Astronomy and Planetary Science Thread

We already have nine planets; it's only for some pretty dubious reasons that currently only eight of them are recognised.


On another note, a short clip of the 2021 Valentine's Day meteor:

www.bbc.com

Meteor lights up Melbourne skies

The celestial spectacle occurred on Valentine's Day, during the city's five-day lockdown.
www.bbc.com www.bbc.com
 
Planet nine looks in a bad way as a theory.

No Evidence for Orbital Clustering in the Extreme Trans-Neptunian Objects

The apparent clustering in longitude of perihelion ϖ and ascending node Ω of extreme trans-Neptunian objects (ETNOs) has been attributed to the gravitational effects of an unseen 5-10 Earth-mass planet in the outer solar system. To investigate how selection bias may contribute to this clustering, we consider 14 ETNOs discovered by the Dark Energy Survey, the Outer Solar System Origins Survey, and the survey of Sheppard and Trujillo. Using each survey's published pointing history, depth, and TNO tracking selections, we calculate the joint probability that these objects are consistent with an underlying parent population with uniform distributions in ϖ and Ω. We find that the mean scaled longitude of perihelion and orbital poles of the detected ETNOs are consistent with a uniform population at a level between 17% and 94%, and thus conclude that this sample provides no evidence for angular clustering.

[2102.05601] No Evidence for Orbital Clustering in the Extreme Trans-Neptunian Objects

arxiv.org

www.cnet.com

'Any evidence for Planet Nine is gone': Scientists dispute probability of mystery planet

Is there a hidden ninth planet far from the sun affecting the orbits of distant space rocks? New research pours cold water on the theory.
www.cnet.com www.cnet.com
 
Detailed response to the Planet Nine paper posted above.

findplanetnine.blogspot.com

Is Planet Nine finally dead?

Konstantin and I have a recurring conversation. One of us says "Wait! I think we're wrong about the evidence for Planet Nine. Here's why......
findplanetnine.blogspot.com findplanetnine.blogspot.com
 
Hobbes said:
Grey Havoc said:
Long since time to bring back the real 'Planet Nine', methinks.
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There is no definition (based in astronomy rather than tradition) in which the solar system has exactly 9 planets. It's either 8 or hundreds.
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Pluto was arguably demoted from planetary status solely because of a combination of rather dodgy science and even more toxic politics. Its later redesignation as a minor planet was an belated (and unsuccessful) attempt to mollify the critics of that move which only helped to illustrate just how wrong headed the IAU's original decision was.
 
I'd like a better estimate for mass / composition of tau Ceti 'f', which is currently Sin(i) due to uncertainties in the system's inclination.

Can't always be lucky and have an inner planet transiting to constrain the geometry...
 
Breakup of a long-period comet as the origin of the dinosaur extinction

The origin of the Chicxulub impactor, which is attributed as the cause of the K/T mass extinction event, is an unsolved puzzle. The background impact rates of main-belt asteroids and long-period comets have been previously dismissed as being too low to explain the Chicxulub impact event. Here, we show that a fraction of long-period comets are tidally disrupted after passing close to the Sun, each producing a collection of smaller fragments that cross the orbit of Earth. This population could increase the impact rate of long-period comets capable of producing Chicxulub impact events by an order of magnitude. This new rate would be consistent with the age of the Chicxulub impact crater, thereby providing a satisfactory explanation for the origin of the impactor. Our hypothesis explains the composition of the largest confirmed impact crater in Earth’s history as well as the largest one within the last million years. It predicts a larger proportion of impactors with carbonaceous chondritic compositions than would be expected from meteorite falls of main-belt asteroids.

www.nature.com

Breakup of a long-period comet as the origin of the dinosaur extinction - Scientific Reports

The origin of the Chicxulub impactor, which is attributed as the cause of the K/T mass extinction event, is an unsolved puzzle. The background impact rates of main-belt asteroids and long-period comets have been previously dismissed as being too low to explain the Chicxulub impact event. Here...
www.nature.com www.nature.com


Other researchers did not agree with the new study's findings and still say several clues point to an asteroid creating the Chicxulub crater.
For one, Iridium -- along with a handful of other chemical elements -- was found scattered around the globe after the impact, said David Kring, principal scientist at the Lunar and Planetary Institute in Houston, who was not involved with the comet study.
Kring said the proportions of those elements are the same proportions seen in meteorite samples of asteroids.
The comet piece would have also been too small to make a crater of that size, said Natalia Artemieva, senior scientist at the Planetary Science Institute, who also was not involved in the study.
The study estimated the size of the comet piece to be about 4 miles wide, and Artemieva argued the comet would need to be at least 7.5 miles wide to make a crater the size of Chicxulub. With the small comet piece, she said, "it is absolutely impossible," and the crater size from the impact would be at least half the size.
Click to expand...

edition.cnn.com

Dinosaurs may have been killed off by a comet instead of an asteroid | CNN

Researchers theorized that a piece of a comet, rather than an asteroid, hit Earth and caused the extinction of many species 66 million years ago.
edition.cnn.com edition.cnn.com
 
Flyaway said:
Breakup of a long-period comet as the origin of the dinosaur extinction

The origin of the Chicxulub impactor, which is attributed as the cause of the K/T mass extinction event, is an unsolved puzzle. The background impact rates of main-belt asteroids and long-period comets have been previously dismissed as being too low to explain the Chicxulub impact event. Here, we show that a fraction of long-period comets are tidally disrupted after passing close to the Sun, each producing a collection of smaller fragments that cross the orbit of Earth. This population could increase the impact rate of long-period comets capable of producing Chicxulub impact events by an order of magnitude. This new rate would be consistent with the age of the Chicxulub impact crater, thereby providing a satisfactory explanation for the origin of the impactor. Our hypothesis explains the composition of the largest confirmed impact crater in Earth’s history as well as the largest one within the last million years. It predicts a larger proportion of impactors with carbonaceous chondritic compositions than would be expected from meteorite falls of main-belt asteroids.

www.nature.com

Breakup of a long-period comet as the origin of the dinosaur extinction - Scientific Reports

The origin of the Chicxulub impactor, which is attributed as the cause of the K/T mass extinction event, is an unsolved puzzle. The background impact rates of main-belt asteroids and long-period comets have been previously dismissed as being too low to explain the Chicxulub impact event. Here...
www.nature.com www.nature.com


Other researchers did not agree with the new study's findings and still say several clues point to an asteroid creating the Chicxulub crater.
For one, Iridium -- along with a handful of other chemical elements -- was found scattered around the globe after the impact, said David Kring, principal scientist at the Lunar and Planetary Institute in Houston, who was not involved with the comet study.
Kring said the proportions of those elements are the same proportions seen in meteorite samples of asteroids.
The comet piece would have also been too small to make a crater of that size, said Natalia Artemieva, senior scientist at the Planetary Science Institute, who also was not involved in the study.
The study estimated the size of the comet piece to be about 4 miles wide, and Artemieva argued the comet would need to be at least 7.5 miles wide to make a crater the size of Chicxulub. With the small comet piece, she said, "it is absolutely impossible," and the crater size from the impact would be at least half the size.
Click to expand...

edition.cnn.com

Dinosaurs may have been killed off by a comet instead of an asteroid | CNN

Researchers theorized that a piece of a comet, rather than an asteroid, hit Earth and caused the extinction of many species 66 million years ago.
edition.cnn.com edition.cnn.com
Click to expand...

I always had a suspicion that the dinosaurs were killed of by a comet instead of an asteroid.
 
Great article on what Avi Loeb is actually trying to across with his recent book, and not what the press would have you believe he’s saying.

We are, as a matter of fact, taking the hypothesis of extraterrestrial life, even intelligent extraterrestrial life, more seriously now than ever before, and this is true not just among the general public but also within the community of working scientists. But I don’t see Avi Loeb saying anything that discounts that work. What I do see him saying in Extraterrestrial is that in the case of ‘Oumuamua, scientists are reluctant to consider a hypothesis of extraterrestrial technology even though it stands up to scrutiny — as a hypothesis — and offers as good an explanation as others I’ve seen. Well actually, better, because as Loeb says, it checks off more of the needed boxes.

Invariably, critics quote Sagan: “Extraordinary claims require extraordinary evidence.” Loeb is not overly impressed with the formulation, saying “evidence is evidence, no?” And he goes on: “I do believe that extraordinary conservatism keeps us extraordinarily ignorant. Put differently, the field doesn’t need more cautious detectives.” Fighting words, those. A solid rhetorical strategy, perhaps, but then caution is also baked into the scientific method, as well it should be. So let’s talk about caution and ‘Oumuamua.
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Can we discuss this alien artifact hypothesis in a rational way? Loeb is not sure we can, at least in some venues, given the assumptions and accumulated inertia he sees plaguing the academic community. He describes pressure on young postdocs to choose career paths that will fit into accepted ideas. He asks whether what we might call the science ‘establishment’ is simply top-heavy, a victim of its own inertia, so that the safer course for new students is not to challenge older models.
Click to expand...

Now we’re at the heart of the book, for as we’ve seen, Extraterrestrial is less about ‘Oumuamua itself and more about how we do science, and what the author sees as a too conservative approach that is fed by the demands of making a career. He’s compelled to ask: Shouldn’t the possibility of ‘Oumuamua being an extraterrestrial artifact, a technological object, be a bit less controversial than it appears to be, given the growth in our knowledge in recent decades?
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Isn’t communicating ideas part of the job description of anyone employed to do scientific research? So much of that research is funded by the public through their tax dollars, after all. If Loeb’s prickly book is forcing some scientists to take the time to explain why they think his hypothesis is unlikely, I cannot see that as a bad thing. Good for Avi Loeb, I’d say.
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Extraterrestrial: On ‘Oumuamua as Artifact | Centauri Dreams

www.centauri-dreams.org
 
Scientists claim that all high-energy cosmic neutrinos are born by quasars
Scientists of the P. N. Lebedev Physical Institute of the Russian Academy of Sciences (LPI RAS), the Moscow Institute of Physics and Technology (MIPT) and the Institute for Nuclear Research of RAS (INR RAS) studied the arrival directions of astrophysical neutrinos with energies more than a trillion electronvolts (TeV) and came to an unexpected conclusion: all of them are born near black holes in the centers of distant active galaxies powerful radio sources. Previously, only neutrinos with the highest energies were assumed to be obtained in sources of this class.
Click to expand...

www.eurekalert.org

Scientists claim that all high-energy cosmic neutrinos are born by quasars

Scientists of the P. N. Lebedev Physical Institute of the Russian Academy of Sciences (LPI RAS), the Moscow Institute of Physics and Technology (MIPT) and the Institute for Nuclear Research of RAS (INR RAS) studied the arrival directions of astrophysical neutrinos with energies more than a...
www.eurekalert.org
 

Astronomers Find an Astonishing 'Super-Earth' That's Nearly as Old as The Universe​

But the TOI-561 system, planets and all, is one of the oldest ever seen, at an estimated age of around 10 billion years.

That's more than twice as old as the Solar System, nearly as old as the Universe itself, and evidence that rocky exoplanets can remain stable for a very long time.

"TOI-561 b is one of the oldest rocky planets yet discovered," said astronomer Lauren Weiss of the University of Hawai'i.

"Its existence shows that the universe has been forming rocky planets almost since its inception 14 billion years ago."

The three planets, named TOI-561 b, TOI-561 c and TOI-561 d, were identified by NASA's planet-hunting space telescope, TESS. TESS stares at sections of the sky, looking for periodic, faint dips in the light of distant stars. These are transits, when a planet passes between us and its star.[/wu
But the TOI-561 system, planets and all, is one of the oldest ever seen, at an estimated age of around 10 billion years.
Click to expand...

www.sciencealert.com

Astronomers Find an Astonishing 'Super-Earth' That's Nearly as Old as The Universe

It turns out that planets can live a very long time indeed.
www.sciencealert.com www.sciencealert.com

View: https://youtu.be/SNjn9bzbN_Y
 
Flyaway said:

Astronomers Find an Astonishing 'Super-Earth' That's Nearly as Old as The Universe​

But the TOI-561 system, planets and all, is one of the oldest ever seen, at an estimated age of around 10 billion years.

That's more than twice as old as the Solar System, nearly as old as the Universe itself, and evidence that rocky exoplanets can remain stable for a very long time.

"TOI-561 b is one of the oldest rocky planets yet discovered," said astronomer Lauren Weiss of the University of Hawai'i.

"Its existence shows that the universe has been forming rocky planets almost since its inception 14 billion years ago."

The three planets, named TOI-561 b, TOI-561 c and TOI-561 d, were identified by NASA's planet-hunting space telescope, TESS. TESS stares at sections of the sky, looking for periodic, faint dips in the light of distant stars. These are transits, when a planet passes between us and its star.[/wu
But the TOI-561 system, planets and all, is one of the oldest ever seen, at an estimated age of around 10 billion years.
Click to expand...

www.sciencealert.com

Astronomers Find an Astonishing 'Super-Earth' That's Nearly as Old as The Universe

It turns out that planets can live a very long time indeed.
www.sciencealert.com www.sciencealert.com

View: https://youtu.be/SNjn9bzbN_Y
Click to expand...

I wonder if there are more 10 billion year old planets out in the Milky Way waiting to be discovered. Surely this planet is not the only one of its kind out on the Galaxy?
 
Hemispheric Tectonics on LHS 3844b

Abstract
The tectonic regime of rocky planets fundamentally influences their long-term evolution and cycling of volatiles between interior and atmosphere. Earth is the only known planet with active plate tectonics, but observations of exoplanets may deliver insights into the diversity of tectonic regimes beyond the solar system. Observations of the thermal phase curve of super-Earth LHS 3844b reveal a solid surface and lack of a substantial atmosphere, with a temperature contrast between the substellar and antistellar point of around 1000 K. Here, we use these constraints on the planet's surface to constrain the interior dynamics and tectonic regimes of LHS 3844b using numerical models of interior flow. We investigate the style of interior convection by assessing how upwellings and downwellings are organized and how tectonic regimes manifest. We discover three viable convective regimes with a mobile surface: (1) spatially uniform distribution of upwellings and downwellings, (2) prominent downwelling on the dayside and upwellings on the nightside, and (3) prominent downwelling on the nightside and upwellings on the dayside. Hemispheric tectonics is observed for regimes (2) and (3) as a direct consequence of the day-to-night temperature contrast. Such a tectonic mode is absent in the present-day solar system and has never been inferred from astrophysical observations of exoplanets. Our models offer distinct predictions for volcanism and outgassing linked to the tectonic regime, which may explain secondary features in phase curves and allow future observations to constrain the diversity of super-Earth interiors.

 
Unprecedented find for the U.K. especially as the object was seen to come down and it’s orbit already worked out so it’s known where it came from, and it was collected so quickly it is almost as good as material brought back by probes to meteorites. Most of the material so far recovered has been lodged at the Natural History Museum.

Winchcombe meteorite is first UK find in 30 years: https://www.bbc.co.uk/news/science-environment-56326246
 
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www.space.com

Black holes could be dark stars with 'Planck hearts'

They may not be black or holes.
www.space.com www.space.com

One theory of black hole singularities replaces those infinitely tiny points of infinitely compressed matter with something much more palatable: an incredibly tiny point of incredibly compressed matter. This is called a Planck core, because the idea theorizes that the matter inside a black hole is compressed all the way down to the smallest possible scale, the Planck length, which is 1.6 * 10^ minus 35 meters.

That's … small.

With a Planck core, which wouldn’t be a singularity, a black hole would no longer host an event horizon — there would be no place where the gravitational pull exceeds the speed of light. But to outside observers, the gravitational pull would be so strong that it would look and act like an event horizon. Only extremely sensitive observations, which we do not yet have the technology for, would be able to tell the difference
Click to expand...
 
Flyaway said:
www.space.com

Black holes could be dark stars with 'Planck hearts'

They may not be black or holes.
www.space.com www.space.com

One theory of black hole singularities replaces those infinitely tiny points of infinitely compressed matter with something much more palatable: an incredibly tiny point of incredibly compressed matter. This is called a Planck core, because the idea theorizes that the matter inside a black hole is compressed all the way down to the smallest possible scale, the Planck length, which is 1.6 * 10^ minus 35 meters.

That's … small.

With a Planck core, which wouldn’t be a singularity, a black hole would no longer host an event horizon — there would be no place where the gravitational pull exceeds the speed of light. But to outside observers, the gravitational pull would be so strong that it would look and act like an event horizon. Only extremely sensitive observations, which we do not yet have the technology for, would be able to tell the difference
Click to expand...
Click to expand...

I wonder what Stephen Hawking would have thought of this theory, since he spent his life trying to understand the inner workings of black holes.
 
A chunk of meteorite found in the desert sands of Algeria could be a piece of a baby planet that never made it.

According to an in-depth analysis of the rock's composition and age, not only is the meteorite known as Erg Chech 002 older than Earth, it formed volcanically - suggesting that it could have once been part of the crust of an object known as a protoplanet.
Click to expand...

www.sciencealert.com

This Is a Piece of a Lost Protoplanet, And It's Officially Older Than Earth

A chunk of meteorite found in the desert sands of Algeria could be a piece of a baby planet that never made it.
www.sciencealert.com www.sciencealert.com

A 4,565-My-old andesite from an extinct chondritic protoplanet

Abstract

The age of iron meteorites implies that accretion of protoplanets began during the first millions of years of the solar system. Due to the heat generated by 26Al decay, many early protoplanets were fully differentiated with an igneous crust produced during the cooling of a magma ocean and the segregation at depth of a metallic core. The formation and nature of the primordial crust generated during the early stages of melting is poorly understood, due in part to the scarcity of available samples. The newly discovered meteorite Erg Chech 002 (EC 002) originates from one such primitive igneous crust and has an andesite bulk composition. It derives from the partial melting of a noncarbonaceous chondritic reservoir, with no depletion in alkalis relative to the Sun’s photosphere and at a high degree of melting of around 25%. Moreover, EC 002 is, to date, the oldest known piece of an igneous crust with a 26Al-26Mg crystallization age of 4,565.0 million years (My). Partial melting took place at 1,220 °C up to several hundred kyr before, implying an accretion of the EC 002 parent body ca. 4,566 My ago. Protoplanets covered by andesitic crusts were probably frequent. However, no asteroid shares the spectral features of EC 002, indicating that almost all of these bodies have disappeared, either because they went on to form the building blocks of larger bodies or planets or were simply destroyed.

www.pnas.org

A 4,565-My-old andesite from an extinct chondritic protoplanet

The crusts of the oldest protoplanets are virtually unknown due to the scarcity of samples. Here, we describe the oldest known lava that crystallized ca. 4,565 Ma ago and formed by partial melting of a chondritic parent body. 26Al-26Mg systematics suggest that the elapsed time between melting...
www.pnas.org www.pnas.org
 
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FighterJock said:
Flyaway said:
www.space.com

Black holes could be dark stars with 'Planck hearts'

They may not be black or holes.
www.space.com www.space.com

One theory of black hole singularities replaces those infinitely tiny points of infinitely compressed matter with something much more palatable: an incredibly tiny point of incredibly compressed matter. This is called a Planck core, because the idea theorizes that the matter inside a black hole is compressed all the way down to the smallest possible scale, the Planck length, which is 1.6 * 10^ minus 35 meters.

That's … small.

With a Planck core, which wouldn’t be a singularity, a black hole would no longer host an event horizon — there would be no place where the gravitational pull exceeds the speed of light. But to outside observers, the gravitational pull would be so strong that it would look and act like an event horizon. Only extremely sensitive observations, which we do not yet have the technology for, would be able to tell the difference
Click to expand...
Click to expand...

I wonder what Stephen Hawking would have thought of this theory, since he spent his life trying to understand the inner workings of black holes.
Click to expand...
In the article itself it says the theory is likely not correct.
 
The discovery of a highly accreting, radio-loud quasar at z=6.82

Radio sources at the highest redshifts can provide unique information on the first massive galaxies and black holes, the densest primordial environments, and the epoch of reionization. The number of astronomical objects identified at z>6 has increased dramatically over the last few years, but previously only three radio-loud (R2500>10) sources had been reported at z>6, with the most distant being a quasar at z=6.18. Here we present the discovery and characterization of P172+18, a radio-loud quasar at z=6.823. This source has an MgII-based black hole mass of ~3x10^8 Msun and is one of the fastest accreting quasars, consistent with super-Eddington accretion. The ionized region around the quasar is among the largest measured at these redshifts, implying an active phase longer than the average lifetime of the z>6 quasar population. From archival data, there is evidence that its 1.4 GHz emission has decreased by a factor of two over the last two decades. The quasar's radio spectrum between 1.4 and 3.0 GHz is steep (alpha=-1.31) and has a radio-loudness parameter R2500~90. A second steep radio source (alpha=-0.83) of comparable brightness to the quasar is only 23.1" away (~120 kpc at z=6.82; projection probability <2%), but shows no optical or near-infrared counterpart. Further follow-up is required to establish whether these two sources are physically associated.

[2103.03295] The discovery of a highly accreting, radio-loud quasar at z=6.82

arxiv.org

phys.org

The most distant radio-loud quasar discovered

In a recent study, an international team of astronomers presents the discovery of PSO J172.3556+18.7734—a highly accreting radio-loud quasar at a redshift of approximately 6.82. This is the most distant radio-loud quasar known to date. The finding is detailed in a paper published March 4 on...
phys.org phys.org
 
1I/‘Oumuamua as an N2 ice fragment of an exo‐Pluto surface: I. Size and Compositional Constraints

1I/‘Oumuamua is very strange and it is hard to explain where it came from. We looked at several different ices and the push they would give ‘Oumuamua as they evaporated. We found that the best ice is nitrogen (N2), which would explain many of the things we know about it. ‘Oumuamua was small, about half as long as a city block and only as thick as a three story building, but it was very shiny. The shininess is about the same as the surfaces of Pluto and Triton, which are also covered in nitrogen ice. We suggest ‘Oumuamua was probably thrown out of a young star system about half a billion years ago. Bodies like ‘Oumuamua may allow us to see what the surfaces of a so far unknown type of exoplanet, “exo‐Plutos”, are made of. In a following paper (Desch & Jackson, 2021) we show that orbital instabilities in which giant planets move around, as happened in our own outer solar system 4 billion years ago, could make and throw out large numbers of small pieces of nitrogen ice like ‘Oumuamua. ‘Oumuamua may be the first piece of an exoplanet brought to us.

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agupubs.onlinelibrary.wiley.com agupubs.onlinelibrary.wiley.com

1I/‘Oumuamua as an N2 ice fragment of an exo‐pluto surface II: Generation of N2 ice fragments and the origin of ‘Oumuamua

Our Kuiper belt originally had much more mass than today, but an instability caused by Neptune’s migration disrupted their orbits, ejecting most of this material from the Solar System, and simultaneously causing numerous collisions among these bodies. There were thousands of bodies like Pluto, with N2 ice (like the gas in Earth’s atmosphere, but frozen) on their surfaces, and this instability would have generated trillions of N2 ice fragments. A similar fragment, generated in another solar system, after travelling for about a half billion years through interstellar space, would match the size, shape, brightness, and dynamics of the interstellar object 1I/‘Oumuamua. The odds of detecting such an object, as well as more comet‐like objects like the interstellar object 2I/Borisov, are consistent with the numbers of such objects we expect in interstellar space if most stellar systems ejected comets and N2 ice fragments with the same efficiency our solar system did. This implies other stellar systems also had Kuiper belts and similar instabilities. There are hints that some N2 ice fragments may have survived in the Oort cloud of comets in our Solar System. ‘Oumuamua may be the first sample of an exoplanet born around another star, brought to Earth.

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agupubs.onlinelibrary.wiley.com agupubs.onlinelibrary.wiley.com
 
Summary
Over time, sea levels have risen and fallen with temperatures—but Earth's total surface water was always assumed to be constant. Now, evidence is mounting that some 3 billion to 4 billion years ago, the planet's oceans held nearly twice as much water—enough to submerge today's continents. Rocks in today's mantle, the thick layer beneath the crust, are thought to sequester an ocean's worth of water or more in their mineral structures. But early in Earth's history, the mantle, warmed by radioactivity, was four times hotter. Work using hydraulic presses has shown that many minerals would be unable to hold as much hydrogen and oxygen at mantle temperatures and pressures. A new model of the mantle's evolution through time, based on these results, suggests the mantle could have held far less water in the past. And the most likely home for that water was the surface. This flood could have primed the engine of plate tectonics and made it more difficult for life to start on land.

Science | AAAS

science.sciencemag.org science.sciencemag.org
 

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