Issue |
A&A
Volume 394, Number 3, November II 2002
|
|
---|---|---|
Page(s) | 1119 - 1128 | |
Section | Celestial mechanics and astrometry | |
DOI | https://doi.org/10.1051/0004-6361:20021116 | |
Published online | 21 October 2002 |
Discovery of X–rays from Mars with Chandra
Max–Planck–Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany
Corresponding author: kod@mpe.mpg.de
Received:
16
July
2002
Accepted:
31
July
2002
On 4 July 2001, X–rays from Mars were detected for the first time.
The observation was performed with the ACIS–I detector onboard
Chandra and yielded data of high spatial and temporal resolution, together
with spectral information. Mars is clearly detected as an almost fully
illuminated disk, with an indication of limb brightening at the sunward
side, accompanied by some fading on the opposite side. The morphology and the
X–ray luminosity of ~ are fully consistent with fluorescent
scattering of solar X–rays in the upper Mars atmosphere. The X–ray spectrum
is dominated by a single narrow emission line, which is most likely caused by
O–Kα fluorescence. No evidence for temporal variability is found.
This is in agreement with the solar X–ray flux, which was almost constant
during the observation. In addition to the X–ray fluorescence, there is
evidence for an additional source of X–ray emission, indicated by a faint
X–ray halo which can be traced to about three Mars radii, and by an
additional component in the X–ray spectrum of Mars, which has a similar
spectral shape as the halo. Within the available limited statistics, the
spectrum of this component can be characterized by 0.2 keV thermal
bremsstrahlung emission. This is indicative of charge exchange interactions
between highly charged heavy ions in the solar wind and exospheric hydrogen
and oxygen around Mars. Although the observation was performed at the onset of
a global dust storm, no evidence for dust–related X–ray emission was found.
Key words: atomic processes / scattering / Sun: solar wind / Sun: X–rays, gamma rays / planets and satellites: individual: Mars / X–rays: individual: Mars
© ESO, 2002
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