Dust from asteroids entering the atmosphere may influence Earth’s weather more than previously believed, researchers have found.

In a study to be published this week in the journal Nature, scientists from the Australian Antarctic Division, the University of Western Ontario, the Aerospace Corporation, and Sandia and Los Alamos national laboratories found evidence that dust from an asteroid burning up as it descended through Earth’s atmosphere formed a cloud of micron-sized particles significant enough to influence local weather in Antarctica.

Micron-sized particles are big enough to reflect sunlight, cause local cooling, and play a major role in cloud formation, the Nature brief observes. Longer research papers being prepared from the same data for other journals are expected to discuss possible negative effects on the planet’s ozone layer.

“Our observations suggest that [meteors exploding] in Earth’s atmosphere could play a more important role in climate than previously recognized,” the researchers write.

Scientists had formerly paid little attention to asteroid dust, assuming that the burnt matter disintegrated into nanometer-sized particles that did not affect Earth’s environment. Some researchers (and science fiction writers) were more interested in the damage that could be caused by the intact portion of a large asteroid striking Earth.

But the size of an asteroid entering Earth’s atmosphere is significantly reduced by the fireball caused by the friction of its passage. The mass turned to dust may be as much as 90 to 99 percent of the original asteroid. Where does this dust go?

The uniquely well-observed descent of a particular asteroid and its resultant dust cloud gave an unexpected answer.

On Sept. 3, 2004, the space-based infrared sensors of the U.S. Department of Defense detected an asteroid a little less than 10 meters across, at an altitude of 75 kilometers, descending off the coast of Antarctica. U.S. Department of Energy visible-light sensors built by Sandia National Laboratories, a National Nuclear Security Administration lab, also detected the intruder when it became a fireball at approximately 56 kilometers above Earth. Five infrasound stations, built to detect nuclear explosions anywhere in the world, registered acoustic waves from the speeding asteroid that were analyzed by LANL researcher Doug ReVelle. NASA’s multispectral polar orbiting sensor then picked up the debris cloud formed by the disintegrating space rock.

Some 7.5 hours after the initial observation, a cloud of anomalous material was detected in the upper stratosphere over Davis Station in Antarctica by ground-based lidar.

“We noticed something unusual in the data,” says Andrew Klekociuk, a research scientist at the Australian Antarctic division. “We’d never seen anything like this before — [a cloud that] sits vertically and things blow through it. It had a wispy nature, with thin layers separated by a few kilometers. Clouds are more consistent and last longer. This one blew through in about an hour.”

The cloud was too high for ordinary water-bearing clouds (32 kilometers instead of 20 km) and too warm to consist of known manmade pollutants (55 degrees warmer than the highest expected frost point of human-released solid cloud constituents). It could have been dust from a solid rocket launch, but the asteroid’s descent and the progress of its resultant cloud had been too well observed and charted; the pedigree, so to speak, of the cloud was clear.

Computer simulations agreed with sensor data that the particles’ mass, shape, and behavior identified them as meteorite constituents roughly 10 to 20 microns in size.

Says Dee Pack of Aerospace Corporation, “This asteroid deposited 1,000 metric tons in the stratosphere in a few seconds, a sizable perturbation.” Every year, he says, 50 to 60 meter-sized asteroids hit Earth.

Peter Brown at the University of Western Ontario, who was initially contacted by Klekociuk, helped analyze data and did theoretical modeling. He points out that climate modelers might have to extrapolate from this one event to its larger implications. “[Asteroid dust could be modeled as] the equivalent of volcanic eruptions of dust, with atmospheric deposition from above rather than below.” The new information on micron-sized particles “have much greater implications for [extraterrestrial visitors] like Tunguska,” a reference to an asteroid or comet that exploded 8 km above the Stony Tunguska river in Siberia in 1908. About 2150 square kilometers were devastated, but little formal analysis was done on the atmospheric effect of the dust that must have been deposited in the atmosphere.

The Sandia sensors’ primary function is to observe nuclear explosions anywhere on Earth. Their evolution to include meteor fireball observations came when Sandia researcher Dick Spalding recognized that ground-based processing of data might be modified to record the relatively slower flashes due to asteroids and meteoroids. Sandia computer programmer Joe Chavez wrote the program that filtered out signal noise caused by variations in sunlight, satellite rotation, and changes in cloud cover to realize the additional capability. The Sandia data constituted a basis for the energy and mass estimate of the asteroid, says Spalding.

The capabilities of defense-related sensors to distinguish between the explosion of a nuclear bomb and the entry into the atmosphere of an asteroid that releases similar amounts of energy — in this case, about 13 kilotons — could provide an additional margin of world safety. Without that information, a country that experienced a high-energy asteroid burst that penetrated the atmosphere might provoke a military response by leaders who are under the false impression that a nuclear attack is underway, or lead other countries to assume a nuclear test has occurred.

More detailed papers are slated for the Journal of Geophysical Research and the Journal of Meteoritics and Planetary Science, Pack says.

Original press release: Nature Paper: Burning Asteroids May Play ‘More Important Climate Role Than Previously Recognized’ (Sandia National Labs)

NASA and the National Oceanic and Atmospheric Administration (NOAA) today outlined research that has helped to improve the accuracy of medium-range weather forecasts in the Northern Hemisphere.

NASA and NOAA scientists at the Joint Center for Satellite Data Assimilation (JCSDA) in Camp Springs, Md., came up with procedures to improve forecasting accuracy. The scientists worked with experimental data from the Atmospheric Infrared Sounder (AIRS) instrument on NASA’s Aqua satellite.

They found incorporating AIRS data into numerical weather prediction models improves the accuracy range of experimental six-day Northern Hemisphere weather forecasts by up to six hours, a four percent increase. AIRS is a high-spectral resolution infrared instrument that takes 3-D pictures of atmospheric temperatures, water vapor and trace gases.

The instrument data have officially been incorporated into NOAA’s National Weather Service’s operational weather forecasts.

“NASA is assisting the world’s weather prediction agencies by providing very detailed, accurate observations of key atmospheric variables that interact to shape our weather and climate,” said Dr. Mary Cleave, associate administrator for NASA’s Science Mission Directorate. “The forecast improvement accomplishment alone makes the AIRS project well worth the American taxpayers’ investment.”

“This AIRS instrument has provided the most significant increase in forecast improvement in this time range of any other single instrument,” said retired U.S. Navy Vice Adm. Conrad C. Lautenbacher, Jr., Ph.D., Undersecretary of Commerce for Oceans and Atmosphere and NOAA administrator.

“Climate and weather forecasts are dependent upon our understanding current global ocean and atmosphere conditions. If we want to be able to predict what the weather will be like in the future, we must adequately define the global conditions today. Satellite data, like AIRS provides, is a vital link for NOAA to continuously take the pulse of the planet.”

“A four percent increase in forecast accuracy at five or six days normally takes several years to achieve,” said JSCDA Director, Dr. John LeMarshall. “This is a major advancement, and it is only the start of what we may see as much more data from this instrument is incorporated into operational forecast models at NOAA’s Environmental Modeling Center.”

The European Center for Medium Range Weather Forecasts began incorporating data from AIRS into their operational forecasts in October 2003. The center reported an improvement in forecast accuracy of eight hours in Southern Hemisphere five-day forecasts.

AIRS is the result of more than 30 years of atmospheric research. It is led by Dr. Moustafa Chahine of NASA’s Jet Propulsion Laboratory, Pasadena, Calif. AIRS is the first in a series of advanced infrared sounders that will provide accurate, detailed atmospheric temperature and moisture observations for weather and climate applications.

The JCSDA is operated by NOAA, NASA, the U.S. Air Force and Navy. The goals of the center are to accelerate the use of observations from Earth-orbiting satellites to improve weather and climate forecasts, and to increase the accuracy of climate data sets.

Original press release: NASA/NOAA Announce Major Weather Forecasting Advancement (NASA)

Plumes of smoke from serious wildfires across Portugal fan into the Atlantic in this Envisat satellite view acquired on 21 August.

Dozens of wildfires are reported throughout the country, which has suffered one of its worst droughts for decades. Fanned by high winds, the fires have destroyed more than 140 000 hectares of land and killed at least 15 people.

Stricken areas include the vicinity of the city of Coimbra, Portugal’s third largest city, around 200 km northeast of Lisbon. On the outskirts of the city firefighters are attempting to keep the blazes at bay.

Other fires are reported to be burning in the northern districts of Viseu and Viana do Castelo. Firefighting aircraft from France, Germany, Italy and the Netherlands are participating in control activities following an appeal for help by Portugal’s government. This international assistance supplements a national firefighting effort of 49 aircraft, around 800 vehicles and 3000 firefighters.

The images here come from the Medium Resolution Imaging Spectrometer (MERIS) aboard Envisat, Europe’s largest-ever Earth Observation satellite, operating in Reduced Resolution mode for a spatial resolution of 1200 metres.

Original press release: Envisat sees smoke from Portuguese wildfires (ESA)

Researchers at Oregon State University and Diversa Corporation have discovered that the smallest free-living cell known also has the smallest genome, or genetic structure, of any independent cell—and yet it dominates life in the oceans, thrives where most other cells would die, and plays a huge role in the cycling of carbon on Earth.

In nature, apparently, bigger is not always better.

In a publication today in the journal Science, scientists outlined the growing knowledge about SAR11, a group of bacteria so dominant that their combined weight exceeds that of all the fish in the world’s oceans. In a marine environment that’s low in nutrients and other resources, they are able to survive and replicate in extraordinary numbers—a milliliter of sea water off the Oregon coast might contain 500,000 of these cells.

“The ocean is a very competitive environment, and these bacteria apparently won the race,” said Stephen Giovannoni, an OSU professor of microbiology. “Our analysis of the SAR11 genome indicates that they became the dominant life form in the oceans largely by being the simplest.”

The new study outlines how SAR11 has one of the most compact, streamlined genomes ever discovered, with only 1.3 million base pairs—the smallest ever found in a free living organism and a number that’s literally tiny compared to something like the human genome.

“SAR11 has almost no wasted DNA,” Giovannoni said. “This organism is extremely small and efficient. Every genetic part serves a purpose, more so than any other genome we’ve studied.”

The organism is able to survive as an unattached cell in a hostile environment, has a complete set of biosynthetic pathways, and can reproduce efficiently by consuming dissolved organic matter.

“By comparison, humans are mostly junk DNA, with large parts of the human genome having no important function,” Giovannoni said.

This type of genome streamlining, researchers say, appears to be a major factor in the evolutionary success of SAR11, which they believe may have been thriving for a billion years or more. One scientific hypothesis holds that natural selection acts to reduce genome size because of the metabolic burden of replicating “junk” DNA with no adaptive value—SAR11 supports that theory.

Researchers are particularly interested in SAR11, Giovannoni said, because of the critical role it plays in geochemistry. Photosynthesis is a process used by plants to convert sunlight energy into organic molecules, creating the foundation of the food chain and producing oxygen. About half of photosynthesis and the resulting oxygen on Earth are produced by algae in the ocean, and microbes like SAR11 recycle organic carbon—producing the nutrients needed for algal growth.

“Ultimately, SAR11 through its sheer abundance plays a major role in the Earth’s carbon cycle,” Giovannoni said. “Quite simply, this is something we need to know more about. SAR11 is a major consumer of the organic carbon in the oceans, which nearly equals the amount of carbon dioxide in the atmosphere. The carbon cycle affects all forms of plant and animal life, not to mention the atmosphere and fossil fuel formation.”

SAR11 was first discovered at OSU in 1990. Since then researchers have learned that populations of SAR11 increase during the summer and decrease during the winter, in a cycle that correlates to the ebb and flow of organic carbon in the ocean surface. Molecular probes, gene cloning, sequencing techniques and other tools have been used in this exploration.

Original press release: Microbe Has Huge Role in Ocean Life, Carbon Cycle (Oregon State University – NASA)

A senior Australian climate scientist has described as ‘encouraging’ the response of governments and authorities to climate change by lifting their focus beyond economics to plan a future for communities which face change.

Research manager of the Indian Ocean Climate Initiative from 1998-2005, Dr Bryson Bates, said today some climate change over the next few decades was inevitable.

Dr Bates said concentrated wet and dry periods would occur in future climate as part of natural variations in the cycle.

“Change has occurred in the past and is evident now in Australia but it is better not to select one future and hope it comes to pass, or find the most probable future and adapt to that.

“Australians need to be mindful that variability in climate will be superimposed on continued warming and changes in rainfall intensity.

“We cannot afford to wait for full scientific certainty about climate change because that may never come, or simply come too late and we must take a balance of evidence approach,” Dr Bates said.

Dr Bates, the Director of CSIRO’s Climate Program and a Lead Author for a Chapter of the Intergovernmental Panel on Climate Change’s next report due in 2007, was speaking at a summary workshop for the Indian Ocean Climate Initiative in Perth.

He said the Western Australian Government was to be commended on its approach and strategic investment in understanding the climatic changes occurring in South West Western Australia.

Dr Bates said the nation’s infrastructure was designed on the assumption that meteorological records captured all the climate information over the course of its economic life.

“We are now acutely aware that this is not the case and that we will need to adapt to change as well as moving towards mitigation of its impacts. Developing policies and plans that are robust across a range of plausible futures will improve environment, food and water security.

“We need to find fair and cost-effective measures to minimise adverse impacts and maximise benefits, understanding that the impacts of climate change extend far beyond just economic theory and into the web of Australian community life,” Dr Bates said.

Original press release: Climate change focus goes beyond economics (CSIRO)

A new NASA-funded study finds that predicted increases in precipitation due to warmer air temperatures from greenhouse gas emissions may actually increase sea ice volume in the Antarctic’s Southern Ocean. This adds new evidence of potential asymmetry between the two poles, and may be an indication that climate change processes may have different impact on different areas of the globe.

“Most people have heard of climate change and how rising air temperatures are melting glaciers and sea ice in the Arctic,” said Dylan C. Powell, co-author of the paper and a doctoral candidate at the University of Maryland-Baltimore County. “However, findings from our simulations suggest a counterintuitive phenomenon. Some of the melt in the Arctic may be offset by increases in sea ice volume in the Antarctic.

The researchers used satellite observations for the first time, specifically from the Special Sensor Microwave/Imager, to assess snow depth on sea ice, and included the satellite observations in their model. As a result, they improved prediction of precipitation rates. By incorporating satellite observations into this new method, the researchers achieved more stable and realistic precipitation data than the typically variable data found in the polar regions. The paper was published in the June issue of the American Geophysical Union’s Journal of Geophysical Research.

“On any given day, sea ice cover in the oceans of the polar regions is about the size of the U.S.,” said Thorsten Markus, co-author of the paper and a research scientist at NASA’s Goddard Space Flight Center, Greenbelt, Md. “Far-flung locations like the Arctic and Antarctic actually impact our temperature and climate where we live and work on a daily basis.”

According to Markus, the impact of the northernmost and southernmost parts on Earth on climate in other parts of the globe can be explained by thermohaline circulation – the movement of ocean water that is caused by temperature and salinity variations in the ocean. Through this process, ocean circulation acts like a heat pump and determines our climate to a great extent. The deep and bottom water masses of the oceans make contact with the atmosphere only at high latitudes near or at the poles. In the polar regions, the water cools down and releases its salt upon freezing, a process that also makes the water heavier. The cooler, salty, water then sinks down and cycles back towards the equator. The water is then replaced by warmer water from low and moderate latitudes, and the process then begins again.

Typically, warming of the climate leads to increased melting rates of sea ice cover and increased precipitation rates. However, in the Southern Ocean, with increased precipitation rates and deeper snow, the additional load of snow becomes so heavy that it pushes the Antarctic sea ice below sea level. This results in even more and even thicker sea ice when the snow refreezes as more ice. Therefore, the paper indicates that some climate processes, like warmer air temperatures increasing the amount of sea ice, may go against what we would normally believe would occur.

“We used computer-generated simulations to get this research result. I hope that in the future we’ll be able to verify this result with real data through a long-term ice thickness measurement campaign,” said Powell. “Our goal as scientists is to collect hard data to verify what the computer model is telling us. It will be critical to know for certain whether average sea ice thickness is indeed increasing in the Antarctic as our model indicates, and to determine what environmental factors are spurring this apparent phenomenon.”

Achim Stossel of the Department of Oceanography at Texas A&M University, College Station, Tex., a third co-author on this paper, advises that “while numerical models have improved considerably over the last two decades, seemingly minor processes like the snow-to-ice conversion still need to be better incorporated in models as they can have a significant impact on the results and therefore on climate predictions.”

Image: Example of North Pole Sea Ice Decrease: This image shows that sea ice in the North Pole has been on the decline, with the most significant loss in the past three years. This occurrence runs counter to the paper’s new finding that sea ice in the Antarctic’s (or South Pole) Southern Ocean appears to be on the increase.

Original press release: Sea Ice May Be on Increase in the Antarctic: A Phenomenon Due to a Lot of ‘Hot Air’? (NASA)