Detection of a strongly negative surface potential at Saturn's moon Hyperion

On 26 September 2005, Cassini conducted its only close targeted flyby of Saturn's small, irregularly shaped moon Hyperion. Approximately 6 min before the closest approach, the electron spectrometer (ELS), part of the Cassini Plasma Spectrometer (CAPS) detected a field-aligned electron population originating from the direction of the moon's surface. Plasma wave activity detected by the Radio and Plasma Wave instrument suggests electron beam activity. A dropout in energetic electrons was observed by both CAPS-ELS and the Magnetospheric Imaging Instrument Low-Energy Magnetospheric Measurement System, indicating that the moon and the spacecraft were magnetically connected when the field-aligned electron population was observed. We show that this constitutes a remote detection of a strongly negative (~ −200 V) surface potential on Hyperion, consistent with the predicted surface potential in regions near the solar terminator

MOLECULAR SPECTROSCOPY OF NUCLEAR PARTICLES

Author Institution: Westinghouse Research Laboratories, Pittsburgh 35The discovery of a rapidly growing number of short-lived, excited systems among high-energy nuclear particles suggests the possibility of an underlying molecular type of structure for these particles to which the concepts of molecular spectroscopy appear to be applicable. It is found that the observed spin and masses of the heavy mesons and ``resonance'' particles can be accounted for in terms of the rotational excited states of ``pionic-molecules'' consisting of 2, 3, 4, and $5 \pi$-mesons. The bond-length and binding energy per bond can be obtained from a relativistic electron-positron model of the $\pi$-mesons which is also able to account for the observed masses, spins, and life-times of the $\pi$-mesons themselves. Such a molecular structure of nuclear particles permits one to obtain a physical interpretation of the ``isotopic spin'' and ``strangeness'' quantum numbers introduced for empirical reasons in terms of the internal structure and angular momenta of these systems. Furthermore, it provides an explanation for the usefulness of group-theoretical symmetry arguments which have recently been widely applied to the classification of the newly discovered particles. The desirability of applying the powerful techniques developed for the analysis of molecular spectra to the problem of nuclear particle structure is suggested