Editors' Choice

Science  07 Aug 2015:
Vol. 349, Issue 6248, pp. 599
  1. Galactic Archaeology

    Exposing an act of galactic cannibalism

    1. KTS

    Artist's depiction of the Sagittarius Dwarf Tidal Stream encircling the Milky Way galaxy


    Our Milky Way galaxy contains two streams of stars that have been stripped by its gravity from the neighboring Sagittarius Dwarf Spheroidal Galaxy (Sgr dSph). de Boer et al. have disentangled the streams from the surrounding Milky Way and analyzed their star formation history. No stars are younger than 6 billion years old, indicating when they were ripped from the Sgr dSph. The streams also reveal how the stars originally formed in the Sgr dSph, including the moment when type Ia supernovae began enriching the galaxy. This galactic archaeology will help us understand how the Milky Way grew by consuming smaller galaxies.

    Mon. Not. R. Astron. Soc. 451, 3489 (2015).

  2. Paternal Chromatin

    Biparental control in remodeling sperm

    1. Beverly A. Purnell

    Maternally and paternally inherited animal genomes reorganize and replicate before entering the first zygotic mitosis. Maternally deposited proteins in the egg recondition the sperm DNA; however, Levine et al. show that paternal factors are also involved. The Drosophila testis-specific protein HP1E localizes to paternal chromosomes and controls sperm DNA reorganization to prime it for embryonic chromosome segregation. Elimination of HP1E in males results in male sterility. Hence, proteins from both parents prime sperm DNA so it can be synchronized with the maternal genome for the first zygotic mitosis.

    eLife 10.7554/eLife.07378 (2015).

  3. Psychology

    Believing you know is not the same as knowing

    1. Gilbert Chin

    Impossibly large numbers of people believe that they are above average drivers; similarly, people often think that they understand how GPS works, but then cannot provide a persuasive explanation. Atir et al. add the phenomenon of overclaiming to this list of meta-cognitive judgments. They find that crowd-sourced workers claim know or to be familiar with nonexistent financial (“fixed-rate deduction”) or biological (“metatoxins”) terms and that this occurs in proportion to their self-assessed knowledge about the topic. Moreover, telling people in advance that some terms did not exist had no effect on how many they claimed to know.

    Psychol. Sci. 26, 10.1177/0956797615588195 (2015).

  4. Solar Cells

    Healing perovskite thin films

    1. Phil Szuromi

    Inorganic-organic perovskite thin films function best in solar cells when they are free of defects and grain boundaries, but the as-synthesized films are often rough and highly poly-crystalline. Zhou et al. now show that methyl ammonium lead iodide (CH3NH3PbI3) rapidly reacts with gas-phase methylamine (CH3NH2) to form a liquid, and then reforms a solid film after degassing. Processed films decreased in root mean square roughness by about a factor of 25, and their overall power conversion efficiency in solar cells increased from 5.0 to 14.5% after treatment.

    Angew. Chem. Int. Ed. 10.1002/anie.201504379 (2015).

  5. Microbiome


    1. Caroline Ash

    Wild legumes, like this red clover, need mycorrhizal fungi to help their Nitrogen fixing symbionts during growth


    Symbiotic microorganisms, such as nitrogen-fixing bacteria and phosphorus-transferring fungi (mycorrhizae), are vital for plant growth in wild systems. The symbionts may scavenge rare nutrients for plants, but how do they interact? Van der Heijden et al. systematically simulated the plant-symbiont communities found in sand dunes in experimental microcosms kept free of contaminating organisms. For wild legume (peas, beans, and their relatives) seedlings, hosting nitrogen-fixing bacteria alone was not enough to guarantee growth; mycorrhizal fungi supplying phosphorous had to be present too. This synergism becomes apparent only when plants live on a nutritional edge.

    ISME 10.1038/ismej.2015.120 (2015).

  6. Climate Adaptation

    How to adapt to climate change

    1. Sacha Vignieri

    In the spiny chromis damselfish, genes involved in metabolism, immunity, and development are up-regulated in cross-generational adaptation to warming


    Climate change is imposing increases in temperature on a wide variety of species. Such warming conditions may be particularly challenging for aquatic animals, for which warming waters bring not only temperature increases but also associated oxygen limitations. Some species have displayed an ability to adapt to warming conditions across generations. Veilleux et al. looked at the transcriptome of parents and offspring in a Pacific damselfish, Acanthrochromis polyacanthus, and found three suites of genes whose expression was altered during transgenerational exposure to increased temperatures. These included genes involved in metabolism, immune response, and tissue development. Notably, heat-shock gene expression did not change, suggesting that these markers of immediate response to increased temperatures may not be involved in longer-term adaptation.

    Nat. Clim. Change 10.138/nclimate2724 (2015).

  7. Climate Change

    Whither carbon capture and storage?

    1. Julia Fahrenkamp-Uppenbrink

    Carbon capture and storage (CCS) is widely considered an essential aspect of efforts to limit global warming. Yet efforts to develop CCS technology are progressing slowly, and no fullscale power plant with CCS is in operation. Maddali et al. analyze the costs and risks associated with CCS and model the effects of its delayed implementation using a dynamic nonlinear simulation tool. Based on a number of emissions and mitigation scenarios, the authors conclude that CCS is not sufficiently mature and, in its current form, is too expensive to contribute significantly to global climate change mitigation. Other mitigation strategies must therefore be developed urgently.

    Environ. Sci. Technol. 10.1021/acs.est.5b00839 (2015).