News this Week

Science  16 Jun 2006:
Vol. 312, Issue 5780, pp. 1580

    Climate Sensors Dropped From U.S. Weather Satellite Package

    1. Jeffrey Mervis

    5 June was the day the music died for geographer Anne Nolin of Oregon State University, Corvallis. That's when the U.S. government decided to strip several climate instruments off a suite of polar-orbiting satellites intended to provide the next generation of weather and climate-monitoring data for military, civilian, and scientific users (Science, 2 June, p. 1296).

    Nolin, who uses passive microwave imaging to study snow and ice at the poles, is one of a legion of climate scientists distraught by the reduced capacity, rising costs, and launch delays in the National Polar-Orbiting Operational Environmental Satellite System (NPOESS) program. And they aren't alone: Last week, members of the House Science Committee excoriated the heads of three government agencies for what they see as a decade of management missteps.

    Weathering a storm.

    From left, NOAA's Conrad Lautenbacher, NASA's Michael Griffin, and the Air Force's Ronald Sega field tough questions on NPOESS from the House Science Committee.


    NPOESS was conceived in 1994 as a joint project of the Department of Defense and the National Oceanic and Atmospheric Administration (NOAA), each of which operates its own polar satellites, with NASA as a junior partner. The government said that NPOESS, in addition to saving money, would provide the nation with an enhanced capability to wage war, track storms, and study a host of climate variables, from electron density in space to solar irradiance to sea-surface interactions. For climate scientists, the alliance would combine NASA's expertise in building and flying high-quality research payloads with NOAA's commitment to operational satellites.

    The payoff was to be a more robust longitudinal record of an ever-changing Earth. But that promise hasn't been realized—and there's a chance it may never come to pass. “We're seeing a disintegration of the U.S. environmental satellite system,” says Richard Anthes, head of the organization that manages the National Center for Atmospheric Research in Boulder, Colorado, and co-chair of an almost-completed U.S. National Academies' exercise to lay out long-range research priorities for the field.

    Geoscientists who rely on space-based observations of Earth regard the downsizing of NPOESS as a serious blow to their discipline. “Essentially, NPOESS is saying NOAA won't be doing climate,” says Kathie Kelly, who studies atmosphere-ocean coupling at the University of Washington's Applied Physics Laboratory in Seattle. “Basically, no one is going to do climate.”

    Last week's hearing was a chance for officials from the three relevant agencies—Air Force Under Secretary Ronald Sega, NASA Administrator Michael Griffin, and NOAA head Conrad Lautenbacher—to explain a 5 June decision that was mandated by the program's budget overruns. The original $6.5 billion plan for NPOESS called for a fleet of six satellites (up to three in orbit at any one time), with nine instruments collecting data on 55 environmental elements. A preparatory satellite would be launched in 2006, and the final one a decade later. The new $11.5 billion plan promises only four satellites (two at one time), bearing only three of those nine instruments. The first launch would be in 2009 and the final one in 2022.

    Key instruments that have been discarded include the Conical Scanning Microwave Imager/Sounder (CMIS) that Nolin was counting on; the Total Solar Irradiance Sensor; the Aerosol Polarimetry Sensor; the Earth Radiation Budget Sensor suite; the Space Environment Sensor suite; and one of two Ozone Mapping and Profiler suite. Those instruments lost out in a competition that gave priority to weather forecasting.

    NPOESS officials told the committee that the new configuration will still be equipped to monitor weather and collect climate information. Lautenbacher said the government will build a smaller and less capable CMIS with the $265 million that remains in CMIS's initial budget of $465 million, and the Navy is studying how to replace an altimeter that would have monitored sea surface height and wave characteristics. Instruments on other missions can take up some of the slack, the agency officials assured legislators, although the sensors may be less capable. “Instead of gold fixtures and marble countertops, we may have to settle for chrome and Formica,” Lautenbacher explained after the hearing. “But we can still get what we need.”

    Legislators aren't nearly as optimistic. “Twelve years into the program, and 3 years before the first launch, we are at a critical point where there is little room left to recover from further missteps,” noted Representative Vern Ehlers (R-MI), chair of the panel's environmental subcommittee, who intoned that “today is not a happy occasion.” The chair, Representative Sherwood Boehlert (R-NY), was even less politic. “How the hell can we do our job without sufficient information?” he exclaimed, joining with ranking Democrat Representative Bart Gordon (D-TN) in a full-throated attack on what they see as the Bush Administration's refusal to explain its latest decision.

    Pressed by Ehlers on what might be added back if more money became available, Griffin pointed to the academies' forthcoming decadal study. But Anthes says the panel didn't expect NPOESS to be cut back so severely and that the report, due out in December, will make a case for a “balanced strategy for all of the earth sciences … and for the importance of the science.”


    Polio Experts Strive to Understand a Puzzling Outbreak

    1. Leslie Roberts

    Health authorities in Namibia are scrambling to vaccinate the entire population, some 2 million people, against poliovirus, which has resurfaced after a 10-year absence in a highly unusual—and deadly—outbreak. Unlike most outbreaks, this one is targeting adults rather than young children. Outbreaks among adults are “as rare as hen's teeth,” says Bruce Aylward, who directs the global campaign to eradicate polio from World Health Organization (WHO) headquarters in Geneva, Switzerland, because adults usually have acquired immunity either through vaccination or exposure to infected children. But when an adult in infected, the disease tends to be much more severe.

    As Science went to press, at least 47 suspected cases were under investigation in Namibia, and wild poliovirus type one had been confirmed in four. Seven people had died, and several others were critically ill. Shipments of vaccine were en route to Namibia for the first of at least three emergency campaigns, and officials were bracing for yet more cases before the virus can be contained.

    Although the latest outbreak is yet another blow to the global campaign to eradicate polio, WHO officials say they are optimistic that the Namibian government can quash it. But the outbreak remains puzzling. A team of epidemiologists has rushed in to investigate, while others have been scouring the genetic sequence of the virus for clues. Genetic evidence suggests that the virus originated in India, one of four countries where polio is endemic, and that it recently jumped across the border from Angola into Namibia. Angola had interrupted transmission of wild poliovirus in 2001 but was reinfected with an Indian virus last year; only a handful of new cases have been reported there.

    When it reached Namibia, the virus found fertile soil. Why is not clear, but the prevailing assumption is that the afflicted adults were not immunized as children. Namibia didn't offer routine vaccinations until the early 1990s, but once the country began polio immunization in earnest, the last case of indigenous poliovirus was reported in 1996. One puzzle, says Aylward, is how the affected adults apparently escaped exposure to the circulating virus before then. In other adult outbreaks, for instance in Albania in 1996 or Cape Verde in 2000, the populations were either culturally or geographically isolated, he notes.

    Index case?

    Namibia's outbreak has been traced to a virus that came from India via Angola. Top: A child in Angola receives polio vaccine.


    The first case identified in Namibia was a 39-year-old farmer from Aranos, about 150 kilometers from the capital of Windhoek. He went to Windhoek for gall bladder surgery and became ill, with sudden paralysis, about 2 weeks later on 8 May. He is now on a respirator. Within days, other cases were reported around Windhoek, mostly among adults between age 20 and 40. Health authorities initially thought they might be dealing with Guillain-Barre syndrome, an autoimmune disorder that may be triggered by infections. But on 2 June, a WHO-accredited laboratory in South Africa confirmed wild poliovirus.

    So far, epidemiologists don't know where the farmer picked up the virus or even whether he is the first in the chain of transmission, says David L. Heymann, the WHO director general's representative for polio eradication. Investigators are looking for any connection among the suspected cases. “We may never know,” says Heymann, who notes that many of the victims are unable to talk because they are on respirators. Investigators are also trying to determine whether a cluster of Guillain-Barre cases reported in April may have been polio as well, he adds.

    A shipment of monovalent oral polio vaccine is scheduled to arrive in Namibia this week. In the first campaign, slated to begin 21 June, and a second scheduled for late July, the government hopes to reach every person in the country, adults and children alike. The age group to be targeted in subsequent campaigns has yet to be determined. “I am very confident [Namibia] will be able to [control the outbreak],” says Heymann. He lauds Namibia's rapid response and says the campaign will also benefit from the country's sparse population and the onset of winter.

    A bigger challenge may be knocking out polio next door in Angola, says Heymann. The last reported case of polio in Angola was in November 2005, but last month, wild poliovirus from Angola also resurfaced in the Democratic Republic of Congo (DRC), which abuts Angola to the north. “They are clearly not doing enough to stop transmission,” says Heymann. New sequencing data from Angola, the DRC, and Namibia suggest that the virus was introduced into one of these countries a year ago and has been circulating in all three.

    Although the new outbreaks are troubling, WHO officials say the most serious threat to polio eradication remains the densely populated states of northern Nigeria, where there has been intense opposition to vaccination and an epidemic is raging out of control. Already, 438 cases have been reported this year, nearly triple the number at the same time last year.

    To Ellie Ehrenfeld, a polio biologist at the U.S. National Institutes of Health, the Namibian outbreak provides yet more evidence that “the world cannot be left unimmunized.” Even if the eradication campaign succeeds, she warns, “the potential for a hideous, hideous outcome is really there.”


    Bone Marrow Fails to Produce Oocytes

    1. Gretchen Vogel

    It was a controversial idea from the start: Last year, researchers suggested that cells in the bone marrow can travel through the circulatory system to the ovaries and become oocytes. If true, the discovery might lead to new fertility and menopause treatments. And it would have meant that women receiving bone marrow transplants could give birth to genetically unrelated children. But a paper in this week's issue of Nature should put that particular worry to rest. In a series of mouse experiments, the authors find no evidence that bone marrow cells become mature oocytes.

    The new results “raise a serious rebuttal to the hypothesis that you could restore someone's fertility by giving them a bone marrow transplant,” says Louis De Paolo of the National Institute of Child Health and Human Development in Bethesda, Maryland.

    Standard textbooks explain that shortly after birth, a female's ovaries have all the potential egg cells she will ever have. But in the past 2 years, a group has claimed that the textbooks may be wrong. In a 2004 Nature paper, Josh Johnson and Jonathan Tilly of Harvard Medical School in Boston and their colleagues presented evidence that new oocytes can develop in adult mice (Science, 12 March 2004, p. 1593). Then, based on experiments in which seemingly sterilized mice appeared to produce new oocytes after a bone marrow transplant, they concluded in Cell last year that the eggs might be derived from bone marrow cells that had migrated to the ovaries (Science, 29 July 2005, p. 678).

    These results were met with skepticism, and to date no other group has reported similar findings. Instead, in the new Nature paper, Amy Wagers of the Joslin Diabetes Center in Boston and her colleagues challenge Johnson and Tilly's second claim.

    Wagers and her colleagues created pairs of parabiotic mice: mice with their skin sewn together between the front and hind legs so that they have a shared circulatory system. Parabiotic pairs can live for more than a year, eating and moving relatively normally. In Wagers's experiments, one parabiotic mouse was normal, and the other came from a strain genetically engineered to express green fluorescent protein (GFP) in all its tissues. The researchers reasoned that if circulating bone marrow cells contribute to oocyte development, they should find GFP-expressing oocytes in the normal mouse and nonfluorescent ones in the mutant. However, even after 8 months of sharing blood, the mice only produced oocytes that matched their own genotype.

    Wagers and her colleagues also checked whether bone marrow cells help repair the damage done to ovaries by chemotherapy drugs, one of the claims that Tilly and his colleagues made. The Joslin team gave doses of two ovary-damaging drugs to a normal mouse and then joined it to a mouse expressing GFP. But again, they found no fluorescent oocytes in the normal mice. The team did find GFP-expressing cells near mature oocytes in those rodents' ovaries, but they were immune-system cells. “We looked at hundreds of oocytes and never saw one that was partner- or donor-derived,” Wagers says.

    Green eggs.

    Shared circulation between a normal mouse and one expressing green fluorescent protein reveals whether bone marrow spawns oocytes.


    But Tilly says the paper does not directly contradict his group's observations. His team reported evidence of immature oocytes, he says, which might help support ovarian function even if they never mature into fertilizable eggs. The new paper “has raised an important issue about the mature egg population, but it in no way addresses seeding of the ovary,” he says, because Wagers's group only examined ovulated oocytes.

    Although Wagers's team doesn't address the still-contentious issue of whether adult mammals keep producing new oocytes, David Albertini of the University of Kansas Medical Center in Kansas City says their data clearly answer the key question of whether bone marrow cells are a source of any such fresh eggs. “The nice thing about these experiments is that a very simple question was asked, and a very clear result was obtained,” he says.


    U.S. Hospital Launches Large Biobank of Children's DNA

    1. Jocelyn Kaiser

    Joining a growing list of “biobank” projects around the world that aim to link genes and common diseases, researchers in Philadelphia, Pennsylvania, last week announced a plan to collect DNA from 100,000 people. This new project comes with a youthful twist: “The focus here is entirely on children,” says study leader Hakon Hakonarson of the Children's Hospital in Philadelphia (CHOP).

    Ethical questions already swirl around existing biobanks, and the storage of children's DNA could raise new issues, notes pediatrician and medical ethicist Jeffrey Botkin of the University of Utah School of Medicine in Salt Lake City. For example, whether to permit DNA to be used for unspecified future projects is “always more ethically sensitive” when decided by parents for their children, he says. However, birth defects researcher Jeffrey Murray of the University of Iowa in Iowa City, who is not connected with the project, contends that a large children's DNA bank is needed and can be operated ethically and safely. “We'd be letting children down by not doing this,” he adds.

    According to its plan, CHOP will spend $40 million from private sources over the next 3 years to analyze DNA from 100,000 children and begin searching for links to childhood diseases such as asthma, diabetes, and obesity. The core population will be drawn “relatively randomly” from the hospital's 1 million patient base, says Hakonarson, a former CHOP staffer who recently returned from working at deCODE Genetics Inc., the Icelandic company that has paved the way for population biobanks (Science, 8 November 2002, p. 1158). The hospital also plans to collaborate with outside groups to recruit youngsters with rarer diseases, such as neuroblastoma, a childhood cancer.

    Banking on DNA.

    Researchers hope that a new DNA database on children will uncover genes involved in diseases such as asthma and will lead to better treatments.


    Each child's DNA will be scanned for some 550,000 common markers. To address privacy concerns, these data will be combined with medical records in a triple-encrypted database that leaves researchers with no way to identify participants, says Hakonarson. He adds that the parents also agree that they won't have access to their child's results, as the DNA scan is only for research purposes. Ultimately, CHOP hopes the project leads to new diagnostics and treatments tailored to a child's genetic makeup.

    Some large epidemiology studies of children in Europe and the United States have collected DNA but have likely not begun comprehensive genotyping, says Murray. Another proposed U.S. effort, the National Children's Study (see graph), would also enroll 100,000 children and store their DNA but would focus initially on environmental disease factors.

    Botkin says institutional review boards (IRBs) evaluating DNA banks vary on whether to allow open-ended consent for studies that could include, for example, identifying genes affecting behavior. The CHOP project will give parents a choice: They can check a box allowing analysis of their child's DNA for specific diseases, or one permitting future studies on unspecified topics. Hakonarson says the biobank approach has been “well-received” by CHOP's IRB. But Botkin, who offered ethics advice to the National Children's Study, says he prefers an “intermediate level of specificity,” such as limiting the studies to cancer research.

    Another issue that troubles some researchers, including Murray, is that CHOP expects to partner with drug companies and patent discoveries. Without intellectual property rights, firms are unlikely to be interested in following up on a promising lead, explains CHOP Chief Scientific Officer Philip Johnson. He adds that after a delay, the database will be open to other investigators: “Our goal is to make all of the information publicly available.”


    Harvard Cloners Get OK to Proceed With Caution

    1. Constance Holden

    Harvard University researchers last week were given the go-ahead to use cloning to create disease-specific lines of human embryonic stem cells. The approval makes Harvard the second U.S. academic institution, after the University of California, San Francisco (UCSF), to use research cloning—known as somatic cell nuclear transfer (SCNT)—as a tool for studying diseases such as diabetes and Parkinson's.

    “I'm very happy to hear” the Harvard news, says Arnold Kriegstein, head of UCSF's new Stem Cell Institute. “The more people who are working on this, the more likely that it will succeed.”

    Scientists described their plans to use the technology at a 6 June press conference at Harvard, noting that five institutions and eight Institutional Review Boards spent 2 years reviewing the arrangement before giving their approval. It's been a “Herculean effort,” said researcher George Daley of Children's Hospital Boston, referring to the ethical, logistical, legal, and financial matters that had to be resolved. Some states have banned the technique because it involves creating and destroying fertilized eggs, and there are no reports of success with SCNT, the procedure Korean scientist Woo Suk Hwang used in now-discredited research (Science, 2 June, p. 1298).

    One major issue that Harvard has addressed involves egg donation procedures. The researchers plan to recruit local “compassionate” donors, who will not be paid anything beyond expenses. To avoid medical problems that have reportedly plagued women who donated eggs for Hwang's research, Kevin Eggan of the Harvard Stem Cell Institute said there will be limits on blood levels of estradiol resulting from hormonal stimulation. He said no more than 8 to 10 eggs will be taken from any individual. Potential donors will be given a 25-page booklet informing them of every conceivable risk.

    All financial backing for the research will be privately donated, in keeping with the federal prohibitions on funding such work. And it's not just scrupulous accounting that will be necessary; Harvard provost Steven Hyman told the Harvard Crimson that rules extend even to what scientists can and cannot touch. In keeping with the extreme caution surrounding the enterprise, Harvard spokesperson B. D. Colen says all the researchers involved will stay mum until the first results are published.

    Several projects now have the green light. Eggan and colleague Douglas Melton are cultivating skin cells from diabetics to insert their nuclei into enucleated eggs. Their goal is disease-specific stem cell lines—moving the study of disease “from patients to a petri dish,” as Melton put it. Eggan also intends to use the technique to study neurodegenerative diseases such as amyotrophic lateral sclerosis. Daley, meanwhile, plans to create customized cell lines using skin biopsies from patients with sickle cell anemia and other blood diseases.

    Last month, UCSF researcher Renee Reijo Pera got permission to attempt nuclear transfer using “failed-to-fertilize” eggs from fertility clinics. Harvard now has the only group in the world with permission to work with fresh donor eggs.

  6. U.S. 2007 BUDGET

    NIH Gets Off to a Slow Start

    1. Jocelyn Kaiser

    A House spending panel last week endorsed a flat budget for the National Institutes of Health (NIH)—but told the agency to make room for a $3.2 billion children's health study that NIH says it cannot afford. Legislators also want NIH to make mandatory a voluntary program in which grantees submit their accepted manuscripts to a free online archive.

    The legislation, a first step toward approving a 2007 budget, essentially matches President George W. Bush's $28.3 billion request for agency programs under the panel's jurisdiction. If the Senate isn't more generous, it would mean the third straight year at that level. Like Bush's request, the House bill would give the NIH director's office a $140 million boost, mainly for biodefense countermeasures and the trans-NIH Roadmap. Most of NIH's 27 individual institutes and centers would suffer cuts of about 0.5% to 0.8%.

    Big-ticket item.

    The cost of NIH's longitudinal study of 100,000 children would peak during enrollment and then level off at $99 million a year after 2014.


    “No question, we're extremely disappointed” by the NIH levels, says Jon Retzlaff, director of legislative relations for the Federation of American Societies for Experimental Biology. NIH expects to fund 656 fewer research grants in 2007 than this year.

    Legislators went against the Administration's wish to cancel the National Children's Study by ordering the National Institute of Child Health and Human Development to spent $69 million of its $1.26 billion budget on preparing to track 100,000 children from birth to age 21. A report accompanying the bill says the committee is “very disappointed” that the president's budget does not explain why it proposed eliminating the study, which is already funding seven “vanguard” centers. Advocates say NIH needs new money to fund the study, and they are hoping that the Senate will be more generous.

    The spending bill would also require researchers to post a copy of every manuscript they generate using NIH funds in the agency's free, full-text PubMed Central archive within 12 months after publication in a journal. The committee resisted calls from open-access advocates to require posting within 6 months, which many scientific societies fear could bankrupt journals that provide funds for their other activities. “The 12 months is a positive step,” says Martin Frank, executive director of the American Physiological Society.

    The bill moves to the floor later this month and then to the Senate, which in March voted to give appropriators an extra $7 billion partly to boost NIH. “Senator [Arlen] Specter (R-PA) feels very strongly about NIH,” says Representative Ralph Regula (R-OH), chair of the spending panel. “So it's very possible that the numbers could change before we're done.”


    A Kinder, Gentler Jeremy Rifkin Endorses Biotech, or Does He?

    1. Erik Stokstad

    For years, activist Jeremy Rifkin was the bête noire of biotechnology. Beginning in 1983, he filed several lawsuits to block field trials of genetically modified (GM) organisms and grabbed headlines around the world. Rifkin, an economist who runs the nonprofit Foundation on Economic Trends in Washington, D.C., said such actions were necessary to force an insulated research world to confront pressing ethical questions. To many in the scientific community, however, Rifkin was simply fanning irrational fears about biotechnology. A headline of a 1989 Time magazine profile called him “The Most Hated Man in Science” and captured the prevailing sentiment.


    To some researchers' surprise, a new report by Jeremy Rifkin endorses genomics for crop breeding, as shown here with soybean DNA.


    After a decade and a half of protests and campaigns to ban GM crops, Rifkin largely moved on to other topics, such as commerce, European politics, and hydrogen fuel. But now Rifkin, 61, is jumping back into agricultural biotech—this time, as a promoter. “This is an amazing twist for Jeremy Rifkin,” says Susan McCouch, a rice geneticist at Cornell University. “I've never seen the man come out in favor of anything.” But, like many others, she doubts his support will make much difference, as he is endorsing a biotech approach, known as marker-assisted selection (MAS), that is already well accepted.

    In a white paper posted to his organization's Web site* this week, Rifkin says MAS offers all the advantages of new genomic science without what he calls the great risks to human health and the environment posed by GM crops. Instead of transferring genes from one species to another, MAS simply speeds and improves traditional plant breeding. Researchers search through maps of a plant's genome for sequence markers that are consistently associated with desired traits such as improved yield or disease resistance. Those markers can then be used to screen breeding stock and the progeny of traditional crosses even before they are grown or planted in the field.

    Rifkin touts MAS as a path toward cheaper organic food and more sustainable agriculture. And to ensure that all reap its benefits, he advocates that MAS be used in a patent-free, or “open source,” system in which the genetic information and techniques used to assist breeding are freely exchanged. “It's not enough to know what you're against. … This paper is my effort to try to frame an opportunity to move into a new age for agriculture,” says Rifkin, whose immediate goal is to “open a conversation” with scientists, industry, and policymakers about the future of MAS.

    Greenpeace and other advocacy groups, which have already come out in favor of MAS, say they welcome the move. But many scientists suspect that Rifkin's newfound enthusiasm for MAS is just a subterfuge for another attack on transgenic modification of crops. “This tract is typical Rifkin material,” says Alan McHughen of the University of California, Riverside. “He still twists information to fit his agenda.” Rifkin does indeed argue that GM crops should be phased out. He claims that few crops have been improved by transgenic modification—“it's primitive science” he says—and, to make matters worse, contamination of wild relatives by transgenes may complicate the process of MAS, he warns.

    As Rifkin describes it, his conversion was gradual. After following MAS for some time, he says he realized last year that it had eclipsed transgenic technology in its potential. MAS certainly has provided an enormous boost to breeders, and the pace has accelerated as ever more DNA is sequenced and as genetic screens have become cheaper and faster. Although scientists and companies share Rifkin's enthusiasm for MAS and predict it will become even more powerful, they disagree that transgenic technology has failed or that MAS has somehow rendered it obsolete. “To say that marker-assisted breeding will replace biotech is simply wrong,” says Roger Beachy, who directs the Donald Danforth Plant Science Center in St. Louis, Missouri. That's because of the enormous task facing plant breeders, says Mike Gale, an emeritus cereal geneticist at the John Innes Centre in Norwich, U.K.: “If we are going to produce enough food to feed the world, we need every tool in the toolbox.”

    McCouch agrees that gene splicing remains a crude approach—like adjusting an intricate watch with a sledgehammer. Yet, she and others say, it is the only way forward in some cases—for instance, if a gene for a particular trait can't be found in a crop or its wild relatives. The classic example is Bt, a toxin from a soil bacterium that was added to corn to provide broad and powerful protection against lepidopteran insects. Now companies are working to add genes for omega-3 fatty acids into soybean, to make the oil more healthful. “Those genes don't exist in soybeans at all,” says David Fischoff, head of technology strategy and development at the Monsanto Co. in St. Louis, Missouri.

    Nor is transgenic technology inherently risky, scientists say. “It is the gene and the management of the crop that make the difference and not the technology used to develop them,” says Les Firbank of the Centre for Ecology and Hydrology in Lancaster, U.K.

    Rifkin's concerns aren't just biological. He couples his endorsement of MAS with a few caveats about policy, as well. He wants to be sure the technology is used in a way that meets his broader goals of sustainable agriculture and open-source technology—in other words, no patents. “We've seen too much how the patent system restricts the cooperative nature in science,” he says. Charles Benbrook, a scientist with the Organic Center in Enterprise, Oregon, agrees that tight constraints on intellectual property are a concern, as ever more technology and markers are locked up in company labs. “I worry that marker-assisted breeding is not going to be able to deliver on its potential.” Although Rifkin stops short of calling for an overhaul of patent law, he predicts that genetic technology and genomic information will eventually make it so easy and cheap to produce germ plasm that companies will have to make profits by selling agroecological consulting to farmers. Rifkin says he plans to start actively hawking his message on the lecture circuit and in his advice to business leaders and governments. “This is what I'm going to hammer away on: MAS should be phased in on the condition of an agroecological approach and open source.”

    Rifkin's pleas aside, Monsanto and other agribusiness companies contacted by Science don't plan to drop their GM research or stop seeking patents. And several in the scientific community say they don't need Rifkin's help promoting a field that's already flourishing. “Having the endorsement of Jeremy Rifkin means nothing,” says Martina Newel l-McGloughlin, director of the University of California's Biotechnology Research and Education Program in Davis. She and others doubt that any conversation with Rifkin would be productive. “Let's just ignore the man,” says Gale. “Let's get on with the job we have, which is to feed the world.” But whether or not Rifkin succeeds in opening the conversation he desires, he no doubt will keep talking.


    Fossil Embryos Hint at Early Start for Complex Development

    1. Katherine Unger

    Evidence of the earliest animals on Earth dates back about 700 million years. But the arrival time of more complex animals—those with mirror symmetry and digestive tracts, known as bilaterians—has remained a mystery.

    Lumps of life.

    Lobed fossils removed from Precambrian rocks in China suggest that complex life forms evolved earlier than previously thought. (Scale bar: 250 micrometers.)


    Now, on page 1644, an international team of paleontologists says it has isolated hundreds of fossil embryos that resemble those of modern bilaterians such as annelids and mollusks. If they check out, it could mean that a wide array of complex animals existed tens of millions of years before the “Cambrian explosion”—the time when paleontologists think hard-bodied animals proliferated as their ecosystems took shape. Precambrian animals have been notoriously difficult to find and study because their fragile bodies likely did not fossilize well. “I'm delighted to see a paper like this because it suggests there's more to look for out there,” says Rudolf Raff of Indiana University in Bloomington.

    Two years ago, Jun-Yuan Chen of Nanjing University in China and colleagues described fossils with bilaterian features in Science (9 July 2004, p. 218). The find, uncovered in 580-million- to 600-million-year-old rocks in the Doushantuo deposit in China's Guizhou Province, drew fire from paleontologists who suggested that the small, almost featureless “fossils” were actually layers of minerals. The latest discovery comes from the same rocks, but this time Chen's team has unearthed what appear to be fossil embryos bearing hallmarks of bilaterian embryos. If they are bilaterians, says Jon Mallatt of Washington State University in Pullman, it would mean these complex animals existed 40 million years earlier than current evidence suggests.

    The researchers say the fossil embryos sport so-called polar lobes, asymmetrical bulges that allow bilaterian embryos to form different tissues in adults. The fossil embryos appear to be in different stages of development: Some have three lobes and some five; some have lobes of equal shape, and some are more lopsided. Chen and colleagues isolated the fossils by dissolving away surrounding rock with acid, then examined them under a scanning electron microscope. The researchers say the relative volumes of the spherical lobes are too regular for the fossils to be unrelated embryos or inorganic lumps of rock stuck together.

    Some scientists are reluctant to give the fossils their unequivocal endorsement. Nicholas Holland, an invertebrate zoologist at the University of California, San Diego, notes that the specimens show a few “slightly bothersome” differences from other bilaterian embryos. “A lot of critters that make polar lobes have reasonably small eggs, around 200 microns,” says Holland, whereas many of the Doushantuo embryos are as much as five times bigger.

    Douglas Erwin of the National Museum of Natural History in Washington, D.C., cautions that the embryos' small size makes it hard for scientists to tell organic structures from mineral deposits and other preservation-related artifacts. “If you have a dinosaur bone, it's easy to tell what's bone or what's not,” he says. “The closer you look, the harder it is to tell what the original bone structure is.” The fossils also lack some characteristics of known annelids and mollusks, Erwin says, although the embryos could represent an extinct lineage of bilaterian.

    Just knowing that complex animals existed 580 million years ago would help scientists better understand biodiversity before the Cambrian Period, says Ronald Jenner of the University of Bath in the United Kingdom. If the bilaterians were there, then the “basic branches of the animal kingdom [had] already been established at this point,” Jenner says, as indirect evidence from modern animals' genes has suggested.


    In Search of the Red Planet's Sweet Spot

    1. Richard A. Kerr

    Planetary scientists are looking for a safe but interesting place to land the next Mars rover, but their track record lately is only one for two in finding both safety and the desired science


    The MSL rover (left) will be the first one able to land within striking distance of rugged outcrops. The smaller MER rover (inset, with MSL) had less dramatic targets.


    PASADENA, CALIFORNIA—The first time scientists landed a spacecraft on Mars, it was—by necessity—pretty much a matter of throwing darts. Who knew in 1977 where it would be safe, much less scientifically fruitful, for Viking to set down? Five safe landings and terabytes of new data later, planetary scientists gathered here at the end of May* to begin the search for the next martian landing site. This time, they're shooting for the bull's-eye: a single spot where a record of a warm, watery, and habitable Mars has been preserved for billions of years. With luck, they could find traces of early martian life as well.

    So far, Mars researchers have a perfect record of identifying safe landing sites. Knowing where the most interesting geology lies has been another matter. In 2004, a “mineralogical beacon” found in data from an orbiting spectrograph drew the Opportunity rover to the flat expanses of Meridiani Planum, where it found the remnants of ancient salty lakes. But Opportunity's sister rover Spirit, landing on what to many researchers looked like an ancient lakebed, found instead a barren lava flow.

    When selecting a landing site by “combining geomorphology [terrain features] and mineralogy, you get a slam dunk,” planetary geologist James Rice of Arizona State University in Tempe told the workshop, “but that's hard to do on Mars.” So hard, said planetary mapper Timothy Parker of the Jet Propulsion Laboratory (JPL) here in Pasadena, that, despite redoubled efforts to get it right this time, “our preconceived notions may be completely wrong when we get to the ground.”

    To avoid such an unpleasant surprise when the $1.5 billion roving Mars Science Laboratory (MSL) lands in 2010, workshop attendees helped begin a 3-year process to select a safe and scientifically productive landing site. More than 120 researchers responded—most at their own expense—to the agency's open invitation to the first of four workshops for community input. To judge by the 35 sites they proposed and initially ranked in this round, experts disagree drastically about the best sort of place to invest NASA's $1.5 billion. Three years won't be too long to whittle 35 down to one.

    Mixed record

    Participants started by reviewing the track record of past site selections. In the earliest Mars missions, all agreed, scientists choosing where to land enjoyed a fair measure of luck. They picked spots for the two Viking landers on the basis of the relatively fuzzy images being returned by the two Viking orbiters; it was a matter of “the blind leading the blind,” said planetary geologist Matthew Golombek of JPL, co-chair of NASA's Landing Site Steering Committee. Predictions of the number and size of unseen rocks that could crush a lander's underside and of slopes that could topple it were “incorrect in every regard,” said Golombek.

    By the time NASA's Mars Pathfinder mission touched down in 1997, far more abundant observations made site selection a more rational process; lander observations bore out scientists' safety-related predictions for the first time. On the science side, researchers found their rock-strewn floodplain seen from orbit, the same sort of terrain the Vikings had landed on. Unfortunately, the rocks were more monotonous and less informative than hoped.

    When it came time for the Mars Exploration Rover (MER) mission—Opportunity and Spirit—“predictions for safety were right on the mark,” said Golombek, but that “was not necessarily the case for the science.” Opportunity found water-formed hematite, as predicted from orbital spectroscopy. But contrary to what many experts expected, the hematite had formed not on a lake bottom conducive to life but in briny, highly acidic groundwaters. Water had flowed on the surface at times, but for the most part, that area of Mars more than 3 billion years ago was salty dune after salty dune. Still, most researchers regard the Opportunity site selection as a complete success; they went looking for signs of water on early Mars, and they found them.

    Not so the selection of Gusev crater for Spirit. Out of 155 sites on the original list, most proved fatally flawed: too windy for landing, too dusty to do geology, too many big rocks, not enough space to land, and on and on. The final four sites included an ultrasafe backup site considered by many to be too boring for words and another with little promise of the sought-after signs of water (Science, 10 May 2002, p. 1006). Gusev, however, looked like a plum. Orbital imaging convinced many experts that floodwaters had once gushed through the crater rim to fill a lake several hundred meters deep.

    On Spirit's arrival, however, the crater floor proved achingly boring: in the words of one team member, a “basalt prison” of impact-pulverized lava that for eons had seen no more than a touch of dampness (Science, 9 April 2004, p. 197). When the long-lived Spirit gained the nearby Columbia Hills, it did find a jumble of water-altered volcanic or impact rock, but that rock's story has proved so complex it has yet to be deciphered.

    The MSL solution

    With MSL, researchers are intent on avoiding another Gusev. Last time, “we had the luxury of two rovers,” noted Rice. “We've only got one shot with this one.” That's because NASA is going for broke with a single massive rover capable not only of assessing formerly wet environments but also of recognizing markers of past life, such as organic matter containing a distinctive mix of isotopes. The mission will focus on “habitability,” the potential of an environment to support life, past or present. MSL will carry 16 times the instrument payload of Opportunity or Spirit, including everything from a subsurface-ice detector to a rock-zapping laser for analyzing elements from afar.

    MSL is also dramatically more capable than the MER rovers in getting where its makers really want it to go. The MER rover entry capsules smashed into the martian atmosphere like bullets, slowing until a parachute could be opened to ease the rest of the descent. With such uncontrolled entry and descent, engineers had to assume the lander could end up anywhere in a narrow 100-kilometer-long landing ellipse on the surface. The solar-powered MER rovers were designed to last 90 days, during which they would travel at least 600 meters each.

    A miss.

    On landing, the MER Spirit rover found a pulverized lava flow, not the hoped-for lakebed.


    MSL, on the other hand, will have the time and energy to explore much farther afield and even investigate “go-to” targets beyond its landing zone. Its entry capsule will sense any high-altitude buffeting and adjust course, shrinking the landing ellipse to a 20-kilometer circle. Once on the ground, a radioisotope thermoelectric generator—unlike MER solar panels, a steady, predictable energy source—will power MSL to a design lifetime of 2 years and a range of at least 20 kilometers. It could thus land in a small, safe landing zone and drive off at top speed to a target too rugged for landing. In addition, it can land in the thin air of higher altitudes and operate at much higher, colder latitudes than the MER rovers could.

    A hit.

    The MER Opportunity rover (here inserted into an image of Burns Cliff) found layered deposits laid down by wind and water, as predicted from orbital spectroscopic data.


    Where to?

    So, exactly where should NASA send its souped-up rover? Scientists at the workshop saw prospects for habitability in a bewildering array of geologic settings, from valleys, canyons, and gullies to craters, plains, and basins. Usually, signs that water had shaped the landscape or altered the rock drew them to a site. If the rock were layered—presumably sediments laid down by water a layer at a time—all the better. And, of course, the site should be safe for landing or at least reachable from a safe landing zone.

    A half-dozen speakers favored sites on or around Meridiani Planum, the plain where the Opportunity rover is still driving on top of an 800-meter-thick stack of layered, sulfate-rich sediments laid down by wind and water about 4 billion years ago. These Meridiani strata presumably record changing environmental conditions over a sizable chunk of martian time and space. But Opportunity has inspected only the top 10 meters of the 800 meters of record where it was exposed in a smallish impact crater. By roving up the plateau's sides hundreds of kilometers from Opportunity, MSL has “the potential to tell a much bigger-picture story” than if it visits smaller, layered deposits, said planetary geologist Michael Malin of Malin Space Science Systems in San Diego, California.

    Meridiani clearly would satisfy the stratum lust of any red-blooded geologist, but some still had reservations. “We've been there,” says Rice. “Let's go somewhere new.” One minus was Meridiani's geologic history. Acid brine would not have been the friendliest habitat for life, and on Earth, rocks left behind by evaporated saltwater tend to harbor little organic matter. Some Meridiani sites also looked dusty enough to cloak any interesting geochemistry. When attendees voted to give high, medium, or low priorities for targeting orbital observations in the coming year, only one Meridiani site—just outside the northern margin of the plateau—made the top 10, coming in at number eight.

    A more popular destination proved to be light-toned layered deposits: banded, presumably sedimentary deposits exposed in canyons, craters, and other protected depressions. Researchers suspect that at least some such deposits formed beneath standing water, and orbital spectroscopy has shown that some are composed of water-related sulfates or clays.

    In 160-kilometer Gale crater just south of the equator, the layers form a mound in the middle of the crater floor. The Gale mound was a popular proposed MER target, but engineers could not fit a landing ellipse on the adjacent crater floor. Now some scientists—including planetary scientist James Bell of Cornell University—want to try again. The 5-kilometer-high stack of 10-meter beds “is one pretty enigmatic feature,” Bell said. Whatever process formed the mound “permeates all of Mars studies,” he added. “It's an enigma in our present understanding.”

    Skeptics, however, wonder whether Gale might be too scientifically risky. “You use ‘enigma’ a lot,” said Carlton Allen, curator of astromaterials at NASA's Johnson Space Center in Houston, Texas. “This is a one-shot, billion-dollar mission, and you're talking about going to a place [that] we have severe questions about how it formed.” Bell conceded that no one “knows for sure” whether the Gale mound deposits are lake sediments, volcanic ash fall, or windblown dust. In the priority voting, curiosity won out over caution. Gale came in sixth, and three other light-toned deposits ranked in the top 10.

    So many choices.

    Questions linger over selection of the MSL landing site. Did water lay down the light-toned layered terrain (upper left)? What is the Eberswalde crater's river delta (upper right) made of? Are the winds over Nili Fossae trough's clays (red) too high for a safe landing?


    Certain water

    Toward the safe end of the science-risk spectrum fall ancient crater lakes such as Eberswalde crater in the southern subtropical latitudes. There, an irrefutable river delta pushes into the crater complete with meandering channels and oxbow river bends. “Eberswalde is the science target” for MSL, says Rice, because a delta means water—and sediment—flowed into standing water in the crater. Any clayey sediments of the delta would have acted like magnets for the much-sought-after organic matter. But even Eberswalde's advocates were quick to point out that there isn't much room for even a 20-kilometer landing zone in Eberswalde. Two other proposed craters—Holden and Terby—show less dramatic evidence of having held lakes but offer more room for a safe landing.

    Craters in general, however, suffer from a serious drawback: wind. At the workshop, atmospheric modelers Scot Rafkin and Timothy Michaels of Southwest Research Institute in Boulder, Colorado, reported on their preliminary modeling of winds around Mars. “Mars is a windy place,” said Rafkin. “There are good parts of Mars that won't be usable.”

    In planning for the MER mission, engineers had to eliminate some otherwise attractive sites—such as Melas Chasma, a side canyon to the great Valles Marineris—when computer simulations predicted that overlying winds could be too fast for a safe descent. Gusev just squeaked by. Craters and canyons, Rafkin said, can create small-scale winds fierce enough to overwhelm larger-scale winds. “So it's going to be like MER,” said Rafkin. That was bad news, responded planetary geologist Jeffrey Moore of NASA's Ames Research Center in Mountain View, California. He called the MER selection “the slaughter of the landing sites.” Undaunted, voters at the workshop put all three proposed craters in the top five.

    The right water

    Once-watery craters might be fine for geologists, but spectroscopists in the crowd—who think about composition before geology—argued that mineralogical composition should be getting more attention. Spectroscopist Jean-Pierre Bibring of the University of Paris-South in Orsay made a pitch for targeting minerals that have been altered by water. “We have to go to hydrated minerals,” he said. They show that water didn't just pass by but lingered long enough to alter mineral chemistry.

    And not just any water-bearing minerals will do. Bibring, who heads the OMEGA spectrometer team on the European Mars Express orbiter, argued from OMEGA observations that life-friendly clays had formed before the acid-generated sulfates of Meridiani and elsewhere. If life ever appeared on Mars, he said, the clay era would be the likeliest time for it. But clays haven't shown up in deltas yet, so MSL should be targeted where clays are found: in the walls of Nili Fossae trough or in Marwth Vallis, although both may be liable to high winds. The two clayey sites finished tied for first and fourth, respectively.

    All 35 proposed sites will eventually get a close look during the next 16 months. Glacierlike features in the extreme south, dust-smothered outcrops, and seemingly barren rock piles will be targeted by the Mars Reconnaissance Orbiter (MRO), which is now trimming its orbit for a November start of operations. MRO will be able to image the smallest of the dangerous rocks and detect even small areas of interesting minerals. Mars Express may also join in. It can refine the steepness of slopes that MSL must deal with. Come the next community workshop in October 2007, researchers must be ready to slash their wish list to the top dozen.

    • *First Landing Site Workshop for the 2009 Mars Science Laboratory, 31 May-2 June, sponsored by the NASA-appointed Landing Site Steering Committee and the MSL Project.


    Vulture Research Soars as the Scavengers' Numbers Decline

    1. Robert Koenig

    A catastrophic die-off of vultures in South Asia and recent sharp declines in some populations in Africa have focused research on this often reviled but majestic bird


    BRITS, SOUTH AFRICA—Awkwardly flapping their injured wings, a half-dozen rescued vultures hunch their long necks and cower in a corner when a visitor walks into their enclosure. “They may look mean, but they are gentle and intelligent birds,” says Director Kerry Wolter of the Vulture Unit at the De Wildt Cheetah and Wildlife Centre in South Africa's North West Province. “Just keep your fingers away from their beaks.”

    It's hard to warm to vultures, quintessential scavengers that gorge themselves on carrion and are the butt of office jokes and Gary Larsen cartoons. But these particular African white-backed vultures—all victims of power-line collisions— have earned a place in scientists' hearts. Following a drastic die-off of vultures in South Asia over the past decade, the birds here have served as sentinels in a research project that aims to shed new light on the crisis in Asia and help prevent similar losses in Africa. “This pool of research birds—injured vultures that could not be reintroduced into the wild—is crucial to the project,” says University of Pretoria veterinary pharmacologist Gerald E. Swan.

    Two years ago, scientists reported that an anti-inflammatory drug used in cattle called diclofenac was responsible for most of the vulture deaths in Asia, but not before about 97% of three species in the region had been lost. The crisis has, however, sparked a renaissance in the study of vultures. Scientists are investigating the birds' habits, physiology, and vulnerabilities to chemicals, as well as their role in transmitting infectious diseases. In West Africa, investigators are trying to determine the extent of vulture killings for traditional medicine and food. In Israel, researchers use satellite tracking to monitor vultures' movements. In Namibia, experts want to determine the role of vultures in the transmission of anthrax. Spanish researchers are counting vultures killed by wind-energy turbines. And conservationists in Africa, Asia, the Middle East, and part of Europe are establishing sanctuaries, “vulture restaurants,” and monitoring campaigns.


    Two of Pakistan's largest colonies of Oriental white-backed vultures (Changa Manga and Dholwala) have been wiped out since 2000.


    There is much to admire about vultures. They are as graceful in the air as they are awkward on the ground, soaring in rising air currents to astonishing heights (one jet collided with a vulture at 10,000 meters) over a wide-ranging territory, and they use their sharp eyesight to spot any sign of carcasses far below. For millennia, vultures and humans have had a love-hate relationship. The ancient Egyptians worshipped the birds, pastoralist tribes revered them for finding dead cattle, and shamans attribute the sharp-eyed scavengers with clairvoyance. Members of the Parsee religion in India do not believe in burying or burning their dead; instead, they leave them out for vultures to consume. For others, vultures' prompt arrival at scenes of death, and their enthusiasm for decaying meat only causes revulsion.

    Despite this human ambivalence, the sudden death of large numbers of birds in Asia caused alarm. Munir Virani, a Nairobi-based conservation biologist who coordinates the Peregrine Fund's Asian Vulture Population Project, says, “Three of the five breeding colonies of the Oriental white-backed vultures in Pakistan are now extinct,” with only about 75 breeding pairs in the remaining two colonies, as compared to 3500 pairs just 6 years ago.

    Although diclofenac was fingered as the culprit 2 years ago (Science, 8 October 2004, p. 223), India did not immediately ban its use. Swan helped lead a study to find an alternative cattle drug, and earlier this year his team and colleagues in India and the United Kingdom reported that the substitute drug, meloxicam, does not harm white-backed vultures (Science, 3 February, p. 587). India banned the manufacture and sale of diclofenac last month; Pakistan, however, has yet to follow suit. Pretoria researchers are now investigating the impact of other veterinary drugs on vultures, as well as diclofenac's mechanism in killing the birds.

    Fetishes and poison Although the African vulture situation is not as bad as South Asia's, populations of some species are dropping sharply. “Vultures are at the top of the food chain, so if their numbers are declining, it is a sign that something is off balance,” says “vulturephile” ornithologist Mark D. Anderson, who is based in Kimberley, South Africa, and is editor of Vulture News. He says that the use of anti-inflammatory drugs in livestock is far less common in Africa than in South Asia, but he worries that other drugs and poisons may be killing vultures and other scavengers.

    The biggest problem is in West Africa, where ornithologist Guy Rondeau says, “We are seeing vulture declines comparable to South Asia.” A 2005 survey supported by the Critical Ecosystem Partnership Fund in Washington, D.C., found that vulture populations in rural areas of eight West African countries had decreased by about 95% since the early 1970s. In his work for the conservation group Africa Nature International in Côte d'Ivoire, Rondeau is helping organize vulture sanctuaries in the few areas that still have significant vulture populations, including sites in Mali and Guinea.

    The causes of the decline in Africa are many. Some farmers, aiming to control other scavengers and predators such as jackals and hyenas, lay out deliberately poisoned carcasses, and vultures become the unintended victims. “One poisoned carcass can kill a huge number of vultures,” says Virani, citing a Kenyan case in which 187 vultures perished after feeding on a cow carcass and four poisoned hyenas.

    Other than that, Rondeau says, the main threats in West Africa are “hunting for fetishism, muti [traditional medicines], and, more recently, for meat.” Stalls in some African markets sell desiccated vulture parts—heads, talons, feathers, eyes, and hearts—for traditional medicine or fetishes. In other areas, smoked vulture meat is traded, and live vultures are exported abroad. In parts of South Africa, a similar vulture trade has flourished with the advent of the National Lottery, because some parts are considered lucky charms, says Steve McKean, an ecologist with KwaZulu-Natal province's wildlife department.

    Dried out.

    A market in Mali offers desiccated vulture heads and feet for sale. Some Africans believe vultures have powers of clairvoyance.


    To help find better ways to protect vultures, researchers are trying to get to know them better. In Namibia, Maria Diekmann of the Rare and Endangered Species Trust has used satellite tracking to follow the path of vultures. “One of them flew more than 500 kilometers a day, ranging over four different countries,” she says. Namibia's population of Cape vultures, estimated at 2000 in the 1950s, was down to 25 birds this spring, including 13 “repopulated” from South Africa.

    The satellite-tracking technology came from scientists in Israel, who have been monitoring that nation's dwindling vulture population since the 1980s. Ohad Hatzofe, an avian ecologist with Israel's Nature and National Parks Protection Authority in Jerusalem, says, “It took only one Griffon vulture with a VHF tag to open our eyes to how ignorant we and the scientific community were” about vulture habits. The telemetry data helped scientists learn the birds' movement patterns and decide where to establish vulture feeding sites; it also gave insight into the factors that are endangering local and migrating vultures.

    At the Vulture Unit, Wolter employs cellphone transmitters and a new wing-tag system to track Cape vultures (also known as Cape Griffons) released into the wild. The numbered yellow tags are part of a wider monitoring project coordinated by the Endangered Wildlife Trust's Birds of Prey Working Group in Parkview, managed by raptor conservationist André Botha. On a recent morning in the Magaliesberg mountains, Botha squinted into a telescope lens toward a Cape vulture colony on the rock ledges above, counting each occupied vulture nest and marking them on a laminated photo of the cliff ‘s face. “These colonies have been getting smaller over the years,” says Botha.

    A hundred kilometers to the north, the Kransberg colony—once the world's largest for Cape vultures—has lost more than 300 nesting pairs over the last 2 decades and is now down to about 650 pairs, says Patrick Benson, who conducts research for the University of the Witwatersrand in Johannesburg. He has compiled a large collection of vulture bones and is completing an analysis of skeletal abnormalities that might give hints to the reasons why so many vultures are dying. He attributes the decline mainly to a loss of food sources, the deliberate poisoning of carcasses, and contact with poorly insulated wires. Other South African scientists are studying whether the growing elephant population in Kruger National Park is driving away vultures by destroying their nesting trees.

    The continent's most threatened vulture species is the African bearded vulture, an uncharacteristically beautiful scavenger that inhabits mountainous areas. Kenya's population was down to three bearded vultures last year, and a survey by the South African province of KwaZulu-Natal's wildlife department indicated that its bearded vulture population is declining in the birds'main habitat, the Drakensberg mountains.

    Disease carriers? Some would see fewer vultures as a blessing. But Peter Mundy, a Zimbabwean ornithologist who wrote The Vultures of Africa, argues that the scavengers help prevent the spread of animal diseases, such as anthrax, by quickly devouring carcasses. Vultures can eat anthrax-infected flesh without apparent harm, studies have shown, but scientists are also looking into whether they distribute anthrax spores and other disease agents adhering to their feathers and feet over long distances, possibly resulting in the periodic spread of the disease.

    Microbiologist Peter Turnbull is trying to learn whether and exactly how vultures are involved. After studying the ecology and epidemiology of anthrax outbreaks in Namibia's Etosha National Park for a quarter-century, Turnbull is now examining vulture blood serum to determine whether the birds spread the anthrax bacterium from one area to another “by dint of actually getting infected or only through mechanical carriage of spores” on their feathers and feet. Because it usually takes many spores to infect an animal with anthrax, he says, “it seems probable that spores deposited by vultures only rarely result in a case of the disease in another animal.”

    With vultures receiving so much scientific attention, some southern African bird groups are cautiously optimistic that the threatened populations will stabilize in the coming years. Conservation biologist Gerhard Verdoorn, who directs BirdLife South Africa, says fewer farmers are poisoning carcasses, and the birds are feeding at 200 vulture restaurants. South Africa's electric company is marking power lines and improving insulation in areas where vultures fly or roost. Verdoorn says the African white-back and some other vulture species seem to be holding their own for now but warns that “one carcass poisoning can wipe out an entire colony of vultures.”

    One factor that may bode well for the vultures' future is their dedication to parenthood. “They mate for life, they lay only one egg per year, and the mother and father share the nest duties,” says Wolter, who cares for 77 vultures at the De Wildt sanctuary. “They are phenomenal parents.”


    Inorganic Electronics Begin to Flex Their Muscle

    1. Robert F. Service

    A dark-horse technology bids to overtake plastics in the race to make circuits that can twist and stretch


    Like a desert mirage, the promise of organic electronics seems to shimmer always on the horizon. Plastic and other types of organics can form the backbone of electronic components that are cheap, thin, lightweight, and flexible, a combination that makes them sought after for applications as diverse as cheap solar cells and roll-up displays. Yet despite a few commercial successes such as small mobile phone displays, organic electronics have had trouble overcoming nagging problems, such as the slow speed at which electrical charges move through the devices and the fact that exposure to air often degrades their performance. Now, organics have something else to worry about: competition from more traditional inorganic electronics now being made to work on top of flexible materials.

    In recent years, several research teams have shown that by making inorganic devices thin enough and layering them on flexible sheets of metal or plastic, they can create circuits that bend and flex much like organics. That approach has enabled researchers to take advantage of the high speed and reliability of inorganic devices and the decades of manufacturing experience that has made them the bedrock of the electronics industry. Now, the two technologies are poised to battle for new electronics applications, such as outfitting robots and medical prostheses with a humanlike “skin” complete with flexible temperature and touch sensors. The number of researchers trying to marry inorganic electronic devices with flexible substrates remains a fraction of the crowd working on organic circuitry. “But it's picking up steam,” says John Rogers, a flexible-electronics expert at the University of Illinois, Urbana-Champaign (UIUC).

    Bend me, shape me.

    Semiconducting wires from inorganic compounds such as gallium arsenide can form the heart of high-performance circuitry atop flexible substrates.


    Researchers worked on thin inorganic electronic devices decades before organic electronics presented a challenge. Labs in the United States first made thin-film inorganic transistors in the 1960s, and today the devices are found everywhere from flat-panel televisions to solar cells. But the devices are still typically deposited on top of glass and other rigid substrates. When organic electronics first entered the picture 30 years ago, the new technology captured the imagination of many groups hoping to create devices atop curved surfaces as well as give electronics the ability to flex and bend. “In the late 1990s, there was a notion by materials and chemical companies that it would be easiest to go with all organics,” says Sigurd Wagner, an electrical engineer at Princeton University. But although many successful prototype products have been developed, organics have proven challenging to turn into a robust and reliable manufacturing technology. “There are so many problems, [people] are returning to an inorganic transistor technology used in industry,” Wagner says.

    Not everybody is returning, of course, and those who make the switch have faced major hurdles. But several groups have recently been showcasing the kinds of things that can be done by putting inorganic electronics on flexible substrates.

    The first challenge was to make a workable device at all. To lay down successive atom-thin layers of material, standard semiconductor technology starts by heating slabs of material to a vapor at several hundred degrees Celsius. The white-hot vapor then condenses atop the substrate at temperatures far higher than most flexible materials, such as plastics, can handle. To create usable circuits, researchers had to find ways to deposit those thin organic layers at temperatures only slightly above the boiling point of water.

    In 2003, for example, Charles Lieber and colleagues at Harvard University reported in Nano Letters that they had deposited a 100-nanometer thin layer of conducting indium tin oxide (ITO) atop a plastic substrate and then patterned an initial set of “gate” electrodes in the ITO using either photolithography or electron beam lithography. The researchers then flowed a solution containing silicon nanowires over the electrodes, depositing the nanowires atop the electrodes when the solvent evaporates. Finally, another lithography step enabled them to pattern the additional metal electrodes needed to create thin-film transistors with a performance comparable to those grown atop crystalline silicon. That same year, Xiangfeng Duan and colleagues at the nanotechnology start-up company Nanosys in Palo Alto, California, reported in Nature a similar scheme for suspending inorganic silicon nanowires and cadmium-selenide nanoribbons in a solution and patterning them into thin-film transistors perched atop plastics and other flexible substrates. The speed of charges in those devices and the voltages at which they switched on and off easily outperformed organic devices.

    More recently, researchers have started taking larger strides. Rogers and colleagues at UIUC and Wright-Patterson Air Force Base in Ohio, for example, reported in the 1 May issue of Applied Physics Letters that they had created ultrahigh-speed gallium arsenide (GaAs) transistors on cheap, flexible plastic substrates. To do so, the Illinois researchers initially fabricated GaAs wires from an inorganic wafer using conventional semiconductor manufacturing techniques. They then applied a thin layer of glue beneath the devices and used a stamping technique to place them atop a plastic film, with additional lithographic steps to create the needed electrodes. The final devices, Rogers's team reported, could switch on and off more than 1 billion times a second, far faster than organic devices and a speed that makes them candidates for use in high-speed communications equipment.

    The newfound prowess of inorganic flexible electronics is also making them attractive for other potentially lucrative markets, such as displays that conform to car dashboards and other contoured surfaces. In December, for example, Wagner and former postdoctoral candidate Stephanie Lacour reported at the International Electron Devices Meeting in Washington, D.C., that they had fabricated amorphous silicon-based circuitry atop tiny islands of rigid silicon nitride. They placed the devices on a flexible substrate of silicone rubber and connected them with ultrathin flexible gold wires. Because both the substrate and the wires between the devices could flex, the researchers could use them to create the flexible equivalent of the electronic “backplane” that controls current liquid-crystal flat-screen displays.

    Rogers and his Illinois team report a similar feat in this month's IEEE Electron Device Letters. They fabricated their circuitry out of ultrathin bendable single-crystalline silicon ribbons. They initially created the ribbons atop a rigid support called “silicon on insulator” (SOI). They then etched away the underlying support and used a printing technique to transfer the silicon ribbons to a flexible polyimide substrate. Finally, they used low-temperature computer chip patterning techniques to lay down the additional layers of metal and insulators needed to complete their circuitry. The result: circuits that performed nearly as well on a flexible substrate as those grown atop crystalline silicon wafers.

    Rogers and his Illinois team also recently detailed an approach that could make inorganic electronics not only fast and flexible, but cheap as well. They set out to bring down the high cost of relying on wafers made from SOI, which can cost $300 each. In the 22 May issue of Applied Physics Letters, the Illinois researchers showed how to carry out the same process using standard bulk crystalline silicon wafers that cost only one-tenth as much as SOI wafers. Marrying conventional crystalline silicon with a flexible substrate “allows us to think about ways to put single-crystal silicon in places you couldn't before,” Rogers says.

    Next wave.

    Undulating ribbons of silicon atop a flexible substrate can be stretched without damage. Such stretchable semiconductors could pave the way for high-speed flexible circuitry in fabrics.


    One of those new places could be in fabrics that not only flex but also stretch, a particularly challenging environment for electronics. Earlier this year, Rogers and a team of Illinois colleagues reported in Science (13 January, p. 208) that they had laid down thin silicon ribbons atop a stretched-out plastic sheet. When they then released the tension on the plastic, the sheet snapped back to its original shape, causing the silicon ribbons to buckle in regular waves. When the researchers then stretched the plastic back out again, the silicon ribbons elongated and continued to function normally as transistors. “It's a very powerful approach,” says Lacour, who is now at Cambridge University in the United Kingdom. Since publication of their Science paper, Rogers says, the team has vastly increased the amount of stretching their devices can tolerate, extended the work to other types of inorganic materials, and allowed materials to stretch in all directions instead of just one.

    Wagner and colleagues have also been looking to take inorganic electronics in new directions, such as integrating them with biological systems. Chunks of rocklike semiconductors aren't typically thought of as biocompatible. But the way they work can make them an ideal choice, Wagner explains. That's because unlike many organic devices, silicon and other standard inorganic semiconductors can be used to make devices that turn on and off with tiny amounts of applied voltage. That's critical, Wagner says, because when large voltages have to be applied they invariably dissipate power as heat. “You can't put them close to biological tissue because that raises the temperature too much,” Wagner says.

    In November, Wagner and colleagues at Princeton and at Columbia University reported at the IEEE Sensors Conference in Irvine, California, that they had made an array of stretchable silicon transistors atop a plastic substrate capable of recording the activity of brain neurons in vitro. The immediate goal of this ongoing project is to understand how neurons respond to rapid stretching, a petri dish analogy to what happens during a car crash or other types of brain trauma.

    But Lacour is already planning to take the next step. At Cambridge, she is helping direct an effort to use flexible circuitry in regenerating severed nerves of accident victims. When nerves are severed, Lacour explains, they quickly die unless they receive consistent electrical inputs, as they would from sensory cells. So Lacour has created flexible gold electrodes on plastic that she hopes to use to integrate with regrowing tissue. By integrating transistors and sensors onto such circuitry, researchers may even be able to create prostheses that communicate touch and temperature to the body's nervous system much as a real limb does, Lacour says. With the progress in flexible inorganic electronics, it's a vision that's beginning to look more real all the time.

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