36th DPS Meeting, 8-12 November 2004
Session 47 Mars Surface and Dust
Oral, Friday, November 12, 2004, 3:30-5:00pm, Lewis

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[47.02] HST/STIS Observations of the Extended Martian Upper Atmosphere

J.T. Clarke (Boston University), J.L. Bertaux (CNRS), T. Owen (Univ. of Hawaii), A Nagy (Univ. of Michigan)

HST observations of Mars near opposition in 2001 and 2003 have been performed to address some key questions about the escape of water from the martian atmosphere. In May 2001 long aperture STIS echelle spectra of Mars were obtained to determine accurate values for the D and H columns, and the D/H ratio, in the upper atmosphere of Mars. The present-day D/H ratio gives vital information needed to understand the evolution of Mars' atmosphere, the historic escape of water into space, and potentially the remaining water abundance on Mars. Since this ratio appears to vary with altitude in the martian atmosphere, it is important to determine the value at the top of the atmosphere, from which D and H may escape into space. In August 2003, UV intensity profiles of H, O, and CO emissions were also measured with STIS across the planet and above the limb with 24 km resolution at Mars. These emission profiles can be used to measure the scale heights of thermal and suprathermal populations, which can be compared with models to constrain the escape flux of H and O from the upper atmosphere. This work was supported by grant HST-GO-08658.05-A from the Space Telescope Science Institute to Boston University.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.