Revising Earth's Early History

Carnegie Institution ^ | 2005-12-30 | NA

[neverdem]

Earth's future was determined at birth. Using refined techniques to study rocks, researchers at the Carnegie Institution's Department of Terrestrial Magnetism (DTM) found that Earth's mantle--the layer between the core and the crust--separated into chemically distinct layers faster and earlier than previously believed. The layering happened within 30 million years of the solar system's formation, instead of occurring gradually over more than 4 billion years, as the standard model suggests. The new work was recognized by Science magazine, in its December 23 issue, as one of the science breakthroughs for 2005.

Carnegie scientists Maud Boyet and Richard Carlson analyzed isotopes--atoms of an element with the same number of protons, but a different number of neutrons--of elements in rock samples for their work. As Carlson explains, "Isotopes exist naturally in different proportions and are used to determine conditions under which rock forms. Radioactive isotopes are particularly handy because they decay at a predictable rate and can reveal a sample's age and when its chemical composition was established."

In the standard model of the geochemical evolution of the Earth, the Earth's mantle has been evolving gradually over Earth's 4.567-billion-year history primarily through the formation of the chemically distinct continental crust. Shortly after solid material began condensing from the hot gas of the cooling early solar system, the object that would become Earth grew by the collision and accretion of smaller rocky bodies. The chemical composition of these building blocks is preserved today in primitive meteorites called chondrites.

In the 1980s, scientists analyzed the ratio of isotopes of the rare earth element neodymium in chondrites and various terrestrial rocks collected at or near the Earth's surface and found that the samples shared a common composition. Researchers believed that this ratio remained constant from the beginning of Earth formation. Using new-generation equipment, Boyet and Carlson found, surprisingly, that the terrestrial samples did not have the same ratio as the meteorites. Compared to chondrites, all terrestrial rocks measured have an excess of the mass 142 isotope of neodymium (142Nd), which is the decay product of a now-extinct radioactive isotope of samarium of mass 146 (146Sm) that was present at the birth of the solar system but decayed away shortly thereafter. The excess in 142Nd allowed the researchers to determine when the composition of the Earth diverged from that of the meteorites--within the first 30 million years after solar system formation, which is less than 1% of the age of our planet.

To explain the excess of 142Nd found in the terrestrial samples, the Carnegie scientists believe that the Earth was largely molten during its formation and that rapid crystallization of Earth's early magma ocean caused the mantle to separate into chemically distinct layers, one containing a high ratio of Sm to Nd similar to that observed today in the mantle source of the volcanism along ocean ridges. The complementary reservoir, with low 142Nd abundance, has never been sampled at the surface and hence could now be deeply buried in the so-called D" layer at the very base of the mantle, above the core. This "missing" layer should be rich in the elements uranium, thorium, and potassium, whose long-lived radioactive decay heats Earth's interior and causes our planet to remain geologically active. This hot layer above the core could help to keep the outer core molten so that circulation of liquid iron can produce Earth's magnetic field, and it could instigate the hot plumes of upwelling mantle material that give rise to volcanically active islands, such as Hawaii.

Measurements by Boyet and Carlson also show that lunar rocks have the same abundance of 142Nd as the terrestrial samples, a finding that adds to the evidence that the Moon formed from the Earth. Since Mars also experienced early melting, as indicated by the chemical and isotopic composition of Martian meteorites, the new results now link the early evolution of Earth, Moon, and Mars and highlights the importance of early events in determining the chemical characteristics of the terrestrial planets.

"The work of Boyet and Carlson, when added to what has already been determined for the Moon and Mars, shows that the earliest days of the inner planets were violent times in solar system history," adds DTM director Sean Solomon. "Theoretical work by Carnegie scientist George Wetherill had pointed to this result, but now we have a clear chemical signature of this episode of Earth history."

[neverdem]

The Boyet and Carlson result requires the Earth to have differentiated early, within 30 million years, leaving most of Earth's mantle (light blue) depleted in those elements that prefer melts over crystallizing solids. The chemical complement to the depleted mantle could be small and quite enriched in radioactive elements, such as uranium and thorium; this complementary material may coincide with the seismically observed D" layer, located between the core and the mantle some 2700 km deep. (Images courtesy Maud Boyet)

[Fiddlstix]

BTTT

[Mamzelle]

You know, between 30M and 4B -- pretty soon you're talking about real time.

[beyond the sea]

Earth's future was determined at birth.

Lost on the first absurd sentence.

Birth? I.D............ B.B. .............. what?

[beyond the sea]

Earth's future was determined at birth.

Thank God there was no Planned Parenthood then.

[CarrotAndStick]

I didn't see it as between 4 billion and 30 million. More like between 4 billion and (4 billion minus 30 million). Isn't that how the article puts it?

[Thinkin' Gal]

The layering happened within 30 million years of the solar system's formation, instead of occurring gradually over more than 4 billion years, as the standard model suggests.

[RunningWolf]

I am very interested in these subjects. Thank you for the article.

Wolf

[aliquando]

I am truly thankful that G_d gave us the ability to figure this stuff out. I love science and do believe that what we learn is what G_d wants us to learn. Look at all that we have gleaned from human embryology over the past 30 years. I just love the way G_d makes things very clear for us when we are ready to see them. Look at quantum mechanics, anything that make complicated physics that neat and simple is truly a gift from above!

[LiteKeeper]

YEC INTREP

[dread78645]

Archive?

[Thinkin' Gal]

Using new-generation equipment, Boyet and Carlson found, surprisingly, that the terrestrial samples did not have the same ratio as the meteorites. Compared to chondrites, all terrestrial rocks measured have an excess of the mass 142 isotope of neodymium (142Nd), which is the decay product of a now-extinct radioactive isotope of samarium of mass 146 (146Sm) that was present at the birth of the solar system but decayed away shortly thereafter.

Main Entry: sa·mar·i·um
Pronunciation: s&-'mer-E-&m, -'mar-
Function: noun
Etymology: New Latin, from French samarskite
: a pale gray lustrous metallic element used especially in alloys that form permanent magnets -- see ELEMENT table

And now for something completely different:

Main Entry: sa·mar·i·um
Pronunciation: s&-'mer-E-&m, -'mar-
Function: noun
Etymology: New Latin, from French samarskite
: a pale gray lustrous metallic element used especially in alloys that form permanent magnets -- see ELEMENT table

###

28 October 1878: Delafontaine reports another new metal found in samarskite from North Carolina, this time he gave this element the name Decipium, after the Latin "decipiens", which means "deceptive, misleading" (note). According to Delafontaine, samarskite contains the earths yttria, erbia, terbia, philippia, decipia, thoria, didymia, and ceria.

16 August 1880: after spectroscopical analysis, Soret found that Decipium was identical with Lecoq's Samarium (note). Later was shown that Decipium was a mixture of Samarium and other rare-earth elements, mainly Neodymium and Praseodymium.

28 July 1879: François Lecoq de Boisbaudran (1838-1912) analyzed samarskite and noted that another earth precipitated before Didymia when ammonium hydroxide was added. Spectral analysis showed two new blue lines, differend from the lines of Decipium. Lecoq called the new earth Samaria after its mineral source. The name for the element within became Samarium. (note). To Vasilij Evgrafovic Samarskij-Byhovec, a rather unknown person, went the honour of being the first individual to give his name to a chemical element.

Despite the suggested chemical symbol of Sm, until the 1920s often Sa was used (note). Later was shown that Lecoq's Samarium was a mixture of Samarium and Europium. Eugène-Anatole Demarçay (1852-1904) separated it in 1901.

19 April 1880: Marignac reports that he has separated two new earths from samarskite. He indicated them provisionally with Ya and Yß (note).

16 August 1880: after spectroscopical analysis, Soret found that Yß was identical with Samarium (note). In 1886 Lecoq de Boisbaudran produced a more pure form of Ya and named it Gadolinium.

Via spectroscopical analysis Sir William Crookes described in 1886 an element Sd, which later proved to be Samarium.

http://www.vanderkrogt.net/elements/elem/sm.html

Basic information:

http://www.chemicalelements.com/elements/sm.html

The symbols one finds in the oddest places. Wonder how it's spelled in Hebrew...

http://www.vanderkrogt.net/elements/lang/hebrew_num(w1255).html

samech, mem, resh, yud, vav, mem
60 + 40 + 200 + 10 + 6 + 40 = 356

Compare:

alef, mem, resh, yud, quf, hei

1 + 40 + 200 + 10 + 100 + 5 = 356

[Mamzelle]

Well, that's not how I take it from what is written. It looks like the article is disputing the older figure.

[Mamzelle]

Could possibly be significant, no? This younger figure could throw a real monkeywrench into a lot of assumptions.

[UnbelievingScumOnTheOtherSide]

The layering happened within 30 million years of the solar system's formation, instead of occurring gradually over more than 4 billion years, as the standard model suggests.

And then again, maybe it was only 6000 years? ;-)

[Havoc]

Tolkien built his mythology pretty much alone. Apparently, vast fictions are still possible, but people don't seem smart enough to create them on their own anymore. It takes vast numbers of people to write broad fictions nowdays. The more stupid the fiction, the more likely it will be called "science" apparently. If it's good fiction, it might make it to the best seller list and maybe even have the name of a single mind attached to it - like Stephen King... Now I'll shut up and let the liberals present take on the parlance of the anti-McCarthy mob. Perhaps once they're done being emotional and irrational, we can imagine why we should bother accepting assumptions as "reasonable" when there is no basis for analyzing how "reasonable" the assumptions are.
Next year, the earth will be nearly 5billion years old - assuming we accept assumptions. lol

[Senator Bedfellow]

Ladies and gents, the polls are now open in the cast-your-vote-for-the-silliest-argument contest. Which argument here is sillier?

A) The person railing about those darned "assumptions" without bothering to do anything so mundane as name any of those assumptions or explain why they are unwarranted, or;

B) the person who thinks this article means that the age of the earth is being revised downward to 30 million years - after all, if you're six feet tall, and it took you about 14 years to grow to your present height of six feet, you must be about 14 years old.

Cast your votes now!

[neverdem]

Tolkien built his mythology pretty much alone.

Mythology and science fiction never caught my fancy. Maud Boyet and Richard Carlson have staked their reputations on their conclusions. Their reputations and their conclusions will be upheld or refuted by the scientific method alone.

IMHO, the recent exposure of fraud with stem cells is instructive. Fraud in science does not withstand scrutiny. Time will tell if it works or not. Faith in the Creator has nothing to do with it. Happy New Year!

[metmom]

read later placemarker

[Havoc]

Fraud in science does not withstand scrutiny.

When fraud withstands scrutiny, none dare call it fraud.. Say for instance - if a group of people decide they like an ideology enough to call it "science"... The response to people calling the bluff might look something like early Democrats going after Joe McCarthy.. Hmm.