Number 296, November 20, 1996 by Phillip F. Schewe and Ben Stein DO NEUTRINOS PUSH PULSARS AROUND? Many pulsars possess a proper motion across the sky, implying that the pulsars get kicked somehow in the act of being born in the violent explosion of a supernova. A new theory holds that these birth velocities might be caused by a non-symmetric shell of neutrinos rushing away from the supernova collapse. (A large fraction of the energy released in a supernova is vested in neutrinos.) According to Gino Segre of the Univ. of Pennsylvania (segre@dept.physics.upenn.edu), an asymmetry in the "neutrinosphere," the surface at which the neutrinos last scattered before emerging from the star, could be caused by neutrino oscillations (the transformation, say, of tau neutrinos into electron neutrinos) under the bias of the star's magnetic field. A 1% anisotropy in the neutrino distribution could result in a "kick velocity" consistent with the measured average pulsar velocity of 450 km/sec. (Alexander Kusenko and Gino Segre, Physical Review Letters, 9 December 1996.) LASER MANIPULATIONS OF ARTIFICIAL CELL MEMBRANES: An Israel-U.S. research team has discovered that lasers can cause artificial versions of cell membranes to expel inner objects as large as 3/4 their diameter. A cell membrane is made of lipid molecules that arrange themselves into a closed, sac-like structure (a vesicle) to prevent energetically unfavorable contact between water and the water-repelling lipid tails. For this reason, it's difficult to rip open a vesicle, let alone expel interior objects. In the experiment, researchers focus a laser spot onto an artificial vesicle. The light's electric field pulls lipid into the spot. The light also causes some of the lipid inside the vesicle to break off into a suspension of smaller objects which escape the laser spot. To increase the entropy (amount of disorder) in the system, water rushes into the vesicle to disperse the smaller structures, driving out an inner object through a reclosable pore in the vesicle. Manipulating membranes with lasers may someday allow researchers to transform living cell membranes in desired ways. (J.D. Moroz et al., upcoming article in Phys. Rev. Lett.; contact Philip Nelson at 215-898-7001; Figure and movie to appear at www.aip.org/png) WHAT'S HAPPENING ON OTHER WORLDS? On Mars an Oklahoma-sized duststorm swirls about near the northern pole, while at Neptune storms and a northern-hemisphere dark spot discovered only last year were tracked by the first movie ever made of the entire Neptune rotation period (Hubble Space Telescope press releases). Saturn's inner ring is dripping water onto the planet below (New Scientist, 26 October). The Galileo spacecraft has updated knowledge of Jupiter and its moons, a miniature solar system all by itself. New reports suggest that the Great Red Spot (essentially a 20,000-km-wide storm rotating at a speed of 110 m/sec) is probably a shallow structure; the volcanic moon Io may be the source of at least some of the interplanetary dust coming from the Jovian environment; many plate-shaped structures on Europa's surface may, like Arctic ice floes on Earth, be fractured ice riding on top of a slushy ocean; the ancient ridges on Ganymede appear now (with the help of Galileo's much better resolving power: 74 m/pixel versus Voyager's 1.1 km/pixel) to be flanked by many more finer ridges, implying a thinner crust and a hotter interior than previously thought (Science, 18 October). Further out yet, a new extrasolar planet has been detected near the star 16 Cygni B; the orbit is the most eccentric of any planet yet known. It comes as close as 0.6 and as far as 2.8 astronomical units from the star (Science News, 26 October).