Wednesday, September 29, 2010
Global satellite-derived map of PM2.5 averaged over 2001-2006. Credit: Dalhousie University, Aaron van Donkelaar
In many developing countries, the absence of surface-based air pollution sensors makes it difficult, and in some cases impossible, to get even a rough estimate of the abundance of a subcategory of airborne particles that epidemiologists suspect contributes to millions of premature deaths each year. The problematic particles, called fine particulate matter (PM2.5), are 2.5 micrometers or less in diameter, about a tenth the fraction of human hair. These small particles can get past the body’s normal defenses and penetrate deep into the lungs.
To fill in these gaps in surface-based PM2.5 measurements, experts look toward satellites to provide a global perspective. Yet, satellite instruments have generally struggled to achieve accurate measurements of the particles in near-surface air. The problem: Most satellite instruments can't distinguish particles close to the ground from those high in the atmosphere. In addition, clouds tend to obscure the view. And bright land surfaces, such as snow, desert sand, and those found in certain urban areas can mar measurements.
However, the view got a bit clearer this summer with the publication of the first long-term global map of PM2.5 in a recent issue of Environmental Health Perspectives. Canadian researchers Aaron van Donkelaar and Randall Martin at Dalhousie University, Halifax, Nova Scotia, Canada, created the map by blending total-column aerosol amount measurements from two NASA satellite instruments with information about the vertical distribution of aerosols from a computer model.
Their map, which shows the average PM2.5 results between 2001 and 2006, offers the most comprehensive view of the health-sapping particles to date. Though the new blending technique has not necessarily produced more accurate pollution measurements over developed regions that have well-established surface-based monitoring networks, it has provided the first PM2.5 satellite estimates in a number of developing countries that have had no estimates of air pollution levels until now.
The map shows very high levels of PM2.5 in a broad swath stretching from the Saharan Desert in Northern Africa to Eastern Asia. When compared with maps of population density, it suggests more than 80 percent of the world's population breathe polluted air that exceeds the World Health Organization's recommended level of 10 micrograms per cubic meter. Levels of PM2.5 are comparatively low in the United States, though noticeable pockets are clearly visible over urban areas in the Midwest and East.
"We still have plenty of work to do to refine this map, but it's a real step forward," said Martin, one of the atmospheric scientists who created the map."We hope this data will be useful in areas that don't have access to robust ground-based measurements."
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite shows fires around the world. Credit: NASA
This summer, wildfires swept across some 22 regions of Russia, blanketing the country with dense smoke and in some cases destroying entire villages. In the foothills of Boulder, Colo., this month, wildfires exacted a similar toll on a smaller scale.
That's just the tip of the iceberg. Thousands of wildfires large and small are underway at any given time across the globe. Beyond the obvious immediate health effects, this "biomass" burning is part of the equation for global warming. In northern latitudes, wildfires actually are a symptom of the Earth's warming.
'We already see the initial signs of climate change, and fires are part of it," said Dr. Amber Soja, a biomass burning expert at the National Institute of Aerospace (NIA) in Hampton, Va.
And research suggests that a hotter Earth resulting from global warming will lead to more frequent and larger fires.
The fires release "particulates" -- tiny particles that become airborne -- and greenhouse gases that warm the planet.
A common perception is that most wildfires are caused by acts of nature, such as lightning. The inverse is true, said Dr. Joel Levine, a biomass burning expert at NASA Langley Research Center in Hampton, Va.
"What we found is that 90 percent of biomass burning is human instigated," said Levine, who was the principal investigator for a NASA biomass burning program that ran from 1985 to 1999.
Levine and others in the Langley-led Biomass Burning Program travelled to wildfires in Canada, California, Russia, South African, Mexico and the wetlands of NASA's Kennedy Space Center in Florida.
Biomass burning accounts for the annual production of some 30 percent of atmospheric carbon dioxide, a leading cause of global warming, Levine said.
Dr. Paul F. Crutzen, a pioneer of biomass burning, was the first to document the gases produced by wildfires in addition to carbon dioxide.
"Modern global estimates agree rather well with the initial values," said Crutzen, who shared the Nobel Prize in Chemistry 1995 with Mario J. Molina and F. Sherwood Rowland for their "work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone."
Whether biomass burning is on the rise globally is not clear. But it definitely is increasing in far northern latitudes, in "boreal" forests comprised largely of coniferous trees and peatlands.
The reason is that, unlike the tropics, northern latitudes are warming, and experiencing less precipitation, making them more susceptible to fire. Coniferous trees shed needles, which are stored in deep organic layers over time, providing abundant fuel for fires, said Soja, whose work at the NIA supports NASA.
"That's one of the reasons northern latitudes are so important," she said, "and the smoldering peat causes horrible air quality that can affect human health and result in death."
Fires in different ecosystems burn at different temperatures due to the nature and structure of the biomass and its moisture content. Burning biomass varies from very thin, dry grasses in savannahs to the very dense and massive, moister trees of the boreal, temperate and tropical forests.
Fire combustion products vary over a range depending on the degree of combustion, said Levine, who authored a chapter on biomass burning for a book titled "Methane and Climate Change," published in August by Earthscan.
Flaming combustion like the kind in thin, small, dry grasses in savannahs results in near-complete combustion and produces mostly carbon dioxide. Smoldering combustion in moist, larger fuels like those in forest and peatlands results in incomplete combustion and dirtier emission products such as carbon monoxide.
Boreal fires burn the hottest and contribute more pollutants per unit area burned.
Being near large wildfires is a unique experience, said Levine. "The smoke is so thick it looks like twilight. It blocks out the sun. It looks like another planet. It's a very eerie experience."
In Russia, the wildfires are believed caused by a warming climate that made the current summer the hottest on record. The hotter weather increases the incidence of lightning, the major cause of naturally occurring biomass burning.
Soja said she hopes the wildfires in Russia prompt the country to support efforts to mitigate climate change. In fact, Russia's president, Dmitri A. Medvedev, last month acknowledged the need to do something about it.
"What's happening with the planet's climate right now needs to be a wake-up call to all of us, meaning all heads of state, all heads of social organizations, in order to take a more energetic approach to countering the global changes to the climate," said Medvedev, in contrast to Russia's long-standing position that human-induced climate change is not occurring.
NASA Langley Research Center
The Expedition 24 crew aboard the International Space Station photographed the Twitchell Canyon Fire in central Utah on Sept. 20. The fire near central Utah’s Fishlake National Forest is reported to cover an area of approximately 13,383 hectares, or 33,071 acres. This detailed image shows smoke plumes generated by several fire spots close to the southwestern edge of the burned area. The fire was started by a lightning strike on July 20, 2010. Whereas many of the space station images of Earth look straight down (nadir), this photograph was exposed at an angle. The station was located over a point approximately 316 miles to the northeast, near the Colorado/Wyoming border, at the time the image was taken. Southwesterly winds continue to extend smoke plumes from the fire to the northeast.
Image Credit: NASA
This high forward oblique view of Rima Ariadaeus on the moon was photographed by the Apollo 10 crew in May 1969. Center point coordinates are located at 17 degrees, 5 minutes east longitude and 5 degrees, 0 minutes north latitude. The Apollo 10 crew aimed a hand-held 70mm camera at the surface from lunar orbit for a series of images of this area.
Image Credit: NASA
Saturday, September 25, 2010
Animals similar to Hypsilophodon appeared early in the history of dinosaurs and persisted until the last dinosaurs became extinct 65 million years ago. They were small, fast-running herbivorous dinosaurs, related to the larger hadrosaurs and Iguanodonts. Hypsilophodon lived in Europe, but fossils of similar animals are known from every continent, including Antarctica and Australia.
Hypsilophodon ran on its long hind legs, with its body held horizontal. Its long tail accounted for half its body length and was stiffened by bony tendons. It is presumed that this helped to hold the tail off the ground while it was running. Recent research suggests that these tendons aided the efficiency of Hypsilophodon when running.
Hypsilophodon, like other ornithopods, had a small beak, broad chiselled teeth that formed a continuous cutting edge, and cheek pouches for storing food for a short time while it was chewed.Early palaeontologists thought that it looked like a tree kangaroo, and for a period thought that it may have perched in trees. These ideas have now been discounted and Hypsilophodon is thought to have lived very successfully on the ground as a small, fast sprinter.
Mamenchisaurus was a giant sauropod with a very long neck — amongst the longest of any animal that has ever lived. Measuring up to 11 metres, the neck was almost half the overall length of the animal. Its long neck and its tail were held in position by a series of ligaments anchored at the hip — a bit like a suspension bridge. Mamenchisaurus would have walked with its stiff neck held almost horizontal. All the vertebrae of its neck, body and tail were hollow and light, while its leg bones were quite solid. This kept its centre of gravity low, which helped the animal maintain its balance.
Like all sauropods, Mamenchisaurus was a plant-eater. Its spoon-shaped teeth were not for chewing, but were used like a rake to strip leaves off plants. These were swallowed into its huge vat-like stomach. Its long neck allowed it to reach food otherwise inaccessible to an animal with such a huge body.
Mamenchisaurus, like all herbivores, would have had to eat continuously to get enough nutrition to sustain its massive body.
Thursday, September 23, 2010
Photograph by Anil Sud
Sunrise lights up the verdant hills of Palouse, Washington, beneath the watchful gaze of a lone early bird.
A tail of smoke chases the space shuttle Endeavour as it lifts off from Cape Canaveral, Florida, on March 11, 2008.
This large tube anemone, photographed in Tulamben, Bali, stood high off the black-sand bottom, allowing me to shoot its spectacular tentacles from below and capture its graceful movement. The flashlight highlighted the anemone's dazzling luminance, while the setting sun added a sense of atmosphere.
Hiram Bingham, a meticulous record keeper, had a Kodak 3A Autographic Special camera among his gear when he discovered the lost Inca city of Machu Picchu in 1911. Among the first views he captured was this stunning panorama of the ruins, with their ancient terraces and stonework buildings of white granite. The mountain Hyana Picchu towers over it all.
Photograph by Desmond Ong, Your Shot
Worth waking up early for this amazing scene. It is an HDR (high dynamic range) image capture during the early blue hour at the Temple of Borobudur. This famous Buddhist temple, dating from the 8th and 9th centuries, is located in central Java. It was built in three tiers: a pyramidal base with five concentric square terraces, the trunk of a cone with three circular platforms and, at the top, a monumental stupa. The walls and balustrades are decorated with fine low reliefs.
Friday, September 03, 2010
Photograph courtesy INDEX-SATAL/NOAA
A sea anemone hitches a ride on a hermit crab in one of the "rare and exciting" new pictures released last week by a joint Indonesian-U.S. ocean expedition.
Taken near the Indonesian island of Sulawesi (map), the high-definition, "never-before-seen views of seascapes and colorful, fascinating marine animals" were captured by a remotely operated vehicle aboard the expedition's U.S. ship Okeanos Explorer.
The ROV conducted 27 dives between 800 feet (240 meters) and 2 miles (3.2 kilometers), spotting at least 40 species that might be unknown to science, according to the U.S. National Oceanic and Atmospheric Administration (NOAA).
(See pictures of a giant undersea volcano released by the project team in June.)
The first in a multiyear partnership between NOAA and the Indonesian Ministry for Marine Affairs and Fisheries, the approximately two-month expedition was meant to document Indonesia's sea life and to learn more about resolving ocean problems, such as acidification and overfishing. (Read about ten things you do can do save the ocean.)
Photograph by David Doubilet
This toxic orange Godiva nudibranch was photographed in the Raja Ampat islands, Papua, Indonesia. There are over 3,000 known species of these colorful sea slug relatives, and new ones are discovered nearly every day.
Photograph by Jennifer Hayes, National Geographic Stock
The islands of Raja Ampat may well be home to the greatest biodiversity in the world, with almost 600 species of coral, abundant plant life, and unique creatures, such as a shark that walks on its fins and a shrimp that looks like a praying mantis.
Photograph by Wolcott Henry
This brilliant purple sea star was photographed in the waters off Sulawesi, Indonesia. Though they are commonly called starfish, these animals are not fish at all. They are echinoderms, closely related to sea urchins.