Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Like ozone hole, polar clouds take bite out of meteoric iron

16.04.2004


Polar clouds are known to play a major role in the destruction of Earth’s protective ozone layer, creating the springtime “ozone hole” above Antarctica. Now, scientists have found that polar clouds also play a significant role in removing meteoric iron from Earth’s mesosphere. The discovery could help researchers refine their models of atmospheric chemistry and global warming.



Using a sensitive laser radar (lidar) system, laboratory experiments and computer modeling, researchers from the University of Illinois at Urbana-Champaign and the University of East Anglia in Norwich, England, studied the removal of meteoric iron by polar mesospheric clouds that they observed during the summer at the South Pole.

“Our measurements and models have shown that another type of reaction that takes place in the upper atmosphere – this time related to ice particles – plays a very important role in the processes that influence the chemistry of metal layers in this region,” said Chester Gardner, a professor of electrical and computer engineering at Illinois and one of the co-authors of a paper to appear in the April 16 issue of the journal Science.


First deployed over Okinawa, Japan, to observe meteor trails during the 1998 Leonid meteor shower, the Illinois lidar system uses two powerful lasers operating in the near ultraviolet region of the spectrum and two telescopes to detect laser pulses reflected from the atmosphere. The system was moved to the Amundsen-Scott South Pole Station in late 1999.

“Simultaneous observations of the iron layer and the clouds revealed nearly complete removal of iron atoms inside the clouds,” Gardner said. “Laboratory experiments and atmospheric modeling done by our colleagues at the University of East Anglia then showed that this phenomenon could be explained by the efficient uptake of iron on the surfaces of ice crystals.”

Polar mesospheric clouds are the highest on Earth, forming at an altitude of about 52 miles. The clouds form over the summertime polar caps when temperatures fall below minus 125 degrees Celsius, and overlap a layer of iron atoms produced by the ablation of meteoroids entering the atmosphere.

“At such cold temperatures, the iron atoms stick when they bump into the ice crystals,” Gardner said. “If the removal of iron is rapid compared to both the input of fresh meteoric ablation and the vertical transport of iron into the clouds, a local depletion or ‘bite-out’ in the iron layer will result.”

To examine whether the observed bite-outs could be fully explained by the removal of iron atoms by ice particles, John Plane, a professor of environmental sciences at East Anglia, and graduate student Benjamin Murray measured the rate of iron uptake on ice.

In their laboratory, Plane and Murray first deposited a layer of ice on the inside of a flow tube. Iron atoms were then generated by laser ablation of an iron target at one end of the tube. At the other end, a second laser measured how much iron made it through the tube.

“By changing the temperature in the tube, we could compare how much iron was absorbed by the ice and calculate the sticking coefficient,” Plane said. “Once we knew how efficiently the iron atoms stick to the ice, our next question was whether there was enough ice surface in the polar clouds to deplete the iron and cause the dramatic bite-outs revealed in the lidar observations.”

The researchers answered this question by carefully modeling the size distribution of ice particles as a function of altitude. They concluded there was sufficient surface area to remove the iron.

“Our results clearly demonstrate the importance of ice particles in the chemistry of this region of the atmosphere,” Gardner said. “Not too many years ago we learned how important polar stratospheric clouds were to the chemistry of the ozone layer. Now we are seeing something very similar happening at higher altitudes.”

In addition to Gardner, Plane and Murray, the team included research scientist Xinzhao Chu from the University of Illinois who made the measurements at the South Pole.

The National Science Foundation, the Royal Society and the Natural Environmental Research Council funded the work.

James E. Kloeppel | UIUC
Further information:
http://www.news.uiuc.edu/news/04/0415meteoriciron.html

More articles from Earth Sciences:

nachricht NASA eyes Pineapple Express soaking California
24.02.2017 | NASA/Goddard Space Flight Center

nachricht 'Quartz' crystals at the Earth's core power its magnetic field
23.02.2017 | Tokyo Institute of Technology

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Stingless bees have their nests protected by soldiers

24.02.2017 | Life Sciences

New risk factors for anxiety disorders

24.02.2017 | Life Sciences

MWC 2017: 5G Capital Berlin

24.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>