Dr. Robert Duncan-Enzmann 1960s

Vertical Wind Profiles of Mars

During the last 3 to 5 km of descent, a capsule will be in the stratosphere and troposphere of Mars. It is possible that at certain times and locations – as is sometimes the case in terrestrial Polar locations – the stratosphere of mares will be in direct contact with its surface, resulting in the local absence of a troposphere.

The following layers, which could strongly perturb descent, will be present in the last 3 to 5 km of descent regardless of whether the general zoning is tropospheric, stratospheric, or both:

• Horizontal crosswinds with shearing as expressed by Helmholtz interference
• Surface turbulent channel extending from the surface to a minimum of 10 meters to a minimum of 300 meters above the surface
• The so-called logarithmic layer a few centimeters above the surface
• The major eddies associated with the topography
• The ground effect when the vehicle is a distance above the surface on the order of its horizontal extent.

It is recommended that these features be examined for the amount of perturbance associated with each feather to be studied. This can be done on the basis of maximum and minimum values. Sufficient information is available to yield such values, which in turn will indicate the maximum and minimum parameters for which the system will have to be built.

The geographic distribution of winds, horizontal wind patterns, and the vertical profiles of winds should be considered in designating landing sites, and in designing landing mechanisms. Winds over the surface of Mars and to approximately 10,000 feet above the surface are estimated to move at relatively low velocities. The estimates have been made by observation of moving cloud patterns, observation of yellow dust cloud movements, computation from thermal gradients as a function of latitude, computations treating the planet as a black body, and estimates of the time necessary to transfer supposed water from the cold trap at one pole to the cold trap at the other pole. (13 Vaucouleurs) Observations and estimates indicate a rather low average wind velocity, perhaps 20 mph. Locally wind velocities may exceed this value.

Conditions indicating winds in excess of 20 mph are to be expected in association with the following features, which are listed in order of importance, the feature with the strongest winds first:

1. Sub-polar Spot: (Capricorn and Cancer) The heat capacity of the atmosphere about Mars is relatively low. Much heat is stored in the rocks of the surface, however, this is released quickly, therefore winds about the sub-polar spot may be expected to be strong. The writer estimates up to 80 mph.
2. Trade Wind Belt: Expected to be a zone of prevailing winds moving from east to west; these winds are positioned somewhat to the south of the geographic equator.
3. Westerly Belts: Zones of northern and southern westerlies seem to show more rapid movements of clouds and fronts than over an average area of the planet.
4. Polar Easterlies: Zones in which winds moving from east to west may be expected to exceed average values.
5. Atmospheric Channels: Winds seem to be stronger over the dry hemisphere from long. 270° to long. 90° and on a lesser scale through the Pandorae-Fretum / Hellespontus structure.
6. Surface Thermal Anomalies: The areas of Noachis seems to show abnormal temperatures. It may be the reason for the localization of cyclonic circulation and the development of darkening in the Pandorae-Fretum. It is located at long 350° and 360°. The writer estimates on the basis of terrestrial differences between ambient winds and winds beneath such cloud structure, that winds could reach velocities of 300% above average in temporary gusts.

Wind Profile Charts: