Number 225, May 8, 1995 by Phillip F. Schewe and Ben Stein ROOM-TEMPERATURE ICE. Microscopic images of water condensing and evaporating can be rendered with an atomic force microscope (AFM) operating in a novel mode. Normally it is difficult to study thin liquid films at a surface with an AFM because capillary forces will cause liquid molecules to wet the probe tip, throwing off the measurements. Miquel Salmeron at LBL gets around this problem by backing off the tip to an altitude of 20 nm above the sample. He charges up the tip (made conducting by a thin coating of Pt). Because of the sharpness of the probe, the electric field is concentrated around the tip apex; this polarizes the atoms in the insulating substrate beneath. By monitoring the polarization force as the tip is scanned across the surface, a topographic map of a water layer on a mica substrate can be made. The name for this new technique is polarization force microscopy. The LBL researchers studied wetting in two humidity regimes. Below 25% humidity a uniform layer of water forms. This water layer is still fluid. For humidity above 25%, a different sort of wetting takes place, one in which water islands having polygonal shapes form, apparently oriented by the underlying mica substrate. That is, the water possesses crystalline structure and is, in effect, a type of ice. The LBL experiments is carried out at room temperature; further research will study the effect of temperature on the water crystal formation. (J. Hu et al., Science, 14 April 1995.) JET-PROPELLED PULSARS . Observations made with the Rosat x-ray satellite reveal the presence of a gas jet shooting out of the Vela pulsar, some 1500 light years from Earth. University of Wisconsin astronomers Craig Markwardt and Hakki Ogelman believe the jet (20 light years long) may indicate a new mechanism for pulsar propulsion. Some pulsars have been observed to move at high speeds (hundreds of km/sec) through the sky. Theorists have thought this motion was essentially the pulsar's reactive rebound away from the asymmetrical supernova that gave birth to the pulsar in the first place. But now rocket power may be another way to move pulsars. The jet may also be a way of accounting for some of the energy lost by a pulsar over time, a loss resulting in a slowing of the pulsar's rotation. Moreover, the idea that some pulsars are blasting themselves out of the plane of our galaxy might contribute to the debate over whether the source of mysterious gamma bursts seen all over the sky are very distant objects or relatively nearby pulsars that have been ejected from our galaxy. (Nature, 4 May 1995.) SOLAR NEUTRINOS AND SOLAR WIND : is there a link between these two particle streams issuing from our local star? The neutrinos are a byproduct of nuclear fusion reactions at the core of the sun while the solar wind is an outward gust of particles originating in the solar corona. Ralph McNutt of the Johns Hopkins University Applied Physics Lab, comparing neutrino data from the Homestake (SD) detector with solar wind data recorded by the IMP-8 satellite, finds a correlation. Over a 16-year period the neutrino flux and the flux of solar wind particles seem to go up and down together. There is no theoretical explanation of why this should be so. (Eos, 18 April 1995.)