Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Superglue of planet formation: Sticky ice

09.03.2005


Pacific Northwest National Lab experiments point to clingy grains of ice to solve age-old mystery of how primordial dust pulled together to form planets



How dust specks in the early solar systems came together to become planets has vexed astronomers for years. Gravity, always an attractive candidate to explain how celestial matter pulls together, was no match for stellar winds. The dust needed help coming together fast, in kilometer-wide protoplanets, in the first few million years after a star was born, or the stellar wind would blow it all away.

Scientists at the Department of Energy’s Pacific Northwest National Laboratory, reporting in the current issue of Astrophysical Journal, offer a cool answer to the planet- formation riddle: Micron-wide dust particles encrusted with molecularly gluey ice enabled planets to bulk up like dirty snowballs quickly enough to overcome the scattering force of solar winds. "People who had calculated the stickiness of dust grains found that the grains didn’t stick," said James Cowin, PNNL lab fellow who led the research. "They bounce, like two billiard balls smacked together. The attraction just wasn’t strong enough."


Cowin’s team has spent years studying, among other things, the chemical and physical properties atmospheric dust and water ice, using an array of instruments suited to the task at the PNNL-based W.R. Wiley Environmental Molecular Sciences Laboratory.

Much of the pre-planetary dust grains were either covered by or largely composed of water ice, having condensed at temperatures close to absolute zero, at 5 to 100 Kelvin. Evidence of this icy solar system can be seen in comets, and planets and moons a Jupiter’s distance from its star and beyond are icy. "This ice is very different from the stuff we chip off our windows in winter," Cowin said. "For example, we saw that at extreme cold temperatures vapor-deposited ice spontaneously becomes electrically polarized. This makes electric forces that could stick icy grains together like little bar magnets."

PNNL staff scientist Martin Iedema, a member of Cowin’s group with an astronomy undergraduate degree, surveyed the astrophysics literature and found that the planet growth mystery resided in the same cold temperatures of the lab ices.

Iedema found that the high background radiation in the early solar system would have neutralized a polarized, micron-sized ice grain in days to weeks--or hundreds of thousands of years before it could accrete a critical mass of material and grow to the size of a medicine ball, enabling it to get over the critical size hurdle in planet formation.

But, Iedema said, ice grains colliding into each other would have chipped and broken in two to upset electrical equilibrium and, in essence, recharging the ice grains and restoring their clinginess. Then he discovered an additional feature that gave the sticky ice theory a new bounce. "More of an anti-bounce," Cowin emended, "from the cushioning, or fluffiness, of this ice. The more technical phrase is ’mechanical inelasticity.’ We knew that ice, when grown so cold, isn’t able to arrange its molecules in a well-ordered fashion; it becomes fluffy on a molecular scale."

Cowin conjured an image of "billiard balls made of Rice Krispies." Such balls would barely bounce. "Colliding fluffy ice grains would have enough residual electrical forces to make them stick, and survive subsequent collisions to grow into large lumps."

To test this, PNNL postdocs Rich Bell and Hanfu Wang grew ice from the vapor in a chamber that reproduced primordial temperatures and vacuum. They measured bounce by dropping hard, 1/16th- inch hard ceramic balls on it. With a high-speed camera, they observed the balls consistently rebound about 8 percent of their dropped height from fluffy ice grown at 40 Kelvin, whereas on the hard, warmer and much more compact ice that forms naturally on Earth, the ice rebound was as high as 80 percent.

"This huge inelasticity provides an ideal way for fluffy icy grains to stick and grow eventually to protoplanets," Cowin said. Cowin and colleagues further speculate that similar electrical forces, minus the fluffy cushioning, were at work during the infancy of hotter inner planets like Earth, involving silicate dust grains instead of ice.

Bill Cannon | EurekAlert!
Further information:
http://www.pnl.gov

More articles from Physics and Astronomy:

nachricht NASA spacecraft investigate clues in radiation belts
28.03.2017 | NASA/Goddard Space Flight Center

nachricht Researchers create artificial materials atom-by-atom
28.03.2017 | Aalto University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Transport of molecular motors into cilia

28.03.2017 | Life Sciences

A novel hybrid UAV that may change the way people operate drones

28.03.2017 | Information Technology

NASA spacecraft investigate clues in radiation belts

28.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>