- Ghostly Bones of Galactic Feast Revealed
- When Good Rockets Go Bad
- Malaria Gaining Resistance to Best Available Treatment
- Dung Fungus Provides New Evidence in Mammoth Extinction Case
- Farmer Ants Fertilize Their Gardens With Bacteria
Posted: 20 Nov 2009 10:08 AM PST
A new infrared image of the galaxy Centaurus A reveals the gassy, ghastly bones of a galaxy that it consumed several hundred million years ago.
The parallelogram of stars leftover from the collision had been obscured by dust. But using new processing techniques in the near-infrared part of the spectrum, European Southern Observatory astronomers were able to glimpse the leftovers of the cosmic dinner.
"There is a clear ring of stars and clusters hidden behind the dust lanes, and our images provide an unprecedentedly detailed view toward it," said Jouni Kainulainen, in a paper on the new data visualized in the image. "Further analysis of this structure will provide important clues on how the merging process occurred and what has been the role of star formation during it."
The black hole lurking in the center of Centaurus A, 11 million light-years away, is 50 times as massive as the one at the center of the Milky Way. It's one of the most active source of radio waves in the universe, which is why astronomers have pointed all kinds of telescopes at it and eventually revealed the basic features of the galaxy that Centaurus A had consumed.
Image: ESO using the New Technology Telescope at the La Silla Observatory.
Posted: 19 Nov 2009 05:08 PM PST
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In the grand scheme of human space programs in Russia and the United States, catastrophic failures are relatively rare. But they are often quite spectacular and make a big impression on the public and on the funding for space exploration. The explosions in the videos we've assembled here were very costly, some in terms of life, some in terms of lost equipment and all in terms of progress of the space programs.
Vanguard TV3 Fuel Tanks Explode
Dec. 6, 1957: The United States' first attempt to launch a satellite into orbit was also its first failure. Two seconds after leaving the launch pad at Cape Canaveral, this rocket lost thrust and sank back down, rupturing and exploding its fuel tanks. It had reached a height of about 4 feet.
Though the rocket was destroyed, the Vanguard satellite it was carrying was thrown clear, its transmitters still signaling. The satellite is now on display at the Smithsonian's Air and Space Museum.
Posted: 19 Nov 2009 04:44 PM PST
WASHINGTON — Malaria that is resistant to the best available drug is more widespread in Southeast Asia than previously reported, new research shows. The worrisome finding poses a risk that travelers could carry this strain of the malaria parasite to other parts of the globe and unwittingly spread it, scientists reported November 19 at a meeting of the American Society of Tropical Medicine and Hygiene.
The frontline drug in question is called artemisinin, the most potent medication currently in use against malaria. Signs of malarial resistance to artemisinin have surfaced over the past several years in Cambodia (SN: 11/22/08, p. 9). The new findings confirm that resistant malaria has now cropped up beyond a spot on the border of Thailand and Cambodia where it was initially detected. Now it has appeared in Vietnam and in two spots along the Burma border with Thailand and China.
"Things are changing. There's no doubt the signs are concerning," said Robert Newman, director of the Global Malaria Programme at the World Health Organization in Geneva. But he added that these signals are early and need further verification.
Patients in these areas take longer on average to overcome a malaria infection when given a standard combination of artemisinin and another antimalarial. This lag results from slower clearance of the malaria parasites from the blood, said WHO's Pascal Ringwald, a medical officer who presented the update.
Patients who remain ill for longer stretches despite treatment need extra medication to recover from malaria and are also more likely to have severe or fatal cases, Ringwald said.
Malaria is caused by a single-celled parasite that infects the blood. Symptoms include fever, headache, chills, anemia and a swollen spleen. Of the more than 350 million people who come down with malaria worldwide each year, up to 1 million die. Mosquitoes spread the parasite from person to person.
Malaria has a history of becoming resistant to drugs, and artemisinin now risks becoming the most recent addition to that list. The new reports are disheartening to doctors because artemisinin normally packs a considerable wallop. Although artemisinin is a short-acting drug that gets cleared from the body in a few hours, it makes the most of its time — driving down parasite levels dramatically.
Using artemisinin alone invites resistance. So the standard therapy teams it with one of the longer-acting drugs, which perform mop-up duty on the remaining parasites, said Christopher King, a physician and epidemiologist at Case Western Reserve University in Cleveland.
The new flashes of resistance may have arisen because combination treatment isn't always available. And since artemisinin can be bought over the counter in many parts of Asia, people seeking relief don't always follow the WHO guidelines of pairing artemisinin with another drug, King said.
Also, taking artemisinin for a fever that isn't caused by malaria can allow resistant strains of the parasite to take hold, Newman said.
In the past, malaria's resistance to other drugs has been linked to specific genetic changes in the parasite. The precise mechanism underlying resistance to artemisinin is still unsolved, King said.
Artemisinin is derived from extracts of the sweet wormwood bush. The bush's leaves have been used as a folk remedy against fevers for roughly 2,000 years in Asia but fell out of use in the 20th century with the introduction of modern antimalarial drugs such as chloroquine.
During the Vietnam War, North Vietnamese leader Ho Chi Minh appealed to China for traditional remedies for soldiers who had malaria. Tea made from sweet wormwood leaves worked and ultimately became the basis for artemisinin drugs. It's not clear whether parasites in Southeast Asia are the first to become resistant because they have had a long history with artemisinin, or if other factors are involved, Newman said.
Image: Malaria from Plasmodium falciparum. Flickr/Got_Jenna
Posted: 19 Nov 2009 01:01 PM PST
The latest evidence in the disappearance of the mammoths, and nine other North American species weighing over a ton, comes from fossilized dung fungus. But despite their lowly origin, if the new findings hold, they point away from human causes and could rule out an asteroid impact altogether.
By studying the abundance over time of a fungus that lived only in the dung of these animals, scientists have revealed that the animals began to decline in numbers earlier than previously believed.
Much of the uncertainty surrounding the extinction of the North American megafauna, which includes mastadons, saber-tooth tigers and giant ground sloths, is due to a scarcity of evidence and difficulty pinning down the timing of events. Several major events occurred around the same time the animals disappeared: Major environmental upheaval associated with the end of the Ice Age; an asteroid explosion over North America; and the arrival of man.
Because the youngest megafauna fossils found are around 13,300 to 12,900 years old, the asteroid which is hypothesized to have impacted Earth's atmosphere around 12,900 years ago seemed like a good bet for the cause of the extinctions. But, the short-lived Clovis culture inhabited North America around the same time.
Now the new study, led by scientists at the University of Wisconsin-Madison and published Thursday in Science, fills some holes with a different type of data. By studying the abundance over time of a particular fungus that produces spores in the dung of big herbivores, a team of scientists determined that the animals' major decline occurred much earlier.
"Megafaunal populations collapsed from 14,800 to 13,700 years ago, well before the final extinctions," the authors wrote.
This effectively exculpates the asteroid impact, and makes the case for human causes thinner.
"If people were responsible for the decline, they must have been pre-Clovis settlers," Christopher Johnson, who studies the extinction of the Australian megafauna at James Cook University in Queensland, wrote in a commentary in Science.
Though the Clovis people were long believed to be the first North American settlers, new evidence of earlier settlers that arrived around the time that the fungus shows the decline beginning has begun popping up.
The idea of a pre-Clovis peopling is still hotly debated, but even if it didn't exist or wasn't robust enough to have a major effect on the animals, the Clovis people could have dealt the final blow or contributed to the ultimate demise of the megafauna.
The scientists also studied pollen from the time period and discovered that as the large herbivores declined, a new set of broad-leaved trees began flourishing. This woodland could have arisen because the animals that fed on those plants and kept them in check weren't around anymore. And because these major changes in the environment occurred after the animals were in decline, this is a strike against the idea that climate caused the changes which then caused the extinctions.
The new research adds much needed information to a spotty fossil record and scattered clues. But the question of whether or not humans caused the demise of North America's giant beasts has always provoked strong feelings and intense debate, and this latest evidence is likely to stir things up more than it helps settle them.
Image: Barry Roal Carlsen, University of Wisconsin-Madison
Citation: "Pleistocene Megafaunal Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America," by J.L. Gill; J.W. Williams; K.B. Lininger at University of Wisconsin-Madison, WI; S.T. Jackson at University of Wyoming, Laramie, WY; G.S. Robinson at Fordham University. Science Vol. 326, Nov. 20, 2009.
Posted: 19 Nov 2009 11:00 AM PST
Thanks to their vast underground fungus farms, leafcutter ants are one of Earth's most successful species — and one secret of their agricultural success is bacteria, which the ants use like fertilizer.
By farming with microbes that pull nitrogen from the air, the ants thrive in nitrogen-poor rain forest soil. Researchers say their bug-harnessing tricks might point people toward better ways of turning plants to fuel, or boosting our own crop yields.
"The reason we're able to produce such massive crops is by the massive fertilization of nitrogen in our fields," said University of Wisconsin bacteriologist Cameron Currie, co-author of a paper published Thursday in Science. "Ants supplement their crops through symbiotic associations with bacteria."
A star of rain forest documentaries, leafcutter ants are one of about 250 ant species that subsist on farmed fungus. Most of these species live in colonies of a few thousand individuals, with tiny garden plots.
Leafcutter colonies have millions of members, with leaf-fed farms yielding more than a ton of fungus every year. Some scientists estimate they account for a full four-fifths of all living, nonplant rain forest matter.
Fascinated by their success, researchers have studied leafcutter gardening, but something wasn't adding up. Though Earth's atmosphere is nitrogen-rich, animals get their nitrogen by eating plants, or eating animals that eat plants. But rain forest foliage is nitrogen poor, as are the soils colonized by the ants.
"Nitrogen is one of the elements that ultimately determines productivity," said Currie. "The nitrogen balance in ants is way off, based on what's predicted from their diet."
Currie's team investigated the mystery of where the ants were getting their extra nitrogen by raising leafcutter colonies in airtight boxes. The soil in the boxes contained normal nitrogen. But the nitrogen in the air was replaced with a nitrogen atom with a different number of neutrons, called an isotope. By measuring the levels of the isotope in fungus and ant bodies, the researchers could track whether nitrogen was coming from the soil or the air.
They found that the fungus was getting nitrogen from the air. They then studied bacteria growing on the fungus, and found microbes from a genus called Klebsiella, which pulls nitrogen from the air at rates comparable to microbes that live on the roots of some plants and give them nitrogen from the soil.
"It's entirely possible that nitrogen-fixing bacteria played a critical role in the evolution of this very different group of ants, with their giant colonies and massive effects on the environment," said Ted Schultz, a Smithsonian Institute entomologist who was not involved in the study. He and Currie both noted that leafcutters are uniquely complex among fungus-growing ants, but evolved just 10 million years ago, or 40 million years after other fungus growers.
"What humans do for nitrogen is mine it from other sources, and dump it on our crops," said Schultz. But this leads to waste and pollution, "and the ants accomplish it through microbes. Who knows? Maybe humans could do something similar, and cultivate microbial communities in the soil around our crops."
And this isn't the only trick farmers might learn from the ants. In March 2008, Schultz showed that leafcutters also use antibiotic-producing microbes to keep their gardens pest-free.
Currie is studying whether nitrogen-fixing bacteria help break down the ants' leaf cuttings into a fungally-digestible form. If so, the bacteria may suggest better ways of turning plants into biofuels. "We need to discover new enzymes, new processes, to convert plant cell walls into simple sugars that can be converted into ethanol," he said. "Ants have been converting plant biomass into energy for millions of years."
Currie added that leafcutter ants are the subject of thousands of papers authored over the last century, "yet this critical aspect of their success was completely unknown."
"This is a well-studied natural system, and we're still learning who the players are," he said. "What does that say about most of the natural world, where mutalisms and associations haven't been studied?"
Images: 1) A leafcutter ant tending fungus, from Cameron Currie. 2) The nitrogen-tracking test apparatus, from Science. 3) An excavated leafcutter colony, from Science. 4) Leafcutters returning to their colony with freshly cut leaves, from Jarrod Scott.
Citation: "Symbiotic Nitrogen Fixation in the Fungus Gardens of Leaf-Cutter Ants," by Adrián A. Pinto-Tomás, Mark A. Anderson, Garret Suen, David M. Stevenson, Fiona S. T. Chu, W. Wallace Cleland, Paul J. Weimer, Cameron R. Currie. Science, Vol. 326, No. 5956, Dec. 20, 2009.
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