Images from the OSIRIS scientific imaging system onboard Rosetta show that the nucleus of 67P/Churyumov-Gerasimenko consists of two lobes connected by a short neck. The nucleus has a bulk density less than half that of water. Activity at a distance from the Sun of >3 astronomical units is predominantly from the neck, where jets have been seen consistently. The nucleus rotates about the principal axis of momentum. The surface morphology suggests that the removal of larger volumes of material, possibly via explosive release of subsurface pressure or via creation of overhangs by sublimation, may be a major mass loss process. The shape raises the question of whether the two lobes represent a contact binary formed 4.5 billion years ago, or a single body where a gap has evolved via mass loss.
Authors: Holger Sierks, Cesare Barbieri, Philippe L. Lamy, Rafael Rodrigo, Detlef Koschny, Hans Rickman, Horst Uwe Keller, Jessica Agarwal, Michael F. A’Hearn, Francesco Angrilli, Anne-Therese Auger, M. Antonella Barucci, Jean-Loup Bertaux, Ivano Bertini, Sebastien Besse, Dennis Bodewits, Claire Capanna, Gabriele Cremonese, Vania Da Deppo, Björn Davidsson, Stefano Debei, Mariolino De Cecco, Francesca Ferri, Sonia Fornasier, Marco Fulle, Robert Gaskell, Lorenza Giacomini, Olivier Groussin, Pablo Gutierrez-Marques, Pedro J. Gutiérrez, Carsten Güttler, Nick Hoekzema, Stubbe F. Hviid, Wing-Huen Ip, Laurent Jorda, Jörg Knollenberg, Gabor Kovacs, J. Rainer Kramm, Ekkehard Kührt, Michael Küppers, Fiorangela La Forgia, Luisa M. Lara, Monica Lazzarin, Cédric Leyrat, Josè J. Lopez Moreno, Sara Magrin, Simone Marchi, Francesco Marzari, Matteo Massironi, Harald Michalik, Richard Moissl, Stefano Mottola, Giampiero Naletto, Nilda Oklay, Maurizio Pajola, Marco Pertile, Frank Preusker, Lola Sabau, Frank Scholten, Colin Snodgrass, Nicolas Thomas, Cecilia Tubiana, Jean-Baptiste Vincent, Klaus-Peter Wenzel, Mirco Zaccariotto, Martin Pätzold
Comets contain the best-preserved material from the beginning of our planetary system. Their nuclei and comae composition reveal clues about physical and chemical conditions during the early solar system when comets formed. ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) onboard the Rosetta spacecraft has measured the coma composition of comet 67P/Churyumov-Gerasimenko with well-sampled time resolution per rotation. Measurements were made over many comet rotation periods and a wide range of latitudes. These measurements show large fluctuations in composition in a heterogeneous coma that has diurnal and possibly seasonal variations in the major outgassing species: water, carbon monoxide, and carbon dioxide. These results indicate a complex coma-nucleus relationship where seasonal variations may be driven by temperature differences just below the comet surface.
Authors: M. Hässig, K. Altwegg, H. Balsiger, A. Bar-Nun, J. J. Berthelier, A. Bieler, P. Bochsler, C. Briois, U. Calmonte, M. Combi, J. De Keyser, P. Eberhardt, B. Fiethe, S. A. Fuselier, M. Galand, S. Gasc, T. I. Gombosi, K. C. Hansen, A. Jäckel, H. U. Keller, E. Kopp, A. Korth, E. Kührt, L. Le Roy, U. Mall, B. Marty, O. Mousis, E. Neefs, T. Owen, H. Rème, M. Rubin, T. Sémon, C. Tornow, C.-Y. Tzou, J. H. Waite, P. Wurz
Images of comet 67P/Churyumov-Gerasimenko acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) imaging system onboard the European Space Agency’s Rosetta spacecraft at scales of better than 0.8 meter per pixel show a wide variety of different structures and textures. The data show the importance of airfall, surface dust transport, mass wasting, and insolation weathering for cometary surface evolution, and they offer some support for subsurface fluidization models and mass loss through the ejection of large chunks of material.
Authors: Nicolas Thomas, Holger Sierks, Cesare Barbieri, Philippe L. Lamy, Rafael Rodrigo, Hans Rickman, Detlef Koschny, Horst Uwe Keller, Jessica Agarwal, Michael F. A'Hearn, Francesco Angrilli, Anne-Therese Auger, M. Antonella Barucci, Jean-Loup Bertaux, Ivano Bertini, Sebastien Besse, Dennis Bodewits, Gabriele Cremonese, Vania Da Deppo, Björn Davidsson, Mariolino De Cecco, Stefano Debei, Mohamed Ramy El-Maarry, Francesca Ferri, Sonia Fornasier, Marco Fulle, Lorenza Giacomini, Olivier Groussin, Pedro J. Gutierrez, Carsten Güttler, Stubbe F. Hviid, Wing-Huen Ip, Laurent Jorda, Jörg Knollenberg, J.-Rainer Kramm, Ekkehard Kührt, Michael Küppers, Fiorangela La Forgia, Luisa M. Lara, Monica Lazzarin, Josè J. Lopez Moreno, Sara Magrin, Simone Marchi, Francesco Marzari, Matteo Massironi, Harald Michalik, Richard Moissl, Stefano Mottola, Giampiero Naletto, Nilda Oklay, Maurizio Pajola, Antoine Pommerol, Frank Preusker, Lola Sabau, Frank Scholten, Colin Snodgrass, Cecilia Tubiana, Jean-Baptiste Vincent, Klaus-Peter Wenzel
Heat transport and ice sublimation in comets are interrelated processes reflecting properties acquired at the time of formation and during subsequent evolution. The Microwave Instrument on the Rosetta Orbiter (MIRO) acquired maps of the subsurface temperature of comet 67P/Churyumov-Gerasimenko, at 1.6 mm and 0.5 mm wavelengths, and spectra of water vapor. The total H2O production rate varied from 0.3 kg s–1 in early June 2014 to 1.2 kg s–1 in late August and showed periodic variations related to nucleus rotation and shape. Water outgassing was localized to the “neck” region of the comet. Subsurface temperatures showed seasonal and diurnal variations, which indicated that the submillimeter radiation originated at depths comparable to the diurnal thermal skin depth. A low thermal inertia (~10 to 50 J K–1 m–2 s–0.5), consistent with a thermally insulating powdered surface, is inferred.
Authors: Samuel Gulkis, Mark Allen, Paul von Allmen, Gerard Beaudin, Nicolas Biver, Dominique Bockelée-Morvan, Mathieu Choukroun, Jacques Crovisier, Björn J. R. Davidsson, Pierre Encrenaz, Therese Encrenaz, Margaret Frerking, Paul Hartogh, Mark Hofstadter, Wing-Huen Ip, Michael Janssen, Christopher Jarchow, Stephen Keihm, Seungwon Lee, Emmanuel Lellouch, Cedric Leyrat, Ladislav Rezac, F. Peter Schloerb, Thomas Spilker
The VIRTIS (Visible, Infrared and Thermal Imaging Spectrometer) instrument on board the Rosetta spacecraft has provided evidence of carbon-bearing compounds on the nucleus of the comet 67P/Churyumov-Gerasimenko. The very low reflectance of the nucleus (normal albedo of 0.060 ± 0.003 at 0.55 micrometers), the spectral slopes in visible and infrared ranges (5 to 25 and 1.5 to 5% kÅ−1), and the broad absorption feature in the 2.9-to-3.6–micrometer range present across the entire illuminated surface are compatible with opaque minerals associated with nonvolatile organic macromolecular materials: a complex mixture of various types of carbon-hydrogen and/or oxygen-hydrogen chemical groups, with little contribution of nitrogen-hydrogen groups. In active areas, the changes in spectral slope and absorption feature width may suggest small amounts of water-ice. However, no ice-rich patches are observed, indicating a generally dehydrated nature for the surface currently illuminated by the Sun.
Authors: F. Capaccioni, A. Coradini, G. Filacchione, S. Erard, G. Arnold, P. Drossart, M. C. De Sanctis, D. Bockelee-Morvan, M. T. Capria, F. Tosi, C. Leyrat, B. Schmitt, E. Quirico, P. Cerroni, V. Mennella, A. Raponi, M. Ciarniello, T. McCord, L. Moroz, E. Palomba, E. Ammannito, M. A. Barucci, G. Bellucci, J. Benkhoff, J. P. Bibring, A. Blanco, M. Blecka, R. Carlson, U. Carsenty, L. Colangeli, M. Combes, M. Combi, J. Crovisier, T. Encrenaz, C. Federico, U. Fink, S. Fonti, W. H. Ip, P. Irwin, R. Jaumann, E. Kuehrt, Y. Langevin, G. Magni, S. Mottola, V. Orofino, P. Palumbo, G. Piccioni, U. Schade, F. Taylor, D. Tiphene, G. P. Tozzi, P. Beck, N. Biver, L. Bonal, J.-Ph. Combe, D. Despan, E. Flamini, S. Fornasier, A. Frigeri, D. Grassi, M. Gudipati, A. Longobardo, K. Markus, F. Merlin, R. Orosei, G. Rinaldi, K. Stephan, M. Cartacci, A. Cicchetti, S. Giuppi, Y. Hello, F. Henry, S. Jacquinod, R. Noschese, G. Peter, R. Politi, J. M. Reess, A. Semery
The provenance of water and organic compounds on Earth and other terrestrial planets has been discussed for a long time without reaching a consensus. One of the best means to distinguish between different scenarios is by determining the deuterium-to-hydrogen (D/H) ratios in the reservoirs for comets and Earth’s oceans. Here, we report the direct in situ measurement of the D/H ratio in the Jupiter family comet 67P/Churyumov-Gerasimenko by the ROSINA mass spectrometer aboard the European Space Agency’s Rosetta spacecraft, which is found to be (5.3 ± 0.7) × 10−4—that is, approximately three times the terrestrial value. Previous cometary measurements and our new finding suggest a wide range of D/H ratios in the water within Jupiter family objects and preclude the idea that this reservoir is solely composed of Earth ocean–like water.
Authors: K. Altwegg, H. Balsiger, A. Bar-Nun, J. J. Berthelier, A. Bieler, P. Bochsler, C. Briois, U. Calmonte, M. Combi, J. De Keyser, P. Eberhardt, B. Fiethe, S. Fuselier, S. Gasc, T. I. Gombosi, K.C. Hansen, M. Hässig, A. Jäckel, E. Kopp, A. Korth, L. LeRoy, U. Mall, B. Marty, O. Mousis, E. Neefs, T. Owen, H. Rème, M. Rubin, T. Sémon, C.-Y. Tzou, H. Waite, P. Wurz
The Rosetta mission shall accompany comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 astronomical units through perihelion passage at 1.25 astronomical units, spanning low and maximum activity levels. Initially, the solar wind permeates the thin comet atmosphere formed from sublimation, until the size and plasma pressure of the ionized atmosphere define its boundaries: A magnetosphere is born. Using the Rosetta Plasma Consortium ion composition analyzer, we trace the evolution from the first detection of water ions to when the atmosphere begins repelling the solar wind (~3.3 astronomical units), and we report the spatial structure of this early interaction. The near-comet water population comprises accelerated ions (<800 electron volts), produced upstream of Rosetta, and lower energy locally produced ions; we estimate the fluxes of both ion species and energetic neutral atoms.
Authors: Hans Nilsson, Gabriella Stenberg Wieser, Etienne Behar, Cyril Simon Wedlund, Herbert Gunell, Masatoshi Yamauchi, Rickard Lundin, Stas Barabash, Martin Wieser, Chris Carr, Emanuele Cupido, James L. Burch, Andrei Fedorov, Jean-André Sauvaud, Hannu Koskinen, Esa Kallio, Jean-Pierre Lebreton, Anders Eriksson, Niklas Edberg, Raymond Goldstein, Pierre Henri, Christoph Koenders, Prachet Mokashi, Zoltan Nemeth, Ingo Richter, Karoly Szego, Martin Volwerk, Claire Vallat, Martin Rubin
Authors: Alessandra Rotundi, Holger Sierks, Vincenzo Della Corte, Marco Fulle, Pedro J. Gutierrez, Luisa Lara, Cesare Barbieri, Philippe L. Lamy, Rafael Rodrigo, Detlef Koschny, Hans Rickman, Horst Uwe Keller, José J. López-Moreno, Mario Accolla, Jessica Agarwal, Michael F. A’Hearn, Nicolas Altobelli, Francesco Angrilli, M. Antonietta Barucci, Jean-Loup Bertaux, Ivano Bertini, Dennis Bodewits, Ezio Bussoletti, Luigi Colangeli, Massimo Cosi, Gabriele Cremonese, Jean-Francois Crifo, Vania Da Deppo, Björn Davidsson, Stefano Debei, Mariolino De Cecco, Francesca Esposito, Marco Ferrari, Sonia Fornasier, Frank Giovane, Bo Gustafson, Simon F. Green, Olivier Groussin, Eberhard Grün, Carsten Güttler, Miguel L. Herranz, Stubbe F. Hviid, Wing Ip, Stavro Ivanovski, José M. Jerónimo, Laurent Jorda, Joerg Knollenberg, Rainer Kramm, Ekkehard Kührt, Michael Küppers, Monica Lazzarin, Mark R. Leese, Antonio C. López-Jiménez, Francesca Lucarelli, Stephen C. Lowry, Francesco Marzari, Elena Mazzotta Epifani, J. Anthony M. McDonnell, Vito Mennella, Harald Michalik, Antonio Molina, Rafael Morales, Fernando Moreno, Stefano Mottola, Giampiero Naletto, Nilda Oklay, José L. Ortiz, Ernesto Palomba, Pasquale Palumbo, Jean-Marie Perrin, Julio Rodríguez, Lola Sabau, Colin Snodgrass, Roberto Sordini, Nicolas Thomas, Cecilia Tubiana, Jean-Baptiste Vincent, Paul Weissman, Klaus-Peter Wenzel, Vladimir Zakharov, John C. Zarnecki
At the end of 2014, construction began on the Grand Canal in Nicaragua, a project shrouded in secrecy since its inception 2.5 years ago. The Nicaraguan government showed scant evidence of having accounted for the impact on the environment and on local residents, or of having adequately consulted the public in selecting the final 278-km route. Such disregard should be alarming to everyone. Projects of this magnitude warrant dialogue among all stakeholders. As construction is projected to span 5 years, there is still time to reconsider it and convene independent assessments and meetings that are transparent, inclusive, and respectful of different perspectives, to guide the project toward the best outcome.
Authors: Jorge A. Huete-Perez, Axel Meyer, Pedro J. Alvarez
In science news around the world, a federal judge rules that BP spilled 3.19 million barrels of oil into the Gulf of Mexico during the 2010 Deepwater Horizon disaster, NASA's Mars Reconnaissance Orbiter spots the long-lost Beagle 2 probe on the Red Planet, Australian environmentalists take the country's environment minister to court over his approval last year of a coal mine, the U.S. National Institute of General Medical Sciences imposes a one-grant limit on scientists who already have plentiful support, and the Next-Generation Transit Survey observatory in Chile gains first light. Also, a grassroots plan to save monarch butterflies by planting milkweed backfires. And a veteran Indian space engineer is tapped to head the Indian Space Research Organisation.
When Europe's Rosetta spacecraft started studying comet 67P/Churyumov-Gerasimenko late in 2014, some scientists feared the comet might turn out to be a boring lump of ice and dust. They needn't have worried. Papers in this issue of Science show that 67P is pocked with pits, incised by cracks and cliffs, and decorated with ripples and flows of dust—all signs of an extraordinarily active place. Many of the intriguing landforms testify to the power of the sun, which heats up 67P during part of every orbit, igniting jets of gas and dust that resculpt the surface of the comet. Other discoveries could be primordial, dating from the comet's formation more than 4.5 billion years ago. Mission scientists say the complexity of the comet suggests that the comet-forming regions of the early solar system were more turbulent and chemically diverse than theorists have thought.
Author: Eric Hand
A slew of new surveys are illuminating demographics in insecure Afghanistan, after decades in which many key population indicators were a mystery. The Socio-Demographic and Economic Survey, a province-by-province count of households carried out by the Afghan Central Statistics Organization with assistance from the United Nations Population Fund, is now under way, and plans for still more ambitious surveys are being rolled out as well. Such projects follow on more limited assessments of fertility, mortality, and other factors. Worsening security concerns are an issue; surveyors now routinely avoid Taliban-controlled parts of the rural south. But even partial results are a boon to researchers, government officials, and aid agencies once starved for data.
Author: Mara Hvistendahl
Later this spring, Japan is likely to restart the first two of the 48 nuclear reactors idled in the aftermath of the 2011 meltdowns at the Fukushima Daiichi Nuclear Power Station. But the resumption of nuclear power generation is refocusing attention on a lingering challenge: what to do with the spent fuel. When Japan turned to nuclear power in the 1960s, it worried about uranium supplies and wanted to minimize the amount of nuclear waste. So it planned on spent fuel reprocessing, which reduces the volume of waste needing long-term storage and produces fresh fuel for reactors. A private firm owned by the country's nuclear utilities started building a reprocessing plant in the northern village of Rokkasho in 1993. But it took more than 2 decades to work the kinks out of an experimental vitrification process. The plant is finally due to come online in spring 2016. But the country is still searching for a site for a deep underground repository for the highly radioactive nuclear waste left over from reprocessing. For the time being, it will be encased in glass and stored until a permanent solution is found.
Author: Dennis Normile
Malaria is a scourge of humankind, but many birds seem to shrug it off. Although they are chronically infected with malaria parasites, their behavior seems unaffected, and they mostly reproduce and raise young just as well as noninfected birds. That was a puzzle not just for ornithologists but also for evolutionary biologists, who have long theorized that parasites inevitably take a toll on fitness. The birds' healthy appearance turns out to be deceiving, however. Drawing on data from a 3-decade study of great reed warblers in southern Sweden, researchers report this week in Science that long-term infection with malaria significantly shortened the birds' lives. The analysis also revealed a possible explanation: The blood cells of infected birds also had shorter telomeres, stretches of DNA that cap the ends of chromosomes and protect them during cell division. In many species, shorter telomeres are associated with aging and shorter life span. The shorter lives had a steep cost when it came to reproduction: lost breeding opportunities. On average, uninfected birds raised more than eight offspring to fledglings, infected birds just four.
Author: Gretchen Vogel
Many decades after their discoveries, the basic building blocks of the atomic nucleus—the proton and the neutron—remain among the most mysterious of subatomic particles. In the cartoon view, the positively charged proton and the uncharged neutron both consist of trios of particles called up quarks and down quarks. In actuality, each is a pullulating mass of countless quarks, antiquarks, and gluons, massless particles that convey the strong nuclear force that holds quarks together. A nucleon is so messy that physicists can't say exactly how its most basic properties, such as its mass and spin, emerge from the tangle. But now physicists at Thomas Jefferson National Accelerator Facility here are finishing a $338 million upgrade to their particle accelerator, the Continuous Electron Beam Accelerator Facility, to double its energy and probe the innards of protons and neutrons with unprecedented precision. In the coming decade, a mosaic of measurements may finally give physicists a clearer view into the proton and the neutron.
Author: Adrian Cho
From a small wooden desk in a row home a few miles north of the U.S. Capitol, Justin Goodman is waging war against animal research as director of laboratory investigations at People for the Ethical Treatment of Animals. Whereas other activists stick to protests and publicity stunts, he and his team have spent the past 5 years challenging scientists on their own turf. In talks and papers published in the peer-reviewed literature, they marshal data in an attempt to show researchers that animal experimentation is flawed, cruel, and just plain worthless. Goodman's papers have questioned the validity of the university committees that oversee animal research, encouraged U.S. allies to explore alternatives to animals in military medical training, and wounded the reputation of the world's largest accreditor of lab animal welfare. But many scientists are unswayed, saying that the work is methodologically flawed and deeply misleading. They say that despite the veneer of science, Goodman's studies are anything but.
Author: David Grimm
Some discoveries are new, others old. Here, we consider one of each from NASA's Curiosity rover. The new discovery, reported by Mahaffy et al. (1) on page 412 of this issue, is a remarkable measurement of the deuterium-hydrogen (D/H) ratio in a Gale crater mudstone from 3 billion years ago. On page 415, Webster et al. (2) report on the latest chapter in the muddy matter of methane on Mars. What links them is that both were made using the tunable laser spectrometer (TLS), part of the SAM (Sample Analysis at Mars) package on the rover.
Author: Kevin Zahnle
Different types of T lymphocytes play a key role in many immune responses, such as killing virally infected or cancerous cells directly, inducing high-affinity antibody responses in B cells, and increasing or decreasing responses from other immune cells. This multiplicity of roles may relate to their recognition properties, which are very difficult to evade. Moreover, cells are very diverse—for CD4+ T cells alone, there are at least six distinct subtypes. This raises the question of just how these different T cells are produced. Early evidence indicated that the type of T cell that dominates the response was dependent on the type of pathogen and route of entry (1, 2). However, over the past several years, more and more flexibility has been observed in a T cell's phenotype (3, 4). On page 400 of this issue, Becattini et al. (5) show that this flexibility is more the rule rather than the exception.
Author: Mark M. Davis
The drug resistance specter looms over most infectious diseases. Malaria provides a particularly urgent example of increasing resistance and treatment failure. In the past decade, artemisinin combination therapies (ACTs) have contributed to impressive reductions in malaria morbidity and mortality (1). However, in 2009, Dondorp et al. found that when patients in western Cambodia infected with Plasmodium falciparum (the deadliest form of malaria) were treated with ACTs, they took longer than normal to clear their parasites. It is the artemisinin component that normally clears parasites quickly, and the authors therefore concluded that this component of the ACT was compromised (2). Slow-clearing parasites were also found in western Thailand and other parts of Cambodia (see the first figure) (3, 4). Two reports in this issue, by Mok et al. (page 431) (5) and Straimer et al. (page 428) (6), apply specialized techniques to better understand the mechanisms that underlie this resistance to artemisinins.
Author: Carol Hopkins Sibley
In advance of a critical Framework Convention on Tobacco Control (FCTC) held in October 2014, two groups of scientists and public health experts launched a global battle royal over electronic cigarettes—devices that heat liquid nicotine but involve no tobacco.
Authors: Amy L. Fairchild, Ronald Bayer
Brazil'fs Soy Moratorium (SoyM) was the first voluntary zero-deforestation agreement implemented in the tropics and set the stage for supply-chain governance of other commodities, such as beef and palm oil [supplementary material (SM)]. In response to pressure from retailers and nongovernmental organizations (NGOs), major soybean traders signed the SoyM, agreeing not to purchase soy grown on lands deforested after July 2006 in the Brazilian Amazon. The soy industry recently extended the SoyM to May 2016, by which time they assert that Brazil'fs environmental governance, such as the increased enforcement and national implementation of the Rural Environmental Registry of private properties (Portuguese acronym CAR) mandated by the Forest Code (FC) (1), will be robust enough to justify ending the agreement (2). We argue that a longer-term commitment is needed to help maintain deforestation-free soy supply chains, as full compliance and enforcement of these regulations is likely years away. Ending the SoyM prematurely would risk a return to deforestation for soy expansion at a time when companies are committing to zero-deforestation supply chains (3).
Authors: H. K. Gibbs, L. Rausch, J. Munger, I. Schelly, D. C. Morton, P. Noojipady, B. Soares-Filho, P. Barreto, L. Micol, N. F. Walker
Recent scientific data suggests that human prosocial behavior is more than just a product of education, culture, and religion. Instead, it seems that the seeds of morality may have a long history in our brains. Frans B. M. de Waal welcomes an accessible introduction to the biology and neuroscience of prosociality in a review of The Altruistic Brain: How We Are Naturally Good.
Author: Frans B. M. de Waal
Spurred by concerns that the American education system was failing to keep pace with the Soviets after the "Sputnik crisis" of the late 1950s, a dramatic change occurred in the mathematics that was taught in American schools in the 1960s. This "new math", as it was known, was controversial from the start and ultimately short-lived. Jeremy Kilpatrick takes a second look at this contentious era in a review of The New Math: A Political History.
Author: Jeremy Kilpatrick