Elevation dependence of bedform wavelength on Tharsis Montes, Mars: Atmospheric density as a controlling parameter

• Examines bedforms over a wide elevation range on martian volcanos.
• High resolution imaging resolves small bedforms ∼1–5 m across.
• Bedforms exhibit systematic size trend, inversely proportional to air density.
• This proportionality is expected from several models.

We measure the wavelength of aeolian bedforms on the surface of martian volcanoes, spanning a 23 km range in elevation, or nearly an order of magnitude in atmospheric pressure and density. We find that the bedform wavelength (∼1–5 m) varies as the reciprocal of density. The observed wavelengths and wavelength dependence are compared with three recent models of bedform spacing. The results are consistent with the expected increase in threshold friction speed and saturation drag length with elevation. The observations lend support to the expectation that such bedforms on Venus or Titan are too small to be observed in present data.