evidence suggests impacts made rare earth

evidence suggests impacts made rare earth

Postby John Galt » Tue Jul 28, 2015 11:07 pm

i thought this was interesting

http://arstechnica.com/science/2015/07/ ... -material/

It’s generally thought that the Earth was built out of asteroids called ordinary chondrites. Chondrites contain some of the most ancient minerals in the Solar System, and their composition suggests that they made up the majority of the material that collapsed to form our planet.

But recent observations have shown that the composition of the Earth’s mantle doesn’t match that of ordinary chondrites, suggesting that something else is going on. If the Earth was indeed formed from chondrites, that material must have separated into two different reservoirs, one of which we haven't identified.

Specifically, the Earth’s mantle has a lower ratio of neodymium-142 to -144 than ordinary chondrites. That means that at some point during the Earth’s formation, the chondrites that formed the planet must have differentiated into higher- and lower-ratio clumps (just as mud, stirred into a cup of water, differentiates with the densest concentration of mud ending up on the bottom). Since this requires the Earth to have been very hot, it would have happened within the first 20 million to 30 million years of the planet’s initial accretion.

In a new paper, researchers argue that the missing material, rather than differentiating and sinking deeper into the Earth, could have instead been lost to space during impact events. If so, it makes predictions for the thermal history of the Earth that conflict with current estimates. That’s because the radioactive elements inside the Earth produce heat, and much of this radioactive material would have been lost to space as part of the missing reservoir. The presence, or absence, of this radioactive material would make a big difference to the Earth, the researchers argue. Among other things, the planet’s plate tectonics would be noticeably affected, as would the planet’s habitability.


basically this is arguing that early impacts removed some radiation from earth. mars had too much removed, venus, not enough, earth, just right. it could help explain why mars' internal dynamo ran out of juice and why its atmosphere is stripped away as a result, and why venus is so inhospitable. if true, that would mean our existence was predicated on impacts happening just right beyond the coalescing of the planet billions of years ago. if true, i think, this lowers expectations of life found elsewhere. not that it wouldn't exist, of course it does, but i think higher forms of intelligence would be rare and this would make it rarer still

http://www.nature.com/articles/ngeo2488 ... chnica.com
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Re: evidence suggests impacts made rare earth

Postby Medius » Tue Jul 28, 2015 11:30 pm

John Galt wrote:i thought this was interesting

http://arstechnica.com/science/2015/07/ ... -material/

It’s generally thought that the Earth was built out of asteroids called ordinary chondrites. Chondrites contain some of the most ancient minerals in the Solar System, and their composition suggests that they made up the majority of the material that collapsed to form our planet.

But recent observations have shown that the composition of the Earth’s mantle doesn’t match that of ordinary chondrites, suggesting that something else is going on. If the Earth was indeed formed from chondrites, that material must have separated into two different reservoirs, one of which we haven't identified.

Specifically, the Earth’s mantle has a lower ratio of neodymium-142 to -144 than ordinary chondrites. That means that at some point during the Earth’s formation, the chondrites that formed the planet must have differentiated into higher- and lower-ratio clumps (just as mud, stirred into a cup of water, differentiates with the densest concentration of mud ending up on the bottom). Since this requires the Earth to have been very hot, it would have happened within the first 20 million to 30 million years of the planet’s initial accretion.

In a new paper, researchers argue that the missing material, rather than differentiating and sinking deeper into the Earth, could have instead been lost to space during impact events. If so, it makes predictions for the thermal history of the Earth that conflict with current estimates. That’s because the radioactive elements inside the Earth produce heat, and much of this radioactive material would have been lost to space as part of the missing reservoir. The presence, or absence, of this radioactive material would make a big difference to the Earth, the researchers argue. Among other things, the planet’s plate tectonics would be noticeably affected, as would the planet’s habitability.


basically this is arguing that early impacts removed some radiation from earth. mars had too much removed, venus, not enough, earth, just right. it could help explain why mars' internal dynamo ran out of juice and why its atmosphere is stripped away as a result, and why venus is so inhospitable. if true, that would mean our existence was predicated on impacts happening just right beyond the coalescing of the planet billions of years ago. if true, i think, this lowers expectations of life found elsewhere. not that it wouldn't exist, of course it does, but i think higher forms of intelligence would be rare and this would make it rarer still

http://www.nature.com/articles/ngeo2488 ... chnica.com


I may be reading it wrong, but it seems to indicate that this tipped earth towards more habitable, not that it was necessary to be habitable. It may mean we aren't quite in the sweet spot, but it doesn't mean there isn't a sweet spot.

Just a minor point as I do think that life and intelligent life is likely to be very rare at any given point anyway, just due to the vastness of space and time and the fragile nature of life and particularly advanced life.
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Re: evidence suggests impacts made rare earth

Postby Spider » Wed Jul 29, 2015 1:31 am

Seems fairly subjective. More or less radioactive material could be more or less beneficial on a case by case basis...but at least in Earth's case the potential effects on the Dynamo effect...pretty awesome findings.

Too bad it's $175 to subscribe and read the thing. :))
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Re: evidence suggests impacts made rare earth

Postby exploited » Wed Jul 29, 2015 8:01 am

Spider wrote:Seems fairly subjective. More or less radioactive material could be more or less beneficial on a case by case basis...but at least in Earth's case the potential effects on the Dynamo effect...pretty awesome findings.

Too bad it's $175 to subscribe and read the thing. :))


You should drive to your local university, sign onto their WiFi, access the article, and post it elsewhere for us to read.
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Re: evidence suggests impacts made rare earth

Postby eynon81 » Wed Jul 29, 2015 8:09 am

Thanks Jesus!

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