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<jats:title>Wet Mercury</jats:title> <jats:p> Radar observations of Mercury's poles in the 1990s revealed regions of high backscatter that were interpreted as indicative of thick deposits of water ice; however, other explanations have also been proposed (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="282" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1232556">Lucey</jats:related-article> </jats:bold> ). MESSENGER neutron data reported by <jats:bold> Lawrence <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="292" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1229953">292</jats:related-article> , published online 29 November) in conjunction with thermal modeling by <jats:bold> Paige <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="300" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1231106">300</jats:related-article> , published online 29 November) now confirm that the primary component of radar-reflective material at Mercury's north pole is water ice. <jats:bold> Neumann <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="296" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1229764">296</jats:related-article> , published online 29 November) analyzed surface reflectance measurements from the Mercury Laser Altimeter onboard MESSENGER and found that while some areas of high radar backscatter coincide with optically bright regions, consistent with water ice exposed at the surface, some radar-reflective areas correlate with optically dark regions, indicative of organic sublimation lag deposits overlying the ice. Dark areas that fall outside regions of high radio backscatter suggest that water ice was once more widespread. </jats:p>

<jats:title>Wet Mercury</jats:title> <jats:p> Radar observations of Mercury's poles in the 1990s revealed regions of high backscatter that were interpreted as indicative of thick deposits of water ice; however, other explanations have also been proposed (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="282" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1232556">Lucey</jats:related-article> </jats:bold> ). MESSENGER neutron data reported by <jats:bold> Lawrence <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="292" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1229953">292</jats:related-article> , published online 29 November) in conjunction with thermal modeling by <jats:bold> Paige <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="300" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1231106">300</jats:related-article> , published online 29 November) now confirm that the primary component of radar-reflective material at Mercury's north pole is water ice. <jats:bold> Neumann <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="296" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1229764">296</jats:related-article> , published online 29 November) analyzed surface reflectance measurements from the Mercury Laser Altimeter onboard MESSENGER and found that while some areas of high radar backscatter coincide with optically bright regions, consistent with water ice exposed at the surface, some radar-reflective areas correlate with optically dark regions, indicative of organic sublimation lag deposits overlying the ice. Dark areas that fall outside regions of high radio backscatter suggest that water ice was once more widespread. </jats:p>

<jats:title>Wet Mercury</jats:title> <jats:p> Radar observations of Mercury's poles in the 1990s revealed regions of high backscatter that were interpreted as indicative of thick deposits of water ice; however, other explanations have also been proposed (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="282" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1232556">Lucey</jats:related-article> </jats:bold> ). MESSENGER neutron data reported by <jats:bold> Lawrence <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="292" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1229953">292</jats:related-article> , published online 29 November) in conjunction with thermal modeling by <jats:bold> Paige <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="300" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1231106">300</jats:related-article> , published online 29 November) now confirm that the primary component of radar-reflective material at Mercury's north pole is water ice. <jats:bold> Neumann <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="296" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1229764">296</jats:related-article> , published online 29 November) analyzed surface reflectance measurements from the Mercury Laser Altimeter onboard MESSENGER and found that while some areas of high radar backscatter coincide with optically bright regions, consistent with water ice exposed at the surface, some radar-reflective areas correlate with optically dark regions, indicative of organic sublimation lag deposits overlying the ice. Dark areas that fall outside regions of high radio backscatter suggest that water ice was once more widespread. </jats:p>

<jats:title>Bicyclic Bridge to Improvement</jats:title> <jats:p> Polymers of intrinsic microporosity are a recently developed class of contorted rigid glassy ladderlike polymers having very high free volume (open internal spaces). The intrinsic porosity of these materials has made them of interest for ultrahigh permeability gas separation membranes. However, while the polymers show good gas permeability, they have only moderate gas selectivity. <jats:bold> Carta <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="303" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1228032">303</jats:related-article> ; see the Perspective by <jats:bold>Guiver and Lee</jats:bold> ) hypothesized that if they could replace the dioxin-like rings in their polymers with stiffer bridged bicyclic rings, they could improve the membrane properties of the polymer. By exploiting reactions connected to the formation of Tröger's base to form the multiple covalent bonds needed to make the bicyclic rings, the resulting polymers showed significantly improved selectivity and permeability. </jats:p>

<jats:title>Putting a C in Cytochrome</jats:title> <jats:p> Cytochrome P450 enzymes oxidize hydrocarbons using a highly reactive iron oxo intermediate. Much research has focused on tuning the protein structure to broaden the range of hydrocarbons that can be functionalized. <jats:bold> Coelho <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="307" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1231434">307</jats:related-article> , published online 20 December; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="283" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1233324">Narayan and Sherman</jats:related-article> </jats:bold> ) substituted a carbene source for the oxygen to make a P450 mutant a cyclopropanation catalyst whereby a carbon fragment is transferred in place of oxygen. Though carbene activation by iron is chemically analogous to the native oxygen activation pathway, the overall reaction is completely different from any known enzymatic transformation. </jats:p>

<jats:title>Compressed Sampling</jats:title> <jats:p> It is often said that a picture is worth a thousand words. But images often contain a lot of redundant information—effectively creating huge data files of meaningless information. While algorithms can compress the size of a file without loss of information, such processing is done after the picture has been taken. <jats:bold> Hunt <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="310" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1230054">310</jats:related-article> ) used a metamaterial sensor to compress the sampled scene directly, obviating the need for postprocessing. Tuning the response of the metamaterial allowed imaging of a scene with a 40:1 compression ratio, which may mean that finding that needle in a haystack may be much easier using a metamaterial camera. </jats:p>

<jats:title>All Together Now</jats:title> <jats:p> Environmental drivers, such as extreme weather events, impact population dynamics and can synchronize such dynamics across populations within a species. Given that many species depend on similar resources, such events might also be expected to synchronize dynamics across species, but the complexity of multispecies communities makes it difficult to reveal potential drivers in common. <jats:bold> Hansen <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="313" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1226766">313</jats:related-article> ) took advantage of the simplicity of the year-round community on the high-arctic island of Spitsbergen to test for the presence of synchrony. Population fluctuations were synchronized across the three herbivore species (Svalbard reindeer, Svalbard rock ptarmigan, and sibling vole) and the single resident predator, the arctic fox, was in lagged synchrony. The driver of these fluctuations appears to be extreme winter rain-on-snow events that reduce the availability of winter forage due to ice cover. </jats:p>

<jats:title>The Scale of Plant Invasions</jats:title> <jats:p> Many studies have shown large effects of invasive species on native species diversity, but at the same time, invaders (especially plants) have rarely been implicated in the extinctions of native species. <jats:bold> Powell <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="316" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1226817">316</jats:related-article> ) noted that studies showing large effects have tended to be focused on smaller spatial scales, while those showing smaller effects have usually been on broader spatial scales. For such a scale-dependent effect to occur, invasive species must alter the shape of the species-area relationship (SAR). Comparing the differences in SARs with invaded and uninvaded communities of plants in three different ecosystem types in the United States revealed smaller effects of invasive species on biodiversity at increasingly broader spatial scales. Empirical data and simulations suggested that the observed patterns result from disproportionately greater influences of invasive species on common relative to rare species that result from a combination of sampling effects and differential responses to invasion. </jats:p>

<jats:title>Recognizing a Stem-Loop Structure</jats:title> <jats:p> Metazoan histone messenger RNAs (mRNAs) have a conserved stem-loop (SL) structure at their 3′-end. The stem-loop is bound by the stem-loop binding protein (SLBP), which is required for histone mRNA 3′-end processing, export, stability, and translation. The 3′-5′ exonuclease 3′hExo also binds the SL and trims off three nucleotides. <jats:bold> Tan <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="318" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1228705">318</jats:related-article> ) determined the high-resolution structure of the SL bound by the RNA-binding domain (RBD) of human SLBP together with human 3′hExo. The conformation of the loop differed substantially from other RNA tetraloops and the SLBP RBD may function as a ruler that can measure the length of the stem. Although the SLBP directly recognizes the guanine base of the second nucleotide of the stem, it appears that SLBP and 3′hExo recognize the unique shape of the SL. </jats:p>

<jats:title>Anonymity Compromised</jats:title> <jats:p> The balance between maintaining individual privacy and sharing genomic information for research purposes has been a topic of considerable controversy. <jats:bold> Gymrek <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="321" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1229566">321</jats:related-article> ; see the Policy Forum by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6117" page="275" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1234593"> <jats:bold> Rodriguez <jats:italic>et al.</jats:italic> </jats:bold> </jats:related-article> ) demonstrate that the anonymity of participants (and their families) can be compromised by analyzing Y-chromosome sequences from public genetic genealogy Web sites that contain (sometimes distant) relatives with the same surname. Short tandem repeats (STRs) on the Y chromosome of a target individual (whose sequence was freely available and identified in GenBank) were compared with information in public genealogy Web sites to determine the shortest time to the most recent common ancestor and find the most likely surname, which, when combined with age and state of residency identified the individual. When STRs from 911 individuals were used as the starting points, the analysis projected a success rate of 12% within the U.S. male population with Caucasian ancestry. Further analysis of detailed pedigrees from one collection revealed that families of individuals whose genomes are in public repositories could be identified with high probability. </jats:p>