Experimental Investigation into the Radar Anomalies on the Surface of Venus

Introduction: Radar mapping of the surface of Venus shows areas of high reflectivity (low emissivity) in the Venusian highlands at altitudes between 2.5-4.75 kilometers [1-5]. The origin of the radar anomalies found in the Venusian highlands remains unclear. Most explanations of the potential causes for these radar anomalies come from theoretical work [1, 7, 9, 10]. Previous studies suggest increased surface roughness or materials with higher dielectric constants as well as surfaceatmospheric interactions [1, 7]. Several possible candidates of high-dielectric materials are tellurium, ferroelectric materials, and lead or bismuth sulfides. While previous studies have been influential in determining possible sources for the Venus anomalies, only a very few hypotheses have been verified via experimentation. This work intends to experimentally constrain the source of the radar anomalies on Venus. This study proposes to investigate four possible materials that could potentially cause the high reflectivities on the surface of Venus and tests their behavior under simulated Venusian conditions. Methods: Four volatile compounds potentially present on Venus were chosen for this experiment. One gram of each Tellurium (Te), Bismuth sulfide (Bi2S3), Mercury sulfide (HgS) and Lead sulfide (PbS) were heated to the average surface temperature (~460°C) and average surface pressure (~90 bars) in a Venus Simulation Chamber (Fig. 1) [13]. We used the Venus simulation chamber at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center. The chamber has dimensions of slightly less than five inches in diameter and twelve inches deep and is constructed of stainless steel. It can maintain temperatures of 467°C and pressures of 95.6 bars for around 48 hours under a carbon dioxide atmosphere [13]. The temperature data from the 460°C run is shown in Figure 2 and shows that the conditions were maintained for 19 hours. The top line is the associated temperature for the samples at the bottom of the chamber. Figure 1: The Venus simulation chamber at NASA Goddard. The samples were then immediately weighted after cooling to determine if they condensed on and/or reacted. Another run was conducted at the average temperature (~380°C) and pressure of the Venusian highlands. In addition to the four samples, one gram of basalt, as an analog of the Venusian surface, was placed in the chamber to test potential reactions of the vaporized samples with the basalt. Once the samples were cooled, these too were weighed to determine condensation and/or reactions.