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Ancient Meteorite Hints Mars Had Water Before There Was Life on Earth

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We know that Mars was once much wetter than it is now, but the questions of when water formed and evaporated away are much more difficult to answer.

A new study now suggests that water was present on the Red Planet some 4.4 billion years ago, much earlier than previously thought.

 

That’s based on an analysis of a meteorite named NWA 7533, picked up in the Sahara Desert and thought to have originated on Mars billions of years ago. The oxidation of certain minerals inside the meteorite hints at the presence of water.

The findings could push back the estimated date of water formation on Mars some 700 million years, from the 3.7-billion-years-ago timeframe that has been the general consensus up until now. The research could also offer up some insights into how planets form in the first place.

“I study minerals in Martian meteorites to understand how Mars formed and its crust and mantle evolved,” says planetary scientist Takashi Mikouchi from the University of Tokyo in Japan.

“This is the first time I have investigated this particular meteorite, nicknamed ‘Black Beauty’ for its dark colour. Our samples of NWA 7533 were subjected to four different kinds of spectroscopic analysis, ways of detecting chemical fingerprints. The results led our team to draw some exciting conclusions.”

Planetary scientists are keenly interested in the story of water on planets and on moons. One of the big unknowns is whether water gets added to a planetary body after it forms, through the impacts of asteroids and comets, or whether it occurs naturally during the planet formation process.

 

Ancient rocks like NWA 7533 can help scientists peer back in time and find out, as they record impact events on the planet they come from, and capture some of the mineral and chemical composition of the surface when they are formed.

In this case, it’s the oxidation that’s the tell-tale sign of water. With certain fragments inside NWA 7533 dated to 4.4 billion years ago, it’s the oldest record we’ve got of Mars (which may be why a single gram of this meteorite can fetch as much as US$10,000).

“Igneous clasts, or fragmented rock, in the meteorite are formed from magma and are commonly caused by impacts and oxidation,” says Mikouchi. “This oxidation could have occurred if there was water present on or in the Martian crust 4.4 billion years ago during an impact that melted part of the crust.”

Such an early appearance suggests that water actually was around when Mars formed and that in turn plays into research into planetary formation in general. With water comes life, which is one reason scientists are so eager to track it down around the Universe. For comparison, we know that the earliest traces of life on Earth date to at least 3.5 billion years ago.

The close study of Mars continues as experts try and figure out when water was present and what form it might have taken. One recent study put forward the idea that both liquid water and surface ice could have existed on the Red Planet at the same time.

The team’s findings also suggest that the chemical make-up of the Martian atmosphere at this time – including high levels of hydrogen – could have made the planet warm enough for water to melt and life to exist, even though the Sun would have been younger and fainter during this period.

“Our analysis also suggests such an impact would have released a lot of hydrogen, which would have contributed to planetary warming at a time when Mars already had a thick insulating atmosphere of carbon dioxide,” says Mikouchi.

The research has been published in Science Advances.

 



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Simulation Gives a Peek Into The Cosmic ‘Dark Age’ of Star Formation

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For astronomers, astrophysicists, and cosmologists, the ability to spot the first stars that formed in our Universe has always been just beyond reach. On the one hand, there are the limits of our current telescopes and observatories, which can only see so far.

 

The farthest object ever observed was MACS 1149-JD, a galaxy located 13.2 billion light-years from Earth that was spotted in the Hubble eXtreme Deep Field (XDF) image.

On the other, up until about 1 billion years after the Big Bang, the Universe was experiencing what cosmologists refer to as the “Dark Ages” when the Universe was filled with gas clouds that obscured visible and infrared light.

Luckily, a team of researchers from Georgia Tech’s Center for Relativistic Astrophysics recently conducted simulations that show what the formation of the first stars looked like.

The study that describes their findings, published in the Monthly Notices of the Royal Astronomical Society, was led by Gen Chiaki and John Wise – a post-doctoral researcher and associate professor from the CfRA (respectively).

They were joined by researchers from the Sapienza Università di Roma, the Astronomical Observatory of Rome, the Istituto Nazionale di Astrofisica (INAF), and the Istituto Nazionale di Fisica Nucleare (INFN).

Based on the life and death cycles of stars, astrophysicists theorize that the first stars in the Universe were very metal-poor. Having formed about 100 million years after the Big Bang, these stars formed from a primordial soup of hydrogen gas, helium, and trace amounts of light metals.

 

These gases would collapse to form stars that were up to 1,000 times more massive than our Sun.

Because of their size, these stars were short-lived and probably only existed for a few million years. In that time, the new and heavier elements in their nuclear furnaces, which were then dispersed once the stars collapsed and exploded in supernovae.

As a result, the next generation of stars with heavier elements would contain carbon, leading to the designation of Carbon-Enhanced Metal-Poor (CEMP) stars.

The composition of these stars, which may be visible to astronomers today, is the result of the nucleosynthesis (fusion) of heavier elements from the first generation of stars.

By studying the mechanism behind the formation of these metal-poor stars, scientists can infer what was happening during the cosmic ‘Dark Ages’ when the first stars formed. As Wise said in a Texas Advanced Computer Center (TACC) press release:

“We can’t see the very first generations of stars. Therefore, it’s important to actually look at these living fossils from the early universe, because they have the fingerprints of the first stars all over them through the chemicals that were produced in the supernova from the first stars.”

“That’s where our simulations come into play to see this happening. After you run the simulation, you can watch a short movie of it to see where the metals come from and how the first stars and their supernovae actually affect these fossils that live until the present day.”

stellar 1Density, temperature, and carbon abundance (top) and the formation cycle of Pop III stars (bottom). (Chiaki, et al.)

For the sake of their simulations, the team relied predominantly on the Georgia Tech PACE cluster. Additional time was allocated by the National Science Foundation’s (NSF) Extreme Science and Engineering Discovery Environment (XSEDE), the Stampede2 supercomputer at TACC and NSF-funded Frontera system (the fastest academic supercomputer in the world), and the Comet cluster at the San Diego Supercomputer Center (SDSC).

With the massive amounts of processing power and data storage these clusters provided, the team was able to model the faint supernova of the first stars in the Universe.

 

What this revealed was that the metal-poor stars that formed after the first stars in the Universe became carbon-enhanced through the mixing and fallback of bits ejected from the first supernovae.

Their simulations also showed the gas clouds produced by the first supernovae were seeding with carbonaceous grains, leading to the formation of low-mass ‘giga-metal-poor’ stars that likely still exist today (and could be studied by future surveys). Said Chiaki of these stars:

“We find that these stars have very low iron content compared to the observed carbon-enhanced stars with billionths of the solar abundance of iron. However, we can see the fragmentation of the clouds of gas. This indicates that the low mass stars form in a low iron abundance regime. Such stars have never been observed yet. Our study gives us theoretical insight of the formation of first stars.”

submillimeter galaxies 1A new study looked at 52 submillimeter galaxies to help us understand the early ages of our Universe. (University of Nottingham/Omar Almaini)

These investigations are part of a growing field known as “galactic archaeology.”

Much like how archaeologists rely on fossilized remains and artifacts to learn more about societies that disappeared centuries or millennia ago, astronomers look for ancient stars to study in order to learn more about those that have long since died.

According to Chiaki, the next step is to branch out beyond the carbon features of ancient stars and incorporate other heavier elements into larger simulations. In so doing, galactic archaeologists hope to learn more about the origins and distribution of life in our Universe. Said Chiaki:

“The aim of this study is to know the origin of elements, such as carbon, oxygen, and calcium. These elements are concentrated through the repetitive matter cycles between the interstellar medium and stars. Our bodies and our planet are made of carbon and oxygen, nitrogen, and calcium. Our study is very important to help understand the origin of these elements that we human beings are made of.”

This article was originally published by Universe Today. Read the original article.

 



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Fireball Meteorite That Struck Michigan Reveals Ancient Extraterrestrial Compounds

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A meteorite that landed on a frozen lake in 2018 contains thousands of organic compounds that formed billions of years ago and could hold clues about the origins of life on Earth.

 

The meteor entered Earth’s atmosphere on Jan. 16, 2018, after a very long journey through the freezing vacuum of space, lighting up skies over Ontario, Canada, and the midwestern United States.

Weather radar tracked the flaming space rock’s descent and breakup, helping meteorite hunters to quickly locate fallen fragments on Strawberry Lake in Hamburg, Michigan.



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Asteroid Bennu Caries Organic Materials Consistent With Ingredients For Life

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In just a few days, NASA is going to bounce its probe OSIRIS-REx off asteroid Bennu. The mission will collect a sample from the asteroid, and return it to Earth for closer study – one of the first missions of its kind.

 

That return sample will help us to understand not just asteroids, but the earliest days of the Solar System’s existence. However, that is not the sole mission of OSIRIS-REx.

The probe arrived in Bennu orbit in December of 2018, and since that time has been using its suite of instruments to learn as much as it can about the asteroid before their long-planned meet-up.

And boy, has it ever. Six separate papers have just dropped in the journals Science and Science Advances detailing Bennu’s physical properties, and how they reveal a surprisingly complex history.

“The spacecraft has been observing the asteroid for nearly two years now,” said astronomer Joshua Emery of Northern Arizona University and a member of the OSIRIS-REx science team. “Bennu has turned out to be a fascinating small asteroid and has given us many surprises.”

Bennu is what is known as a ‘rubble pile‘ asteroid, which is exactly what it sounds like – a relatively loose, low-density conglomerate of rock, thought to have formed when a larger object broke apart, and at least some of the material came back together. In the case of Bennu, the shape it formed is a rough diamond, with a pronounced ridge at the equator.

Now, for the first time, we have a detailed 3D digital terrain map of the asteroid, led by Michael Daly of York University. This reveals that the equatorial ridge isn’t alone – other, much more subtle ridges extend from pole to pole, indicating that, although the asteroid is made of rubble, it does have some internal cohesiveness.

Over the past few years, we’ve had hints of other strange things afoot at the Diamond B (that is, Bennu).

Last year, we found that Bennu was ejecting material from its surface, some of which fell back down, and some of which seemed to enter stable orbit. And scientists found evidence of carbonaceous material that hinted at the presence of water sometime in Bennu’s mysterious past.

A new global spectral survey of the asteroid in infrared and near-infrared, led by Amy Simon of NASA-Goddard, has confirmed the presence of carbon-bearing and organic materials, widespread across the surface of Bennu – the first concrete detection of such things in a near-Earth asteroid. This is consistent with hypotheses that asteroids and meteorites could have carried at least some of the ingredients for life to Earth.

 

There was once water, too

But the asteroid’s carbon content has a more detailed story to tell. A close spectral study has revealed bright veins of carbonate material running through a number of boulders.

This, according to a team of scientists led by Hannah Kaplan of NASA-Goddard, is consistent with carbonates found in “aqueously altered carbonaceous chondrite meteorites” – carbonates that formed through interactions with water.

Some of these veins are metre-length and several centimetres thick. This, the researchers say, is evidence that water once flowed freely over the rocks, an asteroid-scale hydrothermal system that was once present on the parent body that went on to later birth Bennu.

“Fluid flow on Bennu’s parent body would have taken place over distances of kilometres for thousands to millions of years,” the researchers wrote in their paper.

Multispectral images of the surface revealed that Bennu is unevenly weathered in an analysis led by Daniella DellaGiustina of the University of Arizona. By false-colouring visible-light images of the asteroid, the team found that some regions have been exposed to weathering phenomena such as cosmic rays and solar wind longer than others, suggesting processes – such as impact events – that expose fresh material at different times.

 

The Nightingale crater region where the probe is going to retrieve a sample is fresher material, which means it will provide a cleaner look at stuff from the early Solar System, when Bennu is thought to have formed.

And there’s more. A study of temperature changes led by Ben Rozitis of the Open University found something interesting about the boulders on Bennu. They fall into two types – stronger and less porous, and weaker and more porous. The stronger boulders are the ones that have carbonate veins, suggesting that interacting with water may ultimately produce stronger rock as liquid seeps material into the holes.

But the weaker boulders are interesting too. They would be unlikely to survive entry into Earth’s atmosphere, as they’d heat up and explode – which means that they’re likely a type of space rock we’ve not had the opportunity to study up close before.

Finally, we get back to those aforementioned ejected rocks. We still don’t know exactly how they’re getting kicked off the asteroid, but the way they fly up and come back down is a surprisingly useful tool for probing the asteroid’s interior.

 

“It was a little like someone was on the surface of the asteroid and throwing these marbles up so they could be tracked,” said study leader Daniel Scheeres of the University of Colorado Boulder. “Our colleagues could infer the gravity field in the trajectories those particles took.”

When combined with gravity field measurements taken by the orbiting OSIRIS-REx, the team was able to compile an interior density profile of the asteroid, since denser regions create a stronger local gravity field.

And they found something surprising. They thought that the asteroid would roughly have the same density all the way through; but it seems more dense at the surface. The least dense regions are the equatorial ridge and the core of the asteroid – as though it has a large void inside.

Since the asteroid’s rotation is accelerating over time, this means that, eventually, it’s likely to spin itself apart.

That’s a long way into the future, though. For now, the asteroid will have to content itself with a kiss from a probe on the crater. And these new analyses have given researchers a framework within which to interpret the close study of that sample, when it finally makes its way to Earth.

The six papers, published in Science and Science Advances, can be found here, here, here, here, here and here.



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Astronomers Find Monster Black Hole With 6 Galaxies Trapped in Its Gravitational Web

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Astronomers have discovered six galaxies ensnared in the cosmic “spider’s web” of a supermassive black hole soon after the Big Bang, according to research published Thursday that could help explain the development of these enigmatic monsters.

 

Black holes that emerged early in the history of the Universe are thought to have formed from the collapse of the first stars, but astronomers have puzzled over how they expanded into giants.

The newly discovered black hole – which dates from when the Universe was not even a billion years old – weighs in at 1 billion times the mass of our Sun and was spotted by the European Southern Observatory (ESO).

Scientists said the finding helps provide an explanation for how supermassive black holes such as the one at the centre of our Milky Way may have developed.

This is because astronomers believe the filaments trapping the cluster of galaxies are carrying enough gas to “feed” the black hole, enabling it to grow.

“The cosmic web filaments are like spider’s web threads,” said Marco Mignoli, an astronomer at the National Institute for Astrophysics (INAF) in Bologna who led the research, which was published in the journal Astronomy & Astrophysics.

“The galaxies stand and grow where the filaments cross, and streams of gas – available to fuel both the galaxies and the central supermassive black hole – can flow along the filaments.”

Mignoli said that until now there had been “no good explanation” for the existence of such huge early black holes.

The location of the quasar (red circle) in the constellation of Sextans. (ESO/IAU Sky & Telescope)The location of the quasar (red circle) in the constellation of Sextans. (ESO/IAU Sky & Telescope)

Tip of the iceberg

Researchers said the web structure may have formed with the help of dark matter — thought to attract huge amounts of gas in the early Universe.

“Our finding lends support to the idea that the most distant and massive black holes form and grow within massive dark matter halos in large-scale structures, and that the absence of earlier detections of such structures was likely due to observational limitations,” said co-author Colin Norman of Johns Hopkins University.

 

The entire web is over 300 times the size of the Milky Way, according to a statement from ESO.

But it said the galaxies are also some of the faintest that current telescopes can spot, adding the discovery was only possible using the largest optical telescopes available, including ESO’s Very Large Telescope in Chile’s Atacama Desert.

“We believe we have just seen the tip of the iceberg, and that the few galaxies discovered so far around this supermassive black hole are only the brightest ones,” said co-author Barbara Balmaverde, an astronomer at INAF in Torino, Italy.

The research is the latest to try and illuminate the mysterious formation of these cosmic monsters, which are so dense that not even light can escape their gravitational pull.

In September, two consortiums of some 1,500 scientists reported the discovery of GW190521, formed by the collision of two smaller black holes.

What scientists observed were gravitational waves produced more than seven billion years ago when they smashed together, releasing eight solar masses worth of energy and creating one of the most powerful events in the Universe since the Big Bang.

At 142 solar masses, GW190521 was the first “intermediate mass” black hole ever observed.

Scientists said the finding challenges current theories on the formation of supermassive black holes, suggesting it could be through the repeated merger of these mid-sized bodies.

© Agence France-Presse

 



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This Year’s Atlantic Hurricane Season Is So Bad We Ran Out of Names Two Storms Ago

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Here’s how active this year’s Atlantic hurricane season has been: When Tropical Storm Wilfred formed on September 18, the National Hurricane Center exhausted its list of storm names for only the second time since naming began in 1950.

 

Within hours, two more storm had formed – now known as Alpha and Beta.

Even more surprising is that we reached the 23rd tropical storm of the year, Beta, more than a month earlier than in 2005, the only other year on record with so many named storms.

The 2020 Atlantic hurricane season is far from over. With the new storms, forecasters shifted from the alphabetical list of people’s names to letters of the Greek alphabet. The 2005 season had six Greek-letter storms, ending with Zeta.

So, why is the Atlantic so active this year? Meteorologists like myself have been following a few important differences, including many tropical storms forming closer to the US coast.

What’s causing so many tropical cyclones?

When a disturbance – a large blob of convective clouds, or thunderstorms – exists over the Atlantic Ocean, certain atmospheric conditions will help it grow into a tropical cyclone.

Warm water and lots of moisture help disturbances gain strength.

Low vertical wind shear, meaning the wind speeds and directions don’t change much as you get higher in the atmosphere, is important since this shear can prevent convection from growing. And instability enables parcels of air to rise upward and keep going to build thunderstorms.

 

This year, sea surface temperatures have been above average across much of the Atlantic Ocean and wind shear has been below average. That means it’s been more conducive than usual to the formation of tropical cyclones.

La Niña probably also has something to do with it. La Niña is El Niño’s opposite – it happens when sea surface temperatures in the eastern and central Pacific are below average.

That cooling affects weather patterns across the US and elsewhere, including weakening wind shear in the Atlantic basin. NOAA determined in early September that we had entered a La Niña climate pattern.

That pattern has been building up for weeks, so these trending conditions could have contributed to how favorable the Atlantic has been to tropical cyclones this year.

An unusual twist off the US coast

Four hurricanes have hit the US coast this year – Hanna, Isaias, Laura, and Sally, which is more than usual by this point in the hurricane season. But we also have observed many short-lived tropical storms that had less impact.

When a tropical cyclone develops from a disturbance that forms over Africa, it has a lot of ocean ahead of it with room to get organized and gain strength.

 

But this year, many storms have formed farther north, closer to the US coast.

Most came from disturbances that didn’t look too promising – until they moved over the Gulf Stream. The Gulf Stream is a large ocean current that carries warm water from the Gulf of Mexico, up the East Coast and into the North Atlantic.

Tropical cyclones typically need sea surface temperatures over 80 degrees Fahrenheit to form, and the warm water along the Gulf Stream can help disturbances spin up into tropical cyclones.

Because these tropical storms were already fairly far north, however, they didn’t have much time to gain strength. Meteorologists haven’t yet studied why so many storms formed this way this season, but it’s possible that it’s due to both warmer-than-normal Atlantic Ocean waters and the position of the Gulf Stream.

Lots of firsts as the season breaks records

One of the biggest surprises this year has been how consistently we have been breaking records for earliest named storm for their rank. For example, Edouard became the earliest fifth named storm on July 6, beating 2005’s Emily by a week.

Fay was the earliest sixth named storm, showing up almost two weeks earlier than Franklin did in 2005.

 

Wilfred was the earliest to run out the list of designated storm names. In 2005, Hurricane Wilma formed on October 17, but it ended up being the year’s 22nd named storm chronologically, not the 21st like Wilfred, because an unnamed subtropical storm formed on October 4.

The National Hurricane Center discovered this unnamed storm during a post-season analysis.

In all, the 2005 season had 28 qualifying storms. The list of Atlantic tropical cyclone names skips letters where easy-to-distinguish names are harder to find, like Q and Z, then moves to the Greek alphabet.

Could we run out of Greek letters before hurricane season ends on November 30? I don’t think anyone’s ready to consider that.

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Kimberly Wood, Assistant Professor of Meteorology, Mississippi State University

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

 



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Earth’s Deepest Known Freshwater Cave Goes a Lot Deeper Than Anyone Ever Realised

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Several years ago, a remotely operated vehicle was descending down into a freshwater cave system, hidden deep under the Czech Republic, when it came to an abrupt end.

Not the end of the cave, that is, but the end of its cable.

 

Now, new estimates taken from up at the surface suggest we’d need more than twice as much slack to get all the way to the bottom of this profound underwater cavern.

Using recent geophysical surveys of this national gem, known as the Hranice Abyss, scientists have traced the remarkable system of trench-like caves roughly a kilometre down (over half a mile down).

The findings are based on numerous types of geophysical data, including measurements with a gravimeter, in addition to checking electrical conductivity and natural geomagnetic fields in Earth’s subsurface.

Together, this can tell scientists the general locations of rocks, minerals, caverns, and valleys that lie below.

While it’s not a perfect mapping tool, it does suggest the Hranice Abyss extends much deeper than other estimates, like this one below:

It also calls the cave’s origin into question.

The world’s deepest flooded cave systems are notoriously difficult and dangerous to study directly, and even with the help of remotely operated vehicles, our reach is limited.

 

Research has shown that many of these caves contain temperate waters with acidic elements originating from a deep source. The thermal water in the Hranice Abyss, for instance, was found in a 2019 study to contain only five to 10 percent ‘modern water’.

This has led many to suppose these caves were formed from the bottom-up, with the acidic inner core of our planet slowly eating away at the limestone rock above. 

But this idea, known as hypogenic formation, doesn’t take into account each region’s specific geology or tectonic activity, and caves can be formed from the top down, too.

Underneath the Hranice Abyss, the authors of the new research have found evidence for a large-scale network of underground structures made from soluble rock, known as a karst system to geologists.

010 hranice abyss

Conceptual geological cross section showing the Hranice Abyss and a large sedimentary basin called Carpathian Foredeep, in the mid-Miocene (above) and today (below). (Klanica et al., JGR Earth Surface, 2020)

Some of these underground caverns are filled with freshwater, and others with sediment, but the reappraisal suggests they were created by erosion from the top down – at least at first. 

 

In the mid-Miocene, the authors think water probably ran from the mountains into a basin, which gradually carved out caverns in the limestone through erosion. A former drainage system, found connected to the abyss, supports that theory.

“Subsequent sediment deposition (via sea‐level rise) and infill of these canyons caused spring outflows to become blocked and the cave systems to be flooded with fresh water,” the authors suggest.

Only after this would acidic water have welled up from below, the team thinks, bringing deep Earth isotopes up to the surface for us to find later. 

If this origin story is right, we might need to reassess other deep, flooded caves in Italy, South Africa, and Brazil, which we assumed were formed from the bottom up.

Nevertheless, the authors admit it’s very possible that the top-down erosion is somehow masking earlier bottom-up sculpting, making it appear as though the cave was created from above.

Geologist Francesco Sauro from the University of Bologna, who was not involved in the study, told Science it was worth re-examining other sites in light of these new and “impressive” estimates.

The study was published in the Journal of Geophysical Research: Earth Surface.

 





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Where Did Earth’s Water Come From? Study Casts Doubt on The Current Meteorite Theory

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Water covers 70 percent of the Earth’s surface and is crucial to life as we know it, but how it got here has been a longstanding scientific debate.

The puzzle was a step closer to being solved Thursday after a French team reported in the journal Science they had identified which space rocks were responsible, and suggested our planet has been wet ever since it formed.

 

Cosmochemist Laurette Piani, who led the research, told AFP the findings contradicted the prevalent theory that water was brought to an initially dry Earth by far-reaching comets or asteroids.

According to early models for how the Solar System came to be, the large disks of gas and dust that swirled around the Sun and eventually formed the inner planets were too hot to sustain ice.

This would explain the barren conditions on Mercury, Venus and Mars – but not our blue planet, with its vast oceans, humid atmosphere and well-hydrated geology.

Scientists therefore theorized that the water came along after, and the prime suspects were meteorites known as carbonaceous chondrites that are rich in hydrous minerals.

But the problem was that their chemical composition doesn’t closely match our planet’s rocks.

The carbonaceous chondrites also formed in the outer Solar System, making it less likely they could have pelted the early Earth.

Planetary building blocks

Another group of meteorites, called enstatite chondrites, are a much closer chemical match, containing similar isotopes (types) of oxygen, titanium and calcium.

This indicates they were Earth’s and the other inner planets’ building blocks.

 

However, because these rocks formed close to the Sun, they had been assumed to be too dry to account for Earth’s rich reservoirs of water.

To test whether this was really true, Piani and her colleagues at Centre de Recherches Petrographiques et Geochimiques (CRPG, CNRS/Universite de Lorraine) used a technique called mass spectrometry to measure the hydrogen content in 13 enstatite chondrites.

The rocks are now quite rare, making up only about two percent of known meteorites in collections, and it is hard to find them in pristine, uncontaminated condition.

The team found that the rocks contained enough hydrogen in them to provide Earth with at least three times the water mass of its oceans – and possibly much more.

They also measured two isotopes of hydrogen, because the relative proportion of these is very different from one celestial object to another.

“We found the hydrogen isotopic composition of enstatite chondrites to be similar to the one of the water stored in the terrestrial mantle,” said Piani, comparing it to a DNA match.

The isotopic composition of the oceans was found to be consistent with a mixture containing 95 percent of water from the enstatite chondrites – more proof these were responsible for the bulk of Earth’s water.

 

The authors further found that the nitrogen isotopes from the enstatite chondrites are similar to Earth’s – and proposed these rocks could also be the source of the most abundant component of our atmosphere.

Piani added that research doesn’t exclude later addition of water by other sources like comets, but indicates that enstatite chondrites contributed significantly to Earth’s water budget at the time it formed.

The work “brings a crucial and elegant element to this puzzle” wrote Anne Peslier, a planetary scientist for NASA, in an accompanying editorial.

© Agence France-Presse

 



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Earth’s Tectonic Plates May Have Formed in a Vastly Different Process Than We Thought

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How did Earth’s tectonic plates form? You’d think this would be an easy question to answer, considering we’re now trying to nail down the specifics of when it happened, and whether there’s tectonic activity on the Moon. But our knowledge on how this planetary mechanism came to be is surprisingly scant.

 

Researchers from China, Hong Kong, and the United States have now put forward a new hypothesis – one that, on face value, looks incredibly similar to an idea discredited decades ago, but now deserves to be revisited.

Tectonic plates have been shuffling around our planet’s surface anywhere from 3.3 to 4.4 billion years ago, depending on who you ask. But a few billion years of tectonic movement and crust recycling has meant it’s quite difficult to work out how Earth came to have tectonic plates in the first place.

A couple of years ago, researchers developed a model showing that tectonic plates first formed in a process similar to how they’ve continued to shift – with some parts of Earth’s crust taking a dive beneath others and starting a chain reaction of jostling pieces of crust that lasted millennia.

But the new research presents a model that shows something quite different. The research team proposes that billions of years ago, Earth’s recently formed shell became hot, which caused an expansion of the shell, leading to a fracturing that resulted in what we now know as tectonic plates.

“Here we use 3D spherical shell models,” the team writes in their new paper, “to demonstrate a self-organised fracture mechanism analogous to thermal expansion-driven lithospheric uplift.”

full size image tectonic plates earth expansion(Tang et al., Nature Communications, 2020)

Above: A snapshot of the model showing late stages of growth and coalescence into the plate tectonic Earth. Fractures are in black, and colours show stresses.

Now, the expanding Earth hypothesis is not a new idea. In the 1800’s, an expanding Earth was proposed to explain how geographical features like mountains may have formed; however, it was discredited when we discovered plate tectonics.

 

But the new scenario isn’t quite the same as the one put forward during Charles Darwin’s era. The crucial difference comes down to where Earth blew off steam all those years ago.

“The answer lies in consideration of major heat-loss mechanisms that could have occurred during Earth’s early periods,” said University of Hong Kong planetary scientist Alexander Webb.

“If volcanic advection, carrying hot material from depth to the surface, was the major mode of early heat-loss, that changes everything.”

It boils down to whether Earth’s heat loss occurred by conduction (radiating equally across the planet) over a long period of time, or if volcanoes spewed lava (and heat) out from inside the planet onto the surface where it cooled.

This build-up of cooled material would have eventually sunk and cooled the lithosphere, slowing down the volcanoes along with Earth’s overall cooling. In turn, this would have trapped the planet’s inner heat, which expanded the crust, causing it to crack and form tectonic plates.

“Our numerical experiments show that the polygon fissures could develop on Earth’s surface in response to shallow lithospheric processes, with triple junctions as by-products of fracturing,” the team writes in their paper.

 

“The rapid development of the fracture network in each experiment occurs at around 1 km total expansion and takes ~5 million years.”

It’s important to note that this study is just one hypothesis. We’re still a long way off from understanding what happened on ancient Earth to result in tectonic plates. But with more evidence, this hypothesis could be an important part of working out our planet’s unique features.

The research has been published in Nature Communications.

 



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The Moon Is Millions of Years Younger Than We Thought, Scientists Suggest

in Science News by


Looking back through several billion years of history isn’t easy, and new discoveries continually prompt us to rethink just how the Moon came to be. Now, a new study suggests Earth’s satellite is much younger than we tend to think – about 85 million years younger, in fact.

 

Researchers say that lunar rock samples collected on the Apollo missions aren’t old enough to verify the normally accepted 4.51 billion-year figure for the Moon’s age – but that it can be calculated by looking back to the very first moments of our nearest celestial neighbour.

According to the commonly accepted hypothesis, the Moon was formed from the debris of a collision between Earth and a smaller planet called Theia, spewing out molten rock that eventually solidified into one whole body that began orbiting Earth.

That means the rock that makes up the Moon came from Earth, and can be used to date it, with some sophisticated modelling. The new study suggests the Moon was created when Earth was almost fully formed.

“The results of our latest modelling suggest that the young Earth was hit by a protoplanet some 140 million years after the birth of the Solar System 4.567 billion years ago,” says geophysicist Maxime Maurice from the German Aerospace Centre.

“According to our calculations, this happened 4.425 billion years ago – with an uncertainty of 25 million years – and the Moon was born.”

 

The models run by Maurice and her colleagues looked at two timescales: how old the Earth was when Theia hit it, and how long the Moon’s massive magma ocean took to cool after it had begun to solidify.

That second process took around 200 million years from start to finish, the scientists’ models show. Simulations based on how the Moon’s silicate minerals may have evolved over time led the researchers to their final Moon age of 4.425 billion years.

The new analysis goes into serious levels of detail and shows just how many factors need to be taken into account – how holes punctured in the lunar surface may have affected the speed at which the Moon cooled down, for example, and how deep the original ocean of magma may have been.

moon age 2How the early Moon’s interior may have looked. (DLR/Maxime Maurice)

“By comparing the measured composition of the Moon’s rocks with the predicted composition of the magma ocean from our model, we were able to trace the evolution of the ocean back to its starting point, the time at which the Moon was formed,” says geophysicist Sabrina Schwinger from the German Aerospace Centre.

Dating the Moon takes a lot of smart guesswork, and that means we’re probably going to be hearing much more about the age of the Moon in the years ahead. Future crewed missions to the Moon will be able to collect more lunar rock samples, and could hopefully plug some of the remaining gaps in our knowledge.

 

This isn’t the only recent study exploring these mysterious unknowns. It was only three years ago that the age of the Moon was pushed back some 140 million years, while more recent research suggests the Moon is older still.

These corrections seem huge compared to the time we spend alive, but the adjustments are much smaller in the grand scheme of Solar System history, and we should expect more to come as our understanding evolves.

However, the new estimate matches up rather neatly with the period when it’s thought that Earth’s metallic core formed, late in the geological development of our own planet. It also fits in with the timeline of previous research into damage to asteroids – damage that may have been caused by the Earth-Theia collision.

“The convergence of these independent estimates not only provides a robust and precise age for the Moon-forming impact but also consistently links this event to the differentiation of Earth and the dynamical evolution of the inner Solar System,” the researchers write.

The research has been published in Science Advances.

 



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