Tag Archives: atmosphere

Science

Dropping Oxygen Will Eventually Suffocate Most Life on Earth

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For now life is flourishing on our oxygen-rich planet, but Earth wasn’t always that way – and scientists have predicted that, in the future, the atmosphere will revert back to one that’s rich in methane and low in oxygen.

 

This probably won’t happen for another billion years or so. But when the change comes, it’s going to happen fairly rapidly, the study suggests.

This shift will take the planet back to something like the state it was in before what’s known as the Great Oxidation Event (GOE) around 2.4 billion years ago.

What’s more, the researchers behind the new study say that atmospheric oxygen is unlikely to be a permanent feature of habitable worlds in general, which has implications for our efforts to detect signs of life further out in the Universe.

“The model projects that a deoxygenation of the atmosphere, with atmospheric O2 dropping sharply to levels reminiscent of the Archaean Earth, will most probably be triggered before the inception of moist greenhouse conditions in Earth’s climate system and before the extensive loss of surface water from the atmosphere,” write the researchers in their published paper.

At that point it’ll be the end of the road for human beings and most other life forms that rely on oxygen to get through the day, so let’s hope we figure out how to get off the planet at some point within the next billion years.

 

To reach their conclusions, the researchers ran detailed models of Earth’s biosphere, factoring in changes in the brightness of the Sun and the corresponding drop in carbon dioxide levels, as the gas gets broken down by increasing levels of heat. Less carbon dioxide means fewer photosynthesising organisms such as plants, which would result in less oxygen.

Scientists have previously predicted that increased radiation from the Sun would wipe ocean waters off the face of our planet within about 2 billion years, but the new model – based on an average of just under 400,000 simulations – says the reduction in oxygen is going to kill off life first.

“The drop in oxygen is very, very extreme,” Earth scientist Chris Reinhard, from the Georgia Institute of Technology, told New Scientist. “We’re talking around a million times less oxygen than there is today.”

What makes the study particularly relevant to the present day is our search for habitable planets outside of the Solar System.

Increasingly powerful telescopes are coming online, and scientists want to be able to know what they should be looking for in the reams of data these instruments are collecting.

It’s possible that we need to be hunting for other biosignatures besides oxygen to have the best chance of spotting life, the researchers say. Their study is part of the NASA NExSS (Nexus for Exoplanet System Science) project, which is investigating the habitability of planets other than our own.

According to the calculations run by Reinhard and environmental scientist Kazumi Ozaki, from Toho University in Japan, the oxygen-rich habitable history of Earth could end up lasting for just 20-30 percent of the planet’s lifespan as a whole – and microbial life will carry on existing long after we are gone.

“The atmosphere after the great deoxygenation is characterised by an elevated methane, low-levels of CO2, and no ozone layer,” says Ozaki. “The Earth system will probably be a world of anaerobic life forms.”

The research has been published in Nature Geoscience.

 

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Earth’s Magnetic Field Flipped 42,000 Years Ago. The Consequences Were Dramatic

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A global period of upheaval 42,000 years ago was the result of a reversal in Earth’s magnetic field, new research has found.

According to radiocarbon preserved in ancient tree rings, several centuries’ worth of climate breakdown, mass extinctions, and even changes in human behaviour can be directly linked to the last time Earth’s magnetic field changed its polarity.

 

The research team has named the period the Adams Transitional Geomagnetic Event, or Adams Event, after sci-fi writer Douglas Adams, who famously declared the number 42 the ultimate answer to life, the Universe, and everything.

“For the first time ever, we have been able to precisely date the timing and environmental impacts of the last magnetic pole switch,” said Earth scientist Chris Turney of the University of New South Wales in Australia. 

“The findings were made possible with ancient New Zealand kauri trees, which have been preserved in sediments for over 40,000 years. Using the ancient trees we could measure, and date, the spike in atmospheric radiocarbon levels caused by the collapse of Earth’s magnetic field.”

This most recent period of magnetic reversal is known as the Laschamp event, and it is what we call a geomagnetic excursion. This is when the planet’s magnetic poles briefly swap places before returning to their original positions. It’s one of the most well studied of Earth’s magnetic field events, recorded by ferromagnetic minerals.

It took place around 41,000 years ago, and lasted for around 800 years. Exactly what impact this event had on life on the planet was unclear, though – so when scientists uncovered an ancient kauri tree (Agathis australis) in 2019 that had been alive during this time period, they seized on the chance to learn more.

 

That’s because trees record atmospheric activity in their annual growth rings. In particular, carbon-14, or radiocarbon, can reveal a lot of information about celestial activity.

Radiocarbon only occurs on Earth in trace amounts compared to the other naturally occurring carbon isotopes. It’s formed in the upper atmosphere under the bombardment of cosmic rays from space. When these rays enter the atmosphere, they interact with the local nitrogen atoms to trigger a nuclear reaction that produces radiocarbon.

Since cosmic rays are constantly streaming through space, Earth receives a more or less steady supply of radiocarbon. Therefore, a spike in radiocarbon in tree rings tells us that Earth had greater exposure to radiocarbon during that year.

When Earth’s magnetic field is weakened, as it was during the Laschamp event, more cosmic rays penetrate through to the atmosphere to produce more radiocarbon. Because of this, scientists had previously been able to ascertain that Earth’s magnetic field had weakened to about 28 percent of its normal strength during that 800-year period.

The kauri tree, however, allowed the research team to study the years leading up to the Laschamp event. They found that the Adams event took place from about 42,200 years ago, and the magnetic field was at its weakest point before the Laschamp event.

 

“Earth’s magnetic field dropped to only 0-6 percent strength during the Adams Event,” Turney explained. “We essentially had no magnetic field at all – our cosmic radiation shield was totally gone.”

During this time, the Sun’s magnetic field would also have weakened several times, as it, too, experienced magnetic reversal as part of its regular cycle. These periods see less sunspot and flare activity, but the Sun’s magnetic field also provides Earth with a measure of protection from cosmic rays – so, during these solar minima, cosmic ray bombardment would have increased again.

This weakened magnetic field would have triggered substantial changes in Earth’s atmospheric ozone, with dramatic consequences, including electrical storms and spectacular aurorae, and climate change around the world.

“Unfiltered radiation from space ripped apart air particles in Earth’s atmosphere, separating electrons and emitting light – a process called ionisation,” Turney said.

“The ionised air ‘fried’ the ozone layer, triggering a ripple of climate change across the globe.”

This is consistent with climate and environmental changes from this time observed in other records from across the globe, such as the mysterious extinction of Australia’s megafauna.

 

Curiously, it also coincides with some of our oldest cave art on record, prompting the researchers to hypothesise that the Adams Event could have driven humans indoors.

“This sudden behavioural shift in very different parts of the world is consistent with an increasing or changed use of caves during the Adams Event, potentially as shelter from the increase of ultraviolet B, potentially to harmful levels, during grandsolar minima or solar energetic particles, which might also explain an increased use of red ochre sunscreen,” they wrote in their paper.

That’s somewhat speculative, of course, but it suggests that a geomagnetic reversal can be a seriously world-altering event. And recent evidence has suggested that we’re currently on the verge of another.

This, the researchers say, could be absolutely disastrous in the current climate.

“Our atmosphere is already filled with carbon at levels never seen by humanity before. A magnetic pole reversal or extreme change in Sun activity would be unprecedented climate change accelerants,” Turney said.

“We urgently need to get carbon emissions down before such a random event happens again.”

The research has been published in Science.

 

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Science

Researchers Levitated a Small Tray Using Nothing but Light

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Their simulations estimated that a 6-centimeter plate could carry 10 milligrams of cargo in the mesosphere under natural sunlight. Ten milligrams may not sound like much; a drop of water weighs five times as much. But engineering advances have shrunk silicon chips into dust-sized sensors far smaller than that. These “smart dust” systems can fit a power source, radio communication, and a data-collecting sensor in cubes only a millimeter across. “Researchers can do a lot when you give them a cubic millimeter of silicon,” says Bargatin. “And a cubic millimeter of silicon weighs a couple of milligrams.”

In their vacuum chamber test, they found that when cranking the light intensity up past the power of sunlight, that extra rush of energy carried the flyer higher. But after about 30 seconds, the disk began curling up from photophoretic force, eventually collapsing. Ultrathin Mylar is very flimsy on its own, says Bargatin. The shag of carbon nanotubes makes the Mylar disk more rigid, but the force of high-speed molecular collisions eventually buckles the flyer. The team’s model can predict what disk sizes, air pressures, and light intensities cause this, and Bargatin says work to develop a lightweight frame is ongoing.

Bargatin envisions researchers one day releasing sensor-laden levitators in the mesosphere and letting them roam, like weather balloons or floating ocean sensors. “Another approach is to actually develop smart flyers that can control where they’re going,” he says. The same tilting that stabilizes the levitators could be used to steer them. And, he adds, suspending the sensor from the levitator like a parachuter hanging from a canopy would help keep the system upright when faced with wind.

Still, Marsh is not convinced that such a device could withstand mesospheric conditions. “Any instrument is going to have to operate in the extreme conditions of the mesosphere, where the average winds can easily exceed 100 mph,” he writes. Winds in the upper mesosphere can be especially shearing, temperatures can drop to 140 below zero, and space weather radiates through the mesosphere and can damage communication systems.

Paul Newman, chief scientist of Earth Sciences at NASA’s Goddard Space Flight Center, agrees that accounting for mesospheric wind will be a big technical challenge, but he can’t help but delight at the possible applications. “I actually think this is a really cool idea,” he says. One possibility would be to probe water vapor in the mesosphere, where polar clouds form so high that the sun still illuminates them at night. The mysterious clouds aren’t just beautiful, Newman says; their possible link to increased greenhouse gases means they may become more common—but researchers can’t track the mesosphere’s water content and temperature as well as they’d like. Mesospheric clouds are “another sign of climate change. And we need information to show that,” Newman says. “That’s why these could be really cool for getting data on atmospheric composition.”

Newman adds that the plates’ tininess and levitation ability could also be intriguing for Mars research. The air pressure of the Martian atmosphere is similar to Earth’s mesosphere, so perhaps light, autonomous levitators could collect temperature or composition measurements. “You can just take off once per day, and go up and then come back down and land on your little Martian lander,” he imagines. “We don’t have that information on Mars. That would just be fantastic.” (NASA is planning to test out a small helicopter called Ingenuity as part of its soon-to-land Perseverance rover mission, but that craft will be much bigger and is still in the test flight stage; it’s not ready for science missions yet.)

Bargatin says they are currently exploring applications for Mars, and that the team is also hoping to make their microflyers work at sea level on Earth. But regardless of any eventual use, Azadi will always remember seeing the Mylar creation float for the first time, exactly according to his theoretical predictions. “After that,” he says, “I called my girlfriend and I said, ‘I think I’m going to graduate soon.’”

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Science

A Previously Unseen Chemical Reaction Has Been Detected on Mars

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The giant Martian sandstorm of 2018 wasn’t just a wild ride – it also gave us a previously undetected gas in the planet’s atmosphere. For the first time, the ExoMars orbiter sampled traces of hydrogen chloride, composed of a hydrogen and a chlorine atom.

 

This gas presents Mars scientists with a new mystery to solve: how it got there.

“We’ve discovered hydrogen chloride for the first time on Mars,” said physicist Kevin Olsen of the University of Oxford in the UK.

“This is the first detection of a halogen gas in the atmosphere of Mars, and represents a new chemical cycle to understand.”

Scientists have been keeping an eye out for gases that contain chlorine in the atmosphere of Mars, since they could confirm that the planet is volcanically active. However, if hydrogen chloride was produced by volcanic activity, it should only spike very regionally, and be accompanied by other volcanic gases.

The hydrogen chloride detected by ExoMars did not, and was not. It was sniffed out in both the northern and southern hemispheres of Mars during the dust storm, and the absence of other volcanic gases was glaring. 

This suggests that the gas was being produced by some other process; luckily, we have similar processes here on Earth that can help us understand what it could be.

It’s a several-step process that requires a few key ingredients. First, you need sodium chloride (that’s regular salt), left over from evaporative processes. There’s plenty of that on Mars, thought to be the remnants of ancient salt lakes. When a dust storm stirs up the surface, the sodium chloride gets kicked up into the atmosphere.

Then there’s the Martian polar ice caps which, when warmed during the summer, sublimate. When the resulting water vapour mingles with the salt, the resulting reaction releases chlorine, which then reacts further to form hydrogen chloride.

Graphic showing the potentially new chemistry cycle detected on Mars. (ESA)

“You need water vapour to free chlorine and you need the by-products of water – hydrogen ­- to form hydrogen chloride. Water is critical in this chemistry,” Olsen said.

“We also observe a correlation to dust: we see more hydrogen chloride when dust activity ramps up, a process linked to the seasonal heating of the southern hemisphere.”

 

This model is supported by a detection of hydrogen chloride during the following 2019 dusty season, which the team is still analysing.

However, confirmation is still pending. Future and ongoing observations will help put together a more comprehensive picture of the process’s cycles.

Meanwhile, laboratory experiments, modelling and simulations will help scientists rule out or confirm potential mechanisms behind the release of hydrogen chloride in the Martian atmosphere.

The research has been published in Science Advances.

 

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Science

Groundbreaking New Laser System Cuts Through Earth’s Atmosphere Like It’s Nothing

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To artists and romantics, the twinkling of stars is visual poetry; a dance of distant light as it twists and bends through a turbulent ocean of air above our heads.

Not everybody is so enamoured with our atmosphere’s distortions. To many scientists and engineers, a great deal of research and ground-to-satellite communication would be a whole lot easier if the air simply wasn’t there.

 

Losing our planet’s protective bubble of gases isn’t exactly a popular option. But Australian and French researchers have teamed up to design the next best thing – a system that guides light through the tempestuous currents of rippling air with the flick of a mirror.

The result is a laser link capable of holding its own through the atmosphere with unprecedented stability.

While astronomers have a few tricks up their sleeve to correct for the atmosphere’s distortions on incoming light, it’s been a challenge to emit a coherent beam of photons from the ground to a distant receiver so they keep together and on point.

Keeping transmissions on target and coherent – with their phases remaining neatly in line – through hundreds of kilometres of shifting air would allow us to link highly precise measurement tools and communications systems.

Satellites could probe for ores or evaluate water tables with improved precision. High-speed data transfer could require less power, and contain more information.

Lead author Ben Dix-Matthews, an electrical engineer with the International Centre for Radio Astronomy Research in Australia, explained the technology to ScienceAlert.

 

“The active terminal essentially uses a small four-pixel camera, which measures the sideways movement of the received beam,” says Dix-Matthews.

“This position measurement is then used to actively control a steerable mirror that keeps the received beam centred and removes the sideways movement caused by the atmosphere.”

In effect, the system can be used to compensate for the warping effects of the moving air in three dimensions – not just up and down, or left and right, but along the beam’s trajectory, keeping the link centred and its phases in order.

So far it’s only been tested across a relatively short distance of 265 metres (about 870 feet). About 715 metres (just under half a mile) of optical fibre cable was run underground between the transmitter and receiver to carry a beam for comparison.

The results were so stable they could be used to connect the kinds of optical atomic clocks used to test fundamental physics, such as Einstein’s theories of relativity.

With the proof of concept demonstrated, there’s no reason to think a similar technique won’t one day be aiming for the sky, and beyond. Though there are a few hurdles that need to be overcome first.

 

“During this experiment we had to do the initial alignment by hand, using a visible guide laser that was in line with the stabilised infrared beam,” Dix-Matthews told ScienceAlert.

“When making links between optical atomic clocks, it would be good to have a way of doing this coarse alignment more easily.”

Fortunately Dix-Matthews’ French collaborators are working on a device that will speed up the initial coarse alignment process, promising a second generation of laser link technology that won’t require such an involved set-up.

The team also found temperature variations in the equipment affected the phase’s stability, limiting the duration of the signal to around 100 seconds. This hurdle will also be the focus of future improvements.

We might not need to wait long. The researchers are already making headway on upgrades for their system.

“We have started using a high-power laser amplifier that should help us deal with the larger power losses expected over longer distances, such as to space,” says Dix-Matthews.

“We have also completely rebuilt our active terminal to make it more sensitive to low received powers and make it more effective at cancelling out the movement of the received beam.”

With orbiting technology rapidly becoming a major focus for many data providers, potentially filling our skies with satellites, innovations that make linking communications systems across our atmosphere will only become more sought after.

As useful as our atmosphere is for, well, keeping us all alive, there are certainly some downsides to being buried under a restless blanket of warm gas.

This research was published in Nature Communications.

 

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