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<jats:title>Watering the Moon</jats:title> <jats:p> About a year ago, a spent upper stage of an Atlas rocket was deliberately crashed into a crater at the south pole of the Moon, ejecting a plume of debris, dust, and vapor. The goal of this event, the Lunar Crater Observation and Sensing Satellite (LCROSS) experiment, was to search for water and other volatiles in the soil of one of the coldest places on the Moon: the permanently shadowed region within the Cabeus crater. Using ultraviolet, visible, and near-infrared spectroscopy data from accompanying craft, <jats:bold> Colaprete <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="463" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1186986">463</jats:related-article> ; see the news story by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6003" page="434" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.2010.330.6003.330_434">Kerr</jats:related-article> </jats:bold> ; see the cover) found evidence for the presence of water and other volatiles within the ejecta cloud. <jats:bold> Schultz <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="468" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1187454">468</jats:related-article> ) monitored the different stages of the impact and the resulting plume. <jats:bold> Gladstone <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="472" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1186474">472</jats:related-article> ), using an ultraviolet spectrograph onboard the Lunar Reconnaissance Orbiter (LRO), detected H <jats:sub>2</jats:sub> , CO, Ca, Hg, and Mg in the impact plume, and <jats:bold> Hayne <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="477" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197135">477</jats:related-article> ) measured the thermal signature of the impact and discovered that it had heated a 30 to 200 square-meter region from ∼40 kelvin to at least 950 kelvin. <jats:bold> Paige <jats:italic>et al.</jats:italic> </jats:bold> (p. 479) mapped cryogenic zones predictive of volatile entrapment, and <jats:bold> Mitrofanov <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="483" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1185696">483</jats:related-article> ) used LRO instruments to confirm that surface temperatures in the south polar region persist even in sunlight. In all, about 155 kilograms of water vapor was emitted during the impact; meanwhile, the LRO continues to orbit the Moon, sending back a stream of data to help us understand the evolution of its complex surface structures. </jats:p>

<jats:title>Watering the Moon</jats:title> <jats:p> About a year ago, a spent upper stage of an Atlas rocket was deliberately crashed into a crater at the south pole of the Moon, ejecting a plume of debris, dust, and vapor. The goal of this event, the Lunar Crater Observation and Sensing Satellite (LCROSS) experiment, was to search for water and other volatiles in the soil of one of the coldest places on the Moon: the permanently shadowed region within the Cabeus crater. Using ultraviolet, visible, and near-infrared spectroscopy data from accompanying craft, <jats:bold> Colaprete <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="463" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1186986">463</jats:related-article> ; see the news story by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6003" page="434" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.2010.330.6003.330_434">Kerr</jats:related-article> </jats:bold> ; see the cover) found evidence for the presence of water and other volatiles within the ejecta cloud. <jats:bold> Schultz <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="468" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1187454">468</jats:related-article> ) monitored the different stages of the impact and the resulting plume. <jats:bold> Gladstone <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="472" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1186474">472</jats:related-article> ), using an ultraviolet spectrograph onboard the Lunar Reconnaissance Orbiter (LRO), detected H <jats:sub>2</jats:sub> , CO, Ca, Hg, and Mg in the impact plume, and <jats:bold> Hayne <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="477" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197135">477</jats:related-article> ) measured the thermal signature of the impact and discovered that it had heated a 30 to 200 square-meter region from ∼40 kelvin to at least 950 kelvin. <jats:bold> Paige <jats:italic>et al.</jats:italic> </jats:bold> (p. 479) mapped cryogenic zones predictive of volatile entrapment, and <jats:bold> Mitrofanov <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="483" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1185696">483</jats:related-article> ) used LRO instruments to confirm that surface temperatures in the south polar region persist even in sunlight. In all, about 155 kilograms of water vapor was emitted during the impact; meanwhile, the LRO continues to orbit the Moon, sending back a stream of data to help us understand the evolution of its complex surface structures. </jats:p>

<jats:title>Mixing Chaos</jats:title> <jats:p> Modeling the future movement of chaotic fluids is the basis for predicting the weather and ocean currents. Usually parcels of fluid are traced and geometrical and statistical approaches incorporate parameters for mixing and chaos, as well as the resulting uncertainty. <jats:bold> Mezić <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="486" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1194607">486</jats:related-article> , published online 2 September; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6003" page="458" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197554">Thiffeault</jats:related-article> </jats:bold> ) adapted this approach to consider different mixing and stretching regimes to improve predictions. As a test, they simulated and successfully predicted the spread of oil patches from the Deepwater Horizon oil spill in a model for the Gulf of Mexico. </jats:p>

<jats:title>Growing Nanowires</jats:title> <jats:p> In vapor-liquid-solid (VLS) growth of nanowires, the liquid phase acts as a transporter to bring material from the gas phase to the growing solid. By heating a single crystal of sapphire in a high-resolution transmission microscope, <jats:bold> Oh <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="489" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1190596">489</jats:related-article> ) monitored the growth of sapphire (α-Al2O3) nanowires out of an aluminum droplet. The liquid aluminum brings oxygen to the growing wire surface, in alternating growth and dissolution reactions at the edge of the wire. The oscillation created an optimum face at the self-catalytic site for atomic stacking and regenerated the junction between the VLS phases, allowing growth of the nanowire. </jats:p>

<jats:title>Incompatible Self-Compatibility</jats:title> <jats:p> Macroevolutionary processes driving species differences in diversification rates are important in explaining the variation we see in nature, but the extent of this process and how much the traits within a single species can drive changes in the diversification rate are unknown. <jats:bold> Goldberg <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="493" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1194513">493</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6003" page="459" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1198063"> <jats:bold>Wright and Barrett</jats:bold> </jats:related-article> ) analyzed the phylogenetics of the plant family Solanaceae and found that rates of extinction are greater for self-pollinating species than outbreeding species. Species-level selection against the deleterious effects of inbreeding may explain why self-fertilization, despite its short-term evolutionary advantages, has not spread to become more common in the flowering plants. </jats:p>

<jats:title>Cloning Futures</jats:title> <jats:p> Cloning mammals by somatic cell nuclear transfer is a technique with many potential applications in regenerative medicine, agriculture, and pharmaceutics; however, it is inefficient because of the incidence of aberrant genomic reprogramming. <jats:bold> Inoue <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="496" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1194174">496</jats:related-article> , published online 16 September) found that the gene product of <jats:italic>Xist</jats:italic> , which normally inactivates one of the two X chromosomes in females, was unexpectedly expressed ectopically from active X chromosomes in cloned mice. When <jats:italic>Xist</jats:italic> was deleted from the mice, gene expression returned to normal and the efficiency of somatic cell nuclear transfer increased about ninefold, offering promise for future nuclear transfer technology. </jats:p>

<jats:title>Light-Hating Target</jats:title> <jats:p> Young larvae of the fruit fly <jats:italic>Drosophila</jats:italic> like to hide in the dark. Older larvae nearing pupation are less timorous. <jats:bold> Gong <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="499" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1195993">499</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6003" page="454" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197702">Vogt and Desplan</jats:related-article> </jats:bold> ) have identified part of the neural circuit that links perception of light to behavior. The authors used targeted expression of the tetanus toxin to disable neurons selectively in the larval central nervous system. The results identified a neural circuit responsible for regulating the preference—or disinclination—for light. The circuit, which is composed of a bilateral pair of neurons, receives input from the larval visual circuit, and its activation strengthens photoavoidance behavior. The results give a glimmer into how the brain interprets perceptual inputs. </jats:p>

<jats:title>Three's the Charm</jats:title> <jats:p> The molecular machinery mediating membrane fusion during secretion from a cell requires a complex of so-called SNARE protein that forms a coiled bundle of four parallel α-helices. <jats:bold> Mohrmann <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="502" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1193134">502</jats:related-article> , published online 16 September) developed an elegant approach to find out how many SNARE complexes are required to promote secretion of individual secretory vesicles in living chromaffin cells by titrating the ratio of wild-type and mutant SNARE proteins expressed. For fast synchronous release, a minimum of three SNARE complexes per vesicle were required. Fewer SNARE complexes resulted in slower release. </jats:p>

<jats:title>M2 Out of the Envelope</jats:title> <jats:p> The M2 protein from influenza A virus forms an acid-activated tetrameric proton channel in the viral envelope and is essential for viral replication. Two manuscripts shed light on the functional mechanism of this channel. <jats:bold> Sharma <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="509" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1191750">509</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6003" page="456" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197748"> Fiorin <jats:italic>et al.</jats:italic> </jats:related-article> </jats:bold> ) determined the structure of the conductance domain in a lipid bilayer and propose that a histidine and tryptophan from each monomer form a cluster that guides protons through the channel in a mechanism that involves forming and breaking hydrogen bonds between adjacent pairs of histidines. <jats:bold> Hu <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="505" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1191714">505</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6003" page="456" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197748"> Fiorin <jats:italic>et al.</jats:italic> </jats:related-article> </jats:bold> ) focused on the structure and dynamics of the proton-selective histidine at high and low pH, proposing that proton conduction involves histidine deprotonation and reprotonation. </jats:p>

<jats:title>M2 Out of the Envelope</jats:title> <jats:p> The M2 protein from influenza A virus forms an acid-activated tetrameric proton channel in the viral envelope and is essential for viral replication. Two manuscripts shed light on the functional mechanism of this channel. <jats:bold> Sharma <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="509" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1191750">509</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6003" page="456" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197748"> Fiorin <jats:italic>et al.</jats:italic> </jats:related-article> </jats:bold> ) determined the structure of the conductance domain in a lipid bilayer and propose that a histidine and tryptophan from each monomer form a cluster that guides protons through the channel in a mechanism that involves forming and breaking hydrogen bonds between adjacent pairs of histidines. <jats:bold> Hu <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="505" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1191714">505</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6003" page="456" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197748"> Fiorin <jats:italic>et al.</jats:italic> </jats:related-article> </jats:bold> ) focused on the structure and dynamics of the proton-selective histidine at high and low pH, proposing that proton conduction involves histidine deprotonation and reprotonation. </jats:p>