Effects of airbursts on the surface of Venus
Magellan observed quasi-circular, apparently impact-related, radar albedo features on Venus. Pristine examples show dark regions centered within larger bright regions. Dark regions are interpreted as smooth and bright regions are interpreted as rough. Of the 518 features, 256 are centered on impact craters (crater haloes), 53 are centered upon small central disturbances (disrupted splotches), and the remaining 209 exhibit no central structure (craterless splotches). Most researchers interpret these features as airburst scars.
Previous models of airburst formation only reproduced subsets of the observations. Models of splotch and halo formation were often mutually exclusive and no previous model connected them despite their similarities. I rectify this problem with a model that successfully reproduces 514 of the 518 patterns given appropriate airburst altitude and energy conditions combined with erosion. In my model, dark zones are pulverized rock, and bright zones are scoured surfaces. More complicated patterns are obtained with modification of the initial dark/bright pattern.
Small impactors that do not penetrate the atmosphere cannot cause surface damage. Large impactors that penetrate the atmosphere without disruption create an impact crater without an associated airburst scar. Only intermediate-size impactors, partially or wholly disrupted in the near-surface zone, form airburst scars. Typical diameters for airburst scar-forming impactors are 200 meters—2 km for irons, 300 meters—3 km for stones, and >3 km for comets.