A harmonic analysis of Martian topography

The topography of Mars is represented by a spherical harmonic model complete to degree and order 50. The data source is a recently revised U.S. Geological Survey compilation which encompasses a diverse array of spacecraft measurements and Earth-based radar ranges. Because of the disparate nature of the original data sources, it is difficult to obtain reliable estimates of the likely errors in Martian topography. However, the variance spectrum has a shape similar to that found for other terrestrial planets, and the topography correlates well with recent estimates of the gravitational field of Mars. Both of these considerations suggest that the existing data provide a reasonable approximation to the true topography of Mars. Nevertheless, a detailed topographic mapping of the planet, such as will be provided by the Mars Global Surveyor, will be required before significant advances are made in understanding the relationship between topography and gravity on Mars.