What happened to early Mars' atmosphere? New study eliminates one theory

Scientists may be closer to solving the mystery of how Mars changed from a world with surface water billions of years ago to the arid Red Planet of today.

A new analysis of the largest known deposit of carbonate minerals on Mars suggests that the original Martian atmosphere may have already lost most of its carbon dioxide by the era of valley network formation.

"The biggest carbonate deposit on Mars has, at most, twice as much carbon in it as the current Mars atmosphere," said Bethany Ehlmann of the California Institute of Technology and NASA Jet Propulsion Laboratory, both in Pasadena. "Even if you combined all known carbon reservoirs together, it is still nowhere near enough to sequester the thick atmosphere that has been proposed for the time when there were rivers flowing on the Martian surface."

Carbon dioxide makes up most of the Martian atmosphere. That gas can be pulled out of the air and sequestered or pulled into the ground by chemical reactions with rocks to form carbonate minerals. Years before the series of successful Mars missions, many scientists expected to find large Martian deposits of carbonates holding much of the carbon from the planet's original atmosphere. Instead, these missions have found low concentrations of carbonate distributed widely, and only a few concentrated deposits. By far the largest known carbonate-rich deposit on Mars covers an area at least the size of Delaware, and maybe as large as Arizona, in a region called Nili Fossae.

Christopher Edwards, a former Caltech researcher now with the U.S. Geological Survey in Flagstaff, Arizona, and Ehlmann reported the findings and analysis in a paper posted online by the journal Geology. Their estimate of how much carbon is locked into the Nili Fossae carbonate deposit uses observations from numerous Mars missions, including the Thermal Emission Spectrometer (TES) on NASA's Mars Global Surveyor orbiter, the mineral-mapping Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and two telescopic cameras on NASA's Mars Reconnaissance Orbiter, and the Thermal Emission Imaging System (THEMIS) on NASA's Mars Odyssey orbiter.

Edwards and Ehlmann compare their tally of sequestered carbon at Nili Fossae to what would be needed to account for an early Mars atmosphere dense enough to sustain surface waters during the period when flowing rivers left their mark by cutting extensive river-valley networks. By their estimate, it would require more than 35 carbonate deposits the size of the one examined at Nili Fossae. They deem it unlikely that so many large deposits have been overlooked in numerous detailed orbiter surveys of the planet. While deposits from an even earlier time in Mars history could be deeper and better hidden, they don't help solve the thin-atmosphere conundrum at the time the river-cut valleys formed.

The modern Martian atmosphere is too tenuous for liquid water to persist on the surface. A denser atmosphere on ancient Mars could have kept water from immediately evaporating. It could also have allowed parts of the planet to be warm enough to keep liquid water from freezing. But if the atmosphere was once thicker, what happened to it? One possible explanation is that Mars did have a much denser atmosphere during its flowing-rivers period, and then lost most of it to outer space from the top of the atmosphere, rather than by sequestration in minerals.

"Maybe the atmosphere wasn't so thick by the time of valley network formation," Edwards said. "Instead of Mars that was wet and warm, maybe it was cold and wet with an atmosphere that had already thinned. How warm would it need to have been for the valleys to form? Not very. In most locations, you could have had snow and ice instead of rain. You just have to nudge above the freezing point to get water to thaw and flow occasionally, and that doesn't require very much atmosphere."

NASA's Curiosity Mars rover mission has found evidence of ancient top-of-atmosphere loss, based on the modern Mars atmosphere's ratio of heavier carbon to lighter carbon. Uncertainty remains about how much of that loss occurred before the period of valley formation; much may have happened earlier. NASA's MAVEN orbiter, examining the outer atmosphere of Mars since late 2014, may help reduce that uncertainty.

Arizona State University, Tempe, provided the TES and THEMIS instruments. The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland., provided CRISM. JPL, a division of Caltech, manages the Mars Reconnaissance Orbiter and Mars Odyssey project for NASA's Science Mission Directorate, Washington, and managed the Mars Global Surveyor project through its nine years of orbiter operations at Mars. Lockheed Martin Space Systems in Denver built the three orbiters.

For more information about the Mars Reconnaissance Orbiter mission, visit:

http://mars.nasa.gov/mro

For more information about the Mars Odyssey mission, visit:

http://mars.nasa.gov/odyssey

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Oxygen oasis in Antarctic lake reflects Earth in distant past

At the bottom of a frigid Antarctic lake, a thin layer of green slime is generating a little oasis of oxygen, a team including UC Davis researchers has found. It's the first modern replica discovered of conditions on Earth two and a half billion years ago, before oxygen became common in the atmosphere. The discovery is reported in a paper in the journal Geology.

The switch from a planet with very little available oxygen to one with an atmosphere much like today's was one of the major events in Earth's history, and it was all because some bacteria evolved the ability to photosynthesize. By about 2.4 billion years ago, geochemical records show that oxygen was present all the way to the upper atmosphere, as ozone.

What is not clear is what happened in between, or how long the transition - called the Great Oxidation Event - lasted, said Dawn Sumner, professor and chair of earth and planetary sciences at UC Davis and an author on the paper. Scientists have speculated that here may have been "oxygen oases," local areas where was abundant before it became widespread around the planet.

The new discovery in Lake Fryxell in the McMurdo Dry Valleys could be a modern example of such an ancient oxygen oasis, and help geochemists figure out what to look for in ancient rocks, Sumner said.

Lake Fryxell. Credit: Tyler Mackey, UC Davis 

Sumner and collaborators including Ian Hawes of the University of Canterbury, New Zealand have been studying life in these ice-covered lakes for several years. The microbes that survive in these remote and harsh environments are likely similar to the first forms of life to appear on Earth, and perhaps on other planets.

The discovery occurred "a little by accident," Sumner said. Hawes and Tyler Mackey, a UC Davis graduate student working with Sumner, were helping out another research team by diving in Lake Fryxell. The lakes of the Dry Valleys typically contain oxygen in their upper layers, but are usually anoxic further down, Sumner said. Lake Fryxell is unusual because it becomes anoxic at a depth where light can still penetrate.

During their dives below the oxygen zone, Hawes and Mackey noticed some bright green bacteria that looked like they could be photosynthesizing. They took measurements and found a thin layer of oxygen, just one or two millimeters thick, being generated by the bacteria.

Something similar could have been happening billions of years ago, Sumner said.

"The thought is, that the lakes and rivers were anoxic, but there was light available, and little bits of oxygen could accumulate in the mats," she said.

The researchers now want to know more about the chemical reactions between the "oxygen oasis" and the anoxic water immediately above it and sediments below. Is the oxygen absorbed? What reactions occur with minerals in the water?

Understanding how this oxygen oasis reacts with the environment around it could help identify chemical signatures preserved in rocks. Researchers could then go looking for similar signatures in rocks from ancient lake beds to find "whiffs of oxygen" prior to the Great Oxidation Event.

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How we know what lies at Earth’s core

Humans have been all over the Earth. We've conquered the lands, flown through the air and dived to the deepest trenches in the ocean. We've even been to the Moon. But we've never been to the planet's core.

We haven't even come close. The central point of the Earth is over 6,000km down, and even the outermost part of the core is nearly 3,000 km below our feet. The deepest hole we've ever created on the surface is the Kola Superdeep Borehole in Russia, and it only goes down a pitiful 12.3 km.

All the familiar events on Earth also happen close to the surface. The lava that spews from volcanoes first melts just a few hundred kilometres down. Even diamonds, which need extreme heat and pressure to form, originate in rocks less than 500km deep.

What's down below all that is shrouded in mystery. It seems unfathomable. And yet, we know a surprising amount about the core. We even have some idea about how it formed billions of years ago – all without a single physical sample. This is how the core was revealed.

One good way to start is to think about the mass of the Earth, says Simon Redfern of the University of Cambridge in the UK.

We can estimate Earth's mass by observing the effect of the planet's gravity on objects at the surface. It turns out that the mass of the Earth is 5.9 sextillion tonnes: that's 59 followed by 20 zeroes.

There's no sign of anything that massive at the surface.

"The density of the material at the Earth's surface is much lower than the 

average density of the whole Earth, so that tells us there's something much denser," says Redfern. "That's the first thing."

Essentially, most of the Earth's mass must be located towards the centre of the planet. The next step is to ask which heavy materials make up the core.

The answer here is that it's almost certainly made mostly of iron. The core is thought to be around 80% iron, though the exact figure is up for debate.

The main evidence for this is the huge amount of iron in the universe around us. It is one of the ten most common elements in our galaxy, and is frequently found in meteorites.

Given how much there is of it, iron is much less common at the surface of the Earth than we might expect. So the theory is that when Earth formed 4.5 billion years ago, a lot of iron worked its way down to the core.

That's where most of the mass is, and it's where most of the iron must be too. Iron is a relatively dense element under normal conditions, and under the extreme pressure at the Earth's core it would be crushed to an even higher density, so an iron core would account for all that missing mass.

But wait a minute. How did that iron get down there in the first place?

The iron must have somehow gravitated – literally – towards the centre of the Earth. But it's not immediately obvious how.

Most of the rest of the Earth is made up of rocks called silicates, and molten iron struggles to travel through them. Rather like how water on a greasy surface forms droplets, the iron clings to itself in little reservoirs, refusing to spread out and flow.

A possible solution was discovered in 2013 by Wendy Mao of Stanford University in California and her colleagues. They wondered what happened when the iron and silicate were both exposed to extreme pressure, as happens deep in the earth.

By pinching both substances extremely tightly using diamonds, they were able to force molten iron through silicate.

"The pressure actually changes the properties of how iron interacts with the silicate," says Mao. "At higher pressures a 'melt network' is formed."

This suggests the iron was gradually squeezed down through the rocks of the Earth over millions of years, until it reached the core.

At this point you might be wondering how we know the size of the core. What makes scientists think it begins 3000km down? There's a one-word answer: seismology.

When an earthquake happens, it sends shockwaves throughout the planet. Seismologists record these vibrations. It's as if we hit one side of the planet with a gigantic hammer, and listened on the other side for the noise.

"There was a Chilean earthquake in the 1960s that generated a huge amount of data," says Redfern. "All the seismic stations dotted all over the Earth recorded the arrival of the tremors from that earthquake."

Depending on the route those vibrations take, they pass through different bits of the Earth, and this affects how they "sound" at the other end.

Early in the history of seismology, it was realised that some vibrations were going missing. These "S-waves" were expected to show up on one side of the Earth after originating on the other, but there was no sign of them.

The reason for this was simple. S-waves can only reverberate through solid material, and can't make it through liquid.

They must have come up against something molten in the centre of the Earth. By mapping the S-waves' paths, it turned out that rocks became liquid around 3000km down.

That suggested the entire core was molten. But seismology had another surprise in store.

In the 1930s, a Danish seismologist named Inge Lehmann noticed that another kind of waves, called P-waves, unexpectedly travelled through the core and could be detected on the other side of the planet.

She came up with a surprising explanation: the core is divided into two layers. The "inner" core, which begins around 5,000km down, was actually solid. It was only the "outer" core above it that was molten.

Lehmann's idea was eventually confirmed in 1970, when more sensitive seismographs found that P-waves really were travelling through the core and, in some cases, being deflected off it at angles. Sure enough, they still ended up on the other side of the planet.

It's not just earthquakes that sent useful shockwaves through the Earth. In fact, seismology owes a lot of its success to the development of nuclear weapons.

A nuclear detonation also creates waves in the ground, so nations use seismology to listen out for weapons tests. During the Cold War this was seen as hugely important, so seismologists like Lehmann got a lot of encouragement.

Rival countries found out about each other's nuclear capabilities and along the way we learned more and more about the core of the Earth. Seismology is still used to detect nuclear detonations today.

We can now draw a rough picture of the Earth's structure. There is a molten outer core, which begins roughly halfway to the planet's centre, and within it is the solid inner core with a diameter of 1,220 km.

But there is a lot more to try and tease out, especially about the inner core. For starters, how hot is it?

This turns out to be quite tricky to determine, and baffled scientists until quite recently, says Lidunka Vočadlo of University College London in the UK. We can't put a thermometer down there, so the only solution is to create the correct crushing pressure in the lab.

In 2013 a team of French researchers produced the best estimate to date. They subjected pure iron to pressures a little over half that at the core, and extrapolated from there. They concluded that the melting point of pure iron at core temperatures is around 6,230 °C. The presence of other materials would bring the core's melting point down a bit, to around 6,000 °C. But that's still as hot as the surface of the Sun.

A bit like a toasty jacket potato, Earth's core has stayed warm thanks to heat retained from the formation of the planet. It also gets heat from friction as denser materials shift around, as well as from the decay of radioactive elements. Still, it is cooling by about 100 °C every billion years.

Knowing the temperature is useful, because it affects the speed at which vibrations travel through the core. That is handy, because there is something odd about the vibrations.

P-waves travel unexpectedly slowly as they go through the inner core – slower than they would if it was made of pure iron.

"Wave velocities that the seismologists measure in earthquakes and whatnot are significantly lower [than] anything that we measure in an experiment or calculate on a computer," says Vočadlo. "Nobody as yet knows why that is."

That suggests there is another material in the mix.

It could well be another metal, called nickel. But scientists have estimated how seismic waves would travel through an iron-nickel alloy, and it doesn't quite fit the readings either.

Vočadlo and her colleagues are now considering whether there might be other elements down there too, like sulphur and silicon. So far, no-one has been able to come up with a theory for the inner core's composition that satisfies everyone. It's a Cinderella problem: no shoe will quite fit.

Vočadlo is trying to simulate the materials of the inner core on a computer. She hopes to find a combination of materials, temperatures and pressures that would slow down the seismic waves by the right amount.

She says the secret might lie in the fact that the inner core is nearly at its melting point. As a result, the precise properties of the materials might be different from what they would be if they were safely solid.

That could explain why the seismic waves pass through more slowly than expected.

"If that's the real effect, we would be able to reconcile the mineral physics results with the seismological results," says Vocadlo. "People have not been able to do that yet."

There are plenty of riddles about the earth's core still to solve. But without ever digging to those impossible depths, scientists have figured out a great deal about what is happening thousands of kilometres beneath us.

Those hidden processes in the depths of the Earth are crucial to our daily lives, in a way many of us don't realise.

Earth has a powerful magnetic field, and that is all thanks to the partially molten core. The constant movement of molten iron creates an electrical current inside the planet, and that in turn generates a magnetic field that reaches far out into space.

The magnetic field helps to shield us from harmful solar radiation. If the core of the Earth wasn't the way it is, there would be no magnetic field, and we would have all sorts of problems to contend with.

None of us will ever set eyes on the core, but it's good to know it's there.

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Paleobotanist identifies what could be the mythical 'first flower'

Indiana University paleobotanist David Dilcher and colleagues in Europe have identified a 125 million- to 130 million-year-old freshwater plant as one of earliest flowering plants on Earth.

The finding, reported Aug. 17 in the Proceedings of the National Academy of Sciences, represents a major change in the presumed form of one of the planet's earliest flowers, known as angiosperms.

"This discovery raises significant questions about the early evolutionary history of flowering plants, as well as the role of these plants in the evolution of other plant and animal life," said Dilcher, an emeritus professor in the IU Bloomington College of Arts and Sciences' Department of Geological Sciences.

The aquatic plant, Montsechia vidalii, once grew abundantly in freshwater lakes in what are now mountainous regions in Spain. Fossils of the plant were first discovered more than 100 years ago in the limestone deposits of the Iberian Range in central Spain and in the Montsec Range of the Pyrenees, near the country's border with France.

A large intact specimen of the fossil, Montsechia.Credit: David Dilcher 

Also previously proposed as one of the earliest flowers is Archaefructus sinensis, an aquatic plant found in China.

"A 'first flower' is technically a myth, like the 'first human,'" said Dilcher, an internationally recognized expert on angiosperm anatomy and morphology who has studied the rise and spread of flowering plants for decades. "But based on this new analysis, we know now that Montsechia is contemporaneous, if not more ancient, than Archaefructus."

He also asserted that the fossils used in the study were "poorly understood and even misinterpreted" during previous analyses.

"The reinterpretation of these fossils provides a fascinating new perspective on a major mystery in plant biology," said Donald H. Les, a professor of ecology and evolutionary biology at the University of Connecticut, who is the author of a commentary on the discovery in the journal PNAS. "David's work is truly an important contribution to the continued quest to unravel the evolutionary and ecological events that accompanied the rise of flowering plants to global prominence."

The conclusions are based upon careful analyses of more than 1,000 fossilized remains of Montsechia, whose stems and leaf structures were coaxed from stone by applying hydrochloric acid on a drop-by-drop basis. The plant's cuticles - the protective film covering the leaves that reveals their shape - were also carefully bleached using a mixture of nitric acid and potassium chlorate.

Examination of the specimens was conducted under a stereomicroscope, light microscope and scanning electron microscope.

The age of the plant at 125 million to 130 million years is based upon comparisons to other fossils in the same area, notably the freshwater algae charophytes, which places Montsechia in the Barremian age of the early Cretaceous period, making this flowering plant a contemporary of dinosaurs such as the brachiosaurus and iguanodon.

The precise, painstaking analysis of fossilized structures remains crucial to paleobotany, in contrast to other biological fields, due to the current inability to know the molecular characters of ancient plants from millions of years ago, Dilcher said.

This careful examination was particularly important to Montsechia since most modern observers might not even recognize the fossil as a flowering plant.

"Montsechia possesses no obvious 'flower parts,' such as petals or nectar-producing structures for attracting insects, and lives out its entire life cycle under water," he said. "The fruit contains a single seed" -- the defining characteristic of an angiosperm -- "which is borne upside down."

In terms of appearance, Dilcher said, Montsechia resembles its most modern descendent, identified in the study as Ceratophyllum. Also known as coontails or hornworts, Ceratophyllum is a dark green aquatic plant whose coarse, tufty leaves make it a popular decoration in modern aquariums and koi ponds.

Next up, Dilcher and colleagues want to understand more about the species connecting Montsechia and Ceratophyllum, as well as delve deeper into when precisely other species of angiosperms branched off from their ancient forefathers.

"There's still much to be discovered about how a few early species of seed-bearing plants eventually gave rise to the enormous, and beautiful, variety of flowers that now populate nearly every environment on Earth," he said.

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On this day in history – the first antiseptic operation was performed

In 1865, Dr. Joseph Lister became the first surgeon to perform an antiseptic operation by liberal use of carbolic acid (phenol) as a disinfectant. He had studied Louis Pasteur's germ theory of disease, that infections are caused by bacteria.

Lister knew carbolic acid had been effective in municipal use for treating sewage, and decided to try using it to kill germs that would otherwise infect wounds. He poured it on bandages, ligatures, instruments and directly on the wound and hands.

His first patient to benefit from this procedure was James Greenlees, age 12, whose broken leg was treated after being run over by a cart. The dressing was soaked with carbolic acid and linseed oil. The wound healed without infection. Lister continued his protocol of hygiene, and reduced the surgical death rate from 45% to 15%.

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Volcanic rocks resembling Roman concrete explain record uplift in Italian caldera

The discovery of a fiber-reinforced, concrete-like rock formed in the depths of a dormant supervolcano could help explain the unusual ground swelling that led to the evacuation of an Italian port city and inspire durable building materials in the future, Stanford scientists say.

The "natural concrete" at the Campi Flegrei volcano is similar to Roman concrete, a legendary compound invented by the Romans and used to construct the Pantheon, the Coliseum, and ancient shipping ports throughout the Mediterranean.

"This implies the existence of a natural process in the subsurface of Campi Flegrei that is similar to the one that is used to produce concrete," said Tiziana Vanorio, an experimental geophysicist at Stanford's School of Earth, Energy & Environmental Sciences.

Campi Flegrei lies at the center of a large depression, or caldera, that is pockmarked by craters formed during past eruptions, the last of which occurred nearly 500 years ago. Nestled within this caldera is the colorful port city of Pozzuoli, which was founded in 600 B.C. by the Greeks and called "Puteoli" by the Romans.

Beginning in 1982, the ground beneath Pozzuoli began rising at an alarming rate. Within a two-year span, the uplift exceeded six feet-an amount unprecedented anywhere in the world. "The rising sea bottom rendered the Bay of Pozzuoli too shallow for large craft," Vanorio said.

Making matters worse, the ground swelling was accompanied by swarms of micro-earthquakes. Many of the tremors were too small to be felt, but when a magnitude 4 quake juddered Pozzuoli, officials evacuated the city's historic downtown. Pozzuoli became a ghost town overnight.

A teenager at the time, Vanorio was among the approximately 40,000 residents forced to flee Pozzuoli and settle in towns scattered between Naples and Rome. The event made an impression on the young Vanorio, and inspired her interests in the geosciences. Now an assistant professor at Stanford, Vanorio decided to apply her knowledge about how rocks in the deep Earth respond to mechanical and chemical changes to investigate how the ground beneath Pozzuoli was able to withstand so much warping before cracking and setting off micro-earthquakes.

"Ground swelling occurs at other calderas such as Yellowstone or Long Valley in the United States, but never to this degree, and it usually requires far less uplift to trigger earthquakes at other places," Vanorio said. "At Campi Flegrei, the micro-earthquakes were delayed by months despite really large ground deformations."

To understand why the surface of the caldera was able to accommodate incredible strain without suddenly cracking, Vanorio and a post-doctoral associate, Waruntorn Kanitpanyacharoen, studied rock cores from the region. In the early 1980s, a deep drilling program probed the active geothermal system of Campi Flegrei to a depth of about 2 miles. When the pair analyzed the rock samples, they discovered that Campi Flegrei's caprock-a hard rock layer located near the caldera's surface-is rich in pozzolana, or volcanic ash from the region.

The scientists also noticed that the caprock contained tobermorite and ettringite-fibrous minerals that are also found in humanmade concrete. These minerals would have made Campi Flegrei's caprock more ductile, and their presence explains why the ground beneath Pozzuoli was able to withstand significant bending before breaking and shearing. But how did tobermorite and ettringite come to form in the caprock?

Once again, the drill cores provided the crucial clue. The samples showed that the deep basement of the caldera-the "wall" of the bowl-like depression-consisted of carbonate-bearing rocks similar to limestone, and that interspersed within the carbonate rocks was a needle-shaped mineral called actinolite.

"The actinolite was the key to understanding all of the other chemical reactions that had to take place to form the natural cement at Campi Flegrei," said Kanitpanyacharoen, who is now at Chulalongkorn University in Thailand.

From the actinolite and graphite, the scientists deduced that a chemical reaction called decarbonation was occurring beneath Campi Flegrei. They believe that the combination of heat and circulating mineral-rich waters decarbonates the deep basement, prompting the formation of actinolite as well as carbon dioxide gas. 

As the CO2 mixes with calcium-carbonate and hydrogen in the basement rocks, it triggers a chemical cascade that produces several compounds, one of which is calcium hydroxide. Calcium hydroxide, also known as portlandite or hydrated lime, is one of the two key ingredients in humanmade concrete, including Roman concrete. Circulating geothermal fluids transport this naturally occurring lime up to shallower depths, where it combines with the pozzolana ash in the caprock to form an impenetrable, concrete-like rock capable of withstanding very strong forces.

"This is the same chemical reaction that the ancient Romans unwittingly exploited to create their famous concrete, but in Campi Flegrei it happens naturally," Vanorio said.

In fact, Vanorio suspects that the inspiration for Roman concrete came from observing interactions between the volcanic ash at Pozzuoli and seawater in the region. The Roman philosopher Seneca, for example, noted that the "dust at Puteoli becomes stone if it touches water."

"The Romans were keen observers of the natural world and fine empiricists," Vanorio said. "Seneca, and before him Vitruvius, understood that there was something special about the ash at Pozzuoli, and the Romans used the pozzolana to create their own concrete, albeit with a different source of lime."

Pozzuoli was the main commercial and military port for the Roman Empire, and it was common for ships to use pozzolana as ballast while trading grain from the eastern Mediterranean. As a result of this practice, volcanic ash from Campi Flegrei-and the use of Roman concrete-spread across the ancient world. Archeologists have recently found that piers in Alexandria, Caesarea, and Cyprus are all made from Roman concrete and have pozzolana as a primary ingredient.

Interestingly, the same chemical reaction that is responsible for the unique properties of the Campi Flegrei's caprock can also trigger its downfall. If too much decarbonation occurs-as might happen if a large amount of saltwater, or brine, gets injected into the system-an excess of carbon dioxide, methane and steam is produced. As these gases rise toward the surface, they bump up against the natural cement layer, warping the caprock. This is what lifted Pozzuoli in the 1980s. When strain from the pressure buildup exceeded the strength of the caprock, the rock sheared and cracked, setting off swarms of micro-earthquakes. As pent-up gases and fluids vent into the atmosphere, the ground swelling subsided. Vanorio and Kanitpanyacharoen suspect that as more calcium hydroxide was produced at depth and transported to the surface, the damaged caprock was slowly repaired, its cracks "healed" as more natural cement was produced.

Vanorio believes the conditions and processes responsible for the exceptional rock properties at Campi Flegrei could be present at other calderas around the world. A better understanding of the conditions and processes that formed Campi Flegrei's caprock could also allow scientists to recreate it in the lab, and perhaps even improve upon it to engineer more durable and resilient concretes that are better able to withstand large stresses and shaking, or to heal themselves after damage.

"There is a need for eco-friendly materials and concretes that can accommodate stresses more easily," Vanorio said. "For example, extracting natural gas by hydraulic fracturing can cause rapid stress changes that cause concrete well casings to fail and lead to gas leaks and water contamination."

For more information visit:-

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On this day in Science History: The First Iron Lung was Installed

In 1927, the first iron lung (electric respirator) was installed at Bellevue hospital in New York for the post war polio epidemic. The first iron lung was developed at Harvard University by Phillip Drinker and Louis Agassiz Shaw built with two vacuum cleaners.

The iron lung is a negative pressure machine which surrounds the patient's body except for the head, and alternates a negative atmospheric pressure with the ambient one, resulting in rhythmic expansion of the chest cage (and thus inhalation) in response to the negative extra thoracic pressure. During periods of ambient extrathoracic pressure, the lungs deflate.

Humans, like most animals, breathe by negative pressure breathing: the rib cage expands and the diaphragm contracts, expanding the chest cavity. This causes the pressure in the chest cavity to decrease, and the lungs expand to fill the space. This, in turn, causes the pressure of the air inside the lungs to decrease (it becomes negative, relative to the atmosphere), and air flows into the lungs from the atmosphere: inhalation. When the diaphragm relaxes, the reverse happens and the person exhales. If a person loses part or all of the ability to control the muscles involved, breathing becomes difficult or impossible.

The person using the iron lung is placed into the central chamber, a cylindrical steel drum. A door allowing the head and neck to remain free is then closed, forming a sealed, air-tight compartment enclosing the rest of the person's body. Pumps that control airflow periodically decrease and increase the air pressure within the chamber, and particularly, on the chest. When the pressure is below that within the lungs, the lungs expand and atmospheric pressure pushes air from outside the chamber in via the person's nose and airways to keep the lungs filled; when the pressure goes above that within the lungs, the reverse occurs, and air is expelled. In this manner, the iron lung mimics the physiological action of breathing: by periodically altering intrathoracic pressure, it causes air to flow in and out of the lungs. The iron lung is a form of non-invasive therapy.

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