Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


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


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:

More articles from Earth Sciences:

nachricht Gas hydrate research: Advanced knowledge and new technologies
23.03.2018 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

nachricht New technologies and computing power to help strengthen population data
22.03.2018 | University of Southampton

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Space observation with radar to secure Germany's space infrastructure

Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.

The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

New solar solutions for sustainable buildings and cities

23.03.2018 | Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

Latest News

For graphite pellets, just add elbow grease

23.03.2018 | Materials Sciences

Unique communication strategy discovered in stem cell pathway controlling plant growth

23.03.2018 | Agricultural and Forestry Science

Sharpening the X-ray view of the nanocosm

23.03.2018 | Physics and Astronomy

Science & Research
Overview of more VideoLinks >>>