title: Temperatures on europa from galileo photopolarimeter-radiometer: nighttime thermal anomalies
abstract: Galileo observations of Europa's thermal emission show low-latitude diurnal brightness temperatures in the range of 86 to 132 kelvin. Nighttime temperatures form an unexpected pattern, with high temperatures on the bright ejecta blanket of the crater Pwyll and an equatorial minimum in temperatures after sunset, uncorrelated with surface albedo or geology. The nighttime anomalies may be due to regional thermal inertia variations of an unknown origin, which are equivalent to a two- to threefold variation in thermal conductivity, or to endogenic heat fluxes locally reaching 1 watt per square meter. Endogenic heat flow at this high level, although consistent with some geological evidence, is theoretically unlikely.
authors.affiliation: Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001, USA. Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA. Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA.
authors.initials: JR
authors.lastname: Spencer
authors.initials: LK
authors.lastname: Tamppari
authors.initials: TZ
authors.lastname: Martin
authors.initials: LD
authors.lastname: Travis