Characterization of a NNE-trending cluster (2,000 x 500 km) of impact splotches located NW of Phoebe Regio

Almost a 1,000 impact features of six main types are distinguished on the surface of Venus [1]. In addition to the main types, a number of other classes of objects are distinguished, including the so-called "splotches" (also termed crater-less blast haloes) [1-4]. The absence of craters within these splotches is a good indicator that the meteors were destroyed in the atmosphere and did not reach the surface. However, the shockwaves from these meteors were sufficient to form large features. The structure of these splotches includes: a central spot (usually radar-dark), which on rare occasions may include a crater and an annulus, surrounding the spot. Their formation and appearance depend on the parameters of the impact itself its size, velocity, and also on the density of the atmosphere. Determining all these parameters will help in understanding the nature and the differences between the splotches: why are some splotches radar-dark and others radar-bright? What determines the size of the "dark center"? Why do some splotches include centers, while others do not? On the basis of our mapping in Hinemoa planitia, NW of Phoebe Regio in the southeastern part of the Beta-Atla-Themis region, we have mapped in detail a NNE trending cluster of at least 12 bright splotches. The centers of these splotches are dark and they are surrounded by wide radar-bright annuli. Only two splotches have faint central craters, which indicates that the impactors were not completely destroyed by the atmosphere. The most interesting aspect is the elongate NNE distribution of the splotches (2,000 km long, 500 km wide) (Fig. 1). Our hypothesis is that this array of splotches resulted from a single cosmic body that exploded in the atmosphere, with its fragments creating the splotches that are distributed along the extension of the bodys flight path. Further analysis of the elongate splotch cluster is focused on assessing both the incoming direction (NNE or SSW) and the effects of the atmospheric column (altitude). [1] Schaber, et al. 1992. JGR, 97: 13257-13301. [2] Schultz, 1992.JGR, 97:16183-16248. [3] Soderblom et al. 1992. 23rd LPSC #1652 [4] Kirk et al. 1994. 25th LPSC #1353