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View Full Version : Finding Supports Moon Creation Hypothesis



Swift
2016-Sep-27, 02:37 PM
From Laboratory Equipment magazine (http://www.laboratoryequipment.com/news/2016/09/finding-supports-moon-creation-hypothesis?et_cid=5581351&et_rid=54636800&location=top&et_cid=5581351&et_rid=54636800&linkid=http%3a%2f%2fwww.laboratoryequipment.com%2f news%2f2016%2f09%2ffinding-supports-moon-creation-hypothesis%3fet_cid%3d5581351%26et_rid%3d%%subscri berid%%%26location%3dtop)


New research led by Johns Hopkins University scientists argues that a layer of iron and other elements deep under ground is the evidence scientists have long been seeking to support the hypothesis that the moon was formed by a planetary object hitting the infant Earth some 4.5 billion years ago.

Published in the current issue of Nature Geoscience, the paper uses laboratory simulations of an Earth impact as evidence that a stratified layer beneath the rocky mantle – which appears in seismic data — was created when the Earth was struck by a smaller object. The authors argue this was the same impact that sent a great mass of debris hurtling into space, creating the moon.


Their argument is based on seismic evidence of the composition of the stratified layer — believed to be some 200 miles thick and lie 1,800 miles below the Earth’s surface — and on laboratory experiments simulating the turbulence of the impact. The turbulence in particular is believed to account for the stratification – meaning a mix of materials in layers rather than a homogeneous composition – at the top of the core.

The stratified layer is believed to consist of a mix of iron and lighter elements, including oxygen, sulfur and silicon. The very existence of this layer is understood from seismic imaging, as it lies far too deep under ground to be sampled directly.

Up to now, most simulations of the impact have been done numerically, and have not accounted for impact turbulence, Olson said. Olson said turbulence is difficult to simulate mathematically and no computer model has yet done it successfully.

The researchers in this experiment simulated the impact using liquids meant to approximate the turbulent mixing of materials that would have occurred when the planetary object struck when the Earth was just about fully formed – a “proto-Earth,” as scientists call it.


Link to Nature Geoscience (http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2808.html)


A stratified layer below the core–mantle boundary has long been suspected on the basis of geomagnetic and seismic observations 1, 2, 3. It has been suggested that the outermost core has a stratified layer about 100 km thick 3, 4, 5, 6 that could be due to the diffusion of light elements 7, 8. Recent seismological evidence, however, supports a layer exceeding 300 km in thickness of enigmatic origin 9, 10, 11. Here we show from turbulent mixing experiments that merging between projectile and planetary core following a giant impact can lead to a stratified layer at the top of the core. Scaling relationships between post-impact core structure and projectile properties suggest that merging between Earth’s protocore and a projectile core that is enriched in light elements and 20 times less massive can produce the thick stratification inferred from seismic data. Our experiments favour Moon-forming impact scenarios involving a projectile smaller than the proto-Earth 12, 13 and suggest that entrainment of mantle silicates into the protocore led to metal–silicate equilibration under extreme pressure–temperature conditions. We conclude that the thick stratified layer detected at the top of Earth’s core 9, 10 can be explained as a vestige of the Moon-forming giant impact during the late stages of planetary accretion.

geonuc
2016-Sep-27, 09:54 PM
Science in action - a good example of how hypotheses are validated using observations of many different things to form a complete picture.

John Mendenhall
2016-Sep-27, 10:58 PM
Science in action - a good example of how hypotheses are validated using observations of many different things to form a complete picture.

Yes, very nice work. And thanks to Swift for posting.