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Synestia
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Huge impact could have smashed early Earth into a doughnut shape

Many rocky worlds may have spent time as a newly named planetary form called a synestia - a loosely connected blob of molten rock and dust with a dented middle
For a brief time during its infancy, Earth was not a planet. It was a hot, doughnut-shaped blob called a synestia. Rocky worlds can be pulverised by collisions with each other, mushrooming into synestias before cooling off and becoming more familiar-looking celestial spheres, a new study says.
Worlds across the universe come in all shapes and sizes, from planetesimals to dwarf planets to giants with rings, but researchers don't fully understand the ways they can change shape and size throughout their lifetimes, says Simon Lock, a graduate student at Harvard University.

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Moon formation: New spins put on old questions

Scientists have put a new turn on the theory of how the Moon was created.
It has long been thought that the lunar body resulted from an impact between the early Earth and another planet-sized object 4.5 billion years ago.
But this theory predicts Earth and its satellite should have a quite different chemical make-up - and the data shows in fact they are very similar.

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Earth Formed from Diverse Meteorite Mix
 
Earth's building blocks were more eclectic than once thought, according to a new study suggesting our planet formed from collisions of many different types of meteorites.
Our planet is thought to have formed around 4.5 billion years ago from a disk of dust grains left over from the cloud of material that built our sun. These grains slowly clumped together, drawn by gravity into pebbles, then boulders, then planetary embryos. Eventually, enough mass coalesced to form the planet Earth.

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Earliest Stage of Planet Formation Dated

December 19, 2007
Carbonaceous chondrites are made up of globules of silica and grains of metals embedded in black, organic-rich matrix of interstellar dust. The matrix is relatively rich in the element manganese, and the globules are rich in chromium. Looking at a number of different meteorites collected on Earth, the researchers found a straight-line relationship between the ratio of the amount of manganese to that of chromium, the amount of matrix in the meteorites, and the amount of chromium-53.
These meteorites never became large enough to heat up from radioactive decay, so they have never been melted.
By measuring the amount of chromium-53, they could work out how much of the radioactive isotope manganese-53 had initially been present, giving an indication of age. They then compared the amount of manganese-53 to slightly younger igneous (molten) meteorites of known age, called angrites.
The UC Davis researchers estimate the timing of the formation of the carbonaceous chondrites at 4,568 million years ago, ranging from 910,000 years before that date to 1,170,000 years later.

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Missing chromium is clue to planet formation

Early in the formation of the Earth, some forms of the element chromium separated and disappeared deep into the planet's core, a new study by UC Davis geologists shows. The finding, to be published online by the journal Science Feb. 24, will help scientists understand the early stages of planet formation, said Qing-Zhu Yin, professor of geology at UC Davis and coauthor on the paper.
Yin, former postdoctoral scholar Frederic Moynier and Edwin Schauble of the Department and Earth and Space Sciences at UCLA used specialized equipment at UC Davis to make very exact measurements of chromium isotopes in meteorites, compared to rocks from the Earth's crust, and use modern high performance computers to simulate early Earth environment.

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Arctic rocks may contain oldest remnants of Earth

Scientists have found Arctic rocks that may preserve the earliest remnants of Earth.
Over billions of years, much of the material that made up the early Earth was modified by processes such as melting and mixing.
But the Arctic rocks seem to contain chemical signatures that date from just after the Earth's violent origin.
If confirmed, the discovery challenges established theories about the formation of our planet.

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A new geological study has set a more accurate age for planet Earth, according to scientists.
Researchers say their investigation shows the Earth is 70 million years younger than the 4.537 billion-year-old planet "we had previously imagined".

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The Earth could be younger and more than three times as long to form than was previously thought, according to a new study.

Researchers have calculated that the planet could have taken far longer to form following the birth of the solar system 4.567 billion years ago than scientists have previously believed.
By comparing chemical isotopes from the Earth's mantle with those from meteorites, geologists at the University of Cambridge claim the planet reached its current size around 4.467 billion years ago.
Scientists have in the past estimated that the Earth's development, a process known as accretion where gas, dust and other material clumped together to form the planet, happened over just 30 million years.
But the new research suggests this process may have taken up to 100 million years - more than three times.

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Fresh insight into the origins of Planet Earth

For the first time, an international team of researchers has incorporated extensive geochemical data on the formation of Earth into a model with surprising results: more models can be used for the process of Earth's accretion than previously assumed.
Earth was formed during the creation of our Solar System when Moon and Mars-sized protoplanets collided, leaving the Earth to gradually "grow"; just how long it took for the Earth to reach its eventual size and what the accretion of the planet was like, however, is much disputed among the experts.

"The latest models reveal that an accretion period of around 100 million years is the most consistent with the formation of the Moon and the Earth" - Bernard Bourdon, a professor from the Institute of Geochemistry and Petrology at ETH Zurich.

However, there are also models that clearly suggest the Earth reached 70% of its size in just 10 million years.

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Silver Tells a Story of Early Earth: Water Here Since Planet's Very Early Days

Tiny variations in the isotopic composition of silver in meteorites and Earth rocks are helping scientists put together a timetable of how our planet was assembled, beginning 4.568 billion years ago.
Results of a new study, funded by the National Science Foundation (NSF) and published this week in the journal Science, indicate that water and other key volatiles may have been present in at least some of Earth's original building blocks, rather than acquired later from comets, as some scientists have suggested.

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