VENUS AND TITAN: CHARACTERIZATION OF CRATERS VS. TECTONIC FEATURES

Warren Hamilton in "An Alternative Venus" argued that numerous circular features on Venus' surface should be interpreted as impact craters. The thick Venusian atmosphere shrouds its surface, making photographs impossible, so the Magellan probe utilized radar to map nearly the entire surface. Many of the circular features in radar images had been classified as "coronae" volcano-tectonic features unique to this planet. The conventionally-accepted catalog of Venus craters numbers c. 940, establishing the surface age as c. 500 MY. Warren Hamilton's "Alternative Venus" with many 1000's craters would have significantly increased crater density, which would then imply a mucholder surface, c.4 BY, like Mars and the Moon. The physics of impact causes a hemispheric shock wave, resulting in craters, circular features with a high degree of symmetry, transitioning in shape with increasing size. We developed a technique for analysis through correlation of radial profiles to quantitatively assess the of degree of symmetry. This analysis generally distinguishes highly-correlated impact craters (e.g. Cleopatra, Isabella, Mead) from similar-sized features previously classified as coronae (e.g. C21, Maya, Ninhursag).

Titan, the other non-terrestrial body in our solar system with an atmosphere (thick, but one-tenth that of Venus) also hosts craters: only five identified as "Certain", with several dozen others "Nearly Certain" or “Probable" craters. Titan, Saturn's largest satellite with surface temperature of 90K, near the triple point of Methane, has cryovolcanic constructs, some circular, that may resemble craters. Combining Cassini mission's multiple data sets, with subsequent analysis, has been shown to differentiate candidate cryovolcanic features. Here, we investigate whether analysis of topographic data applying a simple geometric criterion would adequately characterize features through degree of correlation, as successfully undertaken on Venus.