another factor that made the team focus on Allied raids was sheer ‘boom’. The German Luftwaffe employed two-engine tactical bombers, which carried relatively small bombs; the Allies, in contrast, relied on four-engine strategic bombers that carried much larger ordinance — such as the 10-tonne ‘earthquake bomb’ Grand Slam. Quantity, it turns out, truly is a quality in and of itself:

“Aircrew involved in the raids reported having their aircraft damaged by the bomb shockwaves, despite being above the recommended height,” says Professor Patrick Major, University of Reading historian and a co-author of the study. “Residents under the bombs would routinely recall being thrown through the air by the pressure waves of air mines exploding, and window casements and doors would be blown off their hinges.”

“There were even rumours that wrapping wet towels around the face might save those in shelters from having their lungs collapsed by blast waves, which would leave victims otherwise externally untouched.”

The team reports that electron concentration in the ionosphere dropped significantly following these events, due to shockwaves generated by air-detonating bombs exploding near the surface. These pressure waves, the team believes, heated up the upper atmosphere, enhancing the loss of ionization.

“The unprecedented power of these attacks has proved useful for scientists to gauge the impact such events can have hundreds of kilometres above the Earth, in addition to the devastation they caused on the ground.”

The researchers now need members of the public to help digitize more early atmospheric data, to understand the impact of the many hundreds of smaller bombing raids during the war, and help determine the minimum explosive energy required to trigger a detectable response in the ionosphere.

The paper has been published in the journal Annales Geophysicae.

Horizon atmosphere.

All this time, outer space was secretly much closer than we thought

Nothing changed with our atmosphere — just our calculations and assumptions have gotten better.

Horizon atmosphere.

Image credits NASA.

A new research paper proposes that we are all one step closer to space than we assumed. If the calculations are proven correct, we might, in fact, be a full 12 miles closer. The exact altitude of this boundary — the plane where the laws that order airspace get superseded by those governing outer space — is an important piece of information in world politics, the authors note.

The recalculated frontier

“The argument about where the atmosphere ends and space begins predates the launch of the first Sputnik,” wrote Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, and sole author of the new paper. “The most widely accepted boundary is the so-called Karman Line, nowadays usually set to be 62 miles altitude.”

The boundary between atmosphere and space is known as the Kármán line after its discoverer, aerodynamics researcher, and engineer Theodore von Kármán. In 1963, when the line was proposed, von Kármán suggested that the speed needed to lift an object into the atmosphere is the same as the speed needed to keep it in orbit around the Earth. He also believed that the horizontal movement of the object on orbit would counteract the effects of gravity. According to McDowell, however, this just isn’t true. The position of the line was therefore calculated based on a faulty assumption and without any real means of testing — this was a time before real-life orbital readings could be performed.

For his study, McDowell drew on North American Aerospace Defense Command (NORAD) data detailing the orbital comings and goings of over 43,000 satellites. Most of these orbited far above the Karman line, so McDowell removed their paths from the study. About 50 satellites, however, were used in the calculations.

What set these 50 apart is that they all performed at least full rotations around the planet at low altitude (below 100km / 63 miles) as they re-entered the atmosphere at the end of their missions. The Soviet satellite Elektron-4, for example, performed ten full rotations around the planet at around 83 km (52 miles) before it burned up in the atmosphere in 1997. In other words, these cases revealed that satellites could still behave as if they were in outer space below the Karman line — which raises the possibility that the altitude line itself is overestimated.

McDowell used a mathematical model to find the altitude at which the orbits of these satellites finally started to degrade and they dropped back into the atmosphere — he found that these events occurred between 70 to 82 kilometers (41 to 55 miles) high. However, for most satellites, the 80-kilometer (50-mile) mark seems to be the lowest possible stable orbit. So McDowell proposes this altitude as the new accepted boundary between our atmosphere and outer space.

The suggestion may actually get some traction in the scientific community. The 80-kilometer mark fits with what we know of the atmosphere’s structure. The mesopause, stretching roughly between 83 and 100 kilometers high, is an area where the air’s chemical composition changes dramatically and charged particles become more abundant — which harkens more to the state of gases in outer space than those in our atmosphere. Below the lower edge of the mesopause, Earth’s atmosphere becomes a stronger force for airborne objects to reckon with, McDowell wrote.

“It is noteworthy that meteors (traveling much more quickly) usually disintegrate in the 43 to 62 miles altitude range, adding to the evidence that this is the region where the atmosphere becomes important,” he adds.

While most outer space operations, such as rocket launches, should remain relatively unchanged if the new boundary is adopted, McDowell wrote, it could raise some important political and territorial issues

The airspace above each country is generally considered to be part of that country — but outer space isn’t owned by anyone. If the limit of space is set at 100 kilometers high, for example, and an unauthorized satellite passes at 80 kilometers high, it could be rightfully considered an act of military aggression between states. Seeing as satellites tend to sometimes wobble up and down along their orbits, a lower limit of the atmosphere might help ease tensions.

The paper “The edge of space: Revisiting the Karman Line” will be published in the October issue of the journal Acta Astronautica.

Atmospheric readings show someone is producing illegal, ozone-depleting industrial gases

Atmospheric readings show that someone, somewhere, isn’t playing by the rules.


Aerosol used to widely incorporate these dangerous chemicals.
Image credits PiccoloNamek / Wikimedia.

Just last November, I’ve had the pleasure to report that, according to NASA’s measurements, 30 years of international effort and cooperation were doing the ozone layer some good. It was, all in all, very good news: it showed states could successfully and sensibly work together on ecological problems, and it meant we won’t get fried by solar radiation — both wins in my book.

However, a new study shows that not all is as well as we thought: someone has been cheating on the Montreal Protocol by producing new ozone-depleting chemicals on an industrial scale.

The ozone hole, renewed?

The Montreal Protocol of 1987 banned the production of three main ozone-destroying classes of chemicals: chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). Since these compounds take an impressively long time to break down in the atmosphere, monitoring systems were set in place to make sure everything went smoothly. And good thing they did.

A team of researchers led by Stephen Montzka of the US National Oceanic and Atmospheric Administration (NOAA) reports that something is off with CFC-11 levels in the atmosphere. This chemical — previously used as a solvent, a refrigerant, as a precursor in styrofoam production, and a propellant in spray cans — is currently banned for production under the protocol. We used to employ a lot of it, however, and there are still sources of this gas leaking into the atmosphere (such as old refrigerators in landfills). However, these secondary sources should gradually decline, then disappear completely. As they do, we should see the decline of CFC-11 levels in the atmosphere accelerate.

But we aren’t. CFC-11 levels dropped some 2.1 ppt (parts-per-trillion) each year between 2002 and 2012. Afterward, however, the decline actually started to slow down: between 2015 and 2017, CFC-11 levels in the atmosphere dropped by only 1.0 ppt per year.

The concentration of CFC-11 in the Northern (red) and Southern (blue) Hemispheres compared to projected decline (gray lines).
Image credits Montzaka et al. (2018), Nature.

First, the team checked whether the change could come from natural processes. Some of these, however, could be ruled out quite easily: the first was whether weather-pattern-induced movements of CFCs in the stratosphere caused the observed variations. Another possible explanation, that a lot of old buildings using CFC-11-based ventilation systems were demolished at the same time, was also ruled out, as it didn’t plausibly fit the data, according to the team.

The team used atmospheric modeling to analyze what effect could lead to the observed rise. The concentration of these gases has always been higher in the (more developed, more industrialized) Northern Hemisphere than in the Southern one. Over the last few years, the team reports, this discrepancy between the two hemispheres has become more pronounced. Other gases haven’t followed the same pattern, the authors add, suggesting that the increase in CFC-11 emissions come from somewhere in the Northern Hemisphere.

Measurements taken at the Mauna Loa observatory in Hawaii also show that CFC-11 isn’t the only anthropic pollutant that’s seeing an uptick roughly since the year 2000. The team’s models showed that natural variability in atmospheric circulation (aka weather patterns) could only explain half of the observed increase — meaning that the only plausible explanation is an increase in emissions.

The team report that the source is most likely somewhere in Eastern Asia. They also estimate that around 6,500 to 13,000 tons of new CFC emissions would fit the observed trend in atmospheric concentrations.

“This is the first time that emissions of one of the three most abundant, long-lived CFCs have increased for a sustained period since production controls took effect in the late 1980s,” the researchers write.

“A delay in ozone recovery […] is anticipated, with an overall importance depending on the trajectory of CFC-11 emissions and concentrations in the future.”

The emissions are a direct violation of the Montreal Protocol. Signatories have taken it upon themselves to monitor CFC production and report it back to the United Nation group which oversees the protocol’s implementation. Against this backdrop, the team was very careful to spell out that they don’t have enough data to point towards a specific nation. They also add that its possible such production is taking place beyond the local government’s back — putting the ball in their court to safeguard the ozone layer.

The paper “An unexpected and persistent increase in global emissions of ozone-depleting CFC-11” has been published in the journal Nature.

Apollo Beach power plant.

Average atmospheric CO2 levels last month were the highest we’ve ever recorded, ever

Atmospheric concentrations of carbon dioxide have set a new and worrying record: for the first time in recorded history, levels averaged higher than 410 parts per million (ppm) throughout the whole month.

Apollo Beach power plant.

Apollo Beach power plant.
Image via Wikimedia.

Last year, CO2 levels in the atmosphere hit the highest concentration they’ve reached in millions of years — 410 ppm. It wasn’t a pretty sight, and it was a testament to humanity’s advancements: for better or worse, we had become a geological force.

This April, we’ve reached an even more ignoble record: we’ve seen average atmospheric CO2 levels rise above the 410 ppm mark and stay there throughout the whole month for the first time in history.

A worrying development

“We keep burning fossil fuels. Carbon dioxide keeps building up in the air. It’s essentially as simple as that,” says Scripps Institution of Oceanography geochemist Ralph Keeling.

When it comes to atmospheric CO2 levels, Keeling is the guy to talk to. You could say he was born and bred for it — the chart we use to keep track of these levels, the Keeling Curve, is based on the work of the late Charles David Keeling, Ralph’s father. It was this curve that first hinted to the possibility of anthropogenic contribution to the greenhouse effect and global warming.

The readings on which the Keeling Curve is based first began at the Mauna Loa Observatory in 1958. At the time, measurements indicated a CO2 concentration of roughly 315 ppm. Just 60 years later, we’ve passed the 410 ppm threshold. This April, the average concentration was 410.31 ppm, according to data published by the Scripps Institution of Oceanography.

This is the first time in the observatory’s history that a monthly average exceeded 410 ppm, the institution adds.

It’s not, strictly speaking, the first time atmospheric CO2 levels have reached 400 ppm. We know of at least one previous case where it happened — we call it the Pliocene warm period, and it lasted from around 5.3 to 2.6 million years ago. What was going on during that time? So glad you asked.

Earth in the mid-Pliocene doesn’t seem very different from that of today at first glance — in general, it was 2 to 3°C warmer than nowadays. Carbon dioxide levels were, again, about the same as today. The seas, however, not so much — the global sea level was about 20 to 25m higher than it is today. The Northern hemisphere couldn’t maintain almost any permanent ice sheets up until very near the end of the Pliocene, around 3 million years ago, and all that liquid water swelled the oceans.

Other things the Pliocene lacked in spades were coastal cities, globalized economies, or masses of people to suffer from the environmental damage.

What’s particularly worrying for researchers today isn’t the CO2 concentrations themselves — it’s how fast we’re increasing them. The Pliocene level “was sustained over long periods of time, whereas today the global CO2 concentration is increasing rapidly,” according to scientists in the Fourth National Climate Assessment, Volume 1, a federal report published last year.

Before the Industrial Revolution, CO2 levels fluctuated very slowly, over thousands of years. According to researchers at the Scripps Institute, however, these levels never once exceeded 300 ppm once in the past 800,000 years. Around 1880, CO2 levels peaked at about 280 ppm. That makes today’s levels a staggering 46% higher than those just over a century ago.

“It’s as if we discovered that something we eat every day is causing our body to run a fever and develop all kinds of harmful symptoms — and instead of cutting back, we right keep on eating it, more and more,” tweeted climate scientist Katharine Hayhoe about the findings.

“If that isn’t alarming, I don’t know what is.”


NASA releases atmospheric simulation of this year’s hurricane season

A gorgeous new animation published by NASA depicts sea salt, dust, and smoke movements in the atmosphere during this year’s hurricane season.


Because air is so hard to see, NASA uses aerosol particles to track movements in the atmosphere. By combining raw satellite data with mathematical models of atmospheric phenomena, NASA researchers can see how smoke, dust, and sea salt are transported across the globe — allowing the agency a glimpse into weather patterns that would otherwise remain hidden to our view.

For example, tracking how sea salt (blue-white) evaporates from oceans will showcase the evolution of all of 2017’s hurricanes. The animation also captures the massive wildfires in the Pacific Northwest on the smoke layer of the simulation (gray). Particles released in these fires made it all the way from Oregon to Washington, though the south, eventually reaching the UK (in early September).

Dust (brown) also makes an appearance, most notably piggybacking on storm systems out of the Sahara and towards the Americas. Unlike sea salt, however, it doesn’t last too long in the eye of the storm. Here, dust particles are captured by cloud droplets and rain down on the ocean.

Advances in computing speed allow scientists to include more details of these physical processes in their simulations than ever before. So in time, they’re only going to become more complex and will more closely reflect reality.