HR: 12:05h
AN: P32A-08    [Abstracts]
TI: The Surprising, Humid Atmosphere at Enceladus
AU: * Burger, M H
EM: mburger@pop600.gsfc.nasa.gov
AF: NASA-Goddard Space Flight Center, CODE 612.2 8800 Greenbelt Rd, Greenbelt, MD 20771 United States
AU: Sittler, E C
EM: edward.c.sittler@nasa.gov
AF: NASA-Goddard Space Flight Center, CODE 612.2 8800 Greenbelt Rd, Greenbelt, MD 20771 United States
AU: Johnson, R E
EM: rej@virginia.edu
AF: University of Virginia, Engineering Physics Program and Astronomy Department, Charlottesville, VA 22903 United States
AU: Shematovich, V I
EM: shematov@inasan.rssi.ru
AF: Institute of Astronomy/Russian Academy of Sciences, 48 Pyatnitskaya Street, Moscow, 119017 Russian Federation
AU: Tokar, R L
EM: rlt@lanl.gov
AF: Los Alamos National Laboratory, Space Science and Applications ISR-1 MS D466, Los Alamos, NM 87545 United States
AB: Perhaps the most unexpected discovery from the Cassini spacecraft has been the detection of an atmosphere at Saturn's moon Enceladus. The icy body is too small to retain an atmosphere or exosphere, indicating that gas must be supplied by currently active processes. Observations from many instruments have helped to clarify the spatial distribution of this atmosphere and its source on the surface (Sources: Various Cassini press releases):

1. ISS (Imaging Science Subsystem) has observed a young surface with evidence of recent tectonic activity in the southern hemisphere. Cracks and fissures on the surface are as much as 25 K warmer than the surrounding areas (temperatures measured by the Composite Infrared Spectrometer (CIRS)).
2. Global temperature maps made by CIRS show that the south polar region is significantly warmer than predictions based on solar heating models, indicating substantial internal heat escaping at this region.
3. The Ion Neutral Mass Spectrometer (INMS) and Cosmic Dust Analyzer (CDA) measured peaks in water vapor and ice grains, respectively, during a flyby of Enceladus' south pole.