Number 104, November 25, 1992 by Phillip F. Schewe and Ben Stein CHARON MAY BE NOTHING BUT ICE . Scientists at the Jet Propulsion Lab have determined from observations made with the Hubble Space Telescope that Pluto's mass is 11 times that of its moon. Previously, the diameters of Pluto (2300 km) and Charon (1190 km) had been worked out from mutual-eclipse measurements. This allows the density of each body to be estimated. Charon, with a density of 1.4 g/cm3, should be mostly water ice. (New Scientist, 21 Nov. 1992.) COULD GALAXY REDSHIFTS BE QUANTIZED? Redshifts are traditionally thought to depend primarily on one simple factor: the velocity by which the galaxy recedes from Earth. However, a few astronomers suggest there may be more complex factors, perhaps even some large-scale quantum effect, at work. As early as 1970, William G. Tifft of the University of Arizona performed comparisons of redshifts within a single galaxy cluster, and found that the individual redshifts differed by multiples of 72 km/sec. Last year Bruce N. G. Guthrie and William M. Napier of the Royal University at Edinburgh compared the redshifts from 89 single spiral galaxies. They found a periodicity of 37.2 km/sec--very close to Tifft's recently revised quantum multiple of 36.2 km/sec for this class of galaxies. Many skeptical astrophysicists, who take notice of this independent study, still believe that further investigations are in order and that the evidence compiled thus far does not yet necessitate the quantization of redshifts. (Scientific American, December 1992.) AMERICAN SCIENCE HAS A TRADE SURPLUS with the rest of the world when it comes to the transmission and impact of research papers as measured by citations in technical journals. According to the Institute for Scientific Information (ISI), U.S. articles had the highest rate of citations-per-paper in the world for the period 1987-91; the U.S. lead in citations was highest in the physics category. In this case the sample size of papers published by U.S. physics authors was 66,353, which represented a 26.8% share of all worldwide physics papers for the period. (Science Watch, Sept. 1992.) JAPANESE ASTRONOMY , like other areas of basic research in that country, is attempting to match the success of Japanese technology. The Astro-D x-ray satellite (to be launched in Feb. 1993) will image the sky over a wider energy range (0.5 to 10 keV) than the German ROSAT and will also carry out x-ray spectroscopic studies. In the area of neutrino astronomy, the Super-Kamiokande detector will employ a volume of water some ten times greater than the present detector (which, along with the IMB detector in the U.S., registered neutrinos from Supernova 1987A). In addition, it will continue to look for proton decay. The Yokhoh satellite (launched in 1991) provides the best moving pictures of solar flares at x-ray wavelengths. The VLBI Space Observatory Project (dubbed VSOP, but having nothing to do with cognac of the same name) entails the use of an 8-m radio telescope in an elliptical Earth orbit as part of a space-based interferometry network. Another major effort is Subaru (meaning "Pleiades"), an 8-m optical telescope to be built at Mauna Kea, Hawaii. (Science, 23 Oct. 1992.)