A ferroelectric model for the low emissivity highlands on Venus

Abstract

A model to explain the low emissivity venusian highlands is proposed utilizing the temperature‐dependent dielectric constant of ferroelectric minerals. Ferroelectric minerals are known to occur in alkaline and carbonatite rocks, both of which are plausible for Venus. Ferroelectric minerals possess extremely high dielectric constants (105) over small temperature intervals and are only required in minor (≪1%) abundances to explain the observed emissivities. The ferroelectric model can account for: (1) the observed reduction in emissivity with increased altitude, (2) the abrupt return to normal emissivities at highest elevations, and (3) the variations in the critical elevation observed from region to region.

Ovda Fluctus, the Festoon Lava Flow on Ovda Regio, Venus: Not Silica‐Rich

“…The highest elevations (b) have the highest emissivity and lowest backscatter (a). Also note that the low elevations of the Ovda Fluctus have flow with somewhat higher emissivity and lower backscatter, consistent with elevations (b), see Arvidson et al (), Shepard et al (), and Treiman et al (). (d) Meter‐scale roughness (r.m.s.…”

“…These changes in elevation are apparent in the radar properties of the flow. Above the critical elevation of ~4.5 km, the flow shows low SAR backscatter and Fresnel reflectance, and high emissivity, (Figure ; Arvidson et al, ; Shepard et al, ; Treiman et al, ). Just below the critical elevation, SAR backscatter and Fresnel reflectance are high and decline significantly with decreasing elevation; emissivity behaves in the opposite way.…”

Electrical Properties of the Venus Surface from Bistatic Radar Observations

“…Once formed, the droplets passed through a scattering chamber where th e gas of interest, SF, was added at a 5 mbar. The known pressure, typically 10 average number of molecules captured by the He droplet depends directly on this pressure (19). Upon capturing a hot SF 6 molecule, the droplet rapidly evaporates He atoms from its surface, and after approximately 10 -6 s, the temperature returns to the initial droplet temperature, cooling the captured molecule.…”

“…Upon capturing a hot SF 6 molecule, the droplet rapidly evaporates He atoms from its surface, and after approximately 10 -6 s, the temperature returns to the initial droplet temperature, cooling the captured molecule. Of the -4000 He atoms that make up the droplet (20), about 600 evaporate during the capture process (19).…”

“…Wood (18) has proposed a plating of pyrites or magnetite as a source of conducting material, and Shepard et nl. (19) have shown that ferroelectrics may also have the electrical properties needed t o account for the radar observations. Both of these types of material require substantial loss mechanisms if they are responsible for the bistatic observations.…”