Radar-Reflective Minerals Tested Under Venus Near-Surface Conditions

Abstract:

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. The origin of the radar anomalies found in the highlands remains unclear. Previous theoretical studies suggest increased surface roughness or materials with higher dielectric constants as well as surface-atmospheric interactions.

This work intends to experimentally constrain the source of the radar anomalies on Venus. Primarily, the suggested explanations for these radar-bright regions involve a reaction between volatiles in the atmosphere and rocks/minerals on the surface. Thus, possible materials that could potentially cause the high reflectivities on the surface of Venus are investigated and their behavior tested under simulated Venusian atmospheric and surface conditions, with special emphasis on the combined effect of pressure and temperature, and chemical composition.

Stability experiments were conducted in the Venus simulation chamber at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center. Several minerals thought to exist on Venus were tested including bismuthinite (Bi₂S₃), tellurobismuthite (Bi₂Te₃), tellurium (Te), coloradoite (HgTe), and pyrite (FeS₂). One gram of each sample was heated in the chamber to average Venusian surface conditions, and separately to highland conditions (460°C and 90 bar, 380°C and 55 bar, respectively) under a simulated Venusian atmosphere of 96.5% CO₂, 3.5% N₂ and 150 ppm SO₂. After each run, the samples were weighed and then analyzed using X-Ray Diffraction (XRD).

Ongoing experiments show several minerals are of potential interest due to their stability at highland conditions where the anomalies are observed. These minerals would exhibit a higher dielectric value than the surrounding basalts, creating a higher radar reflectivity in those regions and potentially being the source of the Venusian radar anomalies.