X-Rays From Mars |
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Authors: | Konrad Dennerl |
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Institution: | 1. Max-Planck-Institut für extraterrestrische Physik, Giessenbachstra?e, 85748, Garching, Germany
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Abstract: | X-rays from Mars were first detected in July 2001 with the satellite Chandra. The main source of this radiation was fluorescent
scattering of solar X-rays in its upper atmosphere. In addition, the presence of an extended X-ray halo was indicated, probably
resulting from charge exchange interactions between highly charged heavy ions in the solar wind and neutrals in the Martian
exosphere. The statistical significance of the X-ray halo, however, was very low. In November 2003, Mars was observed again
in X-rays, this time with the satellite XMM-Newton. This observation, characterized by a considerably higher sensitivity,
confirmed the presence of the X-ray halo and proved that charge exchange is indeed the origin of the emission. This was the
first definite detection of charge exchange induced X-ray emission from the exosphere of another planet. Previously, this
kind of emission had been detected from comets (which are largely exospheres) and from the terrestrial exosphere. Because
charge exchange interactions between atmospheric constituents and solar wind ions are considered as an important nonthermal
escape mechanism, probably responsible for a significant loss of the Martian atmosphere, X-ray observations may lead to a
better understanding of the present state of the Martian atmosphere and its evolution. X-ray images of the Martian exosphere
in specific emission lines exhibited a highly anisotropic morphology, varying with individual ions and ionization states.
With its capability to trace the X-ray emission out to at least 8 Mars radii, XMM-Newton can explore exospheric regions far
beyond those that have been observationally explored to date. Thus, X-ray observations provide a novel method for studying
processes in the Martian exosphere on a global scale. |
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Keywords: | Mars X-rays solar wind charge exchange X-ray scattering |
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