Rare Earth; how rare? (Introduction)

by David Turell @, Saturday, December 10, 2011, 21:35 (4492 days ago)

http://www.bbc.co.uk/news/science-environment-16068809

Another discussion of how special Earth is.

Rare Earth; how rare?

by xeno6696 @, Sonoran Desert, Saturday, December 10, 2011, 22:04 (4492 days ago) @ David Turell

http://www.bbc.co.uk/news/science-environment-16068809

Another discussion of how special Earth is.

Until we've explored a few solar systems... we have NO idea on how special our planet is...

--
\"Why is it, Master, that ascetics fight with ascetics?\"

\"It is, brahmin, because of attachment to views, adherence to views, fixation on views, addiction to views, obsession with views, holding firmly to views that ascetics fight with ascetics.\"

Rare Earth; how rare?

by David Turell @, Sunday, December 11, 2011, 00:49 (4491 days ago) @ xeno6696

http://www.bbc.co.uk/news/science-environment-16068809

Another discussion of how special Earth is.


Until we've explored a few solar systems... we have NO idea on how special our planet is...

Resident skeptic, how do you propose that? How will we get to solar systems with proper planets in the goldylocks zone? When the solar systems we are finding are many light-years away. Send probes at light speed?

Rare Earth; how rare?

by xeno6696 @, Sonoran Desert, Sunday, December 11, 2011, 18:32 (4491 days ago) @ David Turell

http://www.bbc.co.uk/news/science-environment-16068809

Another discussion of how special Earth is.


Until we've explored a few solar systems... we have NO idea on how special our planet is...


Resident skeptic, how do you propose that? How will we get to solar systems with proper planets in the goldylocks zone? When the solar systems we are finding are many light-years away. Send probes at light speed?

First-generation ION drives can currently move objects 10x faster than with chemical propulsion. They just accelerate very slowly. To put that in perspective, the space shuttle would fly at the speed of 27870 km/h (17000mi/h). Increasing that by an order of magnitude, the same mass would reach a speed of 278700km/h.

However... in space, you don't have an atmosphere to push against, so ion drives make more sense: if fueled by a nuclear reactor similar to what powers our naval ships, we could generate a sustained acceleration of 3.6km/s for 13 years. We likely won't reach light speed with that--but near speed of light has already been theorized. (Limited by the mass of the ship, of course.) If you do the math, a small satellite could travel to Alpha Centauri in 6-7yrs.

FTL travel?
NASA doesn't find it impossible. Yet.

But for me, a more personal answer is this: I don't think in terms of my own lifetime, David. An answer now based on obvious ignorance is worth nothing. But preparing the way for the future, so that the question(s) can conceivably be answered? THAT is the true work of a philosopher. THAT is Nietzsche's builder, the ubermensch incarnate.

--
\"Why is it, Master, that ascetics fight with ascetics?\"

\"It is, brahmin, because of attachment to views, adherence to views, fixation on views, addiction to views, obsession with views, holding firmly to views that ascetics fight with ascetics.\"

Rare Earth; how rare?

by David Turell @, Monday, December 12, 2011, 00:04 (4491 days ago) @ xeno6696


But for me, a more personal answer is this: I don't think in terms of my own lifetime, David. An answer now based on obvious ignorance is worth nothing. But preparing the way for the future, so that the question(s) can conceivably be answered? THAT is the true work of a philosopher. THAT is Nietzsche's builder, the ubermensch incarnate.

Fair enough, but I'm happy with a current belief.

Rare Earth; how rare?

by xeno6696 @, Sonoran Desert, Monday, December 12, 2011, 00:53 (4490 days ago) @ David Turell


But for me, a more personal answer is this: I don't think in terms of my own lifetime, David. An answer now based on obvious ignorance is worth nothing. But preparing the way for the future, so that the question(s) can conceivably be answered? THAT is the true work of a philosopher. THAT is Nietzsche's builder, the ubermensch incarnate.


Fair enough, but I'm happy with a current belief.

You don't have to answer this... but the crux of the entire debate over God and religion for me has always been a disdain of faith. Why faith?

Well, maybe not much of a question, but I just... really cannot understand how holding a belief on faith can make anyone feel better. Especially when knowledge is out there. I don't know if I'm just damaged for some reason, but I've gone to great lengths to *remove* faith from my life. I don't just mean this in a religious sense, but in an all-encompassing sense. Part of why I always challenge authority is because titles mean nothing and trust is always better than faith. And trust is earned, not freely given. Faith is freely given.

If knowledge is out there--even if I don't have immediate access to it--then my belief held on faith might be false... so why hold to a belief that might be false? It's... inefficient at the least. Especially considering that our human instincts are to defend beliefs we like, it seems too great an expenditure of life to accept, uproot, accept, uproot, etc...

--
\"Why is it, Master, that ascetics fight with ascetics?\"

\"It is, brahmin, because of attachment to views, adherence to views, fixation on views, addiction to views, obsession with views, holding firmly to views that ascetics fight with ascetics.\"

Rare Earth; how rare?

by David Turell @, Monday, December 12, 2011, 02:21 (4490 days ago) @ xeno6696

If knowledge is out there--even if I don't have immediate access to it--then my belief held on faith might be false... so why hold to a belief that might be false? It's... inefficient at the least. Especially considering that our human instincts are to defend beliefs we like, it seems too great an expenditure of life to accept, uproot, accept, uproot, etc...

Everybody is different. Antony Flew changed his mind. Just keep yours open as you are doing now.

Rare Earth; how rare?

by David Turell @, Thursday, January 12, 2012, 15:04 (4459 days ago) @ David Turell

Another discussion of habitable planets, concentrating on the tilt of the Earth and how that moderates temperature, along with the consideration that our unique moon keeps our tilt in place:

http://www.physorg.com/news/2012-01-loss-planetary-tilt-doom-alien.html

Rare Earth; our amazing mineral supply

by David Turell @, Thursday, August 27, 2015, 14:32 (3136 days ago) @ David Turell

The list of minerals on Earth is very large and perhaps unique in the universe:-http://www.sciencedaily.com/releases/2015/08/150826113615.htm-"New research from a team led by Carnegie's Robert Hazen predicts that Earth has more than 1,500 undiscovered minerals and that the exact mineral diversity of our planet is unique and could not be duplicated anywhere in the cosmos.-"Minerals form from novel combinations of elements. These combinations can be facilitated by both geological activity, including volcanoes, plate tectonics, and water-rock interactions, and biological activity, such as chemical reactions with oxygen and organic material.-"Nearly a decade ago, Hazen developed the idea that the diversity explosion of planet's minerals from the dozen present at the birth of our Solar System to the nearly 5,000 types existing today arose primarily from the rise of life. More than two-thirds of known minerals can be linked directly or indirectly to biological activity, according to Hazen. Much of this is due to the rise of bacterial photosynthesis, which dramatically increased the atmospheric oxygen concentration about 2.4 billion years ago.-***-"Further expanding the link between geological and biological evolution, Hazen's team applied the biological concepts of chance and necessity to mineral evolution. In biology, this idea means that natural selection occurs because of a random "chance" mutation in the genetic material of a living organism that becomes, if it confers reproductive advantage, a "necessary" adaptation.-"But in this instance, Hazen's team asked how the diversity and distribution of Earth's minerals came into existence and the likelihood that it could be replicated elsewhere. What they found is that if we could turn back the clock and "re-play" Earth's history, it is probable that many of the minerals formed and discovered in this alternate version of our planet would be different from those we know today.-"'This means that despite the physical, chemical, and biological factors that control most of our planet's mineral diversity, Earth's mineralogy is unique in the cosmos," Hazen said."-Comment: The presence of life plays a major role

Rare Earth; compared to others

by David Turell @, Thursday, September 17, 2015, 14:08 (3115 days ago) @ David Turell

So far none of the planets in the habitable zone look like the Earth:-https://www.newscientist.com/article/dn28170-earths-composition-might-be-unusual-for-a-planet-with-life/-"Is Earth the odd planet out? Many of our galaxy's habitable planets probably have a chemical composition that is quite different from Earth's.-"Vardan Adibekyan of the Institute of Astrophysics and Space Sciences, Portugal, and colleagues looked at stars with a similar mass and radius to the sun that are known to have planets in their habitable zones, where water stays liquid. They found that these stars tended to have less iron and other metals than stars that host only inhospitable worlds."

Rare Earth; compared to others

by David Turell @, Friday, February 19, 2016, 18:53 (2960 days ago) @ David Turell

Rare Earth and Privileged Planet are two books that point out how special the Earth appears to be, and now planet studies are confirming that impression:-http://www.scientificamerican.com/article/exoplanet-census-suggests-earth-is-special-after-all/?WT.mc_id=SA_DD_20160218-"A new tally proposes that roughly 700 quintillion terrestrial exoplanets are likely to exist across the observable universe—most vastly different from Earth.-"More than 400 years ago Renaissance scientist Nicolaus Copernicus reduced us to near nothingness by showing that our planet is not the center of the solar system. With every subsequent scientific revolution, most other privileged positions in the universe that humans might have held dear have been further degraded, revealing the cold truth that our species is the smallest of specks on a speck of a planet, cosmologically speaking. A new calculation of exoplanets suggests that Earth is just one out of a likely 700 million trillion terrestrial planets in the entire observable universe. But the average age of these planets—well above Earth's age—and their typical locations—in galaxies vastly unlike the Milky Way—just might turn the Copernican principle on its head.-***
"The scientists also have similar concerns about the galactic and cosmological inputs of their model but nonetheless they suspect that their final numbers are accurate to within an order of magnitude.With the estimated errors taken into account, the researchers conclude that Earth stands as a mild violation of the Copernican principle. Our pale blue dot might just be special after all. “It's not too much of a fluke that we could arise in a galaxy like the Milky Way, but nevertheless, it's just enough to make you think twice about it,” says Jay Olson from Boise State University, who was not involved in the study. Both he and Zackrisson think the Copernican principle could be saved by some unknown caveat to the findings. “Whenever you find something that sticks out…” Zackrisson says, “…that means that either we are the result of a very improbable lottery draw or we don't understand how the lottery works.'”-Comment: Just another suggestion that our planet is special.

Rare Earth; compared to others

by David Turell @, Friday, February 26, 2016, 01:15 (2953 days ago) @ David Turell

The source of this latest claim that the Earth is very special is in tis article:-http://blogs.discovermagazine.com/d-brief/2016/02/22/earth-is-a-1-in-700-quintillion-kind-of-place/#.Vs-mRCr2Zdi-"A new study suggests that there are around 700 quintillion planets in the universe, but only one like Earth. It's a revelation that's both beautiful and terrifying at the same time.-"Astrophysicist Erik Zackrisson from Uppsala University in Sweden arrived at this staggering figure — a 7 followed by 20 zeros — with the aid of a computer model that simulated the universe's evolution following the Big Bang. Zackrisson's model combined information about known exoplanets with our understanding of the early universe and the laws of physics to recreate the past 13.8 billion years.-"Zackrisson found that Earth appears to have been dealt a fairly lucky hand. In a galaxy like the Milky Way, for example, most of the planets Zackrisson's model generated looked very different than Earth — they were larger, older and very unlikely to support life. The study can be found on the preprint server arXiv, and has been submitted to The Astrophysical Journal.-***-"But according to Zackrisson, most planets in the universe shouldn't look like Earth. His model indicates that Earth's existence presents a mild statistical anomaly in the multiplicity of planets. Most of the worlds predicted by his model exist in galaxies larger than the Milky Way and orbit stars with different compositions — an important factor in determining a planet's characteristics. His research indicates that, from a purely statistical standpoint, Earth perhaps shouldn't exist.-***-“'It's certainly the case that there are a lot of uncertainties in a calculation like this. Our knowledge of all of these pieces is imperfect,” co-author Andrew Benson told Scientific American.“It was only recently that we even had enough exoplanet data to make a model of this kind possible.”-"Nevertheless, the researchers are confident in the broader implications of their model: Earth is more than your garden-variety planet."-Comment: Same story. we are special.

Rare Earth; compared to others

by dhw, Friday, February 26, 2016, 13:16 (2953 days ago) @ David Turell

DAVID: The source of this latest claim that the Earth is very special is in this article:-http://blogs.discovermagazine.com/d-brief/2016/02/22/earth-is-a-1-in-700-quintillion-ki...-"A new study suggests that there are around 700 quintillion planets in the universe, but only one like Earth. It's a revelation that's both beautiful and terrifying at the same time."-Or maybe even 750 quintillion. Or even 800 quintillion. If only we could see the ends of the universe, we could actually count the planets one by one, couldn't we? Oh, the excitement! But even though we haven't a clue how many, or what those we can't see might be like, I'll go along with our being special. And I can't help feeling that 700 quintillion dramatically reduces the odds against our being lucky too. Alternatively, fancy God having to create 699 quintillion, 999 burble burble zeros and 99 planets just for our sake. Incredible, wouldn't you say?

Rare Earth; compared to others

by David Turell @, Friday, February 26, 2016, 15:05 (2953 days ago) @ dhw

dhw: But even though we haven't a clue how many, or what those we can't see might be like, I'll go along with our being special. And I can't help feeling that 700 quintillion dramatically reduces the odds against our being lucky too. Alternatively, fancy God having to create 699 quintillion, 999 burble burble zeros and 99 planets just for our sake. Incredible, wouldn't you say?-We now know that the universe follows patterns. Stars have orbiting planets like ours but so far not just like ours with its special arrangements like gaseous giants and ones with rocky cores, all adjusted at just the right positions to protect one which is having life thrive. More fine tuning, I think.

Rare Earth; compared to others

by dhw, Saturday, February 27, 2016, 12:36 (2952 days ago) @ dhw

dhw: But even though we haven't a clue how many, or what those we can't see might be like, I'll go along with our being special. And I can't help feeling that 700 quintillion dramatically reduces the odds against our being lucky too. Alternatively, fancy God having to create 699 quintillion, 999 burble burble zeros and 99 planets just for our sake. Incredible, wouldn't you say?-DAVID: We now know that the universe follows patterns. Stars have orbiting planets like ours but so far not just like ours with its special arrangements like gaseous giants and ones with rocky cores, all adjusted at just the right positions to protect one which is having life thrive. More fine tuning, I think.-But it doesn't alter the fact that the more quintillions of planets and solar systems you have, the greater the chance of a stroke of good fortune and the more unlikely the argument that they were all needed for the purpose of producing humans.

Rare Earth; compared to others

by David Turell @, Saturday, February 27, 2016, 14:52 (2952 days ago) @ dhw


> dhw: But it doesn't alter the fact that the more quintillions of planets and solar systems you have, the greater the chance of a stroke of good fortune and the more unlikely the argument that they were all needed for the purpose of producing humans. - Now we have a multi-galaxy theory as opposition to fine-tuning. But it is not as productive as infinite multiverses to deny fine-tuning. This universe is finite!

Rare Earth; compared to others

by dhw, Sunday, February 28, 2016, 13:33 (2951 days ago) @ David Turell

dhw: But it doesn't alter the fact that the more quintillions of planets and solar systems you have, the greater the chance of a stroke of good fortune and the more unlikely the argument that they were all needed for the purpose of producing humans. - DAVID: Now we have a multi-galaxy theory as opposition to fine-tuning. But it is not as productive as infinite multiverses to deny fine-tuning. This universe is finite! - I didn't know multi-galaxies were just a theory. When did you discover that ours was the only one? “700 quintillions” of planets is, of course, a theory, and a pretty pointless one at that. The argument here, however, is not against fine-tuning or about billions, trillions, or quintillions, but simply the fact that the more planets and solar systems there are (and bearing in mind that even if the Big Bang happened, we have no idea what preceded it), the greater the chances that one of them will hit the jackpot. This is no more mind-boggling than the theory that all the untold billions, trillions or quintillians of planets and solar systems were invented by a single mind of unknown provenance for the purpose of creating little ole you and me.

Rare Earth; compared to others

by David Turell @, Sunday, February 28, 2016, 15:32 (2951 days ago) @ dhw

dhw: I didn't know multi-galaxies were just a theory. When did you discover that ours was the only one? - Ours is the only galaxy with life by current knowledge. My comment was only a comparison with multiverse theory with multi-galaxy theory, and in this case we are in the lucky galaxy, which is your point.

Rare Earth: our protective magnetic field

by David Turell @, Sunday, April 17, 2016, 23:38 (2902 days ago) @ David Turell

This paper takes the position that until the magnetic field grew strong enough to protect us from gamma rays and other nastiness, multicellularity did not appear. I think that is a side issue. The magnetic field is protective but it also holds our atmosphere here:-https://www.washingtonpost.com/news/speaking-of-science/wp/2016/04/14/you-might-still-be-a-simple-bacterium-if-not-for-magnetism/-"Earth is a giant magnet, and the atmosphere stays in place because of this magnetism. But the atmosphere wasn't always as thick as it is today, nor was the magnetic field as strong. Scientists think that about 500 million years ago, Earth's core solidified, turbocharging our magnetic field. This would have allowed the atmosphere to hold more gas, in part shielding early life from powerful solar rays - and allowing multicellular life to evolve.-***-"For 3 billion years, life on Earth was only home to water-dwelling, single-celled organisms like bacteria. But suddenly, multicellular life ballooned, knocking over the first domino in an evolutionary cascade that would one day allow you — yes, you — to exist and think and even read stuff on the Internet.-"Scientists think that until 500 million years ago, life on Earth fell victim to high-energy blasts from the sun, which at the time contained a lot more of the cell-killing gamma, ultraviolet and x-rays than it does today. The atmosphere then was too thin to fully protect our single-celled ancestors, whose DNA would have been damaged by such powerful rays. That kept them from becoming more complex.-***
"As Earth got older, heavier metals like iron and nickel sunk to the center and solidified under the pressure of the rest of the planet. Once the inner core was solid, it started spinning separately from the outer core. That would have made Earth into a more powerful magnet, which could have boosted its magnetic field.-***-"Scientists think the stronger magnetic field would have kept more gasses in the atmosphere, just as a stronger magnet can hold more paper clips. That means more oxygen was around to help cells grow, and a thicker atmosphere could protect those budding organisms from solar blasts. Simultaneously, the aging sun's radiation started weakening, which means its flares contained fewer dangerous, DNA-altering rays.-"That perfect confluence allowed the number of species to skyrocket, the authors say.-"Others also emphasize the importance of Earth's magnetic field as crucial to life on the planet. Recent work even suggests Mars's lack of strong magnetic field was what allowed the sun to strip away its atmosphere, leaving the planet barren."-Comment; their theory makes little sense. Bacteria existed in the ocean, protected from the rays. So did the Cambrians, who were multicellular. But as part of 'rarity' of Earth is the magnetic field, absolutely vital.

Rare Earth: our protective magnetic field

by David Turell @, Friday, May 20, 2016, 23:11 (2869 days ago) @ David Turell

Plate tectonics contribute to the oxygen level on Earth:-http://news.rice.edu/2016/05/16/oxygen-atmosphere-recipe-tectonics-continents-life-2/-"Plants and certain types of bacteria produce oxygen as a byproduct of photosynthesis. This oxygen production is balanced by the sink: reaction of oxygen with iron and sulfur in the Earth's crust and by back-reaction with organic carbon. For example, we breathe in oxygen and exhale carbon dioxide, essentially removing oxygen from the atmosphere. In short, the story of oxygen in our atmosphere comes down to understanding the sources and sinks, but the 3-billion-year narrative of how this actually unfolded is more complex.” -***-"Today, some 20 percent of Earth's atmosphere is free molecular oxygen, or O2. Free oxygen is not bound to another element, as are the oxygen atoms in other atmospheric gases like carbon dioxide and sulfur dioxide. For much of Earth's 4.5-billion-year history, free oxygen was all but nonexistent in the atmosphere. -***-"Lee and colleagues showed that around 2.5 billion years ago, the composition of Earth's continental crust changed fundamentally. Lee said the period, which coincided with the first rise in atmospheric oxygen, was also marked by the appearance of abundant mineral grains known as zircons. “The presence of zircons is telling,” he said. “Zircons crystallize out of molten rocks with special compositions, and their appearance signifies a profound change from silica-poor to silica-rich volcanism. The relevance to atmospheric composition is that silica-rich rocks have far less iron and sulfur than silica-poor rocks, and iron and sulfur react with oxygen and form a sink for oxygen. A view of Earth's atmosphere taken from the International Space Station in 2003.(Photo courtesy of ISS Expedition 7 Crew, EOL, NASA) “Based on this, we believe the first rise in oxygen may have been due to a substantial reduction in the efficiency of the oxygen sink,” Lee said. “In the bathtub analogy, this is equivalent to partially plugging the drain.” -***-“'The bathtub analogy is simple and elegant, but there's an added complication that must be taken into account,” he said. “That is because oxygen production is ultimately tied to the global carbon cycle — the cycling of carbon between the Earth, the biosphere, the atmosphere and oceans.” Lee said the model showed that Earth's carbon cycle has never been at a steady state because carbon slowly leaks out as carbon dioxide from Earth's deep interior to the surface through volcanic activity. Carbon dioxide is one of the key ingredients for photosynthesis. -***-"Lee said the team's model showed that volcanic activity and other geologic inputs of carbon into the atmosphere may have increased with time, and because oxygen production is tied to carbon production, oxygen production also must increase. The model showed that the second rise in atmospheric oxygen had to occur late in Earth's history. -***-"Exactly what caused the composition of the crust to change during the first oxygenation event remains a mystery, but Lee said the team believes it may have been related to the onset of plate tectonics, where the Earth's surface, for the first time, became mobile enough to sink back down into Earth's deep interior."-Comment: There is no question the Earth is a most unusual planet. Both carbon and oxygen cycles are closely related to plate tectonics. Good planning?

Rare Earth: our protective magnetic field

by David Turell @, Thursday, June 02, 2016, 02:43 (2856 days ago) @ David Turell

There are two iron layers in the core of Earth. the outer one creates the magnetic field with its movement:-http://phys.org/news/2016-06-sustains-earth-magnetic-field.html-"Earth's magnetic field shields us from deadly cosmic radiation, and without it, life as we know it could not exist here. The motion of liquid iron in the planet's outer core, a phenomenon called a "geodynamo," generates the field. But how it was first created and then sustained throughout Earth's history has remained a mystery to scientists.-*** -"Our planet accreted from rocky material that surrounded our Sun in its youth, and over time the most-dense stuff, iron, sank inward, creating the layers that we know exist today—core, mantle, and crust. Currently, the inner core is solid iron, with some other materials that were dragged along down during this layering process. The outer core is a liquid iron alloy, and its motion gives rise to the magnetic field.-***-"The team used a tool called a laser-heated diamond anvil cell to mimic planetary core conditions and study how iron conducts heat under them. The diamond anvil cell squeezes tiny samples of material in between two diamonds, creating the extreme pressures of the deep Earth in the lab. The laser heats the materials to the necessary core temperatures.-"Using this kind of lab-based mimicry, the team was able to look at samples of iron across temperatures and pressures that would be found inside planets ranging in size from Mercury to Earth—345,000 to 1.3 million times normal atmospheric pressure and 2,400 to 4,900 degrees Fahrenheit—and study how they propagate heat.-"They found that the ability of these iron samples to transmit heat matched with the lower end of previous estimates of thermal conductivity in Earth's core—between 18 and 44 watts per meter per kelvin, in the units scientists use to measure such things. This translates to predictions that the energy necessary to sustain the geodynamo has been available since very early in the history of Earth.-"'In order to better understand core heat conductivity, we will next need to tackle how the non-iron materials that went along for the ride when iron sunk to the core affect these thermal processes inside of our planet," Goncharov added."-Comment: Part of the fine tuning that led to life. Nickel is one of the other components of the core.

Rare Earth: alien planets and life

by David Turell @, Wednesday, July 20, 2016, 22:09 (2808 days ago) @ David Turell

The science writers are so hopeful that life is elsewhere that their wishful thinking poisons their reporting:-http://www.scientificamerican.com/article/2-newfound-alien-planets-may-be-capable-of-supporting-life/?WT.mc_id=SA_WR_20160720-"NASA's Kepler space telescope has spotted four possibly rocky alien planets orbiting the same star, and two of these newfound worlds might be capable of supporting life.-"The four exoplanets circle a red dwarf — a star smaller and dimmer than the sun—called K2-72, which lies 181 light-years from Earth in the Aquarius constellation. All four worlds are between 20 percent and 50 percent wider than Earth, making them good candidates to be rocky, discovery team members said.-"Two of the four planets, known as K2-72c and K2-72e, appear to be in the star's "habitable zone"—that just-right range of distances at which liquid water can exist on a world's surface, the scientists added. [How Habitable Zones for Exoplanets Work (Infographic)]-"Because K2-72 is a red dwarf, its habitable zone is much closer in than that of the sun. For example, K2-72c completes one orbit every 15 Earth days, yet it is likely just 10 percent warmer than our planet. K2-72e has a 24-Earth-day year, and it's about 6 percent colder than Earth, the scientists said. (All four newfound planets complete an orbit in 24 Earth days or less, making them closer to K2-72 than Mercury is to the sun.)"-Comment: Foolishness. It takes lots more than a rocky planet with the right temperature to have life. In this chain of articles many of the many requirements are listed. There are three whole books about the subject, two of which have been noted here.

Rare Earth: once again, how rare?

by David Turell @, Friday, September 02, 2016, 01:00 (2765 days ago) @ David Turell

Another article takes a stab at considering our rarity:-http://www.evolutionnews.org/2016/08/is_earth_the_mo103093.html-"Not all terrestrial-like planets are habitable or can even permit liquid water at the surface. Furthermore, X-rays, extreme UV radiation, and flares make it unlikely that planets around M-dwarf stars are habitable; this removes 98 percent of the terrestrial planet candidates. If super-earths with high gravitational fields are removed, Zackrisson et al. estimate that about 2 x 10^18 habitable planets remain in the observable universe. In addition, they note other factors that would further reduce the number of habitable planets, such as cosmic rays, Oort cloud comet perturbations, interactions with interstellar clouds, the effects of dark matter, and radiation threats to life. They also point out that the vast majority of habitable planets would be far too young to have evolved advanced life, leaving only a tiny fraction of candidates.-"That introduces another problem to overcome. Even if one has a habitable planet, there is no guarantee that life will be found there. Zackrisson et al. state:-"If the probability for the emergence of intelligent life is sufficiently small, we could well be the only advanced civilization in the Milky Way.-***-"Eugene Koonin has shown that the probability of merely attaining RNA replication and translation (a necessary requirement for even the simplest life) is less than 10^-1018. He concludes that it is highly unlikely to occur anywhere in the universe....My own work in bioinformatics supports Koonin's probabilistic conclusions that no life should be expected in this universe if it is a one-shot deal. For example, the probability of obtaining, in a single search, any one of 10^92 functional sequences for the Ribosomal S7 structural domain (necessary for translation from RNA to proteins) is roughly 10^-100.-"Seigel points out that in order to develop a technologically advanced civilization, three major steps must occur. First is the commencement of a simple life form, which requires evolving not just one, but a few hundred mutually specified proteins capable of combining together to form a living cell. For this to take place, the right proteins must fortuitously occur on the same planet, and at the same time and location on that planet. Then, life must survive long enough to evolve intelligence. The third step is to become technologically advanced. The likelihood of these three steps prompts Seigel to write, "the huge uncertainties make it a very real possibility that humans are the only spacefaring aliens our Universe has ever known."-***-"The first option is to grant Koonin's theory that we won a lottery against mind-staggering odds, requiring a near infinite number of unseen, untestable universes. The second option arises out of our observation that the universe and this particular planet seem to be incredibly fine-tuned to support life. It may be more rational, therefore, to conclude that there is, in fact, just one Creator who is greatly interested in Earth and its inhabitants. So the choice is between an infinite number of universes to explain our monstrous stroke of luck, or a Creator of the cosmos who has a purpose in mind for humanity. I suggest we go with Ockham's Razor and opt for the latter."-Comment: Since the multiverse is unprovable and a cop-out, I'll stick with Ockham and God. I've offered Koonin's odds before.

Rare Earth: once again, how rare?

by David Turell @, Monday, September 19, 2016, 18:17 (2747 days ago) @ David Turell

Theory is most of Earth's surface, not the core was delivered by oodles of meteorites. New problem finding is that the meteorite isotopes don't fit the surface isotopes here:-https://www.sciencedaily.com/releases/2016/09/160916110636.htm-"Planetary scientists have long believed that Earth formed from planetary objects similar to meteorites. Then, a decade ago, perplexing new measurements challenged that assumption by showing that Earth and its supposed "building blocks" actually contain significantly different isotopic compositions.-***-"'These recent measurements contribute to the growing evidence that the meteorites delivered to Earth provide an imperfect match to Earth's composition," said Richard Carlson, director of the Department of Terrestrial Magnetism at the Carnegie Institution for Science. Carlson was one of the scientists who found the compositional mismatch between meteorites and Earth 10 years ago. "This realization opens new views both to how Earth formed and to the bulk chemical composition of our home planet.'"-Abstract of the study:-A long-standing paradigm assumes that the chemical and isotopic compositions of many elements in the bulk silicate Earth are the same as in chondrites. However, the accessible Earth has a greater 142Nd/144Nd ratio than do chondrites. Because 142Nd is the decay product of the now-extinct 146Sm (which has a half-life of 103 million years), this 142Nd difference seems to require a higher-than-chondritic Sm/Nd ratio for the accessible Earth. This must have been acquired during global silicate differentiation within the first 30 million years of Solar System formation and implies the formation of a complementary 142Nd-depleted reservoir that either is hidden in the deep Earth6, or lost to space by impact erosion. Whether this complementary reservoir existed, and whether or not it has been lost from Earth, is a matter of debate, and has implications for determining the bulk composition of Earth, its heat content and structure, as well as for constraining the modes and timescales of its geodynamical evolution,. Here we show that, compared with chondrites, Earth's precursor bodies were enriched in neodymium that was produced by the slow neutron capture process (s-process) of nucleosynthesis. This s-process excess leads to higher 142Nd/144Nd ratios; after correction for this effect, the 142Nd/144Nd ratios of chondrites and the accessible Earth are indistinguishable within five parts per million. The 142Nd offset between the accessible silicate Earth and chondrites therefore reflects a higher proportion of s-process neodymium in the Earth, and not early differentiation processes. As such, our results obviate the need for hidden-reservoir or super-chondritic Earth models and imply a chondritic Sm/Nd ratio for the bulk Earth. Although chondrites formed at greater heliocentric distances and contain a different mix of presolar components than Earth, they nevertheless are suitable proxies for Earth's bulk chemical composition.-Comment: Was the Earth specially formed by a special nucleosynthesis as shown by the Neodymium isotopes? Again, how rare is the Earth, which has formed life?

Rare Earth: early Earth warm not frozen

by David Turell @, Sunday, October 09, 2016, 01:27 (2727 days ago) @ David Turell

Life started very early on Earth, and during a time when the sun was weaker it should have been frozen over, but it wasn't:-https://www.sciencedaily.com/releases/2016/10/161007090659.htm-"For at least a billion years of the distant past, planet Earth should have been frozen over but wasn't. Scientists thought they knew why, but a new modeling study from the Alternative Earths team of the NASA Astrobiology Institute has fired the lead actor in that long-accepted scenario.-"Humans worry about greenhouse gases, but between 1.8 billion and 800 million years ago, microscopic ocean dwellers really needed them. The sun was 10 to 15 percent dimmer than it is today -- too weak to warm the planet on its own. Earth required a potent mix of heat-trapping gases to keep the oceans liquid and livable.-"For decades, atmospheric scientists cast methane in the leading role. The thinking was that methane, with 34 times the heat-trapping capacity of carbon dioxide, could have reigned supreme for most of the first 3.5 billion years of Earth history, when oxygen was absent initially and little more than a whiff later on. (Nowadays oxygen is one-fifth of the air we breathe, and it destroys methane in a matter of years.)-***-"... "You can't get significant methane out of the ocean once there is sulfate."
Sulfate wasn't a factor until oxygen appeared in the atmosphere and triggered oxidative weathering of rocks on land. The breakdown of minerals such as pyrite produces sulfate, which then flows down rivers to the oceans. Less oxygen means less sulfate, but even 1 percent of the modern abundance is sufficient to kill methane, Olson said.-***-"Seawater sulfate is a problem for methane in two ways: Sulfate destroys methane directly, which limits how much of the gas can escape the oceans and accumulate in the atmosphere. Sulfate also limits the production of methane. Life can extract more energy by reducing sulfate than it can by making methane, so sulfate consumption dominates over methane production in nearly all marine environments.-The numerical model used in this study calculated sulfate reduction, methane production, and a broad array of other biogeochemical cycles in the ocean for the billion years between 1.8 billion and 800 million years ago.-***-" These papers describe geochemical signatures in the rock record that track extremely low oxygen levels in the atmosphere, perhaps much less than 1 percent of modern values, up until about 800 million years ago, when they spiked dramatically.
Less oxygen seems like a good thing for methane, since they are incompatible gases, but with oxygen at such extremely low levels, another problem arises.-"'Free oxygen [O2] in the atmosphere is required to form a protective layer of ozone [O3], which can shield methane from photochemical destruction," Reinhard said. When the researchers ran their model with the lower oxygen estimates, the ozone shield never formed, leaving the modest puffs of methane that escaped the oceans at the mercy of destructive photochemistry.-***-"With methane demoted, scientists face a serious new challenge to determine the greenhouse cocktail that explains our planet's climate and life story, including a billion years devoid of glaciers, Lyons said. Knowing the right combination other warming agents, such as water vapor, nitrous oxide, and carbon dioxide, will also help us assess habitability of the hundreds of billions of other Earth-like planets estimated to reside in our galaxy.-Comment: Methane is a product of living metabolism, a very powerful heat trapper. And in the early years all life was in the oceans, which is why this study looked at ocean methane. But this study suggests we find another reason for warmer earth while life was evolving.Seems our planet got special treatment in the atmosphere it developed. God?

Rare Earth: our core differes from others

by David Turell @, Tuesday, February 21, 2017, 15:58 (2592 days ago) @ David Turell

The Earth's core of nickel/iron differs from other cores in other bodies in the universe:

https://cosmosmagazine.com/geoscience/nickel-helps-scientists-iron-out-a-core-planetary...

"Lab experiments modelling the extreme pressure and heat of the early solar system are providing clues to why rocky planets do not have identical cores.

"The work, by Stephen Elardo and Anat Shahar of the Geophysical Laboratory at Carnegie Institution of Washington in the US, suggests that the interaction of heat, nickel and iron varies during each planet’s birth – resulting in what the researchers call a range of iron “flavours”.

"The term is used to denote the number of neutrons attached to iron atoms. While every atom has a fixed number of protons (iron has 26), neutron numbers can vary. Atoms with different numbers of neutrons are known as isotopes.

"In the early days of the solar system, planetary cores began to form, with heavier elements, notably iron, moving into the centre of the developing mass. As it did so, the iron interacted with another element, nickel, which in some circumstances stripped away certain isotopes, resulting in “lighter” flavoured atoms.

"The scientists set out to test whether the degree to which this process occurred – mediated by the temperature of the early core – could explain the isotopic differences observed between hardened lava from beneath the Earth’s surface and rock samples from the moon, Mars and an asteroid known as Vesta.

"By setting up laboratory experiments to mimic the conditions of core formations, they found that they way nickel is affected by heat was a critical factor in determining whether iron atoms were separated - or "fractionated" - according to their isotopic mass, so that heavier isotopes tended to end up in the planet’s core while lighter isotopes tended to be incorporated into the mantle, the rocky layer surrounding the core. The results are published in Nature Geoscience.

"The experiments indicated that when the moon, Mars and Vesta formed, nickel interacted vigorously with iron, resulting in high concentrations of lighter flavour isotopes being deposited in their mantles.

"The Earth, however, formed under significantly higher temperatures, which blunted nickel’s effects, greatly reducing isotope fractionation. The results explain why the core flavour of Earth has more in common with samples from primitive meteorites than with its own satellite or closest planetary neighbour."

Comment: The Earth continue to be found as very unusual compared to other plantary and other smaller bodies. Life formed here because of those characteristics. The movements of the liquid core create the Earth's magnetic field which protects life from the dangerous particles and waves that can kill life. Guided by God?

Rare Earth:possible evolution of plate tectonics

by David Turell @, Tuesday, February 28, 2017, 16:30 (2585 days ago) @ David Turell

The Earth may have started with a solid shell with plates appearing later. Plate tectonic activity is vital to the development of life:

https://www.sciencedaily.com/releases/2017/02/170227120347.htm

"Plate tectonics -- a defining feature of modern Earth and the driving force behind earthquakes, volcanoes and mid-ocean spreading ridges -- did not start until later in Earth's history, new research suggests. The work is the latest salvo in a long-standing geological debate: did plate tectonics start right away, or did Earth begin with a solid shell covering the entire planet? The new results suggest the latter.

"Today's Earth is a dynamic planet with an outer layer composed of giant plates that grind together, sliding past or dipping beneath one another, giving rise to earthquakes and volcanoes. Others separate at undersea mountain ridges, where molten rock spreads out from the centers of major ocean basins.

"But new research suggests that this was not always the case. Instead, shortly after Earth formed and began to cool, the planet's first outer layer was a single, solid but deformable shell. Later, this shell began to fold and crack more widely, giving rise to modern plate tectonics.

"Models for how the first continental crust formed generally fall into two groups: those that invoke modern-style plate tectonics and those that do not," said Michael Brown, a professor of geology at the University of Maryland and a co-author of the study. "Our research supports the latter -- a 'stagnant lid' forming the planet's outer shell early in Earth's history."

"To reach these conclusions, Brown and his colleagues from Curtin University and the Geological Survey of Western Australia studied rocks collected from the East Pilbara Terrane, a large area of ancient granitic crust located in the state of Western Australia. Rocks here are among the oldest known, ranging from 3.5 to about 2.5 billion years of age. (Earth is roughly 4.5 billion years old.) The researchers specifically selected granites with a chemical composition usually associated with volcanic arcs -- a telltale sign of plate tectonic activity.

***

"Using the Coucal basalts and Pilbara granites as a starting point, Brown and his colleagues constructed a series of modeling experiments to reflect what might have transpired in an ancient Earth without plate tectonics. Their results suggest that, indeed, the Pilbara granites could have formed from the Coucal basalts.

"More to the point, this transformation could have occurred in a pressure and temperature scenario consistent with a "stagnant lid," or a single shell covering the entire planet.

"Plate tectonics substantially affects the temperature and pressure of rocks within Earth's interior. When a slab of rock subducts under the Earth's surface, the rock starts off relatively cool and takes time to gain heat. By the time it reaches a higher temperature, the rock has also reached a significant depth, which corresponds to high pressure -- in the same way a diver experiences higher pressure at greater water depth.

"In contrast, a "stagnant lid" regime would be very hot at relatively shallow depths and low pressures. Geologists refer to this as a "high thermal gradient."

"Our results suggest the Pilbara granites were produced by melting of the Coucal basalts or similar materials in a high thermal gradient environment," Brown said. "Additionally, the composition of the Coucal basalts indicates that they, too, came from an earlier generation of source rocks. We conclude that a multi-stage process produced Earth's first continents in a 'stagnant lid' scenario before plate tectonics began.'"

Comment: As with other aspects of development, it appears God uses an evolutionary process to create an Earth suitable for life.

Rare Earth:possible evolution of plate tectonics

by dhw, Wednesday, March 01, 2017, 13:27 (2584 days ago) @ David Turell

DAVID's comment: As with other aspects of development, it appears God uses an evolutionary process to create an Earth suitable for life.

Anyone who believes in God and in evolution will agree that God used an evolutionary process to create life. And people who do not believe in God will argue that chance governs it. But I wonder how many of your fellow theists believe God created this process, could/couldn't control it, deliberately used it for the purpose of creating humans, but was forced to design every other life form extant and extinct before he could reach his goal.

Rare Earth:possible evolution of plate tectonics

by David Turell @, Wednesday, March 01, 2017, 18:33 (2584 days ago) @ dhw

DAVID's comment: As with other aspects of development, it appears God uses an evolutionary process to create an Earth suitable for life.

dhw: Anyone who believes in God and in evolution will agree that God used an evolutionary process to create life. And people who do not believe in God will argue that chance governs it. But I wonder how many of your fellow theists believe God created this process, could/couldn't control it, deliberately used it for the purpose of creating humans, but was forced to design every other life form extant and extinct before he could reach his goal.

I have my own theistic theories. I can't give you an analysis of others. Most ID folks don't believe in evolution. God allows us to be free in our suppositions since He remains hidden.

Rare Earth: our iron isotope ratios differ from others

by David Turell @, Friday, March 03, 2017, 15:02 (2582 days ago) @ David Turell

Very sophisticated analysis of light hand heavy iron isotopes on Earth finds that the ratios of heavy and light iron differ from the studies taken from other solar system bodies:

https://www.sciencedaily.com/releases/2017/02/170221110719.htm


"The research, published in Nature Communications on Feb. 20, opens the door for other competing theories about why the Earth, relative to other planets, has higher levels of heavy iron isotopes. Among them: light iron isotopes may have been vaporized into space by a large impact with another planet that formed the moon; the slow churning of the mantle as it makes and recycles the Earth's crust may preferentially incorporate heavy iron into rock; or, the composition of the raw material that formed the planet in its earliest days may have been enriched with heavy iron.

***

"Rock samples from other planetary bodies and objects -- ranging from the moon, to Mars, to ancient meteorites called chondrites -- all share about the same ratio of heavy to light iron isotopes. In comparison to these samples from space, rocks from Earth have about 0.01 percent more heavy iron isotopes than light isotopes.
That might not sound like much, but Lin said it's significant enough to make the Earth's iron composition unique among known worlds.

"'This 0.01 percent anomaly is very significant compared with, say, chondrites," Lin said. "This significant difference thus represents a different source or origin of our planet."

"Lin said that one of the most popular theories to explain the Earth's iron signature is that the relatively large size of the planet (compared with other rocky bodies in the solar system) created high pressure and high temperature conditions during core formation that made different proportions of heavy and light iron isotopes accumulate in the core and mantle. This resulted in a larger share of heavy iron isotopes bonding with elements that make up the rocky mantle, while lighter iron isotopes bonded together and with other trace metals to form the Earth's core.

"But when the research team used a diamond anvil to subject small samples of metal alloys and silicate rocks to core formation pressures, they not only found that the iron isotopes stayed put, but that the bonds between iron and other elements got stronger. Instead of breaking and rebonding with common mantle or core elements, the initial bond configuration got sturdier.

"'Our high pressure studies find that iron isotopic fractionation between silicate mantle and metal core is minimal," said Liu, the lead author.

"Lin said it will take more research to uncover the reason for the Earth's unique iron signature, and that experiments that approximate early conditions on Earth will play a key role because rocks from the core are impossible to attain."

Comment: Studies of the Earth keep coming up with findings that shows this planet is a very special place as an incubator for life. God in control?

Rare Earth: early Earth warm not frozen

by David Turell @, Wednesday, August 22, 2018, 01:06 (2046 days ago) @ David Turell
edited by David Turell, Wednesday, August 22, 2018, 01:12

The early sun was pale and the Earth was cooler, but kept warm by greenhouse gases. One wsas methane, but now N20,laughing gases, is proposed based on a large amount of iron in the oceans:

https://phys.org/news/2018-08-gas-early-earth-life.html

"More than an eon ago, the sun shone dimmer than it does today, but the Earth stayed warm due to a strong greenhouse gas effect, geoscience theory holds. Astronomer Carl Sagan coined this "the Faint Young Sun Paradox," and for decades, researchers have searched for the right balance of atmospheric gases that could have kept early Earth cozy.

"A new study led by the Georgia Institute of Technology suggests that nitrous oxide, known for its use as the dental sedative laughing gas, may have played a significant role.

"The research team carried out experiments and atmospheric computer modeling that in detail substantiated an existing hypothesis about the presence of nitrous oxide (N2O), a powerful greenhouse gas, in the ancient atmosphere. Established research has already pointed to high levels of carbon dioxide and methane, but they may not have been plentiful enough to sufficiently keep the globe warm without the help of N2O.

***

"The study focused on the middle of the Proterozoic Eon, over a billion years ago. The proliferation of complex life was still a few hundred million years out, and the pace of our planet's evolution probably appeared deceptively slow.

***

"'The ocean chemistry was completely different back then," said Glass, the study's principal investigator. "Today's oceans are well-oxygenated, so iron rapidly rusts and drops out of solution. Oxygen was low in Proterozoic oceans, so they were filled with ferrous iron, which is highly reactive."

"In lab experiments, Stanton found that Fe2+ in seawater reacts rapidly with nitrogen molecules, especially nitric oxide, to yield nitrous oxide in a process called chemodenitrification. This nitrous oxide (N2O) can then bubble up into the atmosphere.

"When Stanton plugged the higher fluxes of nitrous oxide into the atmospheric model, the results showed that nitrous oxide could have reached ten times today's levels if mid-Proterozoic oxygen concentrations were 10 percent of those today. This higher nitrous oxide would have provided an extra boost of global warming under the Faint Young Sun.

"Nitrous oxide could have also been what some ancient life breathed.

Even today, some microbes can breathe nitrous oxide when oxygen is low. There are many similarities between the enzymes that microbes use to breathe nitric and nitrous oxides and enzymes used to breathe oxygen. Previous studies have suggested that the latter evolved from the former two.

"The Georgia Tech model provides a plentiful source of nitrous oxide in ancient iron-rich seas for this evolutionary scenario. And prior to the Proterozoic, when oxygen was extremely low, early aquatic microbes could have already been breathing nitrous oxide.


"'It's quite possible that life was breathing laughing gas long before it began breathing oxygen," Glass said. "Chemodenitrification might have supplied microbes with a steady source of it.'"

Comment: It obviously took time to reach the type of atmosphere we have today, but is seems other gases were used for respiration until enough oxygen was present. Note that oxygen is very damaging, and so the organisms had to be designed with antioxidant protections.

Rare Earth: our protective magnetic field

by David Turell @, Monday, May 01, 2017, 14:32 (2523 days ago) @ David Turell

Another brief aricle on howthe magnetic field forms and protects us:

https://cosmosmagazine.com/geoscience/what-creates-earth-s-magnetic-field?utm_source=To...

"Magnetic fields around planets behave in the same way as a bar magnet. But at high temperatures, metals lose their magnetic properties. So it’s clear that Earth’s hot iron core isn’t what creates the magnetic field around our planet.

"Instead, Earth’s magnetic field is caused by a dynamo effect.

"The effect works in the same way as a dynamo light on a bicycle. Magnets in the dynamo start spinning when the bicycle is pedalled, creating an electric current. The electricity is then used to turn on the light.

"This process also works in reverse. If you have a rotating electric current, it will create a magnetic field.

"On Earth, flowing of liquid metal in the outer core of the planet generates electric currents. The rotation of Earth on its axis causes these electric currents to form a magnetic field which extends around the planet.

"The magnetic field is extremely important to sustaining life on Earth. Without it, we would be exposed to high amounts of radiation from the Sun and our atmosphere would be free to leak into space.

"This is likely what happened to the atmosphere on Mars. As Mars doesn’t have flowing liquid metal in its core, it doesn’t produce the same dynamo effect. This left the planet with a very weak magnetic field, allowing for its atmosphere to be stripped away by solar winds, leaving it uninhabitable."

Comment: Electromagnetism is the property that protects us. All part of the fine tuning that makes Earth a special planet supporting life. A planet in another solar system will have to have this same core and process to also have life.

Rare Earth: Scientific Am. discovers plate tectonics

by David Turell @, Friday, July 21, 2017, 01:34 (2442 days ago) @ David Turell

A subject well covered by three books and well exposed here is rediscovered by the magazine Scientific American:

https://www.scientificamerican.com/article/earths-tectonic-activity-may-be-crucial-for-...

Our planet is in constant flux. Tectonic plates—the large slabs of rock that divide Earth’s crust so that it looks like a cracked eggshell—jostle about in fits and starts that continuously reshape our planet—and possibly foster life.

These plates ram into one another, building mountains. They slide apart, giving birth to new oceans that can grow for hundreds of millions of years. They skim past one another, triggering earth-shattering quakes. And they slip under one another in a process called subduction, sliding deep into the planet’s innards and producing volcanoes that spew gases into the atmosphere. And not only is Earth alive, it is a vessel for life. Because it is the only known planet to host both plate tectonics—that ongoing shuffling of tectonic plates—and life, many scientists think the two might be related. In fact, some researchers argue that shifting plates, which have the ability to help regulate a planet’s temperature over billions of years, are a crucial ingredient for life.

This connection raises the tantalizing possibility that if scientists could find exoplanets that quake and rumble, they might be able to find life beyond our Pale Blue Dot.

Comment: Sci. am. worries whether exo-planets have plate tectonics. Read the wnole article if interested.

Rare Earth: Inner core puzzle

by David Turell @, Saturday, February 10, 2018, 00:59 (2238 days ago) @ David Turell

We have no good idea why the Earth's inner core became solid:

https://www.livescience.com/61715-earth-inner-core-paradox.html?utm_source=ls-newslette...

"One day, about a billion years ago, Earth's inner core had a growth spurt. The molten ball of liquid metal at the center of our planet rapidly crystallized due to lowering temperatures, growing steadily outward until it reached the roughly 760-mile (1,220 kilometers) diameter to which it's thought to extend today.

"That's the conventional story of the inner core's creation, anyway. But according to a new paper published online this week in the journal Earth and Planetary Science Letters, that story is impossible.

"In the paper, the researchers argued that the standard model of how the Earth's core formed is missing a crucial detail about how metals crystallize: a mandatory, massive drop in temperature that would be extremely difficult to achieve at core pressures.

"Weirder still, the researchers said, once you account for this missing detail the science seems to suggest that Earth's inner core shouldn't exist at all.

"Everyone, ourselves included, seemed to be missing this big problem," study author Steven Hauck, a professor of Earth, Environmental and Planetary Sciences at Case Western Reserve University in Ohio, said in a statement. Namely, they were missing "that metals don't start crystallizing instantly unless something is there that lowers the energy barrier a lot."

"In chemistry, this extra energy is known as the nucleation barrier: the point at which a compound visibly changes its thermodynamic phase. Liquid water, for example, freezes into a solid at the familiar 32 degrees Fahrenheit (0 degrees Celsius). If you've ever made ice cubes at home though, you know that even water stored at its freezing point can take several hours to fully crystallize. To speed up the process, you need to either expose the water to significantly colder temperatures (this is called "supercooling") or expose it to an already-solid piece of ice to lower the nucleation barrier, reducing the amount of cooling required.

"Supercooling is easily achieved for a single ice cube, but for Earth's gigantic inner core, things get a little trickier, the researchers said.

"At the pressures of the core, it would have to cool 1,000 degrees Kelvin [726 degrees C or 1,340 degrees F] or more below the melting temperature in order to crystallize spontaneously from pure liquid," Hauck told Live Science. "And that's a lot of cooling, especially since at the moment, the scientific community thinks the Earth cools maybe about 100 degrees K per billion years."

"According to this model, "the inner core shouldn't exist at all, because it could not have been supercooled to that extent," study author Jim Van Orman, also a professor of Earth, Environmental and Planetary Sciences at Case Western, told Live Science. The molten inner core's nucleation barrier, he said, must have lowered some other way — but how?

"In their paper, the researchers proposed one possibility: Perhaps a massive nugget of solid metal alloy dropped from the mantle and plunged into the liquid core. Like an ice cube dropped into a glass of slowly freezing water, this solid chunk of metal could have lowered the core's nucleation barrier enough to kick-start a rapid crystallization.

"There's a big caveat, though: It would have to be a truly massive chunk of metal to work.
"In order to be released into the core and then make it all the way down to the center of the Earth without dissolving … this droplet would have to be on the order of about 10 km [6.2 miles] in radius," Van Orman said. That means a diameter about the length of the island of Manhattan.

***

"'We've talked about what ideas are implausible, and we've suggested an idea that's potentially plausible," Hauck said. "If it happened that way, it's possible that some signature of that event might be detectable through seismic studies. Studying the centermost part of the planet is about the hardest to access with these waves, so it'll take time.'"

Comment: Obviously we have no idea how it became solid. We have no idea abou other planet's insides except in our solar system and we have other planets with cores, but they are not studied so far. The Earth seems more and more unusual as we study it and try to study other planets, but the Earth supports life perhaps because it is so unusual.

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