News this Week

Science  12 Apr 2013:
Vol. 340, Issue 6129, pp. 126
  1. Around the World

    1 - Washington, D.C.
    Rallying Against Research Cuts
    2 - Washington, D.C.
    Next Up for NASA: Exoplanets and Neutron Stars
    3 - Klamath River, California and Oregon
    Klamath Dams Should Go, Interior Dept. Says
    4 - Ottawa
    Canada to Investigate Alleged Muzzling of Scientists
    5 - Abu Dhabi
    Camel Connection to New Coronavirus?

    Washington, D.C.

    Rallying Against Research Cuts


    Thousands of scientists and patient advocates poured into a square in downtown Washington, D.C., earlier this week in what organizers called the largest-ever rally to call for more funding for biomedical research. The event, which drew many researchers who were in town for the annual meeting of the American Association for Cancer Research (AACR), highlighted the 5% cut to the National Institutes of Health's (NIH's) $31 billion budget imposed by Congress last month through sequestration, as well as the flat growth of NIH's budget over the past decade.

    AACR attendees and others from more than 200 supporting organizations chanted "more progress, more hope, more life" and listened for nearly 2 hours as members of Congress, patient advocates, and celebrities spoke in support of increasing NIH's budget. Emcee Cokie Roberts of ABC News and NPR declared that "it could not be a stupider time to cut back on funding for medical research." The event was "historic and really unprecedented," said AACR CEO Margaret Foti. For a while, she added, tweets with the rally's tag #RallyMedRes were second to only tweets about former U.K. Prime Minister Margaret Thatcher's death.

    Washington, D.C.

    Next Up for NASA: Exoplanets and Neutron Stars

    NASA's Astrophysics Explorer Program on 5 April announced it has selected two missions—an exoplanet-hunting satellite and an instrument to study neutron stars—for launch in 2017. The Transiting Exoplanet Survey Satellite (TESS) will use wide-field cameras to survey the brightest stars in the sun's neighborhood, searching for gas giants and terrestrial planets, particularly those that are Earth-sized. Those planets, researchers hope, could be candidates for follow-up studies of their atmospheres by the James Webb Space Telescope, scheduled for launch in 2018.

    The Neutron Star Interior Composition Explorer (NICER), which will be deployed on the International Space Station, will observe x-rays flashed by neutron stars, helping researchers understand the nature of matter contained in these dense, spinning objects that result from the collapse of massive stars. TESS will get up to $200 million, and NICER will receive up to $55 million.

    Klamath River, California and Oregon

    Klamath Dams Should Go, Interior Dept. Says

    Worth a dam.

    The Copco 1 Dam is one of four dams recommended for removal to restore salmon habitat.


    Remove four aging dams along the Klamath River in northern California and southern Oregon, the U.S. Department of the Interior advised in an environmental impact statement (EIS) released last week. The dams, completed between 1918 and 1962, block salmon migration and raise water temperatures and algae levels, changes that also lower salmon survival.

    Habitat restoration and sediment removal, together with the dams' demolition, would cost about $1 billion. But that's cheaper than the other three options that the EIS panel considered, which leave some or all of the structures in place. If the dams remain, the operators will be required to pay for maintenance and upgrades, including installing expensive new fish ladders.

    The EIS was carried out as part of the Klamath Hydroelectric Settlement Agreement (KHSA), an agreement reached in 2010 by 40 stakeholder groups—including the states of California and Oregon as well as three Native American tribes—to determine whether removing the dams would restore salmon fisheries. KHSA also requires authorization by Congress before the dams can be removed. But there is now little momentum for such legislation on Capitol Hill.


    Canada to Investigate Alleged Muzzling of Scientists



    Since Stephen Harper was sworn in as Canada's prime minister in February 2006, reporters and government scientists have bristled at the government's restrictions on communications with the press and public. On 27 March, Information Commissioner Suzanne Legault confirmed that she has opened an investigation into whether scientists in seven government departments are being muzzled by senior politicians.

    The government's policy, which it says is to ensure that government employees speak with "one voice," requires federal civil servants and scientists to get permission for press interviews from their minister or the Privy Council Office (Harper's central shop) and that questions be submitted in advance. The Department of Fisheries and Oceans also recently required department scientists to get approval from senior officials before publishing papers.

    Critics contend that these policies are tantamount to a gag order, and in February, two groups—the Environmental Law Centre at the University of Victoria and Democracy Watch, a nonpartisan group that advocates for government accountability—asked Legault to investigate. The timeline on Legault's investigation, or whether a final report will be submitted to Parliament, is unclear.

    Abu Dhabi

    Camel Connection to New Coronavirus?

    Hump hypothesis.

    An nCoV patient from Abu Dhabi had been in close contact with a sick racing camel.


    Scientists in Germany are hoping that a camel owned by a man from the United Arab Emirates who died in Munich on 26 March will give them clues to the origins of a new coronavirus that has killed 11 people so far. The patient, a wealthy 73-year-old man from Abu Dhabi, was taken to the Klinikum Schwabing in Munich on 19 March and was confirmed to suffer from the new virus, nCoV, 4 days later (Science, 5 April, p. 17).

    The patient owned racing camels and had been in close contact with a sick camel shortly before he fell ill, says Clemens Wendtner, a physician at the Munich hospital; a male relative also became sick after contact with the same camel. Researchers from the group of Christian Drosten, a virologist at the University of Bonn, are planning to travel to the United Arab Emirates to take samples from the camel, Wendtner says, to find out if it was infected with nCoV. Previous anecdotal reports had linked the virus to livestock, but so far, its origins remain a mystery.

  2. Random Sample


    After years of pressure, Swiss drug company Roche says it will release all of its clinical trial data on Tamiflu, a controversial anti-influenza drug stockpiled by many nations despite some claims that there is not enough evidence of its efficacy. But some scientists remain skeptical, wondering what Roche might redact.

    Dengue More Prevalent Than Thought


    There is no current vaccine for dengue, a mosquito-borne viral disease so painful that it's sometimes called "breakbone fever." To keep it in check—through mosquito control and vaccination campaigns—planners have to know where the disease is. Now, a new study estimates that there are 390 million global cases of dengue (pictured)—several times the World Health Organization's estimates.

    Jeremy Farrar, a clinician at the University of Oxford Clinical Research Unit in Ho Chi Minh City, Vietnam, and epidemiologist Simon Hay of the University of Oxford in the United Kingdom compiled 8300 reports of dengue infections and considered new evidence on risk factors, such as population growth in urban areas where the virus-carrying Aedes aegypti mosquito thrives. Using new modeling techniques, they concluded that in 2010, dengue sent 96 million people to clinics or caused them to miss school or work, while another 294 million had mild or asymptomatic infections, the researchers reported online on 7 April in Nature.

    They Said It

    "[T]he secretary's action was politically motivated, scientifically unjustified, and contrary to agency precedent."

    —Judge Edward Korman of the Eastern District of New York, slamming a 2011 decision by U.S. Department of Health and Human Services Secretary Kathleen Sebelius to prevent younger teenagers from accessing the emergency contraceptive Plan B without a prescription. Korman ruled last week that Plan B should be available over the counter to women of all ages.

    Game of Habitable Zones

    In the world of Game of Thrones, summer can last for years, winter for a generation. Fans have long debated the reason for these unpredictable seasons—and now astronomers at Johns Hopkins University in Baltimore, Maryland, offer a hypothesis: The show's setting may be a world that orbits two stars instead of one.

    Kit Harington as Jon Snow on Game of Thrones.


    On this hypothetical planet, years last 700 days, and the two sunlike stars orbit each other every 100 days. This complicated dance results in erratic seasons, with winters that can last anywhere from 600 to 850 days. Because the orbit is a three-body problem, predicting the length of the seasons in advance would be impossible for the computerless maesters of Westeros. "With heavy hearts, we conclude that our attempts to provide the good folks of Westeros with a reliable weather forecast are inconclusive," the authors wrote in a paper posted on the arXiv server on 1 April.

    Other earth scientists are skeptical. The pattern of winters and summers plotted in the paper "doesn't quite seem chaotic enough" to cause the turmoil observed in Westeros, says Stephen Kane, an astronomer at the California Institute of Technology in Pasadena who has studied the habitable zones of exoplanets in such circumbinary orbits. He suggests injecting a bit more chaos by introducing a third star to the system or reimagining the planet as an exomoon orbiting a gas giant. Still, this paper "is on the right path to providing a purely physical explanation" of the Westerosi seasons, he says. "Of course, if there's magic involved, all bets are off."

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  3. From Cosmic Dawn to Milkomeda, and Beyond

    1. Robert Irion*

    The thoughts of Harvard University theorist Avi Loeb traverse the universe, past and future—and he urges young researchers to be just as daring.


    CAMBRIDGE, MASSACHUSETTS—A file cabinet drawer in the office of Abraham ("Avi") Loeb is simply labeled "IDEAS." It holds a single hanging file with a few manila folders, each containing sheets of paper displaying equations in Loeb's crisp penmanship. "I have ideas all the time; they just bubble up," he says. "I keep adding a piece of paper here if I don't have time to work on it."

    In Loeb's 20 years at the Harvard-Smithsonian Center for Astrophysics, those minimalistic sheets have seeded a breadth of research rivaled by few theorists in astrophysics. His prodigious publication record spans three books (including an award-winning popular volume), 430 papers, and counting.

    Loeb is best known to cosmologists for illuminating the messy physics of the "cosmic dawn," when light from the first stars and galaxies seared holes into the hydrogen gas that suffused the new universe. He and his many colleagues have also described how to spot ancient gamma ray bursts, how giant black holes may have grown and merged, and how to take the first image of a black hole—key predictions that led to campaigns to observe such extreme physics. But his ruminations have also spawned papers on searching for imprints of life in exoplanet atmospheres, detecting light from nearby alien civilizations, and how astronomers of the far future might deduce the expansion history of the universe.

    Loeb tries to foster this mix of serious data-driven theory and adventuresome projection among students and researchers at Harvard's Institute for Theory and Computation (ITC), which he directs. "Following Avi's work can be quite dizzying," says Mordehai Milgrom of the Weizmann Institute of Science in Rehovot, Israel, one of Loeb's first tutors in astrophysics. Adds Frederic Rasio, an astrophysicist at Northwestern University in Evanston, Illinois: "There is hardly a question in astrophysics—any subject, really—that Avi has not touched at some point."

    Plucked from the farm

    The 51-year-old Loeb traces his far-flung musings to his childhood on a village farm in Israel, about 20 kilometers from Tel Aviv. His father was head of Israel's industry for pecans; the family also raised chickens and grew oranges and grapefruits. After collecting eggs and doing other chores with his two older sisters, Loeb would drive a tractor into the hills and spend hours reading books by existential philosophers. "I often considered returning," he says. "It's a more relaxing style of living."

    At age 18, Loeb was chosen with two dozen other young men for an elite Israeli military program called Talpiot. He studied physics and mathematics at the Hebrew University of Jerusalem and underwent basic training in paratrooping, driving tanks, and other soldiering. During and after his graduate program he worked at the Soreq Nuclear Research Center, where he led a weapons project to propel masses using electric discharges to ignite material with lower atomic weight than gunpowder, such as polyethylene. He earned a Ph.D. in plasma physics at age 24 and completed his compulsory service 2 years later.

    Loeb's innovations at Soreq caught the attention of U.S. Air Force Gen. James Abrahamson, who came to Israel as the first director of President Ronald Reagan's Strategic Defense Initiative program. The general's staff invited Loeb to visit the United States, where the era's leading plasma physicist, Marshall Rosenbluth, steered him toward the Institute for Advanced Study (IAS) in Princeton, New Jersey. There, noted astrophysicist John Bahcall first invited Loeb for a 1-month stay, then stunned him with an offer of a 5-year appointment—but only if Loeb switched from plasma physics to astrophysics. Loeb marvels at the "wild risk" that Bahcall, who died in 2005, took in hiring him. "I owe him my career," he says.

    From IAS, Loeb took an assistant professor job at Harvard in 1993, despite warnings that promotion was improbable. "At the time, Harvard viewed junior faculty almost as a glorified postdoc," says Harvard astrophysicist Jonathan Grindlay. "It was not a healthy environment." But nearly 4 years later, when Loeb had tenure offers from Cornell University and the Weizmann Institute, Harvard made the rare decision to keep him. "He said we would be glad we hired him," chuckles Robert Kirshner, the astronomy department chair at the time. "Avi has mellowed a bit, but this great self-confidence has remained in place."

    From darkness to light

    Loeb's promotion came at a time of profound personal change. He divorced his first wife, who lived separately in New York in a marriage that never had worked, and months later met Ofrit Liviatan in Israel—through a connection arranged by the pair's mothers. Liviatan, a lawyer in Israel, joined Loeb in Cambridge a year later. She now lectures in Harvard's Department of Government.

    The couple lives in a quiet setting in Lexington, about 20 minutes outside Boston, with daughters Klil, age 11, and Lotem, age 7. Loeb works on their 110-year-old house and watches the sky from his back porch, amid a constant flow of ideas. "One day it may stop," he says. "But so far, it hasn't."

    Many of those ideas concern the "epoch of reionization"—the long era when ultraviolet light from stars and galaxies split the universe's dark fog of neutral hydrogen into protons and electrons, starting about 100 million years after the big bang. In papers establishing a now-accepted paradigm, Loeb and his many students and postdocs built up the physics of how ionized hydrogen "bubbles" spread into ever-evolving patterns as stars and quasars lit up, like a cosmic sponge growing more porous with time.

    The leftover neutral hydrogen emitted a hum of radiation at a wavelength of 21 centimeters. Loeb's calculations suggested that low-frequency radio antennae on Earth could tune into that hum, stretched out up to 3 meters long on its way here by the ongoing expansion of space. The more distant the hydrogen, the more its humming gets stretched. Loeb probed in detail how astronomers could harness that "redshift" to create a tomographic atlas of the hydrogen fog burning off during the cosmic dawn, a process that took up to a billion years.

    The Loeb files.

    At home in 1966 in Beit Hanan, Israel, with sister Shoshana; at the Hebrew University of Jerusalem in 1982 during Talpiot military training (Loeb at rear left); playing soccer in 2009 with Harvard University colleagues.


    Colleagues credit Loeb for the theoretical underpinnings supporting major radio astronomy efforts in Australia, Europe, and South Africa to unveil those patterns. "Avi has done more than anybody to explain how important this period of time was and what facilities would be needed to unravel the physical detail of what happened," says astronomer Richard Ellis of the California Institute of Technology in Pasadena.

    Loeb takes as much pride in two other pursuits that helped chart a course for observers. In a 1992 study at IAS, Loeb and Andrew Gould, who is now at Ohio State University, showed that planets circling other stars could reveal themselves by causing brief flares of light from background stars via gravitational "microlensing"—still the only method that exposes exoplanets in distant parts of the Milky Way. And about a decade ago, Loeb and colleagues calculated that gamma ray bursts—the most powerful explosions known—near the margins of the observable universe should remain visible to telescopes. NASA's Swift satellite soon confirmed the predictions.

    The studies reflect an unshakable tenet of Loeb's work: contact with data. He avoids the mathematical conjectures of what he calls "theory bubbles," and he steers students away from them as well. "There is one reality out there," he says. "It's dangerous to work on abstractions with no feedback from data. Some physicists do not understand this."

    Astro-venture capital

    Even Loeb's riskier papers—which gain far more public notice—are grounded in physics that extrapolates from today's data. For example, he and ITC postdoctoral fellow T. J. Cox, who is now at the Carnegie Observatories in Pasadena, simulated the crash of the Milky Way and our galactic neighbor, Andromeda, starting in about 2 billion years. Our solar system, they deduced, would probably be tossed near the outskirts of the gigagalaxy, which Loeb dubbed "Milkomeda." In the far future, he calculated, the relentless acceleration of the universe due to dark energy would render all other galaxies invisible. Still, he claimed in a recent paper, Milkomedan astronomers could retrace what had happened by studying light from closer stars ejected from the merged galaxy by its giant central black hole.

    Lately, Loeb has been drawn to the prospects of detecting life elsewhere. One signpost would be spectral traces of oxygen in the atmosphere of a rocky world. According to Loeb and astrophysicist Dan Maoz of Tel Aviv University, NASA's upcoming James Webb Space Telescope could spy that faint signal from planets orbiting white dwarfs, the dense Earth-size remnants of stars like our sun. In another E.T.-tinged study, Loeb and Princeton astrophysicist Edwin Turner proposed using future telescopes to look for "city lights" from other civilizations—and testing the method now by scanning the outskirts of our solar system.

    Some colleagues compare him to visionary physicist Freeman Dyson of IAS, but Loeb knows that many others regard such speculative work with raised eyebrows or worse. "But frankly, I don't care," he says. Creativity and challenging convention spur the best research, he says. Federal funding agencies have lost sight of this, Loeb says, dooming pioneering missions like the Laser Interferometer Space Antenna to detect gravitational waves.

    In a recent paper, Loeb made waves by urging young astrophysicists to devote 20% of their research to innovative "venture capital" projects outside the mainstream. "It requires a certain amount of bravery to come up with these things," Milgrom of the Weizmann Institute says. "People are afraid to do risky work, but words from Avi can be influential."

    Loeb now has less time to publish papers at will. In addition to directing ITC, he is chair of the Harvard astronomy department. At ITC, his peers note, Loeb has built a team that is at once high-powered and collegial. Prize-winning postdoctoral fellows and graduate students like what they see. "They get all the best young people now," a colleague says privately. "No one can compete with them."

    Despite the demands, notions keep coming to Loeb in his shower and on his porch. Now, edging ever closer to Earth, he and a coauthor are honing a new theory of how the moon formed. "I still have a niche: ideas that other people do not think about," he says with a smile. "There is room for innovation"—and for another sheet in the file drawer.

    • * Robert Irion directs the Science Communication Program at the University of California, Santa Cruz.

  4. Lunar and Planetary Science Conference

    The Mystery of Our Moon's Gravitational Bumps Solved?

    1. Richard A. Kerr

    A group of researchers reported how over millions of years, the moon's subtle adjustment to an impact might eventually create a high spot in the moon's bumpy gravitational field.

    Mottled moon.

    In this GRAIL gravity map, mascon basins are red, circular, and blue-ringed.


    Much to geophysicists' consternation, the first space probes to orbit the moon were misbehaving badly, showing up in the wrong places at the wrong times. Something about the gravitational pull of the moon was throwing off their orbits. But what? In 1968, two NASA scientists found the culprit, or rather culprits: The moon's great basins were exerting an unexpected extra pull on passing satellites.

    That made no sense, of course. Those basins are low spots where huge impacts have gouged out megatons of rock, not added mass. Somehow, there is hidden extra mass under many lunar basins, making them basins with mass concentrations or mascon basins. How did the extra mass get there? At the meeting, a group of researchers reported how over millions of years the moon's subtle adjustment to an impact might eventually create a high spot in the moon's bumpy gravitational field.

    Two developments in planetary science have helped finally generate a solution to the mascon mystery. One was the advent of stunningly detailed lunar observations. NASA's twin-spacecraft Gravity Recovery and Interior Laboratory (GRAIL) mission mapped the subtle variations of gravitational pull with a resolution of 10 kilometers or so over the entire moon (Science, 7 December 2012, p. 1272). That painted a clear gravity picture of mascons: a bull's-eye pattern of higher-than-expected gravity across a basin hundreds of kilometers wide, ringed by a band of lower gravity and an outermost ring of higher gravity.

    The other development came back on Earth. Computer modelers had managed to inject such realism into their models that they could hope to match their simulated mascon formation to the GRAIL gravity map. So at the meeting, physicist Brandon Johnson of Purdue University in West Lafayette, Indiana, and 10 colleagues showed how they simulated the impact of a 50-kilometer-diameter rock plunging vertically into the moon at 54,000 kilometers per hour. In the model, the collision le ft behind a broad, shallow basin, a ring of reduced gravity where less dense ejecta had piled on the crust, and a central pool of melted mantle rock more than 100 kilometers deep.

    In the next talk, planetary scientist Andrew Freed of Purdue, speaking for the same group, reported on their modeling of the next 100 million years of an impact basin's life: This is when all that hot rock slowly cools, a rigid lid of mostly mantle rock forms over top, and relatively dense or light chunks of rock can slowly sink or float in the still-viscous mantle. Both simulations had to get many steps right, Freed said. Most critically, the rigid lid must form and lock the temporarily elevated central basin in place before the ring of thickened crust—which is floating up—sucks mantle rock from beneath the central basin. Losing that mass would rob the central basin of the mass responsible for the mascon.

    Freed reported that their two-step modeling produced the same bull's-eye gravity pattern seen in GRAIL data at two impact basins, even though the two sites had different preimpact crustal thicknesses. The same modeling approach even duplicated the mascon of the humongous 960-kilometer-diameter Orientale basin, the group reported at a poster the same day. The modeling includes physical "mechanisms we know are there," Freed said. "If we model those mechanisms well, the mascons pop out. It's really hard to mess this calculation up."

    Planetary geophysicist William McKinnon of Washington University in St. Louis calls the results "very interesting and a nice step forward" but notes that the studies so far leave out some potentially important mechanisms, such as the flow of pulverized rock in an impact. He will be looking for another round of modeling.

  5. Lunar and Planetary Science Conference

    Pesky Perchlorates All Over Mars

    1. Richard A. Kerr

    Curiosity rover has discovered perchlorates in equatorial Gale crater, implying that they carpet the martian surface and explaining why the rover stumbled in its first search for organic traces of ancient martian life.

    Five years ago, the Phoenix lander found perchlorate salts in one spot in the martian arctic. Now, Curiosity rover has discovered perchlorates in equatorial Gale crater as well, implying that they carpet the martian surface. The discovery explains why the rover stumbled in its first search for organic traces of ancient martian life. Indeed, perchlorates, it seems, have been frustrating three generations of organic analyses on Mars.

    Curiosity's discovery of perchlorate salts—compounds consisting of a chlorine atom, four oxygens, and an element like magnesium—came when it ran its first solid sample through its Sample Analysis at Mars (SAM) instrument package. The rover scooped windblown dust into SAM and gradually heated it up to 835°C. It continuously flushed the resulting gases—which researchers hoped might include volatile organic matter—through a mass spectrometer for identification.

    At the meeting, Paul Archer of NASA's Johnson Space Center in Houston, Texas, and fellow Curiosity team members reported that as the sample temperature passed through about 400°C, SAM identified both molecular oxygen and a variety of chlorine-containing, single-carbon compounds. Together, those molecules made "a strong case for perchlorates" in the sample, Archer said.

    That's because perchlorate salts in martian soil would have decomposed to chlorine and oxygen at that sort of temperature, and the chlorine would have combined with any nearby carbon to form the observed single-carbon compounds. Meanwhile, the oxygen would have burned any other carbon compounds present to carbon dioxide, which also came out then. The coincident release of oxygen and chlorinated compounds plus the previous detection of chlorine in every martian soil ever tested "lead to the conclusion that perchlorates are globally distributed on Mars," at least in the soil, the group said in its meeting abstract.

    Pervasive perchlorates would explain a lot. Their presence on Mars wasn't so surprising once geochemists thought about it: The ultraviolet of sunlight could produce them by zapping other compounds in the atmosphere or directly in the soil, where the aridity of Mars would preserve them, as the aridity of Earth's Atacama Desert does. Heating them together with any sort of carbon-containing compounds—once-living or not—in martian soil would yield Curiosity's result, which closely matches what the two Viking landers saw in their own heated-sample experiments in the late 1970s. The less sensitive Phoenix lander experiment detected only carbon dioxide in its heating experiments.

    Bottom line: Experiments to date on Mars may or may not have detected martian organic matter. And because hot perchlorates react with any kind of carbon, it's unlikely that the question can be settled with heating experiments alone. But Curiosity isn't finished. In a first on Mars, SAM can isolate certain types of organic compounds at low temperatures before sending them on to the mass spectrometer. The catch is that SAM can run this "wet chemistry" analysis only seven times in the entire mission. Choose wisely, Curiosity.

  6. Lunar and Planetary Science Conference

    More Support for an Ocean in Enceladus

    1. Richard A. Kerr

    Researchers argued that the latest Cassini observations make sense if liquid water is escaping from a deep ocean through cracks in Enceladus's outer ice shell.

    Cracked up.

    The four bluish, parallel lines mark cracks on Enceladus from which a deep ocean may vent.


    Now that the Cassini spacecraft has made its last close-up observations of Saturn's moon Enceladus, mission team members are pushing to prove once and for all that the 500-kilometer-diameter moon harbors a salty—and habitable—ocean far below its icy surface. They aren't there yet, but at the meeting, researchers argued that the latest Cassini observations make the most sense if liquid water is escaping from a deep ocean through cracks in Enceladus's outer ice shell to produce the plume spewing from the moon's south polar region.

    Some planetary scientists had thought that they had figured out the mechanics of Enceladus's plume. It appeared to them that Saturn's varying tidal pull on Enceladus was pushing on opposing sides of four great cracks running across the south pole region, moving them back and forth. The resulting frictional h eat would melt some ice, sending plumes into the vacuum of space—no deep ocean required.

    But at the meeting, Carolyn Porco of the Space Science Institute in Boulder, Colorado—Cassini's camera team leader—and colleagues suggested a scenario that better fits the observations. Saturn's tides are, in fact, working on the fractures, they found, but individual plume jets tend to occur where tidal stresses are calculated to be pulling cracks apart, rather than where they create frictional heat. And tidal opening of cracks tends to coincide with the times when the south polar plume is seen to intensify, suggesting that the opening cracks are letting something escape.

    That something, Porco and colleagues conclude, is warm water from a deep ocean. If it were meltwater from any frictional heating in the cracks, their calculations show the surrounding ice would be noticeably heated for several kilometers along a crack. But researchers on Cassini's heat-sensing imager team reported last fall that hot spots on cracks are no bigger than a few tens of meters. So it looks as if tidal stresses are opening cracks through kilometers of ice and letting ocean water escape to space.

    "That's definitely a possibility," says planetary physicist David Stevenson of the California Institute of Technology in Pasadena. Frictional heating doesn't seem to be working out, he says, so "instead they are tapping heat from the ocean." Next up, he adds, is showing how such a plumbing system could keep going for millennia. Still, Stevenson says, "progress is being made."

  7. Lunar and Planetary Science Conference

    Snapshots From the Meeting

    1. Richard A. Kerr

    The Curiosity rover has come across hints of chemical reactions on Mars that could have produced the organic "building blocks of life," but without any life. And big impacts on the moon and Mars have blasted off bits of rock that have been picked up on Earth, so could it be possible that a researcher has found a meteorite from Mercury?


    Although its composition resembles Mercury's, this meteorite may be too old to be from there.


    Hot time on the ol' Mars? The Curiosity rover has come across hints of chemical reactions on Mars that could have produced the organic "building blocks of life," but without any life. Jennifer Stern of NASA's Goddard Space Flight Center in Greenbelt, Maryland, and fellow Curiosity team members reported that when Curiosity gradually heated windblown dust, the process produced molecular fragments at about 800°C. These appear to be cyanide (a carbon-nitrogen compound) and hydrogen cyanide. Another Curiosity team member, Andrew Steele of the Carnegie Institution of Science's Geophysical Laboratory in Washington, D.C., reported the high-temperature release of the same molecules from another martian sample, a piece of the Tissint meteorite recently arrived from Mars. Using high-powered instruments in the lab, Steele could see that the nitrogen-containing compounds in Tissint likely formed when hot water interacted with martian rock. Another product of those reactions appears to have been organic matter. So if Curiosity turns up organic matter on Mars, the next chore will be telling whether it was ever alive.

    A messenger from Mercury? Big impacts on the moon and Mars have blasted off bits of rock that have been picked up on Earth, so why not a meteorite from Mercury? At the meeting, meteoriticist Anthony Irving of the University of Washington, Seattle, and colleagues proposed 345-gram Northwest Africa 7325 as a Mercurial meteorite. "No one has a rock like this," he says. It's a unique combination of elements, minerals, and isotopes that in many ways matches the properties of Mercury's surface as determined by the still-orbiting MESSENGER spacecraft. But "I was unimpressed," says planetary scientist William Vaughan of Brown University. Some of the chemistry doesn't match at all, he notes. What's more, the meteorite is much older than the relatively youthful lavas that cover most of Mercury's surface, where it presumably would have to have originated. Most discouraging, perhaps: "I don't know how we'll get a conclusive result," Irving says.

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