News this Week

Science  12 Jul 2013:
Vol. 341, Issue 6142, pp. 114

You are currently viewing the .

View Full Text

Log in to view the full text

Log in through your institution

Log in through your institution

  1. Around the World

    1 - Madison
    U.S. Stem Cell Patent Challenged
    2 - Kuala Lumpur
    Evidence Mounts for Two More HIV Cures
    3 - London
    Britain Boosts Health Data Research
    4 - Moscow
    Russian Academy Reorganization Moves Ahead
    5 - Geneva, Switzerland
    WHO Names MERS Emergency Committee
    6 - Ankara
    Turkish Scientists See Growing Antievolution Bias in Government


    U.S. Stem Cell Patent Challenged



    Spurred by a recent U.S. Supreme Court decision that ruled out patents on human genes (Science, 21 June, p. 1387), two nonprofit groups are now asking a federal appeals court to throw out the key patent on human embryonic stem cells.

    The Public Patent Foundation of New York City—a leader in the gene patents case—joined with Consumer Watchdog of Washington, D.C., and Santa Monica, California, to argue that human stem cells cannot be patented because they are a product of nature. The suit focuses on research published in 1998 by biologist James Thomson of the University of Wisconsin, Madison. In 2006, a U.S. patent recognized Thomson as the inventor and gave the intellectual property to the Wisconsin Alumni Research Foundation (WARF). The challengers argue that WARF's patent should be rejected for two reasons: It describes a product of nature, and the discovery was "obvious" in that similar work had been done before with nonhuman stem cells.

    WARF's Managing Director Carl Gulbrandsen said that the agency has "not yet" responded with a legal brief.

    Kuala Lumpur

    Evidence Mounts for Two More HIV Cures

    Two HIV-infected men who had stem cell transplants to treat blood cancers have gone off antiretrovirals (ARVs), and early indications suggest that they may have cleared the virus. This resembles the case of Timothy Brown, the first person cured of an HIV infection, who has been virus-free for more than 6 years.

    Researchers from the Brigham and Women's Hospital in Boston last year reported no sign of HIV in the men following the transplants (Science, 3 August 2012, p. 509). But the patients were taking ARVs, which can reduce HIV to undetectable levels.

    On 3 July, the team led by infectious disease clinician Timothy Henrich and virologist Daniel Kuritzkes described at a conference here how the patients stopped treatment 8 and 15 weeks ago, and neither had detectable virus in their blood. Typically, HIV levels climb high within 8 weeks after treatment stops. But, Kuritzkes cautions, "I think we need a minimum of 1 to 2 years before we can say these patients have achieved permanent remission." The researchers, who hope to do more intensive tests for the virus, stress that the costly, risky transplants have little wide-scale applicability.


    Britain Boosts Health Data Research

    A consortium of British funders has pledged £39 million ($59 million) to establish the Farr Institute for health informatics research. Named for William Farr, a 19th century founder of medical statistics, the virtual institute will link main research centers in London, Dundee, Swansea, and Manchester as well as participants at 19 universities across the United Kingdom. A group of 10 funders committed £19 million to the center earlier this year, and on 3 July the Medical Research Council announced a £20 million contribution.

    The effort will allow researchers to connect anonymized electronic health records from Britain's National Health Service and other data sources to analyze hard-to-study epidemiological questions such as postapproval drug side effects and the public health effects of policies such as smoking bans, says Andrew Morris, dean of the School of Medicine at the University of Dundee. "Arguably, health care is the last major industry to be transformed by the information age," says Morris, one of the coordinators of the institute.

    Farr set an example in the late 1800s, however, when he developed a system to routinely record the cause of death—an innovation that led to epidemiological insights into patterns of disease and mortality.


    Russian Academy Reorganization Moves Ahead

    In talks.

    RAS head Fortov and Russian President Putin on 3 July.


    The Russian Academy of Sciences (RAS) last week gained a 3-year reprieve from a government plan to merge it with two smaller academies. But Duma, Russia's parliament, endorsed several other changes, including stripping the academy of control over its property and real estate holdings, which many scientists believe will ultimately destroy the 289-year-old research organization.

    A group of RAS academicians are hoping that academy leaders will draw up a viable alternative to the government's plans before the Duma takes a final vote on the legislation this fall. Newly elected RAS President Vladimir Fortov was picked to lead a new agency with authority to manage RAS property, but that job falls far short of Fortov's wish to be given the chance to reform RAS internally and without direct government intervention. "Previously, how the system worked was very bad, but understandable," says one scientist. "Now it is completely incomprehensible."

    Geneva, Switzerland

    WHO Names MERS Emergency Committee

    Packed tight.

    Public health experts worry that the hajj could increase incidence of MERS.


    The World Health Organization (WHO) has named a panel of 15 experts to advise Director-General Margaret Chan on whether the Middle East respiratory syndrome (MERS) virus constitutes a "public health emergency of international concern." The committee was expected to meet for the first time by telephone on 9 July. It is just the second such emergency panel ever created by WHO; it convened the first in 2009 to combat the H1N1 flu pandemic.

    Members of the international group include Saudi Deputy Health Minister Ziad Memish; Martin Cetron, director for the Division of Global Migration and Quarantine at the U.S. Centers for Disease Control and Prevention; and Theresa Tam, an expert at the Public Health Agency of Canada.

    Under International Health Regulations, declaring a global crisis would give WHO power to recommend actions, such as travel restrictions, to control the spread of the novel coronavirus, which has infected 80 people so far and killed 44. Keiji Fukuda, assistant director-general for health security and environment at WHO, says that although there is "no acute emergency," WHO wants to be "as ready as possible."


    Turkish Scientists See Growing Antievolution Bias in Government

    Evolving bias?

    The workshop's organizers are part of Turkey's Evolution and Ecology Network (in 2009).


    Two weeks ago, the Scientific and Technological Research Council of Turkey (TÜBİTAK), the country's main research-funding agency, rejected a funding application for a summer workshop on quantitative evolutionary biology because "evolution is a controversial subject." Now, the organizers are calling this the first open admission of a bias against evolutionary biology by Turkey's conservative government. The government began blocking educational evolution websites in 2011, and recently TÜBİTAK stopped publishing books on evolution, a decision it claimed was based on copyright issues.

    The workshop was to expose Turkish biology students to population genetics, game theory, and evolutionary modeling, says Erol Akçay, a Turkish evolutionary biologist at Princeton University who is one of the organizers. Akçay and his colleagues asked TÜBİTAK for 35,000 Turkish lira (about $18,000) to cover students' accommodation and speaker travel.

    Murat Üzoǧlu, the deputy chair of Science F ellowships and Grant Programmes at TÜBİTAK, says that the rejection was the result of objective peer review, adding that "TÜBİTAK has no reservations in supporting projects on the subject matter as it was erroneously claimed."

    The meeting will go ahead despite TÜBİTAK's decision, Akçay says, with private donors closing the funding gap.

  2. Newsmakers

    Three Q's



    Japanese Prime Minister Shinzo Abe has made economic revitalization a priority, and fostering innovation is a key part of his plan. He has tasked his advisory Council for Science and Technology Policy (CSTP) with making sure that the nation's R&D budget supports that goal. At a press briefing last week, Yuko Harayama, an executive member of the council, outlined how next year's S&T budget, due to be unveiled at the end of August, will speed the progress of discoveries to the marketplace. Three key comments from her talk:

    Why a stronger policy council is needed:

    Y.H.:We need the ministries to collaborate. It is rational to have a central entity taking an overview of all of the budget related to [for example] life science and health to accelerate [turning] discoveries into products.

    How management of research programs might change:

    Y.H.:We are [examining] the function played by a program manager. Traditionally, once [an administrator] fixed a budget the work was finished. We need someone … to make sure something is really moving ahead.

    On getting more women in science and technology:

    Y.H.:I am [the first woman] in a permanent position at the CSTP. The most important thing [about having] women … in the decision-making sphere is that they may bring in new thinking. What I will try to do is promote women … putting pressure on the universities, but the same should be done in industry.

  3. Random Sample


    Seasons of Love?

    As early as the 1930s, researchers noticed that children born in winter were prone to health problems: slower growth, mental illness, even early death. That observation is grounded in truth, scientists reported online this week in the Proceedings of the National Academy of Sciences: When it comes to low birth weight and prematurity, both linked to diverse health problems, May is the most unfavorable time to get pregnant.

    Using data from vital statistics offices in New Jersey, New York, and Pennsylvania about births between 1994 and 2006, economists Janet Currie and Hannes Schwandt of Princeton University found that babies conceived in May were 13% more likely to be born premature, and gestation time was almost a week below average. For conceptions between January and May, gestation length declined by about a week before shooting back up to average length in June. This closely aligns with the time when the most patients visited the doctor for flulike symptoms, Currie and Schwandt found—suggesting that flu could cause mothers to deliver early.

    Name Those Moons


    Pluto fans should hail planetary scientist Mark Showalter of the SETI Institute in Mountain View, California. Not only did he sign a petition opposing Pluto's demotion from planet to dwarf planet, but he also discovered two new moons circling the far-off world, thereby boosting its planetary cred.

    But what to name the new satellites? "I got hundreds of e-mails from people I don't know," Showalter says. So planetary scientist Alan Stern of the Southwest Research Institute in Boulder, Colorado, suggested an Internet poll. Names had to refer to the underworld, as Pluto was its mythological god.


    With 450,324 votes cast, the winner was one that actor William Shatner championed: Vulcan, home of Star Trek's Mr. Spock. Runners-up included Cerberus, Styx, and Persephone.

    Showalter's team chose the top two, but officials vetoed Vulcan, the Roman god of fire and forges. "Pluto and Vulcan didn't cross paths much," Showalter admits. Cerberus, Pluto's three-headed dog, is already the name of an asteroid but received approval in its Greek form, Kerberos. Styx also made the grade as the goddess of the river dividing the world of the living from the underworld. Showalter says: "I am very happy with the outcome."

    Kerberos and Styx join Pluto's three other moons, Charon, Nix, and Hydra, the last named for a monster whose nine heads signify that many consider Pluto to be the ninth planet. Indeed, the emblem for NASA's Pluto-bound New Horizons spacecraft (bottom right) is nine-sided, and Showalter says that he'd be "almost shocked" if it doesn't find yet more moons when it reaches its target in 2015.

  4. Veterinarian-in-Chief

    1. Mara Hvistendahl

    As China's point person for avian influenza, Chen Hualan is spearheading studies on deadly strains—while fending off critics who say she's playing with fire.

    Flu fighter.

    Chen studied avian influenza in China back when "nobody cared."


    HARBIN, CHINA—On Saturday, 30 March, Chen Hualan was in a meeting in Beijing, pulling a characteristic weekend work session, when a tense call came through on her mobile. It was an official in China's Ministry of Agriculture, reporting that people were coming down with a novel bird flu virus. The Chinese Center for Disease Control and Prevention (Chinese CDC), Chen learned, had confirmed three cases, two in Shanghai and one in Anhui province. The cases appeared in late February and early March; Chinese CDC had subsequently isolated the virus and sequenced it. Researchers identified it as H7N9, a virus not previously detected in humans.

    As the head of China's National Avian Influenza Reference Laboratory, Chen leapt to action. She'd been the go-to person for animal testing during periodic outbreaks of an earlier deadly bird flu, H5N1, and she knew that a novel virus infecting humans was a very serious matter. After she hung up, she dispatched staff members to Shanghai and Anhui to collect samples from poultry markets and farms. On 31 March, Chinese authorities announced the virus to the world.

    Within a few days, Chen's team had sequenced H7N9 strains isolated from chickens and pigeons. The results came back at 11 p.m. on Tomb-Sweeping Day, a national holiday in China that went unobserved in the Harbin lab. Chen sent the sequence data to the agriculture ministry, recommending the immediate closure of poultry markets in areas with infections. But her work had just begun. For the next month, as human cases piled up and poultry samples poured in, Chen's lab worked around the clock, testing 10,703 samples in total. Not until May did Chen get more than 5 hours of sleep a night.

    The 44-year-old virologist didn't need to impress her colleagues. "Chen's massive body of work is of outstanding quality," says Ron Fouchier, a virologist at Erasmus MC in Rotterdam, the Netherlands. But controversy soon engulfed her. After news of China's human cases went public, Chen started receiving e-mails from scientists around the world asking for samples of the virus isolated from birds. China had come under fire during past outbreaks for dragging its feet. But as head of a World Organisation for Animal Health (OIE) reference lab, she had committed to sharing the virus with other labs in a network run by OIE and the Food and Agriculture Organization (FAO), and the implication in the scientists' e-mails that she was unwilling to pony up samples irked her. "They thought we were hiding something," she says. Chen replied to the e-mails that she wasn't holding anything back: "I am also looking for the virus," she wrote. But suspicions die hard.

    A quick ascent

    Like many senior Chinese scientists, Chen did not choose her calling. She grew up in a small city in Gansu, a poor province in western China. When her score on China's college entrance examination did not secure one of her preferred majors—she had hoped to study medicine—she ended up studying veterinary science in Lanzhou, the capital of Gansu. In 1994, her Ph.D. research took her to Harbin, a major city in far northeastern China, near the Russian border, where winter temperatures can plummet to −30°C, and an army of workers uses straw brooms to sweep snow off the streets.

    When she arrived at the agriculture ministry's Harbin Veterinary Research Institute, she asked her supervisor, Yu Kangzhen, what she should research. "Whatever—as long as it's on influenza," he told her, she recalls. Infectious diseases were a top priority in China, yet, "nobody cared about flu," she says. But Yu knew that avian influenza had caused outbreaks in poultry in several other countries and that Chinese farms were lax on biosecurity. If a highly pathogenic virus emerged in Chinese birds, he believed, it would spell trouble.

    Yu had imported a few flu strains from an OIE reference lab in the United Kingdom, and Chen and four colleagues got to work on vaccine development. "We couldn't do any basic research because we didn't have too many strains at that time," she says. Things changed in 1996, when the team isolated H5N1 from a farmed goose in Guangdong province. The agriculture ministry entrusted the lab with surveillance, which became critical the following year, when a 3-year-old boy in Hong Kong became the first person infected with H5N1. He died. That year saw 17 more cases, including five fatalities. Suddenly, bird flu went from a research backwater to a global preoccupation.

    In 1999, Chen wrote Kanta Subbarao, who then headed up molecular genetics research at the U.S. CDC in Atlanta, asking to work in her lab as a postdoc. Subbarao was studying the H5N1 strains that had emerged in Hong Kong. "We were having to get a crash course in avian influenza," Subbarao says. The Hong Kong viruses had acquired the hemagglutinin gene, key to their ability to bind to and infect cells, from the Guangdong goose strain. Chen's familiarity with the strain snared her a job.

    CDC's working conditions wowed Chen. Back then, a scientist looking to use a PCR machine in Harbin had to sign up 2 to 3 weeks in advance. In Atlanta, every scientist had a machine. Chen worked on vaccines for H5N1 and H9N2, learning a technique for developing vaccines called plasmid-based reverse genetics. Instead of waiting to obtain plasmids developed by other labs, Chen decided to make her own—an incredibly time-consuming process, says Subbarao, who is now at the U.S. National Institute of Allergy and Infectious Diseases. Chen, she says, "is not at all intimidated by the amount of work that she takes on."

    After 3 years in Atlanta, Chen, at the tender age of 33, returned to Harbin to head the national avian flu lab. She saw it as a chance to catapult into a prominent position in flu research. But her husband and son had come with her to the United States, and her decision to move the family back to China raised eyebrows. People "asked me, 'Where are you going to go, Shanghai or Beijing'? And I said, 'Harbin.' " Colleagues, she says, "thought I was crazy" to return to the frigid outpost.

    The lab, housed in a pre-1949 building with the feel of a sanatorium, turned out to be the center of action. In 2003 and 2004, human H5N1 cases emerged in Hong Kong, mainland China, South Korea, Thailand, and Vietnam, while poultry outbreaks spread across Asia. Prior to those outbreaks, scientists at the avian flu lab had isolated more than 20 H5N1 strains from apparently healthy ducks. But the staff had been without a director for 2 years before Chen arrived; lacking guidance, they stored the specimens in a freezer. Under Chen's direction, they got to work sequencing strains and testing virulence in mice. They discovered that the nastiest strains were those isolated from more recent samples. In an influential paper published in the Proceedings of the National Academy of Sciences in 2004, the team showed that H5N1 had progressively acquired the ability to kill mammals—meaning a longer list of H5N1 genotypes than previously thought could threaten people.

    Chen's research interests and staff have since multiplied. Her 80-person team has, among other things, developed an avian vaccine against Newcastle disease—a contagious virus that can cause conjunctivitis and flulike symptoms in humans—and an avian H5N1 vaccine now used worldwide. The lab joined OIE's reference network in 2008 and in March was designated an FAO reference center, a badge of global excellence awarded to a select number of labs. The institute that houses the lab is preparing to move to a gleaming new 260,000-square-meter campus. The differences between research conditions in China and in the West are "getting smaller and smaller," Chen says. She may even have an advantage over many colleagues, given the abundant resources and staff members she enjoys. Pondering what her path would have been had she stayed in Atlanta, Chen says: "Maybe a postdoc for many, many years?"


    Risky business?

    On 2 May, Chen and colleagues published a controversial paper online in Science in which they argued that the H5N1 virus could set off a pandemic (Science, 21 June, p. 1459). So far, human-to-human transmission has been limited. Of the 375 deaths attributed to H5N1 as of 4 June, in nearly all cases victims are known to have caught the virus from infected birds. Chen set out to answer a question that others—most notably Fouchier, and Yoshihiro Kawaoka of University of Wisconsin, Madison—had probed as well: What changes in the virus would enable it to spread from human to human?

    Sitting ducks?

    So far, H7N9 appears to be mysteriously absent in farmed birds.


    To find out, Chen's team used plasmid-based reverse genetics to create 127 reassortants, or hybrid viruses, in which they swapped gene segments from H5N1 with those from the H1N1 swine flu virus. In research conducted between January 2010 and December 2011, they infected guinea pigs with the most pathogenic reassortants and found that replacing a single gene was enough to get the virus to leap from infected guinea pigs to healthy ones in adjoining cages.

    It was the right experiment for someone whose work ethic borders on masochistic. The 127 hybrid viruses that Chen generated is an "astounding" number, Subbarao says: "That's a tremendous amount of work, and then a tremendous amount of data to stare at and try to see patterns." Completing the study required more than a dozen researchers working for 2 years with more than 250 guinea pigs, 1000 mice, and 27,000 infected chicken eggs. Fouchier says that he has "thought many times of doing the exact same systematic experiment" but did not proceed because of various constraints. Among other issues, "I do not have a single grant for which I could afford to work with 13 people for 2 years to yield a paper," he says.

    The virus gain-of-function experiments prompted a global outcry. Earlier studies of this type conducted by Fouchier and Kawaoka in ferrets also sparked an uproar in 2011 when word leaked ahead of publication (Science, 2 December 2011, p. 1192), leading to a global moratorium on H5N1 transmissibility studies in January 2012. (The ban was lifted a year later.) In Chen's case, the backlash carried stinging undertones. In comments to British newspaper The Independent that were widely reported elsewhere, theoretical ecologist and former U.K. Royal Society President Robert May called the study by Chen and colleagues "appallingly irresponsible," adding that the researchers were "driven by blind ambition with no common sense whatsoever." Volleys came from within China as well. "People are really concerned about the biosecurity" in Chen's lab, says Liu Wenjun, deputy director of the Chinese Academy of Sciences' Key Laboratory of Pathogenic Microbiology & Immunology in Beijing. Liu notes that the deadly severe acute respiratory syndrome virus reemerged in China in 2004, a year after the initial outbreak, when a Chinese CDC worker was infected following a safety breach.

    Chen insists that she's unfazed by the criticisms. May is out of his depth, she says: "I don't think he understands this kind of science very well. If a flu scientist said this, I would be concerned." Masato Tashiro, the head of a World Health Organization collaborating center for influenza research in Tokyo, says that he has visited Chen's facility, which includes a biosafety level P3 lab; it meets international standards, he says. The lab is "state of the art," Kawaoka adds.

    Some have taken aim at the relevance of Chen's findings. Yi Guan, a virologist at the University of Hong Kong, contends that Chen should have used ferrets, as Fouchier and Kawaoka did. Ferrets better mimic infections in humans, whereas "the guinea pig model has a lot of question marks," Guan says. "You need special lab conditions to make disease happen [in guinea pigs]. I don't think the results are reliable." Chen counters that guinea pigs have both avianlike and humanlike receptors in the respiratory tracts, which makes them an ideal model for evaluating the transmission potential of viruses that bind to both receptor types.

    Chen is now turning her attention to H7N9, which she says appears to infect humans "much, much more easily than H5N1." That naturally raises the question of whether the virus has pandemic potential. But gain-of-function studies are not yet a priority for H7N9, she says. Less is known about this virus than about H5N1, which has circulated for years without acquiring the ability to pass between humans, leading people to ask what changes might make H5N1 transmissible. With H7N9, Chen says, "first we want to answer the question, is it transmissible?"

    As Chen dives into H7N9 studies, she may continue to encounter criticism because she is effectively at the helm of China's veterinary research for flu studies. "China is not totally open," says Robert Webster, a virologist at St. Jude Children's Research Hospital in Memphis, Tennessee. When it comes to animal infections, he says, "I'm not convinced that all of the information is completely shared with the world." But Chen is trying, he says: "She does her very best to put out the information that's relevant."

    Tens of thousands of tests in China, by the Harbin lab and others, have turned up only one case of H7N9 outside of poultry markets, in a farmed homing pigeon. New infections tapered off in May following the closure of poultry markets, emboldening the Shanghai government to reopen some markets on 20 June. A seasonal lull may have given false reassurance. "H5N1 appeared in the cooler months, disappeared in the hot months, and then reappeared in the cooler months," Webster says. H7N9 may follow a similar pattern, he warns. "Did they know the virus was really gone before they reopened the markets?"

    Chen says that she, too, is puzzled by the apparent dearth of H7N9 infections on farms, calling the situation "very strange." If the virus is truly only in poultry markets, she says, "It will be a lucky thing." But she is not the sort to leave matters to chance. Chen says that she had recommended keeping live poultry markets closed permanently. When the mercury starts to fall this winter in Harbin, we'll know who was correct.

  5. Planetary Science

    Meteorite Mystery Edges Closer to an Answer—Or the End of a Field

    1. Richard A. Kerr

    Blobs called chondrules in the fabric of rocks from space have long baffled scientists. A new idea may shed light on their origins, but some experts have given up hope.

    No peas in a pod.

    Colorized by mineral type, millimeter-size chondrules from a single meteorite reveal their diversity.


    How would you like your decades of research on a field's central problem to be summed up by the statement that "these objects remain as enigmatic as ever"? That was part of the title of a session on the formation of chondrules at the 75th annual Meteoritical Society meeting last year.

    For half a century, meteoriticists—scientists who study meteorites—have been trying to understand the origin of chondrules: once-molten, millimeter-size blobs of rock that a 19th century scientist called "drops of fiery rain." Chondrules riddle 85% of the rocks that fall to Earth from the asteroid belt, so meteoriticists are deeply intrigued. And scientists have long presumed that the recipe for making the four rocky planets, including Earth, consisted largely or entirely of chondritic rock. They would like to know how their main ingredient came to be. Yet only two of last year's 14 talks in that chondrule formation session directly addressed the topic, and both of them described a decades-old idea that has made little headway: chondrules splashing off colliding planetesimals.

    A dozen years ago John Wood, a leading light of the field, publicly chided his meteoriticist colleagues for their exclusive focus on deciphering the composition of chondrules on ever-finer scales (Science, 31 August 2001, p. 1581). That narrow approach "has not worked," he told hundreds of planetary scientists in a provocative 2000 plenary talk, "and it won't work."

    What was needed, Wood said the next year, was "a unifying paradigm, and there just isn't one." If chondrules were not to remain "tight-lipped witnesses to the beginning," he said, meteoriticists who know chondrules must collaborate with astrophysicists who know what it was like at the beginning of the solar system.

    Wood soon washed his hands of chondrules and retired to concentrate on oil painting, mostly of landscapes, but "his words really resonated with a lot of people," says astrophysicist Steven Desch of Arizona State University, Tempe. Workshops have been held, meteoriticist-astrophysicist collaborations formed, and papers published. "The progress is there," Desch says.

    But he emphasizes that it has been slow. Although constraints on proposed formation mechanisms have been tightened and theories have become more sophisticated, the field of possible formation mechanisms has hardly been narrowed in decades. But there may be reason for hope. A collaboration of astrophysicists and a meteoriticist has just floated a new mechanism: humongous "short circuits" in the still-forming solar system. All it has to do is run the gantlet of skeptical meteoriticists and astrophysicists.

    Where's the heat?

    Solving the puzzle is hard in part because chondrule formation can't be observed today. The right conditions probably haven't been seen in our planetary system for more than 4.5 billion years. They must have existed during the solar system's first few million years, when only a disk of gas and dust called the protoplanetary nebula swirled around the nascent sun. But meteoriticists have been hard pressed to come up with enough energy even then to rapidly heat rocky dust to 1600 kelvin or more and melt it into globules. The nebula at the time was merely warm—at most several hundred kelvin.

    In 2000, meteoriticist Alan Rubin of the University of California, Los Angeles, counted 14 heating mechanisms proposed up to that time. Several involved strong shock waves, from the bow shocks of planetesimals plowing through the nebula to a shock wave trailing off wandering Jupiter. Others ranged from nebular lightning to gamma ray bursts. None, Rubin noted, struck astrophysicists as particularly plausible.

    "There are a lot of models out there, but I'm not sure how you can really test them," says Harry McSween of the University of Tennessee, Knoxville. As Wood's first student, McSween did his dissertation work mostly on chondrules but later switched in frustration to studying martian rocks. "However [chondrules] formed, they formed beyond our experience. How do you ever prove it?"

    Meanwhile, meteoriticists were generating ever more constraints. By dissecting the chemistry, rock types, and isotopes of chondrules and the fine-grained matrix around them down to the micrometer scale, researchers had divided chondritic meteorites—known as chondrites—into four groups and 12 subgroups. The diversity suggested that formation conditions must have varied across the disk without much mixing between formation regions. The rapid heating, it seems, repeatedly struck small parts of the nebula in which concentrations of dust were almost implausibly high. The newborn molten chondrules held on to even their most volatile elements. Some chondrules must have been remelted or partially melted. And the list goes on.

    Hot enough.

    In this simulation of a "short circuit" in the early solar system, temperatures reach rock-melting levels (white) in under a second.


    Even in 2001, Wood was losing patience with his colleagues' seemingly endless stamp collecting. "One of the problems with mineralogists and petrologists is we can get bogged down in the details," he said. "I don't think the answer is in the chondrules. They've had the living daylights studied out of them." Meteoriticists have since extracted even more telling details from chondrite meteorites, but to little avail. Some of Rubin's heating mechanisms have since fallen from favor, while remaining ones—including shocks of one sort or another and planetesimal impacts—have a handful of supporters each, and no leading contender has ever emerged.

    Joining forces

    With researchers starting to heed Wood's admonition to cross disciplines, communication between meteoriticists and astrophysicists "is enormously improved over John's day," says meteoriticist Conel Alexander of the Carnegie Institution for Science's Department of Terrestrial Magnetism (DTM) in Washington, D.C.

    Two other factors helped as well, Alexander says. Leading astrophysicist Frank Shu of the University of California, Berkeley, made a splash with a proposal that outbursts from the young sun provided the necessary heat (Science, 20 June 1997, p. 1789). The idea has not fared too well (none has), but Shu's entry made speculating about chondrule formation "something respectable to do in astrophysics," Alexander says. And the growing fascination with how planets take shape around other stars "has made people much more interested in what was happening in the early solar system," he says.

    The latest product of this growing collaboration comes from four astrophysicists and a meteoriticist. Each of these researchers has or had an affiliation with the American Museum of Natural History (AMNH) in New York City. The astrophysicists of the group were wondering what role the magnetic fields that pervaded the protoplanetary nebula might play in chondrule formation. "Astrophysicists like to see where the energy goes," says astrophysicist Colin McNally, a former postdoc at AMNH, now at the Niels Bohr Institute in Copenhagen.

    So the AMNH researchers followed the well-known energy cascade starting with the gravitational energy stored in the disk's gas and dust orbiting the sun. That energy moved into the magnetic fields churned in the disk by turbulent ionized gas and dust and then to its ultimate dissipation as heat.

    Astrophysicists have long known that magnetic field energy can be dissipated as heat through "current sheets." These are relatively thin, spread-out electrical currents spun from the magnetized turbulence of the disk. But normal current sheets would not have been powerful enough to forge chrondrules. Last year, though, the AMNH astrophysicists proposed in The Astrophysical Journal that the sheets might be prone to a particular instability in which a temperature-sensitive feedback would drive the sheet temperature to rock-melting heights.

    Just as an electrical short circuit can surge to wire-melting temperatures when a current finds a path of lower resistance, the new instability would drive up temperatures as atoms of potassium in the nebular gas lose electrons from their shells to become current-carrying potassium ions. The faster the temperature rises, the faster potassium ionizes to carry more current, which in turn raises the temperature even faster. In the AMNH computer simulations published on 20 March in The Astrophysical Journal Letters, this runaway current—essentially a short circuit—can raise the core of a current sheet to temperatures ranging from 1650 K to more than 2000 K, depending on the initial width of the current sheet. So in this model, at least, the proposed instability produces just the range of temperatures that various features of chondrules call for. "It's very natural," McNally says.

    Not so fast

    Well, maybe. "It's a new idea, they make a pretty good case for it working, and there's much worth considering," says astrophysicist Alan Boss of DTM, "but I'd put it on the bottom of the list." He doesn't think shortcircuits would work in the core of the disk, where most of the mass resides, because temperatures there weren't high enough there to support the instability. Astrophysicist Desch agrees.

    Discouraged yet? You have company. Meteoriticist Ian Sanders of Trinity College Dublin has been pushing chondrule formation by impact for 20 years, but he notes that "if you read the literature, none of [the models] work. I sometimes wonder whether there are too many uncertainties and variables."

    "We're all a bit disappointed," Alexander allows. What's still needed, Desch says, is better models of chondrule formation. "You have to get your model to the point that you can test it," he says. "You have to make it more quantitative. No one's really doing that."

    But Alexander thinks it's going to happen. To start with, McNally has been funded to do such work. And "I do think we're making progress, though perhaps not as fast as we'd like," Alexander says. "People are trying to put chondrites in an astrophysical context," as Wood wanted. "Sooner or later, someone's going to come up with a mechanism that solves it all. I'm an optimist."