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THIS WEEK IN edited by Stella Hurtley and Phil Szuromi CREDITS (TOP TO BOTTOM): SHUWIRTH ET AL.; PLATTEN ET AL. More Prolific Planet Production Intermittent Ionosphere Layer As the center of a collapsing dust cloud heats up and approach- Mars’s ionosphere, which extends from about 110 to 135 kiloes the conditions for star formation, the dust grains settle into a meters (km) above the planet, consists of two distinct layers and plane to form a disk around the central core. The particles in this helps protect the lower atmosphere from removal by the solar disk eventually combine to form planets and asteroids. Although wind. The existence of a third lower layer has been predicted, and this picture is consistent with observaas discussed by Pätzold et al. (p. 837), has now been detected tional data for the brighter dust disks by radio-wave observations by Mars of intermediate mass stars, Express. However, this third layer, little is known about planet which is seen to extend to as low as Close Up of the formation around smaller 65 km above the planet, appears to be Ribosome stars. Apai et al. (p. 834, intermittent, not permanent as was In the last few years, published online 20 October expected, and is likely formed from high-resolution struc2005) present infrared spectrothe ablation of meteorites. tures of the 30S and scopic observations of proto50 S bacterial riboplanetary disks around brown Decay Discrepancy some subunits have dwarfs, objects that are smaller, Reconciled revealed significant cooler, and often just short of insights into the The beta decay of 176Lu to 176Hf is an being stars. The spectra show mechanism of protein important isotopic system for tracing signs of three key markers for synthesis, in particular the geochemical evolution of Earth planet formation—dust grain revealing that the riboand other planets, as these elements growth, grain crystall