Computer Science
Scientific paper
Oct 1966
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1966saosr.224.....s&link_type=abstract
SAO Special Report #224 (1966)
Computer Science
4
Scientific paper
Observations of apparent frost phenomena occurring preferentially in the Martian bright areas have, in the past, led to the assumption that the bright areas are elevations. Contrary to the conclusions previously drawn, the polar-cap recession data suggest the dark areas are highlands, because of the greater wind velocities and frost-vaporization rates anticipated for highlands. From the quasi-specular component of the radar power reflectivity and from the radar Doppler spectra, both functions of Martian longitude, the Martian dark areas are found to tend to have systematically higher elevations than the adjacent bright areas. Mean slopes of a few degrees or less are deduced, and elevation differences up to 17 km are inferred. These elevation differences are consistent with the yield and tensile strengths of common materials and with unsuccessful searches for elevations at the Martian terminator. The concentration of dark highlands near the Martian equator may help explain the d discrepacy between the dynamical and the optical oblatenesses of Mars. The results bear on the discrepancy between ground-based infrared spectrometric and Mariner 4 occulation values of Martian surface pressures. The infrared pressures (~12 mb) refer to an average over bright and dark areas. The occultation pressures (~ 6 mb) are necessarily biased toward elevations; both ingress and egress occurred in or very near dark areas. If we take the occultation pressures as typical of highlands predicted pressures in the centers of prominent bright areas are ~20 mb, permitting parachute landings of relatively modest spacecraft at these locales. The higher pressures deduced for bright areas make them the preferred locales for liquid water on Mars.
Pollack James B.
Sagan Carl
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