. 24/7 Space News .
EARLY EARTH
Trickle-down is the solution to the planetary core formation problem
by Staff Writers
Austin TX (SPX) Dec 05, 2017


New research from The University of Texas at Austin adds evidence to a theory that claims the metallic cores of rocky planets like Earth were formed when molten metal trapped between grains of silicate rock percolated to the center of the planet during its early formation.

Scientists have long pondered how rocky bodies in the solar system - including our own Earth - got their metal cores. According to research conducted by The University of Texas at Austin, evidence points to the downwards percolation of molten metal toward the center of the planet through tiny channels between grains of rock.

The finding calls into question the interpretation of prior experiments and simulations that sought to understand how metals behave under intense heat and pressure when planets are forming. Past results suggested that large portions of molten metals stayed trapped in isolated pores between the grains.

In contrast, the new research suggests that once those isolated pores grow large enough to connect, the molten metal starts to flow, and most of it is able to percolate along grain boundaries. This process would let metal trickle down through the mantle, accumulate in the center, and form a metal core, like the iron core at the heart of our home planet.

"What we're saying is that once the melt network becomes connected, it stays connected until almost all of the metal is in the core," said co-author Marc Hesse, an associate professor in the UT Jackson School of Geosciences Department of Geological Sciences, and a member of UT's Institute for Computational Engineering and Sciences.

The research was published on Dec. 4 in the Proceedings of the National Academy of Sciences. The work was the doctoral thesis of Soheil Ghanbarzadeh, who earned his Ph.D. while a student in the UT Department of Petroleum and Geosystems Engineering (now the Hildebrand Department of Petroleum and Geosystems Engineering). He currently works as a reservoir engineer with BP America. Soheil was jointly advised by Hesse and Masa Prodanovic, an associate professor in the Hildebrand Department and a co-author.

Planets and planetesimals (small planets and large asteroids) are formed primarily from silicate rocks and metal. Part of the planet formation process involves the initial mass of material separating into a metallic core and a silicate shell made up of the mantle and the crust. For the percolation theory of core formation to work, the vast majority of metal in the planetary body must make its way to the center.

In this study, Ghanbarzadeh developed a computer model to simulate the distribution of molten iron between rock grains as porosity, or melt fraction, increased or decreased. The simulations were perfomed at the Texas Advanced Computing Center. Researchers found that once the metal starts to flow, it can continue flowing even as the melt fraction decreases significantly. This is in contrast to previous simulations that found that once the metal starts flowing, it only takes a small dip in the volume of melt for percolation to stop.

"People have assumed that you disconnect at the same melt fraction at which you initially connected...and it would leave significant amounts of the metal behind," Hesse said. "What we found is that when the metallic melt connects and when it disconnects is not necessarily the same."

According to the computer model, only 1 to 2 percent of the initial metal would be trapped in the silicate mantle when percolation stops, which is consistent with the amount of metal in the Earth's mantle.

The researchers point to the arrangement of the rock grains to explain the differences in how well-connected the spaces between the grains are. Previous work used a geometric pattern of regular, identical grains, while this work relied on simulations using an irregular grain geometry, which is thought to more closely mirror real-life conditions. The geometry was generated using data from a polycrystalline titanium sample that was scanned using X-ray microtomography.

"The numerical model Soheil developed in his Ph.D. thesis allowed for finding three-dimensional melt networks of any geometrical complexity for the first time," said Prodanovic. "Having a three-dimensional model is key in understanding and quantifying how melt trapping works."

The effort paid off because researchers found that the geometry has a strong effect on melt connectivity. In the irregular grains, the melt channels vary in width, and the larges ones remain connected even as most of the metal drains away.

"What we did differently in here was to add the element of curiosity to see what happens when you drain the melt from the porous, ductile rock," said Ghanbarzadeh.

The researchers also compared their results to a metallic melt network preserved in an anchondrite meteorite, a type of meteorite that came from a planetary body that differentiated into discernable layers. X-ray images of the meteorite taken in the Jackson School's High-Resolution X-Ray CT Facility revealed a metal distribution that is comparable to the computed melt networks. Prodanovic said that this comparison shows that their simulation capture the features observed in the meteorite.

EARLY EARTH
Feathered dinosaurs were extra fluffy, new research shows
Washington (UPI) Nov 30, 2017
New analysis of the remains of a bird-like dinosaur called Anchiornis suggests feathered dinosaurs were fluffier than researchers thought. Modern birds are the evolutionary offspring of a group of feathered theropod dinosaurs. Together they comprise the group known as paravians - a group that included the famed Velociraptor. The fossilized remains of an Anchiornis specimen offer ... read more

Related Links
University of Texas at Austin
Explore The Early Earth at TerraDaily.com


Thanks for being there;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Monthly Supporter
$5+ Billed Monthly


paypal only
SpaceDaily Contributor
$5 Billed Once


credit card or paypal


Comment using your Disqus, Facebook, Google or Twitter login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

EARLY EARTH
Building for a future in space: An interview with Dava Newman and Gui Trotti

Space Farms: 'Mark Watney in The Martian Was Right to Add Poop to the Soil'

NASA successfully fires Voyager 1 thrusters after 37 years

Does the Outer Space Treaty at 50 need a rethink

EARLY EARTH
ISRO eyes one rocket launch a month in 2018

Russia to build launch pad for super heavy-lift carrier by 2028

Flat-Earther's self-launch plan hits a snag

Mechanisms are critical to all space vehicles

EARLY EARTH
EU exempts fuel for ExoMars mission from Russian sanctions

Winter wanderings put Opportunity at 28 Miles on the odometer

Earthworms can reproduce in Mars-like soil

Opportunity Greets Winter Solstice

EARLY EARTH
Nation 'leads world' in remote sensing technology

China plans for nuclear-powered interplanetary capacity by 2040

China plans first sea based launch by 2018

China's reusable spacecraft to be launched in 2020

EARLY EARTH
Going green to the Red Planet

Orbital ATK purchase by Northrop Grumman approved by shareholders

UK space launch program receives funding boost from Westminster

Need to double number of operational satellites: ISRO chief

EARLY EARTH
New catalyst controls activation of a carbon-hydrogen bond

New 3-D printer is 10 times faster than commercial counterparts

Device could reduce the carbon footprint of ethylene production

Researchers inadvertently boost surface area of nickel nanoparticles for catalysis

EARLY EARTH
Scientists identify key factors that help microbes thrive in harsh environments

Exoplanet Has Smothering Stratosphere Without Water

Scientists study Earth's earliest life forms in Nevada hot spring

The answer to planetary habitability is blowing in the stellar wind

EARLY EARTH
Jupiter Blues

Pluto's hydrocarbon haze keeps dwarf planet colder than expected

Jupiter's Stunning Southern Hemisphere

Watching Jupiter's multiple pulsating X-ray Aurora









The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.