Number 93, September 9, 1992 by Phillip F. Schewe and Ben Stein AND NOW, A COSMIC-RAY NEUTRINO PROBLEM . When cosmic rays collide with air molecules in the upper atmosphere, they create neutrinos. Experiments at Japan's Kamiokande neutrino detector and a similar setup in a salt mine near Cleveland, however, have found that the proportion of muon neutrinos to electron neutrinos produced from cosmic rays is significantly smaller than the Standard Model predicts. One possibility is that physicists have miscalculated the amount of muon neutrinos that should be produced in the upper atmosphere. Other explanations, however, involve new physics. One possibility is that the muon neutrinos transform into another type of neutrino on their way to Earth. Such neutrino oscillations have been offered as an explanation for the apparent shortfall of electron neutrinos from the Sun. Indeed, electron and muon neutrinos may be in some kind of equilibrium, according to Thomas Gaisser of the University of Delaware. (Science, 22 August 1992.) DOUBTS ABOUT A 17-KEV NEUTRINO are growing. Scientist at last month's International High Energy Physics meeting in Dallas discussed the results of the latest round of experiments seeking to confirm the existence of a 17-keV neutrino. All of them came up short. Eric Norman of LBL, using a solid-state detector, found positive signs for the 17-keV neutrino in the beta-decay of carbon-14, but not in iron-55. Takayoshi Oshima of the National Laboratory for High Energy Physics in Japan looked for evidence of the neutrino in the most sensitive mass spectrometer test designed yet, and found nothing. Finally, Stuart Freedman of LBL studied beta-decay of radioactive sulfur using a solid-state detector, and did not see any signs of the neutrino. Freedman went so far as to test the sensitivity of his detector by mixing in some carbon-14, which produces beta-decay electrons at slightly lower energies than in sulfur, and managed to produce a signal mimicking the 17-keV spike. Although the prospect of a superheavy neutrino now appears dead, physicists are still at a loss to explain why positive signals had previously shown up in six independent solid-state detector experiments. (Science, 22 August 1992.) THE SMALLEST BATTERY consists of two pillars of silver atoms and two of copper, assembled by STM on a graphite substrate (August 6 issue of the Journal of Physical Chemistry). The battery arrangement generates about one-fiftieth of a volt and lasts about 45 minutes. Over that time, the copper pillars shrink while the copper atoms migrate to the silver pillars. One of the Irvine scientists, Reginald Penner, hopes to use the device to study proteins. (Science News, 15 August 1992.) THE PLUTO FAST FLYBY mission, under consideration at NASA would shoot a pair of light spacecraft (150 kg compared to 1500 kg for Galileo) toward Pluto aboard a Titan/Centaur rocket. If approved, the craft would depart as early as 1998 and take seven or eight years to reach the ninth planet, where they would take pictures and perform spectroscopy at radio, infrared, and ultraviolet wavelengths. (Nature, 27 August 1992.)