HR: 10:30h
AN: P42A-01 INVITED     [Abstracts]
TI: Cometary, Martian and Venusian X--rays
AU: * Dennerl, K
EM: kod@mpe.mpg.de
AF: Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, Garching, 85748 Germany
AB: In 1996 an unexpected discovery was made: Comets do emit X--rays. This emission is now understood as the result of charge exchange interactions between heavy, highly charged ions in the solar wind and cometary neutrals. A similar process might occur in the exospheres of Venus and Mars, which can be considered as the closest planetary analogs to comets, due to the presence of an atmosphere, the absence of a strong magnetic field, and their proximity to the Sun. Indeed, X--ray radiation was discovered from both planets in 2001 with Chandra. However, the main source of this radiation was fluorescent scattering of solar X--rays in their upper atmospheres, in agreement with the expectation. While no evidence of a charge--exchange induced X--ray halo was found at Venus, the presence of such a halo was indicated at Mars, although at a very low statistical significance. Mars was observed again in November 2003 with XMM--Newton. This observation, characterized by a considerably higher sensitivity, confirms the presence of the X--ray halo and makes further investigations of its spectral, spatial, and temporal properties possible. The results of this observation will be presented together with those of recent X--ray observations of comets, which allow us now to study the interaction between the solar wind and the cometary coma in unprecedented detail.
DE: 2780 Solar wind interactions with unmagnetized bodies
DE: 6025 Interactions with solar wind plasma and fields
DE: 6210 Comets
DE: 6225 Mars
DE: 6295 Venus
SC: Planetary Sciences [P]
MN: 2005 Joint Assembly