Spectroscopic determination of surface pressure and elevation differences on Mars

Abstract

Observations of a carbon dioxide band at 1.2206 μ (8192.6 cm−1) made at the opposition of Mars in June, 1969, are used with laboratory data to derive a value for the pressure at the surface of Mars. This band is especially suitable because it is sensitive to pressure, lying in the transition region of the curve of growth, but is relatively free of telluric contamination. The pressure derived is , corresponding to the Martian desert region Amazonis.Using a five-channel spectrometer, the strengths of two carbon dioxide bands at 1.5753 and 1.6057 μ (6347.8 and 6227.9 cm−1) were compared over a Martian dark area (Mare Acidalium) and a nearby bright area in Amazonis. The bands were 1.32 times stronger in the dark area than in the bright area. Interpreting this as evidence for elevation differences on the Martian surface, it is found that the dark Mare Acidalium is 2.5 km lower in elevation than the bright area with which it was compared.